EFFECT OF INTRACEREBROVENTRICULAR ADMINISTRATION OF METHIONINE-ENKEPHALIN ON THE STRESS-INDUCED SECRETION OF CORTICOSTERONE IN MICE

Ether stress or intracerebroventricular (i.c.v.) administration of saline, met‐enkephalin, or naltrexone raised plasma corticosterone levels in mice. The response to ether stress was abolished by a preceding ether stress or by pretreatment. with i.c.v. saline or naltrexone. However, following i.c.v. met‐enkephalin, plasma corticosterone was significantly elevated by ether stress, the effect being blocked by simultaneous injection of met‐enkephalin and naltrexone. Met‐enkephalin appears to prevent fast‐feedback inhibition of the hypothalamus‐pituitary‐adrenal system. 1979 British Pharmacological Society