Spontaneous and Ethanol‐Stimulated In Vitro Release of β‐Endorphin by the Hypothalamus of AA and ANA Rats

Abstract

Previous studies demonstrated that both the spontaneous and ethanol-stimulated release of beta-endorphin (beta-EP) like-peptides (beta-EPLPs) by the hypothalami of the ethanol-preferring C57BL/6 mice is more pronounced than by the hypothalami of the ethanol-avoiding DBA/2 mice. The objective of the present studies was to investigate the effects of various concentrations of ethanol on the in vitro release of beta-EP peptides by the hypothalami of the ethanol-preferring Alko-Alcohol (AA) and ethanol-avoiding Alko Non-Alcohol (ANA) lines of rats. Results indicated that although the spontaneous release of hypothalamic beta-EPLPs was higher by the ANA than by the AA rats, the percentage increase following exposure to various concentrations of ethanol was similar in both lines of rats. Furthermore, the release of hypothalamic beta-EPLPs following exposure to 30 mM ethanol was significantly higher than the release following exposure to 10 mM ethanol in the AA, but not the ANA, rats. Analysis of the released beta-EPLPs with Sephadex G-75 and reversed phase HPLC indicated that the nonacetylated beta-EP 1-31 was the major component in the hypothalamic perifusates of the AA rats, whereas the shorter and acetylated forms of beta-EP were the predominant components in the hypothalamic perifusates of the ANA rats. Because the shorter and acetylated forms of beta-EP are devoid of opioid activity, their pronounced release by the hypothalami of the ANA rats may be important in maintaining their low ethanol consumption, even after long-term access to ethanol solutions.