Pain
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This study used concordant behavioral and electrophysiological approaches to examine the actions of the prototypic kappa opioid receptor agonist U69593 in the rostral ventromedial medulla (RVM). In vitro whole-cell voltage clamp recordings indicated that bath application of U69593 produced outward currents in primary cells in the RVM. In secondary cells, which comprised 80% of the population, U69593 produced a concentration-dependent and norbinaltorphimine (norBNI)-reversible inhibition of evoked excitatory postsynaptic currents (EPSCs) in the absence of any postsynaptic effect. ⋯ The highly test-dependent nature of U69593's effects suggests that the mechanisms by which neurons in the RVM modulate thermal nociceptive responses evoked from the tail and hindpaw are not uniform. Collectively, these data suggest that the RVM is a primary site of action for the antinociceptive actions of kappa opioid receptor agonists and that the mechanism most likely involves a presynaptic inhibition of excitatory inputs to secondary cells. Thus, disinhibition of pain inhibitory neurons in the RVM is likely to be a common mechanism by which opioid receptor agonists produce antinociception, whether by the direct inhibition of inhibitory secondary cells, as in the case of mu opioid receptor agonists, or by a reduction in the excitatory drive to these neurons, as in the case of kappa opioid receptor agonists.
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Diffuse noxious inhibitory controls (DNIC), which involve supraspinal structures and modulate the transmission of nociceptive signals, were investigated in rats with chronic constriction injury of the sciatic nerve. Nerve-injured rats with increased sensitivity to mechanical and thermal stimulation on the operated side were anesthetized and recordings were made from trigeminal convergent neurons. Inhibitions of C-fiber-evoked neuronal responses during and after the application of nociceptive conditioning stimuli to the hindpaw, were measured to evaluate DNIC. ⋯ This was true regardless of the intensity and frequency of stimulation and regardless of whether the stimuli were applied transcutaneously or directly to the sciatic nerve. The clear-cut difference between the results obtained with natural and electrical conditioning stimuli suggests that the nociceptive neurons involved in the triggering of DNIC may not be sensitized at the central level. Peripheral mechanisms such as the sensitization of nerve injured fibers and/or sprouting of nerve terminals may thus be the main causes of DNIC increase in this model of neuropathic pain.
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Randomized Controlled Trial Comparative Study Clinical Trial
A randomized comparison of group cognitive--behavioral therapy, surface electromyographic biofeedback, and vestibulectomy in the treatment of dyspareunia resulting from vulvar vestibulitis.
This study compared group cognitive-behavioral therapy (12-week trial), surface electromyographic biofeedback (12-week trial), and vestibulectomy in the treatment of dyspareunia resulting from vulvar vestibulitis. Subjects were 78 women randomly assigned to one of three treatment conditions and assessed at pretreatment, posttreatment and 6-month follow-up via gynecological examinations, structured interviews and standard questionnaires pertaining to pain (Pain Rating Index and Sensory scale of the McGill Pain Questionnaire, vestibular pain index, pain during intercourse), sexual function (Sexual History Form, frequency of intercourse, Information subscale of the Derogatis Sexual Functioning Inventory), and psychological adjustment (Brief Symptom Inventory). As compared with pretreatment, study completers of all treatment groups reported statistically significant reductions on pain measures at posttreatment and 6-month follow-up, although the vestibulectomy group was significantly more successful than the two other groups. ⋯ All three groups significantly improved on measures of psychological adjustment and sexual function from pretreatment to 6-month follow-up. Intent-to-treat analysis supported the general pattern of results of analysis by-treatment-received. Findings suggest that women with dyspareunia can benefit from both medical and behavioral interventions.
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Randomized Controlled Trial Comparative Study Clinical Trial
The Amsterdam Pain Management Index compared to eight frequently used outcome measures to evaluate the adequacy of pain treatment in cancer patients with chronic pain.
There is no 'gold standard' to assess the adequacy of pain treatment in cancer patients. The purpose of the study is to explore the Amsterdam Pain Management Index, a newly designed measure to evaluate the adequacy of cancer pain treatment, and to compare it with eight frequently used outcome measures. The Amsterdam Pain Management Index compares patients' Present Pain Intensity, Average Pain Intensity, and Worst Pain Intensity with a composite score of analgesics used, while correcting for what a patient considers as a tolerable level of pain. ⋯ The ability of the outcome measures to detect changes over time was clearly demonstrated by all outcome measures. Effects of the intervention were only found for the Amsterdam Pain Management Index and patients' Substantial Worst Pain score. Although support was provided for the use of the Amsterdam Pain Management Index, more research is warranted.