Capsaicin-, resiniferatoxin-, and olvanil-induced adrenaline secretions in rats via the vanilloid receptor

Abstract

The effects of capsaicin analogs on adrenaline secretion were investigated in rats. Capsaicin (20-100 μg/kg, iv) caused biphasic adrenaline secretion. Capsazepine (20 mg/kg, iv), a specific competitive antagonist of the vanilloid (capsaicin) receptor, strongly inhibited both phases of adrenaline secretion by capsaicin (50 μg/kg). Next, the effects of two capsaicin analogs on the adrenal catecholamine secretion were examined. Resiniferatoxin (20-200 ng/kg, iv), a naturally occurring phorbolester-like compound, provoked slow onset adrenaline secretion in a dose-dependent manner. Olvanil (2.46-246 g/kg, iv), a synthesized non pungent capsaicin analog, also stimulated delayed catecholamine secretion dose-dependently. Capsazepine (20 mg/kg, iv) pretreatment prevented the resiniferatoxin (50 ng/kg)-and olvanil (24.6 μg/kg)-induced catecholamine secretion. These results suggest that some vanilloids (capsaicin, resiniferatoxin, olvanil) excite adrenaline secretion and such excitation is via the vanilloid receptor.