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Papers: 29 Jan 2022 - 4 Feb 2022

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Rare SLC13A1 variants associate with intervertebral disc disorder highlighting role of sulfate in disc pathology.

Back pain is a common and debilitating disorder with largely unknown underlying biology. Here we report a genome-wide association study of back pain using diagnoses assigned in clinical practice; dorsalgia (119,100 cases, 909,847 controls) and intervertebral disc disorder (IDD) (58,854 cases, 922,958 controls). We identify 41 variants at 33 loci. The most significant association (OR = 0.92, P = 1.6 × 10; OR = 0.92, P = 7.2 × 10) is with a 3'UTR variant (rs1871452-T) in CHST3, encoding a sulfotransferase enzyme expressed in intervertebral discs. The largest effects on IDD are conferred by rare (MAF = 0.07 – 0.32%) loss-of-function (LoF) variants in SLC13A1, encoding a sodium-sulfate co-transporter (LoF burden OR = 1.44, P = 3.1 × 10); variants that also associate with reduced serum sulfate. Genes implicated by this study are involved in cartilage and bone biology, as well as neurological and inflammatory processes.

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Mice expressing fluorescent PAR reveal that endocytosis mediates colonic inflammation and pain.

G protein-coupled receptors (GPCRs) regulate many pathophysiological processes and are major therapeutic targets. The impact of disease on the subcellular distribution and function of GPCRs is poorly understood. We investigated trafficking and signaling of protease-activated receptor 2 (PAR) in colitis. To localize PAR and assess redistribution during disease, we generated knockin mice expressing PAR fused to monomeric ultrastable green fluorescent protein (muGFP). PAR-muGFP signaled and trafficked normally. PAR messenger RNA was detected at similar levels in and wild-type mice. Immunostaining with a GFP antibody and RNAScope in situ hybridization using (PAR) and probes revealed that PAR-muGFP was expressed in epithelial cells of the small and large intestine and in subsets of enteric and dorsal root ganglia neurons. In healthy mice, PAR-muGFP was prominently localized to the basolateral membrane of colonocytes. In mice with colitis, PAR-muGFP was depleted from the plasma membrane of colonocytes and redistributed to early endosomes, consistent with generation of proinflammatory proteases that activate PAR PAR agonists stimulated endocytosis of PAR and recruitment of Gα, Gα, and β-arrestin to early endosomes of T84 colon carcinoma cells. PAR agonists increased paracellular permeability of colonic epithelial cells, induced colonic inflammation and hyperalgesia in mice, and stimulated proinflammatory cytokine release from segments of human colon. Knockdown of dynamin-2 (), the major colonocyte isoform, and Dnm inhibition attenuated PAR endocytosis, signaling complex assembly and colonic inflammation and hyperalgesia. Thus, PAR endocytosis sustains protease-evoked inflammation and nociception and PAR in endosomes is a potential therapeutic target for colitis.

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Maresin 1 promotes nerve regeneration and alleviates neuropathic pain after nerve injury.

Peripheral nerve injury (PNI) is a public health concern that results in sensory and motor disorders as well as neuropathic pain and secondary lesions. Currently, effective treatments for PNI are still limited. For example, while nerve growth factor (NGF) is widely used in the treatment of PNI to promote nerve regeneration, it also induces pain. Maresin 1 (MaR1) is an anti-inflammatory and proresolving mediator that has the potential to regenerate tissue. We determined whether MaR1 is able to promote nerve regeneration as well as alleviating neuropathic pain, and to be considered as a putative therapeutic agent for treating PNI.

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A Synthetically Accessible Small-Molecule Inhibitor of USP5-Cav3.2 Calcium Channel Interactions with Analgesic Properties.

Cav3.2 calcium channels are important mediators of nociceptive signaling in the primary afferent pain pathway, and their expression is increased in various rodent models of chronic pain. Previous work from our laboratory has shown that this is in part mediated by an aberrant expression of deubiquitinase USP5, which associates with these channels and increases their stability. Here, we report on a novel bioactive rhodanine compound (II-1), which was identified in compound library screens. II-1 inhibits biochemical interactions between USP5 and the Cav3.2 domain III-IV linker in a dose-dependent manner, without affecting the enzymatic activity of USP5. Molecular docking analysis reveals two potential binding pockets at the USP5-Cav3.2 interface that are distinct from the binding site of the deubiquitinase inhibitor WP1130 (a.k.a. degrasyn). With an understanding of the ability of some rhodanines to produce false positives in high-throughput screening, we have conducted several orthogonal assays to confirm the validity of this hit, including in vivo experiments. Intrathecal delivery of II-1 inhibited both phases of formalin-induced nocifensive behaviors in mice, as well as abolished thermal hyperalgesia induced by the delivery of complete Freund's adjuvant (CFA) to the hind paw. The latter effects were abolished in Cav3.2 null mice, thus confirming that Cav3.2 is required for the action of II-1. II-1 also mediated a robust inhibition of mechanical allodynia induced by injury to the sciatic nerve. Altogether, our data uncover a novel class of analgesics─well suited to rapid structure-activity relationship studies─that target the Cav3.2/USP5 interface.

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Characteristics of pre-cluster symptoms in cluster headache: A cross-sectional multicentre study.

Contrary to pre-attack symptoms before an individual cluster headache attack, little is known about the pre-cluster symptoms before the onset of cluster bouts. We previously described pre-attack symptoms before cluster headache attacks. The aim of this study was to investigate characteristics of pre-cluster symptoms in patients with episodic cluster headache.

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Modulation of itch and pain signals processing in ventrobasal thalamus by thalamic reticular nucleus.

Thalamic reticular nucleus (TRN) is known to be crucial for dynamically modulating sensory processing. Recently, the functional role of TRN in itch and pain sensation processing has drawn much attention. We found that ventrobasal thalamus (VB) neurons exhibited scratching behavior-related and nociceptive behavior-related neuronal activity changes, and most of VB neurons responsive to pruritic stimulus were also activated by nociceptive stimulus. Inhibition of VB could relieve itch-induced scratching behaviors and pathological pain without affecting basal nociceptive thresholds, and activation of VB could facilitate scratching behaviors. Tracing and electrophysiology recording results showed that VB mainly received inhibitory inputs from ventral TRN. Furthermore, optogenetic activation of TRN-VB projections suppressed scratching behaviors, and ablation of TRN enhanced scratching behaviors. In addition, activation of TRN-VB projections relieved the pathological pain without affecting basal nociceptive thresholds. Thus, our study indicates that TRN modulates itch and pain signals processing via TRN-VB inhibitory projections.

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EFFECTIVENESS AND TOLERABILITY OF DRONABINOL USE IN PATIENTS WITH CHRONIC PAIN – A RETROSPECTIVE ANALYSIS OF 12-WEEK OPEN-LABEL REAL-WORLD DATA PROVIDED BY THE GERMAN PAIN E-REGISTRY.

To evaluate the effectiveness of Δ9-tetrahydrocannabinol (dronabinol, DRO), as an add-on treatment in patients with refractory chronic pain (CP).

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Deep learning algorithms for magnetic resonance imaging of inflammatory sacroiliitis in axial spondyloarthritis.

To develop a deep learning algorithm for detection of active inflammatory sacroiliitis in short tau inversion recovery (STIR) sequence magnetic resonance imaging (MRI).

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Computerized migraine diagnostic tools: a systematic review.

Computerized migraine diagnostic tools have been developed and validated since 1960. We conducted a systematic review to summarize and critically appraise the quality of all published studies involving computerized migraine diagnostic tools.

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Engineering human skin model innervated with itch sensory neuron-like cells differentiated from induced pluripotent stem cells.

Atopic dermatitis (AD), driven by interleukins (IL-4/IL-13), is a chronic inflammatory skin disease characterized by intensive pruritus. However, it is unclear how immune signaling and sensory response pathways cross talk with each other. We differentiated itch sensory neuron-like cells (ISNLCs) from iPSC lines. These ISNLCs displayed neural markers and action potentials and responded specifically to itch-specific stimuli. These ISNLCs expressed receptors specific for IL-4/IL-13 and were activated directly by the two cytokines. We successfully innervated these ISNLCs into full thickness human skin constructs. These innervated skin grafts can be used in clinical applications such as wound healing. Moreover, the availability of such innervated skin models will be valuable to develop drugs to treat skin diseases such as AD.

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fNIRS brain measures of ongoing nociception during surgical incisions under anesthesia.

: Functional near-infrared spectroscopy (fNIRS) has evaluated pain in awake and anesthetized states. : We evaluated fNIRS signals under general anesthesia in patients undergoing knee surgery for anterior cruciate ligament repair. : Patients were split into groups: those with regional nerve block (NB) and those without (non-NB). Continuous fNIRS measures came from three regions: the primary somatosensory cortex (S1), known to be involved in evaluation of nociception, the lateral prefrontal cortex (BA9), and the polar frontal cortex (BA10), both involved in higher cortical functions (such as cognition and emotion). : Our results show three significant differences in fNIRS signals to incision procedures between groups: (1) NB compared with non-NB was associated with a greater net positive hemodynamic response to pain procedures in S1; (2) dynamic correlation between the prefrontal cortex (PreFC) and S1 within 1 min of painful procedures are anticorrelated in NB while positively correlated in non-NB; and (3) hemodynamic measures of activation were similar at two separate time points during surgery (i.e., first and last incisions) in PreFC and S1 but showed significant differences in their overlap. Comparing pain levels immediately after surgery and during discharge from postoperative care revealed no significant differences in the pain levels between NB and non-NB. : Our data suggest multiple pain events that occur during surgery using devised algorithms could potentially give a measure of "pain load." This may allow for evaluation of central sensitization (i.e., a heightened state of the nervous system where noxious and non-noxious stimuli is perceived as painful) to postoperative pain levels and the resulting analgesic consumption. This evaluation could potentially predict postsurgical chronic neuropathic pain.

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Evidence of Anti-Inflammatory Effect of Transcranial Direct Current Stimulation in a CFA-Induced Chronic Inflammatory Pain Model in Wistar Rats.

