title: Topical capsaicin treatment suppresses formalin-induced fos expression in rat spinal cord.
abstract: Capsaicin (Cap) is a pharmacological tool to inactivate nociceptive afferents. The present study was undertaken to investigate the effects of topical application of Cap to sciatic nerve on the formalin-induced expression of proto-oncogene proteins c-fos in the rat spinal cord using immunohistochemical display of fos-like protein. In rats subjected to formalin injection into the hind paw, numerous fos-like immunoreactivity (FLI) neurons were found in the spinal dorsal horn, with heavy labeling in laminae I-II and V-VI. Following pretreatment of Cap, formalin-induced FLI expression was significantly abolished. It was suggested that activation of Cap-sensitive unmyelinated nociceptive afferents following formalin injection was primarily responsible for the activation of c-fos gene. Our data also provided further evidence supporting that topical application was an effective way to block the transmission of noxious primary afferents.
authors.affiliation: Department of Physiology, Beijing Medical University, China.
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: R R
authors.initials: RR
authors.lastname: Ji
authors.forename: Y
authors.initials: Y
authors.lastname: Fang
authors.forename: J S
authors.initials: JS
authors.lastname: Han
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D005260:Female; D005557:Formaldehyde; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000502:physiology; D013116:Spinal Cord / Q000378:metabolism*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D005557:Formaldehyde; D002211:Capsaicin