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Exercise induced hypoalgesia (EIH) can be impaired in patients with chronic pain and may be dependent on exercise type. Factors predictive of EIH are not known. This study aimed to: (1) compare EIH in participants with chronic WAD to asymptomatic controls, (2) determine if EIH differs between aerobic and isometric exercise, (3) determine predictors of EIH.
Learn More >The opioid epidemic is a significant public health problem that is associated with overdose and death. The increase in opioid-related problems can largely be attributed to increases in opioid prescriptions for the treatment of chronic pain. Unfortunately, there is not a consensus on a definition of opioid misuse in the context of chronic pain, making measurement a challenge. One commonly used measure to assess opioid misuse in the context of chronic pain is the Current Opioid Misuse Measure (COMM). The COMM was designed to assess opioid misuse generally, as captured by psychiatric symptoms and aberrant drug use behaviors. Although studies have examined cross-validation using correlations, little psychometric work has been conducted, and therefore it is currently unknown what domains the measure is assessing.
Learn More >The frequent use of medication to treat migraine attacks can lead to an increase in migraine frequency and is called medication-overuse headache (MOH).
Learn More >To provide an updated review of the pathophysiology, diagnosis, and management of migraine with aura.
Learn More >Hemiplegic migraine (HM) is a clinically and genetically heterogeneous condition with attacks of headache and motor weakness which may be associated with impaired consciousness, cerebellar ataxia and intellectual disability. Motor symptoms usually last <72 hours and are associated with visual or sensory manifestations, speech impairment or brainstem aura. HM can occur as a sporadic HM or familiar HM with an autosomal dominant mode of inheritance. Mutations in CACNA1A, ATP1A2 and SCN1A encoding proteins involved in ion transport are implicated. The pathophysiology of HM is close to the process of typical migraine with aura, but appearing with a lower threshold and more severity. We reviewed epidemiology, clinical presentation, diagnostic assessment, differential diagnosis and treatment of HM to offer the best evidence of this rare condition. The differential diagnosis of HM is broad, including other types of migraine and any condition that can cause transitory neurological signs and symptoms. Neuroimaging, cerebrospinal fluid analysis and electroencephalography are useful, but the diagnosis is clinical with a genetic confirmation. The management relies on the control of triggering factors and even hospitalisation in case of long-lasting auras. As HM is a rare condition, there are no randomised controlled trials, but the evidence for the treatment comes from small studies.
Learn More >Chemotherapy-induced neuropathic pain is a common dose-limiting side effect of cancer treatment but the underlying mechanisms are largely unknown. Here, we used a whole genome expression microarray and gene ontology analysis to identify the upregulation of a sequence-specific DNA-binding protein, HOXA6, in the spinal dorsal horn on day 10 after injection of rats with oxaliplatin. Genetic disruption of HOXA6 with siRNAs alleviated mechanical allodynia after oxaliplatin administration. Reduced representation bisulfite sequencing assays indicated that oxaliplatin decreased the methylation levels of the SOX10 promoter but not of HOXA6. TET1 was also upregulated by oxaliplatin. Genetic disruption of TET1 with siRNA blocked the promoter demethylation of SOX10 and the upregulation of HOXA6 and SOX10. Importantly, inhibition of SOX10 by intrathecal application of SOX10 siRNA ameliorated the mechanical allodynia induced by oxaliplatin and downregulated the expression of HOXA6. Consistently, overexpression of SOX10 through intraspinal injection of AAV-SOX10-EGFP produced mechanical allodynia and upregulated the expression of spinal dorsal horn HOXA6. Moreover, chromatin immunoprecipitation assays demonstrated that oxaliplatin increased the binding of SOX10 to the promoter region of HOXA6. Taken together, our data suggest that HOXA6 upregulation through the TET1-mediated promoter demethylation of SOX10 may contribute to oxaliplatin-induced neuropathic pain. This article is protected by copyright. All rights reserved.
Learn More >The P2X receptor family of ATP-gated cation channels are attractive drug targets for pain and inflammatory disease, but no subtype-selective agonists, and few partially selective agonists have been described to date. As proof-of-concept for the discovery of novel P2X receptor agonists, here we demonstrate the use of Drosophila taste neurons heterologously expressing rat P2X2 receptors as a screening platform. We demonstrate that wild-type rat P2X2 expressed in Drosophila is fully functional (ATP EC 8.7 µM), and that screening of small (2 µl) volumes of a library of 80 adenosine nucleotide analogues is rapid and straightforward. We have determined agonist potency and specificity profiles for rat P2X2 receptors; triphosphate-bearing analogues display broad activity, tolerating a number of substitutions, and diphosphate and monophosphate analogues display very little activity. While several ATP analogues gave responses of similar magnitude to ATP, including the previously identified agonists ATPγS and ATPαS, we were also able to identify a novel agonist, the synthetic analogue 2-fluoro-ATP, and to confirm its agonist activity on rat P2X2 receptors expressed in human cells. These data validate our Drosophila platform as a useful tool for the analysis of agonist structure-activity relationships, and for the screening and discovery of novel P2X receptor agonists.
