The journal of pain : official journal of the American Pain Society
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Meta Analysis
Characterisation of common genetic variants in P2RX7 and their contribution to chronic pain conditions.
The adenosine triphosphate (ATP)-gated channel P2X7 is encoded by a gene enriched for common nonsynonymous variants. Many of these variants have functional cellular effects, and some have been implicated in chronic pain. In this study, we first systematically characterized all 17 common nonsynonymous variants using whole-cell patch clamp electrophysiology. ⋯ Cumulative allele count analysis did not provide additional insights. In conclusion, our results go beyond reproducing association for rs7958311 with chronic pain and suggest that its unique combination of gain-of-function in channel and loss-of-function in pore activity may explain why it is likely the only common P2RX7 variant with contribution to chronic pain. PERSPECTIVE: This study characterizes all common P2RX7 variants using cellular assays and statistical association analyses with chronic pain, with Markov state modeling of the most robustly associated variant.
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Randomized Controlled Trial
Placebo hypoalgesia and nocebo hyperalgesia induced by observational learning may be difficult to disentangle in a laboratory setting.
Observational learning (OBL) (seeing pain/pain treatment in others) can evoke placebo hypoalgesia and nocebo hyperalgesia. Data that compare these effects and illuminates the role of expectations and empathy are scarce. Healthy participants (n = 105) were randomized to: 1) placebo OBL, 2) nocebo OBL, or 3) no-observation control group. ⋯ Implications for existing theories are discussed. PERSPECTIVE: Data that systematically compare placebo hypoalgesia and nocebo hyperalgesia induced by OBL are scarce. The current work illustrates that these effects may be more difficult to disentangle than previously assumed, which could have implications for existing theories on OBL and placebo effects and their translation to clinical practice.
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The evidence that athletes respond to and report indices of experimental pain differently to non-athlete populations was analysed. Databases screened were SPORTDiscus, PubMED, PsycArticles, the Cochrane Library (Cochrane Database of Systematic Reviews), Web of Science, Scopus, and CINAHL. Studies that compared experimentally induced pain responses (threshold, tolerance, intensity, unpleasantness, bothersomeness, and effect on performance) in athletes and controls were included. ⋯ This study was registered on the PROSPERO site in January 2019 (ref ID: CRD42019119611). PERSPECTIVE: This review examined differences in pain outcomes (threshold, tolerance, intensity, unpleasantness, bothersomeness) and the effect of pain on performance, in athletes versus controls. Meta-analyses revealed athletes had higher threshold and tolerance and found pain less intense than controls; there was some evidence of differences in bothersomeness and performance.
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Randomized Controlled Trial
Efficacy of home-based transcranial direct current stimulation over the primary motor cortex and dorsolateral prefrontal cortex in the disability due to pain in fibromyalgia: A factorial sham-randomized clinical study.
This randomized, double-blind, controlled clinical trial compared the effectiveness of home-based-(HB) active transcranial direct current stimulation (a-tDCS) over the left dorsolateral prefrontal cortex (l-DLPFC) or primary motor cortex (M1) with their respective sham-(s)-tDCS to determine whether a-tDCS would be more effective than s-tDCS in reducing pain and improving disability due to pain. The study included 102 patients with fibromyalgia aged 30 to 65 years old randomly assigned to 1 of 4 tDCS groups using a ratio of 2:1:2:1. The groups included l-DLPFC (a-tDCS, n = 34) and (s-tDCS, n = 17), or tDCS on the M1 (a-tDCS, n = 34) or (s-tDCS, n = 17). ⋯ PERSPECTIVE: These findings provide important insights: (1) HB-tDCS has effectively reduced pain scores and improved disability due to fibromyalgia. (2) The study provides evidence that HB-a-tDCS is a viable and effective therapeutic approach. (3) HB-a-tDCS over M1 improved the function of the descending pain inhibitory system and increased the heat pain threshold. Finally, our findings also emphasize that brain-derived neurotrophic factor, as an index of neuroplasticity, may serve as a valuable marker associated with changes in clinical pain measures. TRIAL REGISTRATION: Number NCT03843203.
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Interoception refers to the ability to sense internal bodily sensations. Research suggests that dysfunctions in interoception may be implicated in the transition to chronic pain, however, little work has examined interoceptive ability in pain states. Therefore, this systematic review aimed to assess whether interoception is altered in individuals experiencing pain. ⋯ This review was registered on the PROSPERO International Prospective Register of Systematic Reviews (Registration ID = CRD42022318843). PERSPECTIVE: This review considered the relationship between interoception and pain and found that an individual's ability to accurately sense internal signals is decreased in those with chronic pain, despite them reporting being more aware of internal sensations. However, there remains little research examining interoception in non-chronic pain states.