Local application of capsaicin alleviates mechanical hyperalgesia after spinal nerve transection.

Abstract	Whether modulation of C afferent fiber activities could relieve peripheral neuropathic pain was tested. After establishment of neuropathic pain induced by L5 and 6 spinal nerve transection (SNT), the sciatic nerve was treated with 2% capsaicin at the level of the midthigh. Mechanical hyperalgesia (von Frey filaments) was significantly alleviated from 7 days to 4 weeks after capsaicin treatment, but cold allodynia (acetone) was unchanged. Immunohistochemical studies showed a significant increase in the number of calcitonin gene-related peptide (CGRP)-positive neurons, but not TRPV1-positive neurons in intact L4 dorsal root ganglia after SNT. Capsaicin treatment decreased TRPV1- and CGRP-positive neurons in L4 DRG of the treated side, but not the opposite side. These results suggest that local application of capsaicin onto the sciatic nerve can alleviate mechanical hyperalgesia, but not cold allodynia, in a peripheral neuropathic pain model and the pain alleviation may result from a decrease of TRPV1- and CGRP-positive sensory neurons of which fibers pass through the sciatic nerve.
Authors	Sung Min Kim, Jisang Kim, Eunhyun Kim, Se Jin Hwang, Hong Kee Shin, Seo Eun Lee
Journal	Neuroscience letters (Neurosci Lett) Vol. 433 Issue 3 Pg. 199-204 (Mar 15 2008) ISSN: 0304-3940 [Print] Ireland
PMID	18242851 (Publication Type: Journal Article)
Chemical References	Analgesics Biomarkers Sensory System Agents TRPV Cation Channels Trpv1 protein, rat Calcitonin Gene-Related Peptide Capsaicin
Topics	Analgesics (pharmacology) Animals Biomarkers (analysis, metabolism) Calcitonin Gene-Related Peptide (metabolism) Capsaicin (pharmacology) Cell Count Denervation Ganglia, Spinal (drug effects, metabolism, physiopathology) Hyperalgesia (drug therapy, metabolism, physiopathology) Male Nerve Degeneration (metabolism, physiopathology) Neuralgia (drug therapy, metabolism, physiopathology) Neurons, Afferent (drug effects, metabolism) Pain Measurement Peripheral Nerve Injuries Peripheral Nerves (drug effects, physiopathology) Peripheral Nervous System Diseases (drug therapy, metabolism, physiopathology) Physical Stimulation Rats Rats, Sprague-Dawley Sensory System Agents (pharmacology) TRPV Cation Channels (metabolism)

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