Given that chronic inflammatory pain is highly prevalent worldwide, it is important to study new techniques to treat or relieve this type of pain. The present study evaluated the effect of transcranial direct current stimulation (tDCS) in rats submitted to a chronic inflammatory model by nociceptive response, biomarker levels (brain-derived neurotrophic factor [BDNF] and interleukin [IL]-6 and IL-10), and by histological parameters.

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Epigenetic Mechanisms of Neural Plasticity in Chronic Neuropathic Pain.

Neuropathic pain is a challenging clinical problem and remains difficult to treat. Altered gene expression in peripheral sensory nerves and neurons due to nerve injury is well documented and contributes critically to the synaptic plasticity in the spinal cord and the initiation and maintenance of chronic pain. However, our understanding of the epigenetic mechanisms regulating the transcription of pro-nociceptive (e.g., NMDA receptors and α2δ-1) and antinociceptive (e.g., potassium channels and opioid and cannabinoid receptors) genes are still limited. In this review, we summarize recent studies determining the roles of histone modifications (including methylation, acetylation, and ubiquitination), DNA methylation, and noncoding RNAs in neuropathic pain development. We review the epigenetic writer, reader, and eraser proteins that participate in the transcriptional control of the expression of key ion channels and neurotransmitter receptors in the dorsal root ganglion after traumatic nerve injury, which is commonly used as a preclinical model of neuropathic pain. A better understanding of epigenetic reprogramming involved in the transition from acute to chronic pain could lead to the development of new treatments for neuropathic pain.

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Novel TRPV1 Modulators with Reduced Pungency Induce Analgesic Effects in Mice.

Capsaicin, the compound in hot chili peppers responsible for their pungency and an agonist of the transient receptor potential cation channel, subfamily V, member 1 (TRPV1), has long been known to promote the desensitization of nociceptors at high concentrations. This has led to the utilization and implementation of topical capsaicin cream as an analgesic to treat acute and chronic pain. Critically, the application of capsaicin cream is limited due to capsaicin's high pungency, which is experienced prior to analgesia. To combat this issue, novel capsaicin analogues were developed to provide analgesia with reduced pungency. Analogues reported in this paper add to and show some differences from previous structure-activity relationship (SAR) studies of capsaicin-like molecules against TRPV1, including the necessity of phenol in the aromatic "A-region", the secondary amide in the "B-region", and modifications in the hydrophobic "C-region". This provided a new framework for small-molecule design using capsaicin as the starting point. In this study, we describe the synthesis of capsaicin analogues, their activity in Ca assays, and initial pungency and feasibility studies of capsaicin analogues YB-11 and YB-16 as analgesics. Our results demonstrate that male and female mice treated with YB capsaicin analogues showed diminished pain-associated behavior in the spontaneous formalin assay as well as reduced thermal sensitivity in the hotplate assay.

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Calcitonin gene-related peptide-targeting drugs for migraine: how pharmacology might inform treatment decisions.

Migraine is the second most disabling disorder across all age groups worldwide. Since 2018, two classes of drugs that inhibit the actions of calcitonin gene-related peptide (CGRP), which is implicated in migraine pathophysiology, have become available: gepants (CGRP receptor antagonists) and monoclonal antibodies directed against CGRP or its receptor. Despite phase 3 clinical trials and some real world evidence, knowledge of the pharmacology and related clinical effects of these drugs is low, and trial data are not necessarily generalisable to all populations. Additionally, several pharmacodynamic processes affected by both gepants and monoclonal antibodies to CGRP and its receptor are not fully understood. Sex, body-mass index, age, ethnic background, and other characteristics, which are subject to considerable variation, might affect the pharmacokinetics of these therapies, especially gepants. If studies confirm this possibility, these characteristics could assist clinicians in choosing the optimal treatment for patients with migraine. The choice between a gepant or monoclonal antibody should be made carefully, taking into consideration a patient's comorbidities and preferences. As more becomes known about CGRP-targeted therapies, management based on the characteristics of patients could have a more prominent role in the treatment of migraine.

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The increased in vivo firing of pyramidal cells but not interneurons in the anterior cingulate cortex after neuropathic pain.

Chronic pain damages the balance between excitation and inhibition in the sensory cortex. It has been confirmed that the activity of cortical glutamatergic pyramidal cells increases after chronic pain. However, whether the activity of inhibitory interneurons synchronized changed remains obscure, especially in in vivo conditions. In the present study, we checked the firing rate of pyramidal cells and interneurons in the anterior cingulate cortex, a main cortical area for the regulation of nociceptive information in mice with spared nerve injury by using in vivo multi-channel recording system. We found that the firing rate of pyramidal cells but not interneurons increased in the ACC, which was further confirmed by the increased FOS expression in pyramidal cells but not interneurons, in mice with neuropathic pain. Selectively high frequency stimulation of the ACC nociceptive afferent fibers only potentiated the activity of pyramidal cells either. Our results thus suggest that the increased activity of pyramidal cells contributes to the damaged E/I balance in the ACC and is important for the pain hypersensitivity in mice with neuropathic pain.

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Cranial autonomic symptoms: prevalence, phenotype and laterality in migraine and two potentially new symptoms.

Whilst cranial autonomic symptoms (CAS) are typically associated with trigeminal autonomic cephalalgias (TAC's), they have also been reported in migraine. Identification and understanding of these symptoms in migraine is important to ensure timely diagnosis and effective management.

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Risk factors for low back pain outcome: Does it matter when they are measured?

The early identification of factors that increase risk of poor recovery from acute low back pain (LBP) is critical to prevent the transition to chronicity. Although most studies of risk factors for poor outcome in LBP tend to investigate the condition once it is already persistent, there is evidence to suggest that this differs from risk factors measured during the early-acute stage. This study aimed to identify early risk factors for poor outcome in the short- and long-term in individuals with acute LBP, and to compare this with factors identified at 3 months in the same cohort.

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Associations between pain and physical activity among older adults.

Chronic pain is a significant societal problem and pain complaints are one of the main causes of work absenteeism and emergency room visits. Physical activity has been associated with reduced risk of suffering from musculoskeletal pain complaints, but the exact relationship in an older adult sample is not known.

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Scalp EEG-based Pain Detection using Convolutional Neural Network.

Pain is an integrative phenomenon coupled with dynamic interactions between sensory and contextual processes in the brain, often associated with detectable neurophysiological changes. Recent advances in brain activity recording tools and machine learning technologies have intrigued research and development of neurocomputing techniques for objective and neurophysiology-based pain detection. This paper proposes a pain detection framework based on Electroencephalogram (EEG) and deep convolutional neural networks (CNN). The feasibility of CNN is investigated for distinguishing induced pain state from resting state in the recruitment of 10 chronic back pain patients. The experimental study recorded EEG signals in two phases: 1. movement stimulation (MS), where induces back pain by executing predefined movement tasks; 2. video stimulation (VS), where induces back pain perception by watching a set of video clips. A multi-layer CNN classifies the EEG segments during the resting state and the pain state. The novel approach offers high and robust performance and hence is significant in building a powerful pain detection algorithm. The area under the receiver operating characteristic curve (AUC) of our approach is 0.83±0.09 and 0.81±0.15, in MS and VS, respectively, higher than the state-of-the-art approaches. The sub-brain-areas are also analyzed, to examine distinct brain topographies relevant for pain detection. The results indicate that MS-induced pain tends to evoke a generalized brain area, while the evoked area is relatively partial under VS-induced pain. This work may provide a new solution for researchers and clinical practitioners on pain detection.

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Genetic basis of thermal nociceptive sensitivity and brain weight in a BALB/c reduced complexity cross.

Thermal nociception involves the transmission of temperature-related noxious information from the periphery to the CNS and is a heritable trait that could predict transition to persistent pain. Rodent forward genetics complement human studies by controlling genetic complexity and environmental factors, analysis of end point tissue, and validation of variants on appropriate genetic backgrounds. Reduced complexity crosses between nearly identical inbred substrains with robust trait differences can greatly facilitate unbiased discovery of novel genes and variants. We found BALB/cByJ mice showed enhanced sensitivity on the 53.5°C hot plate and mechanical stimulation in the von Frey test compared to BALB/cJ mice and replicated decreased gross brain weight in BALB/cByJ versus BALB/cJ. We then identified a quantitative trait locus (QTL) on chromosome 13 for hot plate sensitivity (LOD = 10.7; p < 0.001; peak = 56 Mb) and a QTL for brain weight on chromosome 5 (LOD = 8.7; p < 0.001). Expression QTL mapping of brain tissues identified H2afy (56.07 Mb) as the top transcript with the strongest association at the hot plate locus (FDR = 0.0002) and spliceome analysis identified differential exon usage within H2afy associated with the same locus. Whole brain proteomics further supported decreased H2AFY expression could underlie enhanced hot plate sensitivity, and identified ACADS as a candidate for reduced brain weight. To summarize, a BALB/c reduced complexity cross combined with multiple -omics approaches facilitated identification of candidate genes underlying thermal nociception and brain weight. These substrains provide a powerful, reciprocal platform for future validation of candidate variants.

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Dorsal Column and Root Stimulation at Aβ-fiber Intensity Activate Superficial Dorsal Horn Glutamatergic and GABAergic Populations.

Neurostimulation therapies are frequently used in patients with chronic pain conditions. They emerged from Gate Control Theory (GCT), which posits that Aβ-fiber activation recruits superficial dorsal horn (SDH) inhibitory networks to "close the gate" on nociceptive transmission, resulting in pain relief. However, the efficacy of current therapies is limited, and the underlying circuits remain poorly understood. For example, it remains unknown whether ongoing stimulation of Aβ-fibers is sufficient to drive activity in SDH neurons. We used multiphoton microscopy in spinal cords extracted from mice expressing the genetically encoded calcium indicator GCaMP6s in glutamatergic and GABAergic populations; activity levels were inferred from deconvolved calcium signals using CaImAn software. Sustained Aβ-fiber stimulation at the dorsal columns or dorsal roots drove robust yet transient activation of both SDH populations. Following the initial increase, activity levels decreased below baseline in glutamatergic neurons and were depressed after stimulation ceased in both populations. Surprisingly, only about half of GABAergic neurons responded to Aβ-fiber stimulation. This subset showed elevated activity for the entire duration of stimulation, while non-responders decreased with time. Our findings suggest that Aβ-fiber stimulation initially recruits both excitatory and inhibitory populations but has divergent effects on their activity, providing a foundation for understanding the analgesic effects of neurostimulation devices.

