Pain
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Post-exertional muscle pain is an important reason for disability in patients who are diagnosed to have Chronic Fatigue Syndrome (CFS). We compared changes in pain threshold in five CFS patients with five age and sex matched controls following graded exercise. Pain thresholds, measured in the skin web between thumb and index finger, increased in control subjects with exercise while it decreased in the CFS subjects. Increased perception of pain and/or fatigue after exercise may be indicative of a dysfunction of the central anti-nociceptive mechanism in CFS patients.
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We examined congruence between chronic pain patients and their spouses on their reports of patient pain severity, patient disability, and spouse responses to pain. Patients reported that they were more physically and psychosocially disabled than their spouses reported them to be. However, spouses reported that the patients' pain was more severe than patients reported. ⋯ Male patient couples did not report differences on physical disability. Findings relating to other forms of disability and to spouse responses are also described. The results are discussed in the context of an interpersonal perspective of chronic pain and have implications for the assessment of pain and disability.
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Nicotinic agonists have well-documented antinociceptive properties when administered subcutaneously or intrathecally in mice. However, secondary mild to toxic effects are observed at analgesic doses, as a consequence of the activation of the large family of differentially expressed nicotinic receptors (nAChRs). In order to elucidate the action of nicotinic agonists on spinal local circuits, we have investigated the expression and function of nAChRs in functionally identified neurons of neonate mice spinal cord. ⋯ Whereas GABA/glycine interneurons preferentially expressed alpha4alpha6beta2* nAChRs, alpha3beta2alpha7* nAChRs were preferentially expressed by CA or NK1-R expressing neurons. Recorded neurons were also classified by firing pattern, for comparison to results from single-cell RT-PCR studies. Altogether, our results identify distinct sites of action of nicotinic agonists in circuits of the dorsal horn, and lead us closer to an understanding of mechanisms of nicotinic spinal analgesia.
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Diabetes can induce a bewildering list of sensory changes, including alteration in pain sensitivity. Painful diabetic neuropathy is refractory to most common analgesics. This study examined the effect of a p38alpha MAPK inhibitor, SD-282, on mechanical allodynia, thermal hyperalgesia, and formalin-evoked nociception in streptozotocin-induced diabetic rats. ⋯ Repeated administration of 45 mg/kg SD-282 attenuated flinching behaviors during the quiescent period and the second phase of the formalin response in diabetic rats. Acute and repeated administration of 15 or 45 mg/kg SD-282 had no effect on mechanical, thermal or formalin responses in age-matched control rats. These results indicate a potential therapeutic value of p38alpha MAPK inhibitors in the treatment of aberrant pain sensitivity produced by diabetes.
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In the peripheral nervous system, N-methyl-D-aspartate receptors (NMDAR) expressed on the central and peripheral terminals of primary afferent neurons are involved in nociception. We used single cell imaging of intracellular calcium concentration ([Ca2+]i) and patch clamp techniques to characterize the functional properties of NMDARs on adult rat dorsal root ganglia (DRG) neurons in primary culture and selectively on those innervating the distal colon. In Mg2+-free extracellular solution, rapid perfusion of DRG neurons with 250 microM NMDA and 10 microM glycine caused a significant increase in [Ca2+]i, and elicited inward currents in whole cell patch clamp recordings when the holding potential was -60 mV. ⋯ There was no evidence of multiple binding sites for ifenprodil. There was no significant difference in the NMDAR current density on DRG neurons that had innervated the colon, nor was there a difference in the EC50 for ifenprodil. These results demonstrate that functional NMDARs expressed by DRG neurons innervating both somatic and visceral tissues of adult rats are composed predominantly of NR2B subunits.