The journal of pain : official journal of the American Pain Society
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Previous studies have established that the activation of peripheral nociceptors alters the central processing of nociceptive stimuli. In this study, we examined whether noxious heating of the dental pulp enhances the nociceptive jaw-opening reflex (JOR) and the expression of the immediate early gene c-fos in chloral hydrate/pentobarbital-anesthetized ferrets. We hypothesized that the application of noxious heat to the dental pulp, a procedure that evokes a preferential activation of pulpal C-fibers, will enhance JOR responses to electrical stimulation of the tooth pulp and that this enhanced response will be associated with the expression of Fos protein in discrete regions of the trigeminal nucleus. ⋯ The enhancement in JOR responses was independent of temporal summation of the electrical stimulus for test stimuli delivered at either 1.0 or 0.1 Hz. Sensitization of the JOR was associated with an increase in the number of immunohistochemically identified Fos-positive nuclei in trigeminal caudalis (Vc) and the transition zone between trigeminal interpolaris and caudalis (Vi/Vc) ipsilateral to the site of stimulation compared with sham stimulated animals. These findings suggest that neuronal populations in Vc and Vi/Vc play a role in the enhanced reflex responses to tooth pulp stimulation and may contribute to the pain and hyperalgesia associated with a symptomatic pulpitis.
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Although the effects of aging on the experience of clinical pain seem relatively clear, investigations of age-related changes in pain perception using laboratory-based pain assessment procedures have yielded contradictory findings. One potential source of variability in this literature is the type of experimental noxious stimulus that is used. Although thermal pain thresholds are the most commonly reported measure of pain sensitivity, use of suprathreshold stimuli in pain assessment procedures may yield additional, more clinically relevant information concerning the effects of aging on the experience of pain. ⋯ Results suggested that for the 47 degrees C and 50 degrees C stimulus trains, older adults exhibited higher ratings of the intensity and unpleasantness of thermal pain and enhanced temporal summation of thermal pain relative to younger adults. Moreover, thermal pain sensitivity was inversely related to perceptions of general health and to reports of recent clinical pain among younger, but not older, subjects. Collectively these findings may indicate small, although potentially significant, age-related alterations in the plasticity of the central nervous system or endogenous pain-modulatory capacities.
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Recent reports indicate that several descriptors of pain sensations in the McGill Pain Questionnaire (MPQ) are difficult to classify within MPQ sensory subcategories because of incomprehension, underuse, or ambiguity of usage. Adopting the same methodology of recent studies, the present investigation focused on the affective and evaluative subcategories of the MPQ. ⋯ Despite notable changes in classification, the intensity ratings of the retained words correlated very highly with those originally reported for the MPQ. In conclusion, although the intensity ratings of MPQ affective and evaluative descriptors need no revision, selective reduction and reorganization of these descriptors can enhance the efficiency of this approach to pain assessment.
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Empirical research supports the existence of sex differences in pain; yet these differences are poorly understood. Although biological mechanisms have been posited to explain variability, results of pain modeling manipulations suggest social learning may be a stronger influence on pain response. In this report we use the term sex to refer to the biological category of male or female. ⋯ Sex accounted for 46% of the variance in willingness to report pain. Results suggest that the GREP distinguished between the socially learned reactions to pain for men and women. It is recommended that the influence of gender-related expectations for pain be assessed in all studies investigating human sex differences in pain.
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The objective of this international, multicenter, open-label trial was to assess the efficacy and safety of up to 12 months of therapy with transdermal therapeutic system (TTS) fentanyl in patients (n = 532) with chronic noncancer pain. The trial was completed by 301 (57%) of the patients. The main outcome measures were pain control assessment, global treatment satisfaction, patient preference for TTS fentanyl, and quality of life. ⋯ It was preferred by the majority of patients compared with their previous opioid medication. Overall, long-term treatment with TDF was generally well tolerated, particularly in view of the low incidence of potentially serious side effects such as drug abuse/dependence and respiratory depression. However, at present, it is important that patients receiving TDF should still be subject to careful assessment and monitoring.