Pain
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Opioid receptors are major actors in pain control and are broadly distributed throughout the nervous system. A major challenge in pain research is the identification of key opioid receptor populations within nociceptive pathways, which control physiological and pathological pain. In particular, the respective contribution of peripheral vs. central receptors remains unclear, and it has not been addressed by genetic approaches. ⋯ Delta receptors in these neurons tonically inhibit mechanical hypersensitivity in both inflammatory and neuropathic pain, and they are essential to mediate delta opioid analgesia under conditions of persistent pain. This delta receptor population represents a feasible therapeutic target to alleviate chronic pain while avoiding adverse central effects. The conditional knockout of delta-opioid receptor in primary afferent Na(V)1.8 neurons augmented mechanical allodynia in persistent pain models and abolished delta opioid analgesia in these models.
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The benefits of transcutaneous electrical nerve stimulation (TENS) for pain relief have not been reliably established, as most systematic reviews find poor methodological quality in many studies. The paradox within the evidence base for TENS is that despite identified sources of bias that may lead to an overestimation of treatment effects, no benefits for TENS can be clearly demonstrated. Conventional assessments of quality assume a single direction of bias, and little work has been undertaken examining other directions of bias. ⋯ We propose criteria for judging directions of bias in future studies of TENS that may be adapted to assess other trials in which implementation fidelity is important, such as other nonpharmacological interventions for pain. Poor implementation fidelity was identified as a significant source of bias in systematic reviews of TENS studies and might explain lack of consistent treatment effects of TENS in pain. Here, criteria for assessing methodology are proposed for use in designing future clinical trials of TENS.
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"Pain exposure" physical therapy (PEPT) is a new treatment for patients with complex regional pain syndrome type 1 (CRPS-1) that consists of a progressive-loading exercise program and management of pain-avoidance behavior without the use of specific CRPS-1 medication or analgesics. The aim of this study was to investigate primarily whether PEPT could be applied safely in patients with CRPS-1. Twenty patients with CRPS-1 were consecutively enrolled in the study after giving informed consent. ⋯ Three patients initially showed increased vegetative signs but improved in all other CRPS parameters and showed good functional recovery at follow-up. We conclude that PEPT is a safe and effective treatment for patients with CRPS-1. A progressive-loading exercise program and management of pain-avoidance behavior without the use of specific medication ("pain exposure" physical therapy) is safe and effective for patients with complex regional pain syndrome.