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Effects of rTMS and tDCS on neuropathic pain after brachial plexus injury: a randomized placebo-controlled pilot study.

Neuropathic pain after brachial plexus injury (NPBPI) is a highly disabling clinical condition and is increasingly prevalent due to increased motorcycle accidents. Currently, no randomized controlled trials have evaluated the effectiveness of non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct-current stimulation (tDCS) in patients suffering from NPBPI. In this study, we directly compare the efficacy of 10-Hz rTMS and anodal 2 mA tDCS techniques applied over the motor cortex (5 daily consecutive sessions) in 20 patients with NPBPI, allocated into 2 parallel groups (active or sham). The order of the sessions was randomised for each of these treatment groups according to a crossover design and separated by a 30-day interval. Scores for "continuous" and "paroxysmal" pain (primary outcome) were tabulated after the last stimulation day and 30 days after. Secondary outcomes included the improvement in multidimensional aspects of pain, anxiety state and quality of life from a qualitative and quantitative approach. Active rTMS and tDCS were both superior to sham in reducing continuous (p < 0.001) and paroxysmal (p = 0.002; p = 0.02) pain as well as in multidimensional aspects of pain (p = 0.001; p = 0.002) and anxiety state (p =  < 0.001; p = 0.005). Our results suggest rTMS and tDCS are able to treat NPBPI with little distinction in pain and anxiety state, which may promote the use of tDCS in brachial plexus injury pain management, as it constitutes an easier and more available technique.Clinical Trial Registration: http://www.ensaiosclinicos.gov.br/, RBR-5xnjbc – Sep 3, 2018.

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EEG theta and beta bands as brain oscillations for different knee osteoarthritis phenotypes according to disease severity.

This study aims to investigate the multivariate relationship between different sociodemographic, clinical, and neurophysiological variables with resting-state, high-definition, EEG spectral power in subjects with chronic knee osteoarthritis (OA) pain. This was a cross-sectional study. Sociodemographic and clinical data were collected from 66 knee OA subjects. To identify associated factors, we performed independent univariate and multivariate regression models by frequency bands (delta, theta, alpha, beta, low-beta, and high-beta) and by pre-defined regions (frontal, central, and parietal). From adjusted multivariate models, we found that: (1) increased frontocentral high-beta power and reduced central theta activity are positively correlated with pain intensity (β = 0.012, 95% CI 0.004-0.020; and β = - 0.008; 95% CI 0.014 to - 0.003; respectively); (2) delta and alpha oscillations have a direct relationship with higher cortical inhibition; (3) diffuse increased power at low frequencies (delta and theta) are associated with poor cognition, aging, and depressive symptoms; and (4) higher alpha and beta power over sensorimotor areas seem to be a maladaptive compensatory mechanism to poor motor function and severe joint degeneration. Subjects with higher pain intensity and higher OA severity (likely subjects with maladaptive compensatory mechanisms to severe OA) have higher frontocentral beta power and lower theta activity. On the other hand, subjects with less OA severity and less pain have higher theta oscillations power. These associations showed the potential role of brain oscillations as a marker of pain intensity and clinical phenotypes in chronic knee OA patients. Besides, they suggest a potential compensatory mechanism of these two brain oscillators according to OA severity.

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Regulation of Two-Pore-Domain Potassium TREK Channels and their Involvement in Pain Perception and Migraine.

The ability to sense pain signals is closely linked to the activity of ion channels expressed in nociceptors, the first neurons that transduce noxious stimuli into pain. Among these ion channel, TREK1, TREK2 and TRAAK from the TREK subfamily of the Two-Pore-Domain potassium (K) channels, are hyperpolarizing channels that render neurons hypoexcitable. They are regulated by diverse physical and chemical stimuli as well as neurotransmitters through G-protein coupled receptors activation. Here, we review the molecular mechanisms underlying these regulations and their functional relevance in pain and migraine induction.

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Endogenous opiates and behavior: 2020.

This paper is the forty-third consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2020 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

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Effect of caffeine and caffeine cessation on cerebrovascular reactivity in patients with migraine.

To investigate the effect of chronic caffeine use and caffeine cessation on vasodilatory function in the posterior circulation in patients with migraine.

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The Long-Term Outcome of Radiofrequency Ablation in Multiple Sclerosis-Related Symptomatic Trigeminal Neuralgia.

Radiofrequency lesioning (RFL) is used to surgically manage trigeminal neuralgia (TN) secondary to multiple sclerosis (MS). However, the long-term outcome of RFL has not been established.

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Increased serum diamine oxidase activity in non-allergic patients with migraine.

Histamine has shown a possible role in the etiopathogenesis of migraine. It has been reported an association between some polymorphisms in the diamine oxidase (DAO) gene and migraine (specially in women). Two studies addressing DAO activity in migraine patients showed conflicting results. We investigated the possible relationship of serum DAO activity and histamine levels and 3 polymorphisms in the DAO gene with the risk for migraine.

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Psychological Interventions for Pediatric Headache Disorders: A 2021 Update on Research Progress and Needs.

This review summarizes key findings from recent investigations of psychological interventions for pediatric headache disorders and discusses important avenues for future research.

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Racial and ethnic disparities in surgical care for endometriosis across the United States.

Despite an estimated 10% prevalence of endometriosis among reproductive-age women, surgical population-based data is limited.

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Recent advances on transdermal delivery systems for the treatment of arthritic injuries: From classical treatment to nanomedicines.

Arthritic injuries happen frequently during a lifetime due to accidents, sports, aging, diseases, etc. Such injuries can be cartilage/bone injuries, tendon injuries, ligament injuries, inflammation, pain, and/or synovitis. Oral and injective administration of therapeutics are typically used but cause many side effects. Transdermal administration is an alternative route for safe and efficient delivery. Transdermal formulations of non-steroidal anti-inflammatory drugs have been available on market for years and show promising efficacy in pain relieving, inflammation alleviation, infection control, and so on. Innovative transdermal patches, gels/films, and microneedles have also been widely explored as formulations to deliver therapeutics to combat arthritic injuries. However, transdermal formulations that halt disease progression and promote damage repair are translated slowly from lab bench to clinical applications. One major reason is that the skin barrier and synovial capsule barrier limit the efficacy of transdermal delivery. Recently, many nanocarriers, such as nanoparticles, nanolipids, nanoemulsions, nanocrystals, exosomes, etc., have been incorporated into transdermal formulations to advance drug delivery. The combined transdermal formulations show promising safety and efficacy. Therefore, this review will focus on stating the current development of nanomedicine-based transdermal formulations for the treatment of arthritic injuries. The advances, limitations, and future perspectives in this field will also be provided to inspire future studies and accelerate clinical translational studies. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Biology-Inspired Nanomaterials > Lipid-Based Structures.

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CGRP-targeted drugs for migraine: still many uncertainties.

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[The new Parkinson’s disease pain classification system (PD-PCS)].

Chronic pain is a common non-motor symptom in patients with Parkinson's disease (PD).

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Advances in migraine and headache therapy (BJP 75th anniversary).

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Including Arts in Rehabilitation Enhances Outcomes in the Psychomotor, Cognitive, and Affective Domains: A Scoping Review.

The purpose of this scoping review was to analyze the published literature regarding the use of art in the context of rehabilitation for consideration in physical therapy.

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Collaboration between adult patients and practitioners when making decisions about prescribing opioid medicines for chronic non-cancer pain in primary care: a scoping review.

Long-term opioid therapy (>12 months) is not effective for improving chronic non-cancer pain and function. Where patients are not experiencing pain relief with long-term opioids, the opioid should be tapered and discontinuation considered. Practitioners may find it challenging to tell patients experiencing pain that they are better off reducing or not taking medicines that do not help. This review aims to ascertain what is published about: (1) the interaction and (2) the nature of the relationship between practitioners and patients when prescribing opioids for chronic non-cancer pain in primary care.

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Association of neovascular age-related macular degeneration with migraine.

Patients with early onset vascular pathology have been reported to manifest neovascular age-related macular degeneration (AMD). While the blood vessels involved in pathogenesis of migraine remains controversial, it is generally accepted that a major contributor is blood vessel pathology. This study aimed to examine the association between migraine and AMD using a nationwide population-based dataset. Retrospective claims data were collected from the Taiwan National Health Insurance Research Database. We identified 20,333 patients diagnosed with neovascular AMD (cases), and we selected 81,332 propensity score-matched controls from the remaining beneficiaries in Taiwan's National Health Insurance system. We used Chi-square tests to explore differences in the prevalence of migraine prior to the index date between cases and controls. We performed multiple logistic regressions to estimate the odds of prior migraine among neovascular AMD patients vs. controls after adjusting for age, sex, monthly income, geographic location, residential urbanization level, hyperlipidemia, diabetes, coronary heart disease, hypertension, and previous cataract surgery. A total of 5184 of sample patients (5.1%) had a migraine claim before the index date; 1215 (6.1%) among cases and 3969 (4.9%) among controls (p < 0.001), with an unadjusted OR of 1.239 (95% CI 1.160~1.324, p < 0.001) for prior migraine among cases relative to controls. Furthermore, the adjusted OR was 1.201 (95% CI 1.123~1.284; p < 0.001) for AMD cases relative to controls. The study offers population-based evidence that persons with migraine have 20% higher risk of subsequently being diagnosed with neovascular AMD.

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Racial Differences in Pain, Nutrition, and Oxidative Stress.

Investigating the disproportionate rates of chronic pain and their related comorbidities between Black and non-Hispanic White (White) individuals is a growing area of interest, both in the healthcare community and in general society. Researchers have identified racial differences in chronic pain prevalence and severity, but still very little is known about the mechanisms underlying them. Current explanations for these differences have primarily focused on socioeconomic status and unequal healthcare between races as causal factors. Whereas these factors are informative, a racial gap still exists between Black and White individuals when these factors are controlled for. One potential cause of this racial gap in chronic pain is the differences in nutrition and dietary intake between groups. Certain foods play a key role in the inflammatory and oxidative stress pathways in the human body and could potentially influence the severity of the pain experience. Here, we review the previous literature on the surrounding topics and propose a potential mechanism to explain racial differences in the chronic pain population, based on established racial differences in diet and oxidative stress.

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Effect of topical local anaesthesia on injection pain associated with administration of sterile water injections – a randomized controlled trial.

Sterile water injections can provide effective pain relief during childbirth, particularly for low back pain related to childbirth. However, the pain associated administering the injections can negatively impact women's impressions of the procedure. It may discourage women from considering repeat doses despite the quality of analgesia experienced. Determining strategies to reduce the pain related to the administration of sterile water injections would improve the acceptability of the technique. Therefore, the aim of this study was to evaluate the effect of topical local anesthesia on the pain associated with administration of sterile water injections.

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Enhanced antidepressant-like effects of a delta opioid receptor agonist, SNC80, in rats under inflammatory pain.

Depression is a debilitating mental disorder that affects a large population worldwide. Depression and pain comorbidity is well recognized in both clinical and preclinical settings. Research studies suggest delta opioid receptor (DOR) may be involved in modulating pain as well as depression. DOR agonists produce antidepressant-like effects in animal models and their antihyperalgesic effects are enhanced in rats under inflammatory pain. However, it is unclear whether the antidepressant-like effects of DOR agonists may change in the models of pain. In this study, the antidepressant-like effects of a DOR agonist, SNC80, and a tricyclic antidepressant, amitriptyline, were compared following intracerebroventricular (i.c.v.) administration in rats under normal or inflammatory pain state elicited by injection of complete Freund's adjuvant. The forced swim test was used to determine the antidepressant-like effects. Results showed that i.c.v. SNC80 and amitriptyline dose-dependently produced antidepressant-like effects in rats under normal state. The potency of SNC80-induced antidepressant-like effects, but not amitriptyline, was enhanced in rats under inflammatory pain. This study provides functional evidence of the state-dependent effects of DOR agonists and suggests that DOR agonists may be more effective as potential antidepressants for patients experiencing both depression and pain.

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Potential Use for Chronic Pain: Poly(Ethylene Glycol)-Poly(Lactic-Co-Glycolic Acid) Nanoparticles Enhance the Effects of Cannabis-Based Terpenes on Calcium Influx in TRPV1-Expressing Cells.

The objective of these in vitro studies was to investigate the impact of the encapsulation of three cannabis-based terpenes, namely β-myrcene (MC), β-caryophyllene (CPh), and nerolidol (NL), on their potential efficacy in pain management. Terpene-encapsulated poly(ethylene glycol)-poly(lactic-co-glycolic acid) nanoparticles (PEG-PLGA NPs) were prepared by an emulsion-solvent evaporation method. The terpene-loaded NPs were examined in HEK293 cells that express the nociceptive transient receptor potential vanilloid-1 (TRPV1), an ion channel involved in pain perception. TRPV1 activation was assessed by monitoring calcium influx kinetics over 1h in cells pre-treated with the fluorescent indicator Fluo-4. In addition, the fluorescence intensity changes induced by the NPs in living cells were also explored by a fluorescence microscope. Furthermore, the cytotoxicity of the terpene-loaded NPs was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl tetrazolium bromide (MTT) proliferation assay. The terpene-loaded NPs had a diameter in the range of 250-350nm and a zeta potential of approximately -20mV. The encapsulation efficiency was 18.5%, 51.3%, and 60.3% for MC, NL, and CPh NPs, respectively. The nano-formulations significantly increased the fluorescence intensity in comparison with free terpenes. Furthermore, combinations of terpene-loaded NPs produced significantly higher calcium responses when compared to combinations of free terpenes. Similar findings were shown by the fluorescence images. In conclusion, the terpene-PLGA NPs can be promising therapeutics for more effective pain management.

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Temporomandibular disorders cases with high-impact pain are more likely to experience short-term pain fluctuations.

Temporomandibular disorders (TMD) patients can present clinically significant jaw pain fluctuations which can be debilitating and lead to poor global health. The Graded Chronic Pain Scale evaluates pain-related disability and its dichotomous grading (high/low impact pain) can determine patient care pathways and in general high-impact pain patients have worse treatment outcomes. Individuals with low-impact TMD pain are thought to have better psychosocial functioning, more favorable disease course, and better ability to control pain, while individuals with high-impact pain can present with higher levels of physical and psychological symptoms. Thereby, there is reason to believe that individuals with low- and high-impact TMD pain could experience different pain trajectories over time. Our primary objective was to determine if short-term jaw pain fluctuations serve as a clinical marker for the impact status of TMD pain. To this end, we estimated the association between high/low impact pain status and jaw pain fluctuations over three visits (≤ 21-day-period) in 30 TMD cases. Secondarily, we measured the association between jaw pain intensity and pressure pain thresholds (PPT) over the face and hand, the latter measurements compared to matched pain-free controls (n = 17). Jaw pain fluctuations were more frequent among high-impact pain cases (n = 15) than low-impact pain cases (n = 15) (OR 5.5; 95% CI 1.2, 26.4; p value = 0.033). Jaw pain ratings were not associated with PPT ratings (p value > 0.220), suggesting different mechanisms for clinical versus experimental pain. Results from this proof-of-concept study suggest that targeted treatments to reduce short-term pain fluctuations in high-impact TMD pain is a potential strategy to achieve improved patient perception of clinical pain management outcomes.

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The applicability research of the diagnostic criteria for 6.7.2 angiography headache in the international classification of headache disorders-3rd edition.

Angiography headache (AH) is common but not negligible, and the criteria for AH have been based on only a few studies. The purpose of this study was to investigate the incidence, risk factors and possible mechanism of AH and reappraise the diagnostic criteria for AH in the International Classification of Headache Disorders 3 (ICHD-3).

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Effectiveness of Calcitonin Gene-Related Peptide Receptor Antagonists for Migraine Treatment: A Meta-Analysis.

The pathophysiology of migraine has been researched incessantly, and it has been suggested that calcitonin gene-related peptide (CGRP) is associated with migraine attacks. CGRP receptor blockers are attracting attention as potential agents for migraine prevention and treatment of acute episodes. This meta-analysis aimed to assess the effects of available CGRP receptor antagonists, focusing on their therapeutic doses for acute migraine treatment.

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Predictors of Sustained Response and Effects of Anti-CGRP Antibodies Discontinuation and Reinitiation in Resistant Chronic Migraine.

Guidelines for migraine prophylaxis suggest stopping medication after 6-12 months to reevaluate treatment appropriateness. The Italian Medicines Agency (AIFA) set a mandatory regulation to stop anti-CGRP (calcitonin gene related protein) pathway monoclonal antibody (anti-CGRP mAbs) treatments for 3 months after 12-months of treatment. Herein, we assess the effects of discontinuation and retreatment of anti-CGRP mAbs in resistant chronic migraine patients, evaluating predictive factors of sustained response.

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microRNA-Based Network and Pathway Analysis for Neuropathic Pain in Rodent Models.

Neuropathic pain (NP) is poorly managed, and in-depth mechanisms of gene transcriptome alterations in NP pathogenesis are not yet fully understood. To determine microRNA-related molecular mechanisms of NP and their transcriptional regulation in NP, PubMed, Embase, Web of Science and CINAHL Complete (EBSCO) were searched from inception to April 2021. Commonly dysregulated miRNAs in NP were assessed. The putative targets of these miRNAs were determined using TargetScan, Funrich, Cytoscape and String database. A total of 133 literatures containing miRNA profiles studies and experimentally verify studies were included. Venn analysis, target gene prediction analysis and functional enrichment analysis indicated several miRNAs (miR-200b-3p, miR-96, miR-182, miR-183, miR-30b, miR-155 and miR-145) and their target genes involved in known relevant pathways for NP. Targets on transient receptor potential channels, voltage-gated sodium channels and voltage-gated calcium channels may be harnessed for pain relief. A further delineation of signal processing and modulation in neuronal ensembles is key to achieving therapeutic success in future studies.

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Decrease of IL-1β and TNF in the Spinal Cord Mediates Analgesia Produced by Ankle Joint Mobilization in Complete Freund Adjuvant-Induced Inflammation Mice Model.

This study aims to investigate the effects of ankle joint mobilization (AJM) on mechanical hyperalgesia and peripheral and central inflammatory biomarkers after intraplantar (i.pl.) Complete Freund's Adjuvant (CFA)-induced inflammation.

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Nuclear Factor κB-COX2 Pathway Activation in Non-myelinating Schwann Cells Is Necessary for the Maintenance of Neuropathic Pain .

Chronic neuropathic pain leads to long-term changes in the sensitivity of both peripheral and central nociceptive neurons. Glial fibrillary acidic protein (GFAP)-positive glial cells are closely associated with the nociceptive neurons including astrocytes in the central nervous system (CNS), satellite glial cells (SGCs) in the sensory ganglia, and non-myelinating Schwann cells (NMSCs) in the peripheral nerves. Central and peripheral GFAP-positive cells are involved in the maintenance of chronic pain through a host of inflammatory cytokines, many of which are under control of the transcription factor nuclear factor κB (NFκB) and the enzyme cyclooxygenase 2 (COX2). To test the hypothesis that inhibiting GFAP-positive glial signaling alleviates chronic pain, we used (1) a conditional knockout (cKO) mouse expressing Cre recombinase under the hGFAP promoter and a floxed COX2 gene to inactivate the COX2 gene specifically in GFAP-positive cells; and (2) a tet-Off tetracycline transactivator system to suppress NFκB activation in GFAP-positive cells. We found that neuropathic pain behavior following spared nerve injury (SNI) significantly decreased in COX2 cKO mice as well as in mice with decreased glial NFκB signaling. Additionally, experiments were performed to determine whether central or peripheral glial NFκB signaling contributes to the maintenance of chronic pain behavior following nerve injury. Oxytetracycline (Oxy), a blood-brain barrier impermeable analog of doxycycline was employed to restrict transgene expression to CNS glia only, leaving peripheral glial signaling intact. Signaling inactivation in central GFAP-positive glia alone failed to exhibit the same analgesic effects as previously observed in animals with both central and peripheral glial signaling inhibition. These data suggest that the NFκB-COX2 signaling pathway in NMSCs is necessary for the maintenance of neuropathic pain .

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The influence of the significant other on treatment adherence in chronic pain management: a qualitative analysis.

. Adherence to treatment recommendations is critical for optimising quality of life for individuals with chronic pain, however adherence rates are low. This study explores the role that significant others are perceived to play in supporting or impeding treatment adherence, as well as examining patient views of the impact of their adherence regimes on their significant others.. 25 treatment seeking adults with chronic pain, who were currently living with a romantic partner or adult family member, took part in individual semi-structured interviews. Interviews were transcribed verbatim and analysed using thematic analysis. Three treatment adherence support themes emerged: social support (emotional, instrumental), positive social control, and supporting autonomy. Participants did not perceive significant others as having any negative influence on their adherence. By contrast, patients perceived that their adherence behaviors had both positive and negative effects on their significant others.. These data present an encouraging perspective on the interpersonal context of coping with chronic pain. Significant others facilitated adherence in a range of ways. Future research identifying how best to integrate significant other support into patient self-management programs is needed, in order to lift the poor treatment adherence rates that are noted in the literature.

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Disrupted White Matter Functional Connectivity With the Cerebral Cortex in Migraine Patients.

In attempts to understand the migraine patients' overall brain functional architecture, blood oxygenation level-dependent (BOLD) signals in the white matter (WM) and gray matter (GM) were considered in the current study. Migraine, a severe and multiphasic brain condition, is characterized by recurrent attacks of headaches. BOLD fluctuations in a resting state exhibit similar temporal and spectral profiles in both WM and GM. It is feasible to explore the functional interactions between WM tracts and GM regions in migraine. Forty-eight migraineurs without aura (MWoA) and 48 healthy controls underwent resting-state functional magnetic resonance imaging. Pearson's correlations between the mean time courses of 48 white matter (WM) bundles and 82 gray matter (GM) regions were computed for each subject. Two-sample -tests were performed on the Pearson's correlation coefficients (CC) to compare the differences between the MWoA and healthy controls in the GM-averaged CC of each bundle and the WM-averaged CC of each GM region. The MWoAs exhibited an overall decreased average temporal CC between BOLD signals in 82 GM regions and 48 WM bundles compared with healthy controls, while little was increased. In particular, WM bundles such as left anterior corona radiata, left external capsule and bilateral superior longitudinal fasciculus had significantly decreased mean CCs with GM in MWoA. On the other hand, 16 GM regions had significantly decreased mean CCs with WM in MWoA, including some areas that are parts of the somatosensory regions, auditory cortex, temporal areas, frontal areas, cingulate cortex, and parietal cortex. Decreased functional connections between WM bundles and GM regions might contribute to disrupted functional connectivity between the parts of the pain processing pathway in MWoAs, which indicated that functional and connectivity abnormalities in cortical regions may not be limited to GM regions but are instead associated with functional abnormalities in WM tracts.

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Development of a Model for Predicting the Effectiveness of Pulsed Radiofrequency on Zoster-Associated Pain.

Zoster-associated pain (ZAP), which may cause anxiety, depression, and sleep disorders and reduce quality of life, is often refractory to current standard treatments. Studies have shown that pulsed radiofrequency (PRF) can alleviate ZAP and reduce the incidence of postherpetic neuralgia (PHN). This study aimed to explore the clinical characteristics associated with PRF responsiveness, develop a model for identifying risk factors of inadequate PRF management, and help clinicians make better decisions.

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The Role of ATP Receptors in Pain Signaling.

Since new roles of nucleotides as neurotransmitters were proposed by Geoffrey Burnstock, the roles of ATP and P2 receptors (P2Rs) have been extensively studied in pain signaling. Chronic pain is a debilitating condition that often occurs following peripheral tissue inflammation and nerve injury. Especially neuropathic pain is a significant clinical problem because there are few clinically effective drugs. This review summarizes the findings for the role of ATP signaling through P2X3Rs and P2X2/3Rs in primary afferent neurons and through P2X4Rs, P2X7Rs, and P2YR in spinal microglia in chronic pain to discuss the therapeutic potentials with considering active situation of drug development of P2R compounds.

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Novel bivalent ligands carrying potential antinociceptive effects by targeting putative mu opioid receptor and chemokine receptor CXCR4 heterodimers.

The functional interactions between opioid and chemokine receptors have been implicated in the pathological process of chronic pain. Mounting studies have indicated the possibility that a MOR-CXCR4 heterodimer may be involved in nociception and related pharmacologic effects. Herein we have synthesized a series of bivalent ligands containing both MOR agonist and CXCR4 antagonist pharmacophores with an aim to investigate the functional interactions between these two receptors. In vitro studies demonstrated reasonable recognition of designed ligands at both respective receptors. Further antinociceptive testing in mice revealed compound 1a to be the most promising member of this series. Additional molecular modeling studies corroborated the findings observed. Taken together, we identified the first bivalent ligand 1a showing promising antinociceptive effect by targeting putative MOR-CXCR4 heterodimers, which may serve as a novel chemical probe to further develop more potent bivalent ligands with potential application in analgesic therapies for chronic pain management.

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The efficacy and safety of atogepant for the prophylactic treatment of migraine: evidence from randomized controlled trials.

Migraine is a common neurovascular disorder that has a severe impact on the individual daily life. Atogepant (AGN-241689) is an orally ingested, small-molecule drugs belonging to calcitonin gene-related peptide receptor antagonist, which has been initiated for the prophylactic treatment of migraine. However, there is no comprehensive literature to study the efficacy and safety of atogepant for the treatment of migraine. In this article, we present a meta-analysis of the available studies.

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Changes in median eminence of fatty acid-binding protein 3 in a mouse model of pain.

Fatty acid-binding protein (FABP) regulates polyunsaturated fatty acid (PUFA) intracellular trafficking and signal transduction. Our previous studies demonstrated that the alteration of PUFA in the hypothalamus is involved in pain process. However, how FABP subtypes change during pain remain unclear. Here, we examined the expression changes and localization in the hypothalamic FABP subtype in postoperative pain model mice.

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The regulatory role of nitric oxide in morphine-induced analgesia in the descending path of pain from the dorsal hippocampus to the dorsolateral periaqueductal gray.

Nitric oxide (NO) levels in brain nuclei, such as the hippocampus and brainstem, are involved in morphine analgesia, but the relationship between the dorsal hippocampus (dH) and the dorsolateral periaqueductal gray matter (dlPAG) needs to be clarified, which is our goal.

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Applicability and Validity of an e-Health Tool for the Appropriate Referral and Selection of Patients With Chronic Pain for Spinal Cord Stimulation: Results From a European Retrospective Study.

To support rational decision-making on spinal cord stimulation (SCS), a European expert panel developed an educational e-health tool using the RAND/University of California at Los Angeles Appropriateness Method. This retrospective study aimed to determine the applicability and validity of the tool using data from patients for whom SCS had been considered.

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The Association Between Bodily Functions and Cognitive/Emotional Factors in Patients With Chronic Pain Treated With Neuromodulation: A Systematic Review and Meta-Analyses.

To date, pain relief in general continues to be the most prominent outcome measurement in daily routine care and clinical research. Nevertheless, the awareness of a shift toward more functional outcomes and/or emotional and cognitive outcomes has been raised. The interplay between bodily functions (such as pain intensity) and emotional or cognitive factors, however, has not yet been fully elucidated. The aim of this study was to systematically review the evidence for associations between bodily functions and cognitive and emotional factors in patients with chronic pain who are treated with neuromodulation.

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Spinal Cord Stimulation With Additional Peripheral Nerve/Field Stimulation vs Spinal Cord Stimulation Alone on Back Pain and Quality of Life in Patients With Failed Back Surgery Syndrome.

Failed back surgery syndrome (FBSS) refers to new or persistent pain following spinal surgery for back or leg pain in a subset of patients. Spinal cord stimulation (SCS) is a neuromodulation technique that can be considered in patients with predominant leg pain refractory to conservative treatment. Patients with predominant low back pain benefit less from SCS. Another neuromodulation technique for treatment of chronic low back pain is subcutaneous stimulation or peripheral nerve field stimulation (PNFS). We investigated the effect of SCS with additional PNFS on pain and quality of life of patients with FBSS compared with that of SCS alone after 12 months.

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North American Neuromodulation Society Educational Curriculum for Intrathecal Drug Delivery Systems Implantation and Management.

Intrathecal drug delivery systems (IDDSs) are used for the treatment of pain and spasticity. A wide range of educational criteria exist for these devices. The North American Neuromodulation Society (NANS) Education Committee developed a comprehensive IDDS curriculum to function as a standard for physician graduate education and assessment through training and into practice.

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Observing Altered Nociceptive Detection Thresholds in Patients With Persistent Spinal Pain Syndrome Type 2 With a Dorsal Root Ganglion Stimulator.

There is a lack of clinically relevant measures for quantification of maladaptive mechanisms of the nociceptive system leading to chronic pain. Recently, we developed a method that tracks nociceptive detection thresholds (NDTs) using intraepidermal electrical stimulation. In this study, we explored the feasibility of using this NDT method in patients with persistent spinal pain syndrome type 2 (PSPS-T2) and its potential to enable observation of altered nociceptive processing induced by dorsal root ganglion (DRG) stimulation. In addition, we compared NDTs with quantitative sensory testing (QST) measurements and numeric rating scale (NRS).

