Microinjection of a corticotropin-releasing factor antagonist into the central nucleus of the amygdala reverses anxiogenic-like effects of ethanol withdrawal

Abstract

Previous studies have shown that spontaneous exploration of the Elevated Plus Maze provides a sensitive measure of 'anxiety' induced by pharmacological or behavioral stressors. In particular, the percent time spent exploring the open arms of the plus maze is decreased during ethanol withdrawal, and this effect is antagonized by intracerebroventricular administration of 25 micrograms of alpha-helical CRF, a corticotropin-releasing factor antagonist (H.A. Baldwin et al., Psychopharmacology, 103 (1991) 227-232). The present study was designed to examine the effect of alpha-helical CRF infusion within the central nucleus of the amygdala during ethanol withdrawal. Rats were made dependent on ethanol by maintenance on an ethanol-containing liquid diet for 16 days, withdrawn from ethanol and tested on the elevated plus maze at 8 h post-ethanol access. In comparison with pair-fed control rats, ethanol withdrawn subjects spent significantly less percent time exploring the open arms of the plus maze. This decrease in open arm exploration was antagonized by administration of alpha-helical CRF (250 ng) bilaterally into the central nucleus of the amygdala, but not by intracerebroventricular administration of 250 ng of alpha-helical CRF. The ability of intra-amygdala alpha-helical CRF to antagonize decreased open arm exploration is unlikely to be due to changes in motor activity, since general activity on the maze was reduced in all EtOH withdrawal groups. These results suggest that the central nucleus of the amygdala may be an effective site for endogenous CRF systems to mediate anxious behavior associated with ethanol withdrawal.