European journal of pain : EJP
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Somatostatin (SST) in spinal cord has been linked with the inhibition of nociceptive neurotransmission in several experimental paradigms. The SST2 receptor (SSTR2) is the main SST receptor subtype in the superficial dorsal horn (DH) and is activated, besides to the naïve peptide, by the SST synthetic analogue octreotide (OCT). In the present work, we have studied the central effects of SSTR2 activation on capsaicin (CAP)-induced glutamate release in mouse DH. ⋯ A subset of them was also found to express the CAP receptor TRPV1. These data show that the SST analogue OCT inhibits CAP-mediated activation of non-peptidergic nociceptive PAFs in lamina II. Our data indicate that SSTR2a plays an important role in the pre-synaptic modulation of central excitatory nociceptive transmission in mouse.
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Sex differences in pain perception have been reported in an expanding literature based on adult samples in epidemiological as well as laboratory studies. Especially with respect to the latter, studies with children and adolescents do not consistently show that females report higher pain ratings and display lower pain tolerance than males. The first aim of the presented studies is to comparably examine sex differences in children and adolescents based on experimental and questionnaire approach indices of pain perception. ⋯ In Study 2, sex differences are also present for masculinity, femininity, catastrophizing as well as pain self-efficacy. However, while the relation between sex and the CPT rating is partially mediated by pain self-efficacy, catastrophizing partially mediates the relation between sex and the questionnaire based pain ratings. The results of both studies are discussed with respect to the difference between experimental assessments of pain perception and assessments by questionnaire in children and adolescents.
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The aim of the study was to investigate the effect of acute trapezius pain, induced by delayed onset of muscle soreness (DOMS), on habitual trapezius activity. Long-term (5 h) surface electromyographic (sEMG) activity was recorded bilaterally from the clavicular, descending, transverse, and ascending trapezius on two consecutive weekdays in eleven female subjects (mean age 22 years, range 20-24 years). Body and arm posture were recorded by inclinometers. ⋯ In contrast, trapezius sEMG activity remained unchanged for all other trapezius parts and postures. This study indicates that acute trapezius pain induces elevated habitual trapezius activity during periods with low biomechanical loading of the shoulder/neck muscles with the elevated sEMG activity being restricted to the painful part of the muscle. In contrast to the pain-adaption model, the current study indicates a relation between acute muscle pain and elevated low-level muscle activity; however, it remains unknown if development of chronic muscle pain can be preceded by an initial stage with elevated muscle activity.
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Randomized Controlled Trial
The anticonvulsant levetiracetam for the treatment of pain in polyneuropathy: a randomized, placebo-controlled, cross-over trial.
Levetiracetam is an anticonvulsant which is assumed to act by modulating neurotransmitter release via binding to the vesicle protein SV2A. This could have an impact on signaling in the nociceptive system, and a pilot study indicated relief of neuropathic pain with levetiracetam. ⋯ This study indicates that the anticonvulsant levetiracetam has no clinically relevant effect on painful polyneuropathy.
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Randomized Controlled Trial
Self-reported sleep duration associated with distraction analgesia, hyperemia, and secondary hyperalgesia in the heat-capsaicin nociceptive model.
Although sleep deprivation is known to heighten pain sensitivity, the mechanisms by which sleep modifies nociception are largely unknown. Few studies of sleep-pain interactions have utilized quantitative sensory testing models that implicate specific underlying physiologic mechanisms. One possibility, which is beginning to receive attention, is that differences in sleep may alter the analgesic effects of distraction. ⋯ Individuals who slept less than 6.5 h/night in the month prior to the study experienced significantly less behavioral analgesia, increased skin flare and augmented secondary hyperalgesia. These findings suggest that reduced sleep time is associated with diminished analgesic benefits from distraction and/or individuals obtaining less sleep have a reduced ability to disengage from pain-related sensations. The secondary hyperalgesia finding may implicate central involvement, whereas enhanced skin flare response suggests that sleep duration may also impact peripheral inflammatory mechanisms.