Capsaicin, a pungent principle of hot red pepper, evokes catecholamine secretion from the adrenal medulla of anesthetized rats.

Using a direct monitoring system for catecholamine (CA) secretion into the adrenal vein, we have demonstrated that capsaicin (CAP) evokes CA secretion from the adrenal medulla of pentobarbital-anesthetized rats. A significant increase in epinephrine (E) secretion was seen in rats infused with CAP (200 micrograms/kg, i.v.) without a detectable lag after the infusion. Norepinephrine (NE) secretion evoked by CAP was fairly weak compared with E secretion. The secretion of E evoked by CAP was dose-amount dependent. The stimulation of E release by CAP was barely detectable at 20 micrograms/kg, half-maximal at 100 micrograms/kg, and maximal at 600 micrograms/kg. When CAP (200 micrograms/kg) was infused into rats, the weight-ratio of E to NE was significantly higher (47.6) than when acetylcholine (12.5 micrograms/kg) was infused (13.0). These results indicate that CAP can evoke CA secretion from the adrenal medulla of rats.