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Cannabis is widely used for chronic pain. However, there is some evidence of an inverse dose-response relationship between cannabis effects and pain relief which may negatively affect analgesic outcomes. In this cross-sectional survey, we examined whether daily cannabis use frequency was associated with pain severity and interference, quality of life measures relevant to pain (e.g., anxiety and depressive symptoms), and cannabis use preferences (administration routes, cannabinoid ratio). Our analysis included 989 adults who used cannabis every day for chronic pain. Participant use was designated as light, moderate, and heavy (1-2, 3-4, and 5 or more cannabis uses per day, respectively). The sample was also sub-grouped by self-reported medical only use (designated MED, n=531, 54%) vs. medical use concomitant with a past-year history of recreational use (designated MEDREC, n=458, 46%). In the whole sample, increased frequency of use was significantly associated with worse pain intensity and interference, and worse negative affect, although high frequency users also reported improved positive affect. Subgroup analyses showed that these effects were driven by MED participants. Heavy MED participant consumption patterns showed greater preference for smoking, vaporizing, and high THC products. In contrast, light MED participants had greater preference for tinctures and high CBD products. Selection bias, our focus on chronic pain, and our cross-sectional design likely limit the generalizability our results. Our findings suggest that lower daily cannabis use frequency is associated with better clinical profile as well as lower risk cannabis use behaviors among MED participants. Future longitudinal studies are needed to examine how high frequency of cannabis use interacts with potential therapeutic benefits. PERSPECTIVE: Our findings suggest that lower daily cannabis use frequency is associated with better clinical profile as well as safer use behaviors (e.g., preference for CBD and non-inhalation administration routes). These trends highlight the need for developing cannabis use guidelines for clinicians to better protect patients using cannabis.
Learn More >Anecdotal evidence that cannabis preparations have medical benefits together with the discovery of the psychotropic plant cannabinoid Δ-tetrahydrocannabinol (THC) initiated efforts to develop cannabinoid-based therapeutics. These efforts have been marked by disappointment, especially in relation to the unwanted central effects that result from activation of cannabinoid receptor 1 (CB1), which have limited the therapeutic use of drugs that activate or inactivate this receptor. The discovery of CB2 and of endogenous cannabinoid receptor ligands (endocannabinoids) raised new possibilities for safe targeting of this endocannabinoid system. However, clinical success has been limited, complicated by the discovery of an expanded endocannabinoid system – known as the endocannabinoidome – that includes several mediators that are biochemically related to the endocannabinoids, and their receptors and metabolic enzymes. The approvals of nabiximols, a mixture of THC and the non-psychotropic cannabinoid cannabidiol, for the treatment of spasticity and neuropathic pain in multiple sclerosis, and of purified botanical cannabidiol for the treatment of otherwise untreatable forms of paediatric epilepsy, have brought the therapeutic use of cannabinoids and endocannabinoids in neurological diseases into the limelight. In this Review, we provide an overview of the endocannabinoid system and the endocannabinoidome before discussing their involvement in and clinical relevance to a variety of neurological disorders, including Parkinson disease, Alzheimer disease, Huntington disease, multiple sclerosis, amyotrophic lateral sclerosis, traumatic brain injury, stroke, epilepsy and glioblastoma.
Learn More >Drugs selectively targeting CB2 hold promise for treating neurodegenerative disorders, inflammation, and pain while avoiding psychotropic side effects mediated by CB1. The mechanisms underlying CB2 activation and signaling are poorly understood but critical for drug design. Here we report the cryo-EM structure of the human CB2-G signaling complex bound to the agonist WIN 55,212-2. The 3D structure reveals the binding mode of WIN 55,212-2 and structural determinants for distinguishing CB2 agonists from antagonists, which are supported by a pair of rationally designed agonist and antagonist. Further structural analyses with computational docking results uncover the differences between CB2 and CB1 in receptor activation, ligand recognition, and G coupling. These findings are expected to facilitate rational structure-based discovery of drugs targeting the cannabinoid system.
