Articles: hyperalgesia.
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Although nonnoxious, high-frequency electrical stimulation applied segmentally (ie, conventional transcutaneous electrical nerve stimulation [TENS]) has been proposed to modulate pain, the mechanisms underlying analgesia remain poorly understood. To further elucidate how TENS modulates pain, we examined evoked responses to noxious thermal stimuli after the induction of sensitization using capsaicin in healthy volunteers. We hypothesized that sensitization caused by capsaicin application would unmask TENS analgesia, which could not be detected in the absence of sensitization. Forty-nine healthy subjects took part in a series of experiments. The experiments comprised the application of topical capsaicin (.075%) on the left hand in the C6 dermatome, varying the location of TENS (segmental, left C6 dermatome, vs extrasegmental, right shoulder), and assessing rating of perception (numeric rating scale: 0-10) and evoked potentials to noxious contact heat stimuli. The extrasegmental site was included as a control condition because previous studies indicate no analgesic effect to remote conventional TENS. Conventional TENS had no significant effect on rating or sensory evoked potentials in subjects untreated with capsaicin. However, segmental TENS applied in conjunction with capsaicin significantly reduced sensation to noxious thermal stimuli following a 60-minute period of sensitization. ⋯ The study indicates that sensitization with capsaicin unmasks the analgesic effect of conventional TENS on perception of noxious contact heat stimuli. Our findings indicate that TENS may be interacting segmentally to modulate distinct aspects of sensitization, which in turn results in analgesia to thermal stimulation.
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J Basic Clin Physiol Pharmacol · Jul 2015
A hydro-ethanolic extract of Synedrella nodiflora (L.) Gaertn ameliorates hyperalgesia and allodynia in vincristine-induced neuropathic pain in rats.
The hydro-ethanolic extract of Synedrella nodiflora (L.) Gaertn whole plant has demonstrated analgesic effects in acute pain models. The extract has also demonstrated anticonvulsant effects in murine models of experimental epilepsy. The present study illustrates an evaluation of the hydro-ethanolic extract of the plant for possible analgesic properties in hyperalgesia and allodynia associated with vincristine-induced neuropathy in rats. ⋯ The findings suggest that hydro-ethanolic extract of S. nodiflora possesses anti-hyperalgesic and anti-allodynic effects in vincristine-induced neuropathic pain in rats.
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Trigeminal (TG) pain often lacks a satisfactory pharmacological control. A better understanding of the molecular cross-talk between TG neurons and surrounding satellite glial cells (SGCs) could help identifying innovative targets for the development of more effective analgesics. We have previously demonstrated that neuronal pro-algogenic mediators upregulate G protein-coupled nucleotide P2Y receptors (P2YRs) expressed by TG SGCs in vitro. ⋯ Conversely, the selective P2Y1 R antagonist MRS2179 was completely ineffective. Moreover, similarly to the anti-inflammatory drug acetylsalicylic acid and the known anti-migraine agent sumatriptan, the P2X/P2Y nonselective antagonist PPADS was only partially effective, and completely lost its activity under sub-chronic conditions. Taken together, our results highlight glial P2Y2 Rs as potential "druggable" targets for the successful management of TG-related pain.
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J Obstet Gynaecol Can · Jul 2015
Case ReportsThe Significance of Cutaneous Allodynia in a Woman With Chronic Pelvic Pain.
This is a case report of sensory assessment in a woman with severe chronic pelvic pain following uterine artery embolization, and a discussion of a commonly observed sensory manifestation (allodynia) associated with chronic pelvic pain due to gynaecological conditions. Allodynia, as a common sensory abnormality can be readily detected at the bedside and represents the development of pain sensitization. Emergence of abdominal and perineal allodynia (assessed by cotton swap stroking and/or questionnaire) is associated with the development of the clinical features of sensitization: continuous pelvic pain, muscle tenderness, and reduced pressure pain thresholds. ⋯ Testing for allodynia is a validated bedside test for pain sensitization. A clinical trial of botulinum toxin is indicated for the management of chronic pelvic pain associated with allodynia and pain sensitization.
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Although still used by hundreds of millions of people worldwide, the mechanism of the analgesic action of the pyrazolone derivatives (PDs), dipyrone, propyphenazone and antipyrine remains unknown. The transient receptor potential ankyrin 1 (TRPA1) channel, expressed by nociceptors, is emerging as a major pain transduction pathway. We hypothesized that PDs target the TRPA1 channel and by this mechanism produce their analgesic effect. ⋯ Evidence that in rodents the nociceptive/hyperalgesic effect produced by TRPA1 activation is blocked by PDs suggests that a similar pathway is attenuated by PDs in humans and that TRPA1 antagonists could be novel analgesics, devoid of the adverse haematological effects of PDs.