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Potent opioid-based therapies are often unsuccessful in promoting satisfactory analgesia in neuropathic pain. Moreover, the side-effects associated with opioid therapy are still manifested in neuropathy-like diseases, including tolerance, abuse, addiction and hyperalgesia, although the mechanisms underlying these effects remain unclear. Studies in the spinal cord and periphery indicate that neuropathy alters the expression of mu-[MOR], delta-[DOR] or kappa-[KOR] opioid receptors, interfering with their activity. However, there is no consensus as to the supraspinal opioidergic modulation provoked by neuropathy, the structures where the sensory and affective-related pain components are processed. In this study we explored the effect of chronic constriction of the sciatic nerve over 7 and 30 days (CCI-7d and CCI-30d, respectively) on MOR, DOR and KOR mRNAs expression, using in situ hybridization, and the efficacy of G-protein stimulation by DAMGO, DPDPE and U-69593 (MOR, DOR and KOR specific agonists, respectively), using [35S]GTPγS binding, within opioid-sensitive brain structures. After CCI-7d, CCI-30d or both, opioid receptor mRNAs expression was altered throughout the brain: MOR – in the paracentral/centrolateral thalamic nuclei, ventral posteromedial thalamic nuclei, superior olivary complex, parabrachial nucleus and posterodorsal tegmental nucleus; DOR – in the somatosensory cortex [SSC], ventral tegmental area, caudate putamen [CPu], nucleus accumbens [NAcc], raphe magnus [RMg] and PB; and KOR – in the locus coeruleus. Agonist-stimulated [35S]GTPγS binding was altered following CCI: MOR – CPu and RMg; DOR – prefrontal cortex [PFC], SSC, RMg and NAcc; and KOR -PFC and SSC. Thus, this study shows that several opioidergic circuits in the brain are recruited and modified following neuropathy.
Learn More >Non-steroidal anti-inflammatory drugs (NSAIDs), commonly known as COX-1/COX-2 inhibitors, can be effective in treating mild to moderate migraine headache. However, the mechanism by which these drugs act in migraine is not known, nor is the specific contribution of COX-1 versus COX-2 known. We sought to investigate these unknowns using celecoxib, which selectively inhibits the enzymatic activity of COX-2, by determining its effects on several migraine-associated vascular and inflammatory events. Using in vivo two-photon microscopy, we determined intraperitoneal celecoxib effects on CSD-induced blood vessel responses, plasma protein extravasation, and immune cell activation in the dura and pia of mice and rats. Compared to vehicle (control group), celecoxib reduced significantly CSD-induced dilatation of dural arteries and activation of dural and pial macrophages but not dilatation or constriction of pial arteries and veins, or the occurrence of plasma protein extravasation. Collectively, these findings suggest that a mechanism by which celecoxib-mediated COX-2 inhibition might ease the intensity of migraine headache and potentially terminate an attack is by attenuating dural macrophages activation and arterial dilatation outside the blood brain barrier (BBB), and pial macrophages activation inside the BBB.
Learn More >Low back pain is a chronic, highly prevalent, and hard-to-treat condition in the elderly. Clinical studies indicate that AXL, which belongs to the tyrosine kinase receptor subfamily, mediates pathological pain. However, it is not clear exactly how AXL regulates pain behaviors. In the present study, we used a model of chronic compression of dorsal root ganglion (CCD)-induced neuropathic pain to recreate clinical intervertebral foramen stenosis and related lumbocrural pain to explore whether AXL in primary sensory neurons contributes to this neuropathic pain in rats. Using double-labeling immunofluorescence, we observed that both phosphorylated AXL (p-AXL) and AXL were localized primarily on isolectin B4 (IB4)-positive and calcitonin gene-related peptide (CGRP)-positive neurons, while AXL was also localized in neurofilament-200 (NF200)-positive neurons. CCD-induced pain was associated with the upregulation of AXL mRNA and protein in injured DRGs. Repeated intrathecal administration of the AXL inhibitor, TP0903, or the AXL small interfering RNA (AXL siRNA), effectively alleviated CCD-induced pain hypersensitivities. Moreover, repeated intrathecal administration of either TP0903, or AXL siRNA, reduced the expression of mTOR in injured DRGs, suggesting that mTOR may mediate AXL's actions. These results indicate that the upregulation of DRG AXL may be part of a peripheral mechanism of neuropathic pain via an intracellular mTOR-signaling pathway. Thus, while AXL inhibitors have so far primarily shown clinical efficacy in tumor treatment, AXL intervention could also serve as a potential target for the treatment of neuropathic pain.
Learn More >We pursued the hypothesis that complex regional pain syndrome (CRPS) signs observed by neurologic examination display a structure allowing for alignment of patients to particular phenotype clusters.
Learn More >Women remain underrepresented on faculties of medicine and the life sciences more broadly. Whether gender differences in self presentation of clinical research exist and may contribute to this gender gap has been challenging to explore empirically. The objective of this study was to analyze whether men and women differ in how positively they frame their research findings and to analyze whether the positive framing of research is associated with higher downstream citations.
