Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0849640 (skin damage)
 1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In areas of secondary hyperalgesia, innocuous mechanical stimuli evoke pain (allodynia). We have proposed that this is produced by a central pre-synaptic interaction whereby A beta-fibers evoke spike activity (dorsal root reflexes) in nociceptive afferents (Pain, 68 (1996) 13). This activity should conduct centrally, evoking allodynia, and peripherally, evoking neurogenic vasodilatation. Here we tested this hypothesis by examining the effects of electrical stimulation of A beta-fibers on cutaneous blood flow before and after producing secondary hyperalgesia in anesthetized rats. Cutaneous blood flow was recorded in the hind paw skin innervated by the sural nerve using a laser Doppler flowmeter. The sural nerve was prepared for electrical stimulation, and the evoked activity was recorded from the sciatic nerve in continuity. Electrical stimulation (1 Hz, 4 x 0.2 ms pulses, 20 s) was applied to the sural nerve at 2T (A beta-fibers only) and 4T and 6T (A beta + A delta-fibers). Flux was recorded at baseline and after capsaicin or mustard oil application outside the sural nerve territory. The effects of intravenous administration of the calcitonin gene-related peptide (CGRP) receptor antagonist, alpha-CGRP(8-37), or of section of the sciatic nerve or of the L4-L6 dorsal roots were examined. Selective activation of the sural nerve A beta-fibers reliably evoked increases in cutaneous blood flow close to areas of chemical irritation or skin damage. A beta-fiber-evoked vasodilatation was abolished by sciatic nerve or dorsal root section and had a spatial arrangement and optimal stimulation pattern suggesting a central synaptic interaction similar to that responsible for dorsal root reflexes. The flux increases were dose-dependently and reversibly inhibited by alpha-CGRP(8-37), indicating that the A beta-fiber-evoked vasodilatation resulted from the antidromic activation of nociceptive cutaneous afferent fibers. These results support our hypothesis by showing activation of nociceptive primary afferents by A beta-fibers in areas of allodynia in a manner consistent with a pre-synaptic interaction evoking dorsal root reflexes.
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PMID:Vasodilatation in hyperalgesic rat skin evoked by stimulation of afferent A beta-fibers: further evidence for a role of dorsal root reflexes in allodynia. 1173 Oct 65

Capsaicin is used to investigate the role of peripheral sensory nerve fibers. In previous studies of rats treated by injection of capsaicin into the skin of the neck, 'spontaneous' lesions in the head and neck region were observed. In this study, the course of development over time, the regional distribution and the innervation of capsaicin-induced dermal lesions were assessed in young male Sprague-Dawley rats. In one experiment, capsaicin was administered subcutaneously by injection in the skin of the neck. In a second experiment, capsaicin was injected in the back by a long needle that tunneled under the skin and allowed the capsaicin to be deposited in the subcutaneous fat of the neck. The density and the distribution of dermal nerve fibers were investigated by immunohistochemistry, using antisera against a panneuronal marker, protein gene product 9.5 (PGP), and calcitonin gene-related peptide (CGRP). In the first experiment, rats developed lesions in the neck area 11 days after injection. In the second experiment, lesions appeared in the skin of the back and occasionally in the neck area 10 days after injection. Development of lesions in the afflicted areas was paralleled by local reduction in the density of CGRP-immunoreactive (IR) nerve fibers, 80% in the first experiment and 72% in the second. The number of PGP-IR fibers was likewise reduced, by 39 and 41%, respectively. The density of the CGRP-IR fibers in the wound area was the same as in the adjacent, nonlesioned skin. The healing of the capsaicin-induced lesions was slow compared with surgical wounds in control animals. The wounds healed with hypertrophic scars. The healing process in the skin of the back was associated with the proliferation of CGRP-IR fibers. The study shows cutaneous lesions to appear in the region of the subcutaneous deposition of capsaicin. A uniform depletion of capsaicin-sensitive nerve fibers in the area of deposition suggests that an additional factor is needed to induce lesions. Possibly, impaired nociception in the afflicted area results in more vigorous grooming behavior and this, in turn, in a local skin damage.
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PMID:Local skin lesions in the rat after subcutaneous deposition of capsaicin. 1207 68