Local application of capsaicin alleviates mechanical hyperalgesia after spinal nerve transection.
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.
Kim
Sung Min
SM
Department of Physiology, College of Medicine, Hanyang University, 17 Haengdang-Dong, Sungdong-Gu, Seoul 133-791, South Korea.
Kim
Jisang
J
Kim
Eunhyun
E
Hwang
Se Jin
SJ
Shin
Hong Kee
HK
Lee
Seo Eun
SE
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology*; D002452:Cell Count; D003714:Denervation; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D006930:Hyperalgesia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009437:Neuralgia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism; D010147:Pain Measurement; D059348:Peripheral Nerve Injuries; D010525:Peripheral Nerves / Q000187:drug effects* / Q000503:physiopathology; D010523:Peripheral Nervous System Diseases / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D018689:Sensory System Agents / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000378:metabolism
D000700:Analgesics; D015415:Biomarkers; D018689:Sensory System Agents; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin