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P2Y purinergic receptors expressed in neurons and satellite glial cells (SGCs) of the trigeminal ganglion (TG) contributes to inflammatory and neuropathic pain. P2Y receptor expression is reported in the spinal cord, dorsal root ganglion (DRG), and TG. In present study, the role of P2Y receptor in the TG in inflammatory orofacial pain of Sprague-Dawley (SD) rats was investigated. Peripheral injection of complete Freund's adjuvant (CFA) induced mechanical hyperalgesia with the rapid upregulation of P2Y receptor, glial fibrillary acidic protein (GFAP), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), C-C chemokine CCL2, phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), and phosphorylated p38 (p-p38) proteins in the TG. Furthermore, immunofluorescence staining confirmed the CFA-induced upregulation of P2Y receptor. Double immunostaining showed that P2Y receptor colocalized with glutamine synthetase (GS) and neuronal nuclei (NeuN). Finally, trigeminal injection of a selective antagonist (PPTN) of P2Y receptor attenuated CFA-induced mechanical hyperalgesia. PPTN also decreased the upregulation of the GFAP, IL-1β, TNF-α, CCL2, p-ERK1/2, and p-p38 proteins. Our findings showed that P2Y receptor in TG may contribute to orofacial inflammatory pain via regulating SGCs activation, releasing cytokines (IL-1β, TNF-α, and CCL2), and phosphorylating ERK1/2 and p38.
Learn More >Ubrogepant is a novel, oral calcitonin gene-related peptide (CGRP) receptor antagonist in development for the acute treatment of migraine. This trial evaluated the safety and tolerability of ubrogepant, focusing on hepatic safety, when administered intermittently with high-frequency dosing to healthy participants.
Learn More >Chronic back pain is a major global health problem, while its treatment is hampered by a lack of efficacy and restricted safety profile of common front-line therapies. The present trial aims to determine whether a 3-week open-label placebo treatment reduces pain intensity, and subjective and objective functional disability in chronic back pain patients. This randomized controlled trial, following a pretest-posttest design, enrolled 127 chronic back pain patients (pain duration > 12 weeks) from the Back Pain Center, Neurology, University Hospital Essen, Germany. Patients randomized to the open-label placebo group received a 3-week open-label placebo treatment. Patients in the treatment as usual group received no intervention. Both groups continued treatment as usual. Primary outcome was the change in pain intensity. Secondary outcomes included patient-reported functional disability, objective measures of spine mobility and depression, anxiety and stress. 122 chronic back pain patients were randomized to the open-label placebo group (N=63) or treatment as usual group (N=59). Open-label placebo application led to a larger reduction of pain intensity (-0.62±0.23 vs. 0.11±0.17, all M ± SE, p=.001, d=-0.44) as well as patient-reported functional disability (3.21±1.59 vs. 0.65±1.15, p=.020, d=-0.45) and depression scores (-1.07±0.55 vs. 0.37±0.39, p=.010, d=-0.50) compared to treatment as usual only. OLP treatment did not affect objective mobility parameters, anxiety and stress. Our study demonstrates that a 3-week open-label placebo treatment is safe, well tolerated and reduces pain, disability and depressive symptoms in chronic back pain. Trial registration: German Clinical Trials Register, DRKS00012712.
Learn More >Itch is the commonest skin-related symptom and sex differences are increasingly recognised as important determinants in stratified medicine, but only little is known about sex differences in itch. Questionnaire-based studies indicated that women perceive itch as more intensive and bothersome in comparison to men. However, data of studies using standardised itch models to objectify sex differences are scarce and inconsistent. To determine sex differences in intensity, skin flares and central processing of histaminergic itch we compared 15 female and 15 male healthy subjects in a double-blinded, within-subject, placebo-controlled study using a histamine skin prick itch-model (histamine 1% applied onto the volar forearm) and functional MRI. We found trends in higher mean itch intensity (0.58 VAS, CI 95% 0.004-1.19, p=0.056) and maximum itch intensity (men 3.93 VAS ± 0.39 SD at 3 minutes, women 4.73 VAS ± 0.31 SD at 4 minutes, p=0.073) in women paralleled by a trend in a stronger positive correlation between itch intensity and blood oxygen level dependent (BOLD) activity in brain structures identified during itch in comparison to men (r in women: 0.46, p=0.08, r in men: 0.07, p=0.79). The erythema and wheal following histamine skin pricking were (non-significantly) larger in men indicating that higher mean itch intensities on the right volar forearm in women may not be explained by more intense flares. The comparison of the activation patterns between the sexes revealed increased activity in men compared to women in the left middle temporal gyrus (temporooccipital part)/lateral occipital cortex. Thus, our findings indicate that histaminergic itch perception and central itch processing differ between the sexes under standardised conditions.
Learn More >Chronic pain is a common and severely disabling disease whose treatment is often unsatisfactory. Insights into the brain mechanisms of chronic pain promise to advance the understanding of the underlying pathophysiology and might help to develop disease markers and novel treatments. Here, we systematically exploited the potential of electroencephalography (EEG) to determine abnormalities of brain function during the resting state in chronic pain. To this end, we performed state-of-the-art analyses of oscillatory brain activity, brain connectivity and brain networks in 101 patients of either sex suffering from chronic pain. The results show that global and local measures of brain activity did not differ between chronic pain patients and a healthy control group. However, we observed significantly increased connectivity at theta (4 – 8 Hz) and gamma (> 60 Hz) frequencies in frontal brain areas as well as global network reorganization at gamma frequencies in chronic pain patients. Furthermore, a machine learning algorithm could differentiate between patients and healthy controls with an above-chance accuracy of 57%, mostly based on frontal connectivity. These results suggest that increased theta and gamma synchrony in frontal brain areas are involved in the pathophysiology of chronic pain. While substantial challenges concerning the reproducibility of the findings and the accuracy, specificity and validity of potential EEG-based disease markers remain to be overcome, our study indicates that abnormal frontal synchrony at theta and gamma frequencies might be promising targets for non-invasive brain stimulation and/or neurofeedback approaches.
Learn More >Whiplash associated disorder (WAD), a common and disabling condition, incurs huge burden and costs to Australia. Yet, current treatments for whiplash are not very effective; improved outcomes are urgently needed. Clinical guidelines recommend simple analgesia (paracetamol and non-steroidal anti-inflammatory drugs) but there have been no trials of guideline-recommended drugs. This study will investigate the effectiveness of evidence-based advice (EBA), paracetamol, naproxen, and both paracetamol and naproxen, in reducing daily neck pain and preventing chronic neck pain after whiplash injury.
Learn More >: Chronic neuropathic pain (NP) is an incapacitating illness caused by alesion of the somatosensory nervous system and is associated with several disease or syndromes. Since current treatment options lack adequate efficacy in the majority of patients, ketamine is often administered to treat refractory NP.: This review gives an overview of new ketamine pharmacokinetic data including data on intranasal and inhaled ketamine. The outcome of seven systematic reviews and meta-analyses, published since 2012, on ketamine efficacy in NP is discussed. The reader will additionally get an understanding of ketamine's complex metabolism with emphasis on the metabolite hydroxynorketamine.: Proof of sustained, large effects of ketamine in the treatment of NP from randomized controlled clinical trials is lacking, although we cannot exclude selective ketamine efficacy in patients with central sensitization, opioid-induced hyperalgesia or opioid tolerance. Interestingly, data from observational trials and case series do suggest efficacy of ketamine in producing effective pain relief in NP with positive patient-related outcome measures. Additional randomized trials in often ill-defined groups of chronic pain patients are not useful and we suggest to conduct future studies in NP patients with central sensitization and/or with opioid refractory severe NP.
Learn More >Nummular headache is a primary headache characterised by superficial, coin-shaped pain. Superficial sensory fibre dysfunction might be involved in its pathophysiology. Considering the mechanism of action of onabotulinumtoxinA, it could be a reasonable option in treatment of nummular headache. The aim of the study was to evaluate the efficacy and tolerability of onabotulinumtoxinA in a series of nummular headache patients.
Learn More >Cannabidiol (CBD), the non-psychoactive component of Cannabis sativa, acts on a diverse selection of membrane proteins with promising therapeutic potential in epilepsy and chronic pain. One such protein is the voltage-gated sodium channel (Na). CBD shows a lack of specificity for sodium channels; however, the method of interaction is still unknown. In this review, we will outline the studies that report reproducible results of CBD and other cannabinoids changing membrane channel function, with particular interest on Na. Na are implicated in fatal forms of epilepsy and are also associated with chronic pain. This makes Na potential targets for CBD interaction since it has been reported to reduce pain and seizures. One potential method of interaction that is of interest in this review is whether CBD affects channel function by altering lipid bilayer properties, independent of any possible direct interaction with membrane channels. CBD's ability to interact with its targets is a novel and important discovery. This discovery will not only prompt further research towards CBD's characterization, but also promotes the application of cannabinoids as potentially therapeutic compounds for diseases like epilepsy and pain.
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