Chronic ethanol treatment: Effects on the activation of brain beta-endorphin system by novelty

Abstract

Chronic ethanol ingestion in rats abolishes novelty-induced antinociception, as measured by a tailflick method. This treatment also inhibited the posttraining facilitatory effect of naloxone and the posttraining amnesic effect of β-endorphin in a step-down inhibitory avoidance task. Measurement of hypothalamic β-endorphin-like immunoreactivity (β-EPLIR) shows that there is a decrease in the levels of this peptide in chronic ethanol-treated rats. Exposure to a novel situation, which causes a decrease of β-EPLIR in control (water-treated) rats, had no effect in ethanol-treated rats. Taken together, these results suggest that chronic ethanol treatment decreases hypothalamic β-endorphin levels and makes this system unresponsive to novelty. © 1991, Psychonomic Society, Inc.. All rights reserved.