Pain
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Randomized Controlled Trial
Effects of spatially targeted transcutaneous electrical nerve stimulation using an electrode array that measures skin resistance on pain and mobility in patients with osteoarthritis in the knee: a randomized controlled trial.
A novel device was developed that measured local electrical skin resistance and generated pulsed local electrical currents that were delivered across the skin around the knee for patients with osteoarthritis (termed eBrace TENS). Currents were delivered using an electrode array of 16 small circular electrode elements so that stimulation could be spatially targeted. The aim of this study was to investigate the effects of spatially targeted transcutaneous electrical nerve stimulation (TENS) to points of low skin resistance on pain relief and mobility in osteoarthritis of the knee (OAK). ⋯ Lowest-resistance TENS reduced pain intensity during walking relative to resting baseline compared with random TENS (95% confidence interval of the difference: -20.8mm, -1.26 mm). There were no statistically significant differences between groups in distance during the walk test, maximum voluntary contraction (MVC) or range-of-motion (ROM) measures or WOMAC scores. In conclusion, we provide evidence that use of a matrix electrode that spatially targets strong nonpainful TENS for 30 to 45 minutes at sites of low resistance can reduce pain intensity at rest and during walking.
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Comparative Study
Differential effects of experimental central sensitization on the time-course and magnitude of offset analgesia.
Pain perception is temporally altered during states of chronic pain and acute central sensitization; however, the mechanisms contributing to temporal processing of nociceptive information remain poorly understood. Offset analgesia is a phenomenon that reflects the presence of temporal contrast mechanisms for nociceptive information and can provide an end point to study temporal aspects of pain processing. In order to investigate whether offset analgesia is disrupted during sensitized states, 23 healthy volunteers provided real-time continuous visual analogue scale responses to noxious heat stimuli that evoke offset analgesia. ⋯ Increased latencies to maximal offset analgesia and prolonged aftersensations were observed only in the primary regions directly treated by capsaicin-heat or heat alone. However, contrary to the hypothesis that offset analgesia would be reduced following capsaicin-heat sensitization, the magnitude of offset analgesia remained remarkably intact after both capsaicin-heat and heat-only sensitization in zones of both primary and secondary mechanical allodynia. These data indicate that offset analgesia is a robust phenomenon and engages mechanisms that interact minimally with those supporting acute central sensitization.
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Effector CD4(+) T lymphocytes generated in response to antigens produce endogenous opioids. Thus, in addition to their critical role in host defenses against pathogens, effector CD4(+) T lymphocytes contribute to relieving inflammatory pain. In this study, we investigated mechanisms of opioid release by antigen-experienced effector CD4(+) T cells that leave draining lymph nodes and come back into the inflammatory site. ⋯ Analgesia was observed by transferring effector CD4(+) T lymphocytes with Th1 or Th2 phenotype, suggesting that antinociceptive activity is a fundamental property of effector CD4(+) T lymphocytes irrespective of their effector functions. Based on the use of agonists and antagonists selective for each of the opioid receptor subclasses, we showed that analgesia induced by T cell-derived opioids is elicited via activation of δ-type opioid receptors in the periphery. Thus, the antinociceptive activity is a fundamental property associated with the effector phase of adaptive immunity, which is driven by recognition of the cognate antigen by effector CD4(+) T lymphocytes at the inflammatory site.
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Randomized Controlled Trial
Effect of intravenous tropisetron on modulation of pain and central hypersensitivity in chronic low back pain patients.
The activation of 5-hydroxytryptamine-3 (5-HT-3) receptors in spinal cord can enhance intrinsic spinal mechanisms of central hypersensitivity, possibly leading to exaggerated pain responses. Clinical studies suggest that 5-HT-3 receptor antagonists may have an analgesic effect. This randomized, double-blind, placebo-controlled crossover study tested the hypothesis that the 5-HT-3 receptor antagonist tropisetron attenuates pain and central hypersensitivity in patients with chronic low back pain. ⋯ However, there was no statistically significant difference between tropisetron and placebo in VAS scores. Compared to placebo, tropisetron produced a statistically significant increase in pain threshold after single electrical stimulation, but no difference in all other secondary outcomes was found. A single-dose intravenous administration of tropisetron in patients with chronic low back pain had no significant specific effect on intensity of pain and most parameters of central hypersensitivity.