Topical capsaicin treatment suppresses formalin-induced fos expression in rat spinal cord.
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.
Zhang
M
M
Department of Physiology, Beijing Medical University, China.
Ji
R R
RR
Fang
Y
Y
Han
J S
JS
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*
D016760:Proto-Oncogene Proteins c-fos; D005557:Formaldehyde; D002211:Capsaicin