Pain
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Comparative Study
Spinal nociceptive transmission in the spontaneously hypertensive and Wistar-Kyoto normotensive rat.
Background and noxious heat-evoked responses of wide-dynamic-range (WDR) and high-threshold (HT) lumbosacral spinal dorsal horn neurons were recorded in spontaneously hypertensive rats (SHRs), Wistar-Kyoto normotensive rats (WKYs), lifetime captopril-treated SHRs, SHRs with bilateral cervical vagotomy, SHRs with bilateral sino-aortic deafferentation (SAD), and SHRs with either a single or repeated administration of naloxone methobromide (NMB). Stimulus-response functions (SRFs) were generated for neurons using 15 sec of heating of the foot at temperatures ranging from 38 to 52 degrees C. Comparisons were made of neuronal response thresholds, slopes of the SRFs, mean discharge frequency during heat stimulation, arterial blood pressure (ABP), and heart rate (HR). ⋯ However, repeated administration of NMB in SHRs resulted in a parallel, leftward shift in SRFs of both WDR and HT neurons. In all strains and treatments studied, there were no significant differences in background activities of these neurons that might contribute to the observed outcomes. In conclusion, the hypoalgesia reported in human essential hypertensives and animals with chronic hypertension may be due to a significant attenuation in spinal nociceptive transmission.(ABSTRACT TRUNCATED AT 400 WORDS)
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Nociceptive primary afferents have the capacity to induce a state of increased excitability or central sensitization in dorsal horn neurones. This contributes to the mechanical hypersensitivity (allodynia) which occurs after peripheral tissue injury where low-mechanothreshold primary afferent activation begins to elicit pain. The relative susceptibility of dorsal horn cells with an apparent exclusive nociceptive input (nociceptive-specific (NS) or high-threshold (HT) cells) and those with a convergent input from low- and high-threshold mechanoreceptors (wide-dynamic-range (WDR) or multireceptive neurones) to sensitivity changes has been disputed. ⋯ In 3 cells, an increase in the response to A-fibre afferents occurred, a novel A-fibre response was recruited in 2 cells and the C-fibre response increased in 2 cells. Cells in the superficial dorsal horn of the rat spinal cord that are normally NS can begin, therefore, to respond to LT primary afferent mechanoreceptors after an increase in central excitability produced by activation of peripheral chemoreceptors. Sensitization of these, as well as of WDR cells, may contribute to the generation of post-injury mechanical pain and reflex hypersensitivity.
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Comparative Study Clinical Trial
Are runners stoical? An examination of pain sensitivity in habitual runners and normally active controls.
Anecdotal and clinical reports suggest that athletes are stoical. However, there are few studies comparing persons who exercise regularly with those who do not. This study compared two independent samples of regular runners and normally active controls, both without recent exercise, on cold pressor, cutaneous heat, and tourniquet ischemic pain tests. ⋯ The cohorts also did not differ in their report of ischemic pain sensations. Thus, these data do not generally support the hypothesis of pain insensitivity or stoicism in habitual runners. Rather, insensitivity occurs only in their response to noxious cold, which is suggested to be an adaptation to regular training.
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Clinical Trial
A psychophysical study of secondary hyperalgesia: evidence for increased pain to input from nociceptors.
Substantial evidence suggests that the hyperalgesia to mechanical stimuli that occurs in an area of uninjured skin surrounding a site of injury (area of secondary hyperalgesia) arises from activity in low-threshold mechanoreceptors (LTMs). In this study, we have investigated if activity in mechanically sensitive nociceptors also contributes to this secondary hyperalgesia. It is known that all woollen fabrics excite LTMs, but that only the prickly ones activate mechanically sensitive nociceptors. ⋯ On the other hand, little if any pain was evoked by the fabrics when applied to normal skin, but substantial pain was produced by all fabrics when applied to hyperalgesic skin. The pain ratings were graded with the ratings of prickle so that fabrics that evoked the greatest prickle also evoked significantly more pain. The magnitude of pain increased linearly with prickle sensation; the slope of this regression function increased substantially in hyperalgesic skin.(ABSTRACT TRUNCATED AT 250 WORDS)
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Low Back Pain Rating scale is an index scale which includes measurements of pain intensity, disability, and physical impairment. The scale was designed to monitor the outcome of clinical trials of low back pain treatment. It has been validated in 58 patients following first-time discectomy. ⋯ In the study, a high rater agreement (97.7%) was found without level difference between two observers using the scale. The validation process included: construct validity, criterion-related validity and item bias, relative to Global Assessments pronounced by the patient and an experienced clinician. Low Back Pain Rating scale hs been shown to be valid and reliable in the assessment of low back pain.