The effect of capsaicin on C-fiber reflex and heat evoked discharge in the acute spinal cat.
The effects of capsaicin were studied electrophysiologically on C-fiber reflex and heat-evoked discharge in adult spinal cats. The results can be summarized as follows: 1) 125 micrograms/Kg of capsaicin, administered intravenously, induced an increase in spontaneous discharge in the L7 ventral root; 2) 250 micrograms/Kg of capsaicin, administered intravenously, induced an increase in the C-fiber reflex response; 3) 125 micrograms/Kg of capsaicin, administered intravenously, induced an increase in the heat-evoked discharge; but 4) 25 micrograms/Kg of capsaicin, administered through the femoral artery, did not show significant alteration of the heat-evoked discharge. These findings suggest that capsaicin which produced a release of substance-P from primary afferent nerves may principally act on C-fiber and A delta-fiber. Capsaicin was much more effective on the heat-evoked discharge than on the C-fiber reflex when administered intravenously.
D000344:Afferent Pathways / Q000187:drug effects; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects*; D009413:Nerve Fibers, Myelinated / Q000187:drug effects; D010543:Peroneal Nerve / Q000187:drug effects; D012018:Reflex / Q000187:drug effects*; D013126:Spinal Nerve Roots / Q000187:drug effects*; D013373:Substance P / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects*; D013823:Thermoreceptors / Q000187:drug effects*
D013373:Substance P; D002211:Capsaicin