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Transcutaneous Electrical Nerve Stimulation in Nerve Regeneration: A Systematic Review of In Vivo Animal Model Studies.

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive electrical stimulation therapy indicated for pain control that has been applied for the regeneration of nerves. This systematic review aimed to analyze the evidence on TENS effectiveness on nerve regeneration.

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Inhibition of IRE1 Suppresses the Catabolic Effect of IL-1β on Nucleus Pulposus Cell and Prevents Intervertebral Disc Degeneration in vivo.

Neck pain and low back pain are two of the major diseases, which causes patients a low quantify of life and a heavy economic burden, intervertebral disc degeneration (IDD) contributes to them, and the mechanism is not totally clear. The increased inflammatory cytokines including interleukin (IL)-1β and tumor necrosis factor (TNF)α and downstream signaling pathways are involved. Inositol requiring enzyme 1 (IRE1) is a crucial enzyme that regulates endoplasmic reticulum (ER) stress. It is reported that IRE1 plays an important role in the activation of NF-κB, PI3K/Akt and MAPK signaling pathways. Considering this, we performed a series of experiments in vitro and in vivo to evaluate the role of IRE1 in the progress of IDD. We demonstrated that IRE1 pathway was induced by IL-1β, inhibition of IRE1 suppressed the matrix degeneration of NP cells and ameliorated IDD grade in the punctured rat model. Further results indicated that inhibition of IRE1 suppressed HO induced cell senescence, IL-1β-induced cellular reactive oxygen species (ROS) level and the activation of NF-κB, PI3K/Akt and MAPK signaling pathways. It also played a crucial role in the apoptosis of NP cells and the progress of macrophage polarization. Our findings demonstrated that inhibition of IRE1 could suppress the degeneration of NP cells and prevent IDD in vivo. IRE1 may be a potential target for IDD treatment.

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The pan-JAK inhibitor delgocitinib in a cream formulation demonstrates dose-response in chronic hand eczema in a 16-week randomised phase 2b trial.

Chronic hand eczema (CHE) is a burdensome disease, and new well-documented, safe, and efficacious treatments are warranted. In a recent CHE phase 2a trial, the pan-Janus kinase (JAK) inhibitor delgocitinib in an ointment formulation was found to be efficacious and well-tolerated.

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Increased gray matter following mindfulness-based stress reduction in breast cancer survivors with chronic neuropathic pain: preliminary evidence using voxel-based morphometry.

To investigate the impact of Mindfulness-Based Stress Reduction (MBSR) on gray matter volume (GMV) in female breast cancer survivors who suffer from chronic neuropathic pain (CNP).

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Clonidine is better than zopiclone for insomnia treatment in chronic pain patients.

Chronic pain is associated with insomnia. The objective of this clinical study is to compare the efficacy and safety of different prescribed doses of zopiclone and clonidine; for the management of insomnia in patients with chronic pain.

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Antinociceptive effect of N-acetyl glucosamine in a rat model of neuropathic pain.

This study was aimed at evaluating the efficacy of glucosamine and potential mechanisms of actions in a neuropathic pain model in rats.

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What changes occurred in patients with chronic pain in the early phase of the COVID-19 pandemic?

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Effects of mechanical stimulation on metabolomic profiles of SW1353 chondrocytes: shear and compression.

Mechanotransduction is a biological phenomenon where mechanical stimuli are converted to biochemical responses. A model system for studying mechanotransduction are the chondrocytes of articular cartilage. Breakdown of this tissue results in decreased mobility, increased pain, and reduced quality of life. Either disuse or overloading can disrupt cartilage homeostasis, but physiological cyclical loading promotes cartilage homeostasis. To model this, we exposed SW1353 cells to cyclical mechanical stimuli, shear and compression, for different durations of time (15 and 30 min). By utilizing liquid chromatography-mass spectroscopy (LC-MS), metabolomic profiles were generated detailing metabolite features and biological pathways that are altered in response to mechanical stimulation. In total, 1457 metabolite features were detected. Statistical analyses identified several pathways of interest. Taken together, differences between experimental groups were associated with inflammatory pathways, lipid metabolism, beta-oxidation, central energy metabolism, and amino acid production. These findings expand our understanding of chondrocyte mechanotransduction under varying loading conditions and time periods. This article has an associated First Person interview with the first author of the paper.

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Population Pharmacokinetics of Tanezumab Following Intravenous or Subcutaneous Administration to Patients with Osteoarthritis or Chronic Low Back Pain.

Describe population pharmacokinetics of intravenous (IV) and subcutaneous (SC) tanezumab across Phase 2b/3 studies of osteoarthritis (OA) and chronic low back pain (CLBP). Methods Data from 10 studies of IV or SC tanezumab (2.5-20 mg every 8 weeks for up to 56 weeks) were included in a multi-step analysis. In Step 1, a two-compartment model with linear and non-linear elimination (based on prior analysis of pre-2015 IV osteoarthritis studies) was expanded to include other pre-2015 studies. In Step 2, post-2015 SC studies were combined into the model. Steps 3 and 4 evaluated impact of baseline nerve growth factor (NGF) and treatment-emergent anti-drug antibodies (TE ADA).

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Comment on the paper by George and colleagues and entitled Chronic Pain Prevalence and Factors Associated with High Impact Chronic Pain following Total Joint Arthroplasty: An Observational Study.

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Biopsychosocial risk factors for pain and pain-related disability 1 year after surgery for breast cancer.

Knowledge regarding risk factors for pain in the long term after surgery for breast cancer may be of great value in preventing this prevalent and debilitating side effect. Despite the biopsychosocial nature of pain, the predictive value of both pre- and postoperative biopsychosocial functioning for long-term pain intensity and pain-related disability has not yet been studied.

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The Mediating Role of Illness Cognitions in the Relationship between Caregiving Demands and Caregivers’ Psychological Adjustment.

The present study investigated whether illness cognitions mediated the relationship between caregiving demands and positive and negative indicators of adjustment in partners of patients with chronic pain.

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Recent advances in nanoplatforms for the treatment of neuropathic pain.

Narrative review.

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Gamma Knife radiosurgery for the treatment of cluster headache: a systematic review.

Cluster headache (CH) is a severe trigeminal autonomic cephalalgia that, when refractory to medical treatment, can be treated with Gamma Knife radiosurgery (GKRS). The outcomes of studies investigating GKRS for CH in the literature are inconsistent, and the ideal target and treatment parameters remain unclear. The aim of this systematic review is to evaluate the safety and the efficacy, both short and long term, of GKRS for the treatment of drug-resistant CH. A systematic review of the literature was performed to identify all clinical articles discussing GKRS for the treatment of CH. The literature review revealed 5 studies describing outcomes of GKRS for the treatment of CH for a total of 52 patients (48 included in the outcome analysis). The trigeminal nerve, the sphenopalatine ganglion, and a combination of both were treated in 34, 1, and 13 patients. The individual studies demonstrated initial meaningful pain reduction in 60-100% of patients, with an aggregate initial meaningful pain reduction in 37 patients (77%). This effect persisted in 20 patients (42%) at last follow-up. Trigeminal sensory disturbances were observed in 28 patients (58%) and deafferentation pain in 3 patients (6%). Information related to GKRS for CH are limited to few small open-label studies using heterogeneous operative techniques. In this setting, short-term pain reduction rates are high, whereas the long-term results are controversial. GKRS targeted on the trigeminal nerve or sphenopalatine ganglion is associated to a frequent risk of trigeminal disturbances and possibly deafferentation pain.

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CGRP-mediated trigeminovascular reactivity in migraine patients treated with erenumab.

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Comparison of the effectiveness of an e-health program versus a home rehabilitation program in patients with chronic low back pain: A double blind randomized controlled trial.

We conducted a randomized double blind clinical trial, to compare the effectiveness of McKenzie exercises and electroanalgesia via an e-Health program versus a home rehabilitation program on functionality, pain, fear of movement and quality of life in patients with non-specific chronic low back pain.

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What is the content of virtually delivered pain management programmes for people with persistent musculoskeletal pain? A systematic review.

Virtual consultations (VC) have been embraced by healthcare organisations during the COVID-19 pandemic. VC allows continuation of patient care while adhering to government advised restrictions and social distancing measures. Multidisciplinary pain management programmes (PMPs) are a core element of many pain services and utilising virtual methods to deliver PMPs has allowed them to continue to provide care. This systematic review aimed to explore the content of existing virtually delivered PMPs and discuss if and how these findings can be used to guide clinical delivery.

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Effectiveness of caregiver interventions for people with cancer and non-cancer-related chronic pain: a systematic review and meta-analysis.

People with chronic pain frequently have difficulties in completing everyday tasks to maintain independence and quality of life. Informal caregivers may provide support to these individuals. However, the effectiveness of interventions to train and support these individuals in caregiving remains unclear. The purpose of this study was to systematically review the evidence to determine the effectiveness of caregiver interventions to support informal caregivers of people with chronic pain.

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Effectiveness of hypnosis on pain and anxiety in dentistry: Narrative review.

Hypnosis presents an auxiliary adjunct in medical, dental, physiotherapeutic, and other clinical fields. This narrative review verified the effect of hypnosis in the control of pain and anxiety in dentistry. It presents the importance and effectiveness of hypnosis to aid dental procedures. It´s use in dentistry allows a wide range of applications such as sedation, analgesia, anesthesia, and hemostasis to facilitate treatment and improve the experience of dental care for dental patients. A discussion about the regulation of hypnosis in dentistry in Brazil, the attributions of dentists qualified in hypnosis, as well as the benefits of application based on evidence of hypnosis in dentistry, and the need for certification by hypnosis practitioners due to the possible risks inherent to the use of hypnosis are presented. Hypnosis is useful in the management of pain and anxiety in dentistry, when the dental practitioner is adequately experienced in this modality and the patients are carefully selected.