Learn More >Migraine headache pathophysiology involves trigeminovascular system activation, calcitonin gene-related peptide (CGRP) release and dysfunctional nociceptive transmission. Triptans are 5-HT1B/1D/(1F) receptor agonists that prejunctionally inhibit trigeminal CGRP release, but their vasoconstrictor properties limit their use in migraine patients with cardiovascular disease. In contrast, lasmiditan is a novel antimigraine and selective 5-HT1F receptor agonist devoid of vasoconstrictor properties. On this basis, the present study has investigated the modulation of trigeminal CGRP release by lasmiditan.For this purpose, we have comparatively analysed the inhibition of several components of the trigeminovascular system induced by lasmiditan and sumatriptan through: ex vivo KCl-induced CGRP release from isolated dura mater, trigeminal ganglion and trigeminal nucleus caudalis of mice; and in vivo dural vasodilation in the rat closed-cranial window model induced by endogenous (electrical stimulation, capsaicin) and exogenous CGRP.The ex vivo release of CGRP was similarly inhibited by sumatriptan and lasmiditan in all trigeminovascular system components. In vivo, i.v. lasmiditan or higher doses of sumatriptan significantly attenuated the vasodilatory responses to endogenous CGRP release, but not exogenous CGRP effects. These data suggest that lasmiditan prejunctionally inhibits CGRP release in peripheral and central trigeminal nerve terminals. Since lasmiditan is a lipophilic drug that crosses the blood-brain barrier, additional central sites of action remain to be determined.
Learn More >Investigate the potential role of (mu-opioid receptor) and (catechol-O-methyltransferase enzyme) polymorphisms in postoperative acute, chronic and experimental thermal pain. A secondary analysis of 125 adult cardiac surgery patients that were randomized between fentanyl and remifentanil during surgery and genotyped. Patients in the fentanyl group with the high-pain sensitivity haplotype required less postoperative morphine compared with the average-pain sensitivity haplotype (19.4 [16.5; 23.0] vs 34.6 [26.2; 41.4]; p = 0.00768), but not to the low-pain sensitivity group (30.1 [19.1; 37.7]; p = 0.13). No association was found between haplotype and other pain outcomes or polymorphisms and the different pain modalities. haplotype appears to explain part of the variability in acute postoperative pain in adult cardiac surgery patients.
Learn More >The primary outcome of this study was to assess the efficacy and safety of preventive treatment with amitriptyline on headache frequency and severity after mild traumatic brain injury (mTBI).
Learn More >Consistent associations between the severity of neuropathic pain and cutaneous innervation have not been described. We collected demographic and clinical data, McGill Pain Questionnaires (MPQ) and skin biopsies processed for PGP9.5 and CGRP immunohistochemistry from patients with bortezomib-induced peripheral neuropathy (BiPN; n=22), painful diabetic neuropathy (PDN; n=16), chronic idiopathic axonal polyneuropathy (CIAP; n=16) and 17 age-matched healthy volunteers. Duration of neuropathic symptoms was significantly shorter in patients with BiPN in comparison with PDN and CIAP patients. BiPN was characterized by a significant increase in epidermal axonal swellings and upper dermis nerve fiber densities (UDNFD) and a decrease in subepidermal nerve fiber densities (SENFD) of PGP9.5-positive fibers and of PGP9.5 containing structures that did not show CGRP labeling, presumably non-peptidergic fibers. In PDN and CIAP patients, intraepidermal nerve fiber densities (IENFD) and SENFD of PGP9.5-positive and of non-peptidergic fibers were decreased in comparison with healthy volunteers. Significant unadjusted associations between IENFD and SENFD of CGRP-positive, i.e. peptidergic, fibers and the MPQ sensory-discriminative, as well as between UDNFD of PGP9.5-positive fibers and the MPQ evaluative/affective component of neuropathic pain, were found in BiPN and CIAP patients. No significant associations were found in PDN patients. Cutaneous innervation changes in BiPN confirm characteristic features of early, whereas those in CIAP and PDN are in line with late forms of neuropathic pathology. Our results allude to a distinct role for non-peptidergic nociceptors in BiPN and CIAP patients. The lack of significant associations in PDN may be caused by mixed ischemic and purely neuropathic pain pathology.
Learn More >"Ion Channels and Neuropharmacology: From the Past to the Future" is the main theme of articles in Volume 60 of the . Reviews in this volume discuss a wide spectrum of therapeutically relevant ion channels and GPCRs with a particular emphasis on structural studies that elucidate drug binding sites and mechanisms of action. The regulation of ion channels by second messengers, including Ca and cyclic AMP, and lipid mediators is also highly relevant to several of the ion channels discussed, including KCNQ channels, HCN channels, L-type Ca channels, and AMPA receptors, as well as the aquaporin channels. Molecular identification of exactly where drugs bind in the structure not only elucidates their mechanism of action but also aids future structure-based drug discovery efforts to focus on relevant pharmacophores. The ion channels discussed here are targets for multiple nervous system diseases, including epilepsy and neuropathic pain. This theme complements several previous themes, including "New Therapeutic Targets," "New Approaches for Studying Drug and Toxicant Action: Applications to Drug Discovery and Development," and "New Methods and Novel Therapeutic Approaches in Pharmacology and Toxicology."
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