Learn More >Anxiety is common in patients suffering from chronic pain. Here, we report anxiety-like behaviors in mouse models of chronic pain and reveal that nNOS-expressing neurons in ventromedial prefrontal cortex (vmPFC) are essential for pain-induced anxiety but not algesia, using optogenetic and chemogenetic strategies. Additionally, we determined that excitatory projections from the posterior subregion of paraventricular thalamic nucleus (pPVT) provide a neuronal input that drives the activation of vmPFC nNOS-expressing neurons in our chronic pain models. Our results suggest that the pain signal becomes an anxiety signal after activation of vmPFC nNOS-expressing neurons, which causes subsequent release of nitric oxide (NO). Finally, we show that the downstream molecular mechanisms of NO likely involve enhanced glutamate transmission in vmPFC CaMKIIα-expressing neurons through S-nitrosylation-induced AMPAR trafficking. Overall, our data suggest that pPVT excitatory neurons drive chronic pain-induced anxiety through activation of vmPFC nNOS-expressing neurons, resulting in NO-mediated AMPAR trafficking in vmPFC pyramidal neurons.
Learn More >This randomized, double-blind, Phase 3 study (56-week treatment; 24-week follow-up) assessed tanezumab in patients with chronic low back pain (CLBP) and history of inadequate response to standard-of-care analgesics (NCT02528253). Patients received placebo, subcutaneous tanezumab (5mg or 10mg every 8 weeks), or oral tramadol prolonged-release (100-300mg/day). Primary endpoint was change in Low Back Pain Intensity (LBPI) at week 16 for tanezumab versus placebo. Key secondary endpoints were proportion of patients with ≥50% decrease in LBPI at week 16, change in Roland Morris Disability Questionnaire (RMDQ) at week 16, and change in LBPI at week 2 for tanezumab versus placebo. Adverse events and joint safety were assessed through weeks 56 and 80, respectively. Tanezumab 10mg met the primary endpoint by significantly improving LBPI at week 16 versus placebo; least squares (LS) mean (95% CI) difference = -0.40 (-0.76, -0.04; P=0.0281). Tanezumab 10mg significantly improved all key secondary endpoints. Tanezumab 5mg did not meet the primary endpoint (LS mean [95% CI] treatment difference versus placebo = -0.30 [-0.66, 0.07; P=0.1117]), preventing formal testing of key secondary endpoints for this dose. The proportion of patients with ≥50% improvement in LBPI at week 16 was 37.4% in the placebo group, 43.3% in the tanezumab 5mg group (Odds ratio [95% CI] vs placebo = 1.28 [0.97, 1.70; P=0.0846]) and 46.3% in the tanezumab 10mg group (Odds ratio [95% CI] vs placebo = 1.45 [1.09, 1.91; P=0.0101]). Prespecified joint safety events were more frequent with tanezumab 10mg (2.6%) than tanezumab 5mg (1.0%), tramadol (0.2%), or placebo (0%). Seven patients, all in the tanezumab 10mg group (1.4%), underwent total joint replacement. In conclusion, tanezumab 10mg significantly improved pain and function versus placebo in patients with difficult-to-treat CLBP. Tanezumab was associated with a low rate of joint safety events, some requiring joint replacement. Sponsored by Pfizer Inc. and Eli Lilly & Company.
Learn More >Diseases and disorders such as Parkinson's, schizophrenia, and chronic pain are characterized by altered mesolimbic dopaminergic neurotransmission. Dopamine release in the nucleus accumbens (NAc) influences behavior through both tonic and phasic signaling. Tonic dopamine levels are hypothesized to inversely regulate phasic signals via dopamine D2 receptor feedback inhibition. We tested this hypothesis directly in the context of ongoing pain. Tonic and phasic dopamine signals were measured using fast-scan controlled-adsorption voltammetry and fast-scan cyclic voltammetry, respectively, in the NAc shell of male rats with standardized levels of anesthesia. Application of capsaicin to the cornea produced a transient decrease in tonic dopamine levels. During the pain-induced hypodopaminergic state, electrically evoked phasic dopamine release was significantly increased when compared to baseline evoked phasic release. A second application of capsaicin to the same eye had a lessened effect on tonic dopamine suggesting desensitization of TRPV1 channels in that eye. Capsaicin treatment in the alternate cornea, however, again produced coincident decreased dopaminergic tone and increased phasic dopamine release. These findings occurred independently of stimulus lateralization relative to the hemisphere of dopamine measurement. Our data show that (a) the mesolimbic dopamine circuit reliably encodes acute noxious stimuli; (b) ongoing pain produces decreases in dopaminergic tone; and (c) pain-induced decreases in tonic dopamine correspond to augmented evoked phasic dopamine release. Enhanced phasic dopamine neurotransmission resulting from salient stimuli, may contribute to increased impulsivity and cognitive deficits often observed in conditions associated with decreased dopaminergic tone, including Parkinson's disease and chronic pain.
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