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Involvement of the BDNF-TrkB-KCC2 pathway in neuropathic pain after brachial plexus avulsion.

Brachial plexus avulsion significantly increased brain-derived neurotrophic factor (BDNF) release in the spinal cord. Here we investigated the involvement of the BDNF-TrkB-KCC2 pathway in neuropathic pain caused by BPA injury. We hypothesized that activation of BDNF-TrkB may inhibit neuronal excitability by downregulating KCC2 to maintain a high intracellular Cl-concentration. We established a neuropathic pain rat model by avulsion of the lower trunk brachial plexus, and investigated the effects of the TrkB-specific antibody K-252a on the expression of BDNF, TrkB, and KCC2.

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General practitioners’ attitudes towards opioids for non-cancer pain: a qualitative systematic review.

Worldwide the use of opioids, both doctor-prescribed and illicit, has increased. In most countries, opioids are first prescribed by general practitioners (GPs). Identifying factors that influence GPs' opioid prescription decision-making may help reduce opioid misuse and overuse. We performed a systematic review to gain insight into GP attitudes towards opioid prescription and to identify possible solutions to promote changes in the field of primary care.

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Medical Cannabis for Gynecologic Pain Conditions: A Systematic Review.

The endocannabinoid system is involved in pain perception and inflammation. Cannabis contains delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), which are cannabinoids that bind to endocannabinoid system receptors. A fatty acid amide called palmitoylethanolamide (PEA) enhances endogenous cannabinoids. Given that use of medical cannabis is increasing, we sought to characterize patterns of cannabis use for gynecologic pain and its effectiveness as an analgesic.

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The complexities of migraine: A debate among migraine researchers: A review.

Migraine is indeed a neurovascular disorder for which several genes have been identified in this era of Genome-Wide Association Studies (GWAS) and neuroimaging studies have already revealed structural changes and different mechanisms that cause migraine, but the exact cause of this debilitating and disabling neurovascular disorder remained unclear. Low neuronal hyperexcitability ("the migrainous brain") is set and hindered by genetic and environmental factors, respectively. Migraine is also found to be associated with different diseases (co-morbidity). There is still a subject of contention: is migraine a disease of evolution or disease of pathology? This research review seeks to provide a brief overview on the genetics of disorders, structural abnormalities in the brain, CSD-like symptoms, and faulty Trigeminovascular System activation for migraine pain phenotype. This review briefly covered here to provide some ideas that may also be utilized in migraine research and to serve as motivation for future research.

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Genotoxic, biochemical and histopathological studies to assessment the topiramate hepatorenal toxicity in mice.

Liver and kidney role in detoxification and drug metabolism increases the risk of their poisonous injury. Topiramate (TMP) is an effective popular migraine prophylaxis that is accepted for utilize in adults and teenagers. Therefore, the target of this research is to estimate the potential toxic effects of TMP on liver and kidney in male mice. Thirty-two adult albino male mice were divided into four groups ( = 8 mice). Group I of animals was given saline solution and used as negative control. The other three groups were administrated TPM at doses (100, 200 and 400 mg/kg) for 28 days. Genotoxicity was evaluated by comet assay and DNA fragmentation by Diphenyleamine. Biochemical investigation was achieved by estimating liver enzymes (AST, ALT), alkaline phosphatase (ALP) creatinine and uric acid. In addition, measurement of the antioxidant enzymes, malondialdehyde and nitric oxide were performed in both two tissues of liver and kidney. Microscopic examination of hematoxyline and eosin (H&E), tumor necrosis factor (TNF-α) and caspase3 stained sections were done to explore the effect of topiramate on mice tissues of liver and kidney. The data revealed that TPM showed dose dependent toxicity that represented in: DNA damage in tested cells and increased level of liver enzymes, creatinine and uric acid as markers of toxicity. Topiramate significantly diminished antioxidant enzymes activities and elevated the level of malondialdehyde and nitric oxide. In addition, TPM caused histopathological alterations and dose dependent positive immune reaction for TNF–α and caspase 3 in kidney and liver tissues. The results showed that Topiramate has marked toxicity in liver and kidney of mice.

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Simulated opioid choice linked to opioid use disorder severity among veterans with chronic pain: initial validation of a novel paradigm.

Modeling addictive behavior among individuals with, or at risk for, opioid use disorder (OUD) in a way that is accurate, ethical, and reproducible presents a pressing concern. OUD risk is elevated among people with chronic pain on long-term opioid therapy (LTOT).

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A Comprehensive Review of Yoga Research in 2020.

Accumulated evidence garnered in the last few decades has highlighted the role of yoga in health and disease. The overwhelming mortality and morbidity mediated by noncommunicable epidemics such as heart disease and cancer have fostered a search for mechanisms to attenuate them. Despite overwhelming success in acute care, the efficacy of modern medicines has been limited on this front. Yoga is one of the integrative therapies that has come to light as having a substantial role in preventing and mitigating such disorders. It thus seems trite to analyze and discuss the research advancements in yoga for 2020. The present review attempts to distill recent research highlights from voluminous literature generated in 2020. This review was conducted on the articles published or assigned to an issue in 2020. The authors searched the PubMed database for clinical studies published in the English language, using yoga (including meditation) as the intervention, and having an adequate description of the intervention. Then, they extracted data from each study into a standardized Google sheet. A total of 1149 citations were retrieved in the initial search. Of these, 46 studies met eligibility criteria and were finally included. The studies were predominantly on mental health and neuropsychology, addressing various issues such as anxiety, postural balance, migraine, academic performance, and childhood neglect. Anxiety, stress, and depression were other common denominators. Eight studies were on cardiorespiratory systems, including exercise capacity, cardiac rehabilitation, myocardial infarction, and hypertension. Three studies were on diabetes, evaluating the effect of yoga. Five studies focused on cognition, health status, and autonomic regulation and few others included cancers, infertility, ulcerative colitis, urinary incontinence, restless leg syndrome, rheumatoid arthritis, chronic pain, and metabolic syndrome. Finally, most studies were on noncommunicable diseases with one exception, human immunodeficiency virus; two randomized controlled trials were dedicated to it. Yoga has been studied under a wide variety of clinicopathological conditions in the year 2020. This landscape review intends to provide an idea of the role of yoga in various clinical conditions and its future therapeutic implications.

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Pain catastrophizing in rheumatoid arthritis, psoriatic arthritis and axial spondyloarthritis: biopsychosocial perspective and impact on health-related quality of life.

Pain catastrophizing (PC), defined as tendency to describe pain in more exaggerated terms, to ruminate more or to feel helpless about it. Main objective was to illuminate PC in rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA), revealing its prevalence and associations from a biopsychosocial perspective, including its association with health-related quality of life (HRQoL). Measures reflecting the biological, social and psychological perspective were recorded in RA, PsA and axSpA outpatients. Biological variables including demographics, disease activity and patient reported outcomes (PROs) along with variables reflecting psychological and social domains were collected. RAND12 questionnaire was used to explore HRQoL and standardized questionnaire was used to reveal pain catastrophizing score (PCS). 1229 patients were recruited (RA 580, PsA 394, axSpA 255). Mean (SD) PCS were for RA 1.88 (1.39), PsA 2.06 (1.45) and axSpA 2.27 (1.37). Proportion of pain catastrophizers (score ≥ 4) was not statistically different between RA (10.5%), PsA (12.7%) and axSpA (15.3%). Across all diagnoses, variables reflecting biological subjective domain explained more PCS variability (adjusted R 35.3-49.9%) than psychological (28.4-33.6%), social (22.4-28.4%) and biological objective (4.3-9.9%) domains. HRQoL was significantly lower in pain catastrophizers across all diagnoses. No substantial differences in proportion of pain catastrophizers between RA, PsA and axSpA patients were found. Higher PCS (score ≥ 4) was best explained by biological subjective measures and corresponded with inferior HRQoL in all diseases. Several biological objectives, psychological and social measures were also associated with higher PCS.

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Trends in Opioid Use Among Cancer Patients in the United States: 2013-2018.

In response to the US opioid epidemic, the Centers for Disease Control and Prevention updated their guideline on prescription opioids for chronic pain management in March 2016. The aim of this study was to provide detailed analysis of trends in opioid claims among cancer patients in the United States during 2013-2018.

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Neuropeptides and the Nodes of Ranvier in Cranial Headaches.

The trigeminovascular system (TGV) comprise of the trigeminal ganglion with neurons and satellite glial cells, with sensory unmyelinated C-fibers and myelinated Aδ-fibers picking up information from different parts of the head and sending signals to the brainstem and the central nervous system. In this review we discuss aspects of signaling at the distal parts of the sensory fibers, the extrasynaptic signaling between C-fibers and Aδ-fibers, and the contact between the trigeminal fibers at the nerve root entry zone where they transit into the CNS. We also address the possible role of the neuropeptides calcitonin gene-related peptide (CGRP), the neurokinin family and pituitary adenylyl cyclase-activating polypeptide 38 (PACAP-38), all found in the TGV system together with their respective receptors. Elucidation of the expression and localization of neuropeptides and their receptors in the TGV system may provide novel ways to understand their roles in migraine pathophysiology and suggest novel ways for treatment of migraine patients.

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Rostral Anterior Cingulate Cortex-Ventrolateral Periaqueductal Gray Circuit Underlies Electroacupuncture to Alleviate Hyperalgesia but Not Anxiety-Like Behaviors in Mice With Spared Nerve Injury.

Neuropathic pain is a common cause of chronic pain and is often accompanied by negative emotions, making it complex and difficult to treat. However, the neural circuit mechanisms underlying these symptoms remain unclear. Herein, we present a novel pathway associated with comorbid chronic pain and anxiety. Using chemogenetic methods, we found that activation of glutamatergic projections from the rostral anterior cingulate cortex (rACC ) to the ventrolateral periaqueductal gray (vlPAG) induced both hyperalgesia and anxiety-like behaviors in sham mice. Inhibition of the rACC -vlPAG pathway reduced anxiety-like behaviors and hyperalgesia in the spared nerve injury (SNI) mice model; moreover, electroacupuncture (EA) effectively alleviated these symptoms. Investigation of the related mechanisms revealed that the chemogenetic activation of the rACC -vlPAG circuit effectively blocked the analgesic effect of EA in the SNI mice model but did not affect the chronic pain-induced negative emotions. This study revealed a novel pathway, the rACC -vlPAG pathway, that mediates neuropathic pain and pain-induced anxiety.

