European journal of pain : EJP
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Topical high-dose capsaicin acting on TRPV1 receptors and inducing an intraepidermal decrease in the small nerve fibre count is effective in treating neuropathic pain (NP). Sensory changes after capsaicin application, their correlation with pain relief and their role as possible predictors of response have been insufficiently analysed. We hypothesized a positive correlation between pain relief and increase in the warmth detection threshold (WDT), indicating loss of C-fibre function, and higher response rates in patients with preserved C-fibre function or heat hyperalgesia before application. ⋯ Efficacy of capsaicin does not correlate with the induced loss of function of small fibres, measured by QST. Presence of cold and pinprick hyperalgesia seems to be predictive of response to capsaicin (8%).
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Thermoregulation and pain perception: Evidence for a homoeostatic (interoceptive) dimension of pain.
Experimental and clinical observations of interactions between the nociceptive and thermoceptive systems have suggested that they could be part of the homoeostatic system relating to the condition of the body, described as 'interoception'. Homoeostatic physiological systems are extensively interconnected. Thus, consistent with this hypothesis, we would expect thermoregulatory challenges to be associated with changes in pain perception. ⋯ Our results are consistent with the notion that pain has a homoeostatic (interoceptive) dimension and showed that the thermal grill-induced pain is a unique experimental model to investigate this differentiable pain dimension.
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Pain is a prominent feature of interstitial cystitis/painful bladder syndrome (IC/PBS), but the underlying mechanisms are not fully understood. There is a lack of well-characterized research tools, such as pain evaluation methods and experimental animal models, for investigating non-ulcerative cystitis. We developed a novel method for evaluating bladder pain in mice with cyclophosphamide (CYP)-induced cystitis. ⋯ The blunt probe method is useful for evaluating bladder pain signalling in mice, and revealed the involvement of an NGF-sensitive pain pathway in chronic cystitis pain. This assessment method may be useful for studying the pathophysiology of bladder pain and for developing therapeutic strategies for non-ulcerative IC/PBS in patients.