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

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