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Using Virtual Reality Exposure Therapy in Pain Management: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

This study aimed to assess the effectiveness of virtual reality (VR) in managing different types of pain in different age groups and to provide evidence for the clinical application of new alternative strategy for pain management.

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The Role of Transient Receptor Potential A1 and G Protein-Coupled Receptor 39 in Zinc-Mediated Acute and Chronic Itch in Mice.

Itching is a common symptom of many skin or systemic diseases and has a negative impact on the quality of life. Zinc, one of the most important trace elements in an organism, plays an important role in the regulation of pain. Whether and how zinc regulates itching is largely unclear. Herein, we explored the role of Zn in the regulation of acute and chronic itch in mice. It is found that intradermal injection (i.d.) of Zn dose-dependently induced acute itch and transient receptor potential A1 (TRPA1) participated in Zn-induced acute itch in mice. Moreover, the pharmacological analysis showed the involvement of histamine, mast cells, opioid receptors, and capsaicin-sensitive C-fibers in Zn-induced acute itch in mice. Systemic administration of Zn chelators, such as N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), pyrithione, and clioquinol were able to attenuate both acute itch and dry skin-induced chronic itch in mice. Quantitative polymerase chain reaction (Q-PCR) analysis showed that the messenger RNA (mRNA) expression levels of zinc transporters (ZIPs and ZnTs) significantly changed in the dorsal root ganglia (DRG) under dry skin-induced chronic itch condition in mice. Activation of extracellular signal-regulated kinase (ERK) pathway was induced in the DRG and skin by the administration of zinc or under dry skin condition, which was inhibited by systemic administration of Zn chelators. Finally, we found that the expression of GPR39 (a zinc-sensing GPCR) was significantly upregulated in the dry skin mice model and involved in the pathogenesis of chronic itch. Together, these results indicated that the TRPA1/GPR39/ERK axis mediated the zinc-induced itch and, thus, targeting zinc signaling may be a promising strategy for anti-itch therapy.

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Efficacy of Treatments for Cholestatic Pruritus: A Systemic Review and Meta-analysis.

Cholestatic itch is a disabling symptom that may be secondary to liver or biliary diseases. Management of cholestatic pruritus is complex. A systematic review and meta-analysis on the efficacy of treatments for cholestatic pruritus were performed. PubMed and Cochrane Library were searched using the algorithm "(hepatitis OR cholestatic OR liver) AND (pruritus OR itch) AND (management OR treatment OR treatments)" for 1975-2019. Of the 2,264 articles identified, 93 were included in a systematic review and 15 in a meta-analysis (studies evaluating pruritus with a visual analogue scale). Some treatments act by reducing levels of pruritogens in the enterohepatic cycle, others modify the metabolism or secretion of these pruritogens, or act on pruritus pathways. A further possible treatment is albumin dialysis. However, due to many heterogeneities in the reviewed studies it is difficult to identify and recommend an optimum treatment. Only 15 studies were included in the meta-analysis, due to the small number of randomized studies using a visual analogue scale.

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Beyond the pain: A qualitative study exploring the physical therapy experience in patients with chronic low back pain.

Chronic low back pain (cLBP) is a complex condition that is physically and psychologically debilitating, with vulnerable populations experiencing more severe outcomes. Physical therapy (PT) includes evidence-based treatments that can reduce disability, however the experience of PT can vary amongst different populations. Empirical evidence is largely based on majority samples that are predominantly white with high educational attainment. Little is known regarding how people from vulnerable groups (e.g. low income and racial minority) experience physical therapy treatment for low back pain.

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Electrophysiological characterization of ectopic spontaneous discharge in axotomized and intact fibers upon nerve transection: a role in spontaneous pain?

Many patients experience positive symptoms after traumatic nerve injury. Despite the increasing number of experimental studies in models of peripheral neuropathy and the knowledge acquired, most of these patients lack an effective treatment for their chronic pain. One possible explanation might be that most of the preclinical studies focused on the development of mechanical or thermal allodynia/hyperalgesia, neglecting that most of the patients with peripheral neuropathies complain mostly about spontaneous forms of pains. Here, we summarize the aberrant electrophysiological behavior of peripheral nerve fibers recorded in experimental models, the underlying pathophysiological mechanisms, and their relationship with the symptoms reported by patients. Upon nerve section, axotomized but also intact fibers develop ectopic spontaneous activity. Most interestingly, a proportion of axotomized fibers might present receptive fields in the skin far beyond the site of damage, indicative of a functional cross talk between neuromatose and intact fibers. All these features can be linked with some of the symptoms that neuropathic patients experience. Furthermore, we spotlight the consequence of primary afferents with different patterns of spontaneous discharge on the neural code and its relationship with chronic pain states. With this article, readers will be able to understand the pathophysiological mechanisms that might underlie some of the symptoms that experience neuropathic patients, with a special focus on spontaneous pain.

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Gabapentinoid Use in Perioperative Care and Current Controversies.

This review summarizes the risks and benefits of gabapentinoids (gabapentin and pregabalin) for perioperative pain control and the controversies surrounding their use in a variety of settings. We review current literature with the goal of providing patient-centric and procedure-specific recommendations for the use of these medications.

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Constipation Caused by Anti-calcitonin Gene-Related Peptide Migraine Therapeutics Explained by Antagonism of Calcitonin Gene-Related Peptide’s Motor-Stimulating and Prosecretory Function in the Intestine.

The development of small-molecule calcitonin gene-related peptide (CGRP) receptor antagonists (gepants) and of monoclonal antibodies targeting the CGRP system has been a major advance in the management of migraine. In the randomized controlled trials before regulatory approval, the safety of these anti-CGRP migraine therapeutics was considered favorable and to stay within the expected profile. Post-approval real-world surveys reveal, however, constipation to be a major adverse event which may affect more than 50% of patients treated with erenumab (an antibody targeting the CGRP receptor), fremanezumab or galcanezumab (antibodies targeting CGRP). In this review article we address the question whether constipation caused by inhibition of CGRP signaling can be mechanistically deduced from the known pharmacological actions and pathophysiological implications of CGRP in the digestive tract. CGRP in the gut is expressed by two distinct neuronal populations: extrinsic primary afferent nerve fibers and distinct neurons of the intrinsic enteric nervous system. In particular, CGRP is a major messenger of enteric sensory neurons which in response to mucosal stimulation activate both ascending excitatory and descending inhibitory neuronal pathways that enable propulsive (peristaltic) motor activity to take place. In addition, CGRP is able to stimulate ion and water secretion into the intestinal lumen. The motor-stimulating and prosecretory actions of CGRP combine in accelerating intestinal transit, an activity profile that has been confirmed by the ability of CGRP to induce diarrhea in mice, dogs and humans. We therefore conclude that the constipation elicited by antibodies targeting CGRP or its receptor results from interference with the physiological function of CGRP in the small and large intestine in which it contributes to the maintenance of peristaltic motor activity, ion and water secretion and intestinal transit.

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Sterility of Sustained-release Buprenorphine.

Sustained-release formulations of controlled substances are commonly used to provide analgesia in research animals.These formulations represent refinements that offer the advantage of prolonged, multiday pain relief with a single injection, thereby decreasing handling stress in animals and saving time for scientists. Compounding pharmacies produce sustained-release buprenorphine for veterinary use (i.e., buprenorphine SR-LAB); one of these pharmacies has shortened the original 6-mo shelf-life to 28 d to comply with United States Pharmacopeia standards for ensuring sterility. This limitation risks increasing the waste of controlled substances, which require an expensive destruction process that is legally enforced in our state. To assess whether the sterility of buprenorphine SR-LAB is preserved for at least 6 mo in a general laboratory setting, we tested 5 bottles for the presence of endotoxin and bacterial and fungal contamination monthly for 6 mo. Overall, results of the study showed that the bottles remained sterile over the 6-mo duration as no endotoxin was detected and the bottles did not become contaminated with bacteria or fungi. In conclusion, when stored securely and used with aseptic handling techniques, buprenorphine SR-LAB can be maintained in a sterile state for 6 mo in a general laboratory setting.

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Aprepitant Inhibits JNK and p38/MAPK to Attenuate Inflammation and Suppresses Inflammatory Pain.

Substance P contributes to the pathogenesis of pain by acting on NK-1R, specialized sensory neurons that detect noxious stimuli. Aprepitant, an antagonist of NK-1R, is widely used to treat chemotherapy-induced nausea and vomiting. In this study, we used LPS-stimulated BV-2 microglia cell line and animal models of inflammatory pain to explore the analgesic effect of aprepitant on inflammatory pain and its underlying mechanism. The excitability of DRG neurons were measured using whole-cell patch-clamp recordings. The behavioral tests were measured and the morphological changes on inflamed paw sections were determined by HE staining. Changes in the expressions of cytokine were measured by using real-time quantitative PCR analysis and ELISA method. Immunofluorescence and western blotting were used to detect the microglia activation and MAPK. Aprepitant treatment significantly inhibited the excitability of DRG neurons. The pain behavior and the paw tissues inflammatory damage were significantly relived after the administration of aprepitant compared to formalin group. Aprepitant significantly suppressed the activation of microglia, phosphorylation of JNK and p38 MAPK, as well as the mRNA and protein expressions of MCP-1, TNF-α, IL-6, and IL-1β, and . The LPS-induced over-translocation into nucleus of NF-κBp65 was down-regulated following aprepitant treatment in BV-2 cells. The present study suggests that aprepitant attenuates inflammatory pain in mice via suppressing the phosphorylation of JNK and p38, and inhibiting the NF-κB signaling pathway.

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