Capsaicin-induced reflex fall in rat blood pressure is mediated by afferent substance P-containing neurones via a reflex centre in the brain stem.
Injection of 0.03 micrograms capsaicin into one femoral artery elicited a fall in blood pressure in the rat. This effect was completely and reversibly abolished following intrathecal injection of 1 nmol of the specific substance P antagonist, [D-Pro2,D-Trp7,9] substance P. The capsaicin-evoked depressor reflex is therefore exclusively mediated by substance P-containing primary afferent fibres. Using spinal rats or decerebration experiments, the centre of the capsaicin-evoked reflex fall in blood pressure could be localized in the brain stem.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001933:Brain Stem / Q000187:drug effects; D002211:Capsaicin / Q000494:pharmacology*; D003655:Decerebrate State; D007269:Injections, Intra-Arterial; D007278:Injections, Spinal; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects*; D051381:Rats; D012018:Reflex / Q000187:drug effects; D013373:Substance P / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D013373:Substance P; C032132:substance P, prolyl(2)-tryptophan(7,9)-; D002211:Capsaicin