Learn More >Temporomandibular disorder (TMD) is a common condition that frequently transitions to chronic symptoms. Experimental pain models that mimic the symptoms of clinical TMD may be useful in understanding the mechanisms, and sex differences, present in this disorder. Here we aimed to comprehensively characterise the nature and time-course of pain, functional impairment and hyperalgesia induced by repeated intramuscular injection of nerve growth factor (NGF) into the masseter muscle, and to investigate sex differences in the NGF-induced pain experience.
Learn More >The voltage-gated sodium NaV1.7 channel sets the threshold for electrogenesis. Mutations in the gene encoding human NaV1.7 () cause painful neuropathies or pain insensitivity. In dorsal root ganglion (DRG) neurons, activity and trafficking of NaV1.7 are regulated by the auxiliary collapsin response mediator protein 2 (CRMP2). Specifically, preventing addition of a small ubiquitin-like modifier (SUMO), by the E2 SUMO-conjugating enzyme Ubc9, at lysine-374 (K374) of CRMP2 reduces NaV1.7 channel trafficking and activity. We previously identified a small molecule, designated , that prevented CRMP2 SUMOylation by Ubc9 to reduce NaV1.7 surface expression and currents, leading to a reduction in spinal nociceptive transmission, and culminating in normalization of mechanical allodynia in models of neuropathic pain. In this study, we investigated whether NaV1.7 control via CRMP2-SUMOylation is conserved in nodose ganglion (NG) neurons. This study was motivated by our desire to develop as a safe, non-opioid substitute for persistent pain, which led us to wonder how would impact NaV1.7 in NG neurons, which are responsible for driving the cough reflex. We found functioning NaV1.7 channels in NG neurons; however, they were resistant to downregulation via either CRMP2 knockdown or pharmacological inhibition of CRMP2 SUMOylation by CRMP2 SUMOylation and interaction with NaV1.7 was consered in NG neurons but the endocytic machinery was deficient in the endocytic adaptor protein Numb. Overexpression of Numb rescued CRMP2-dependent regulation on NaV1.7, rendering NG neurons sensitive to Altogether, these data point at the existence of cell-specific mechanisms regulating NaV1.7 trafficking.
Learn More >Clinical production pressure is a significant problem for faculty of anesthesiology departments who seek to remain involved in research. Lack of protected time to dedicate to research and insufficient external funding add to this long-standing issue. Recent trends in funding to the departments of anesthesiology and their academic output validate these concerns. A 2022 study examining National Institutes of Health (NIH) grant recipients associated with anesthesiology departments across 10 years (2011-2020) outlines total awarded funds at $1,676,482,440, with most of the funds awarded to only 10 departments in the United States. Of note, the total 1-year NIH funding in 2021 for academic internal medicine departments was 3 times higher than the 10-year funding of anesthesiology departments. Additionally, American Board of Anesthesiology (ABA) diplomats represent a minority (37%) of the anesthesiology researchers obtaining grant funding, with a small number of faculty members receiving a prevalence of monies. Overall, the number of publications per academic anesthesiologist across the United States remains modest as does the impact of the scholarly work. Improving environments in which academic anesthesiologists thrive may be paramount to successful academic productivity. In fact, adding to the lack of academic time is the limited bandwidth of senior academic physicians to mentor and support aspiring physician scientists. Given then the challenges for individual departments and notable successes of specialty-specific collaborative efforts (eg Foundation for Anesthesia Education and Research [FAER]), additional pooled-resource approaches may be necessary to successfully support and develop clinician scientists. It is in this spirit that the leadership of , unified with the Association of University Anesthesiologists, aim to sponsor the Introduction to Clinical Research for Academic Anesthesiologists (ICRAA) Course. Directed toward early career academic anesthesiologists who wish to gain competency specifically in the fundamentals of clinical research and receive mentorship to develop an investigative project, the yearlong course will provide participants with the skills necessary to design research initiatives, ethically direct research teams, successfully communicate ideas with data analysts, and write and submit scientific articles. Additionally, the course, articulated in a series of interactive lectures, mentored activities, and workshops, will teach participants to review articles submitted for publication to medical journals and to critically appraise evidence in published research. It is our hope that this initiative will be of interest to junior faculty of academic anesthesiology departments nationally and internationally.
Learn More >There are numerous strategies to combat postoperative analgesia and expedite recovery after total knee arthroplasty (TKA). The purpose of this study was to determine opioid consumption, length of stay, and functional outcomes after robotic versus standard TKA in the setting of various regional pain modalities.
Learn More >In countries like India, many migraine patients presenting to primary care clinics fail to fulfill standard (ICHD 3) migraine diagnostic criteria. Since they do not present with typical ICHD 3 migraine diagnostic symptoms, it is necessary to define the criteria for atypical migraine. This would ensure that the patients receive the right treatment approach, both non-pharmacological and pharmacological. Looking for triggers, family history, activity affected and absolute normality in between attacks, past episodes of episodic syndromes, prodromal and oculonasal autonomic symptoms will help in identifying the migraine origin of these headaches.
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