Characterization of the effects of acute ethanol administration on the release of β-endorphin peptides by the rat hypothalamus

Abstract

In the present studies the direct effect of ethanol on the release of β-endorphin by the rat hypothalamus was investigated. When various concentrations of ethanol (10–120 mM) were added into the incubation medium, it was noticed that though low concentrations of ethanol (10, 20 and 30 mM) induced a pronounced increase in the release of β-endorphin-like peptides from the hypothalamus, high concentrations of ethanol (40, 60 and 120 mM) induced a less pronounced increase. Exposure of hypothalamus to depolarizing concentrations of potassium chloride (following washing of the ethanol), provoked a significant release of β-endorphin-like peptides, regardless of the ethanol concentration the tissues were exposed prior to the stimulation with the potassium chloride. Chromatographic analysis of the incubation media with Sephadex-G-75 revealed that the hypothalamus released mainly β-endorphin-sized peptides. Analysis of the β-endorphin-sized peptides with reverse-phase high performance liquid chromatography indicated the presence of β-endorphin-(1–31) as well as non-acetyl and acetyl β-endorphin-(1–27). Thus ethanol exerts a biphasic effect on the release of β-endorphin-like peptides by the rat hypothalamus, with low concentrations inducing a dose-dependent increase, reaching maximum at 20 mM ethanol, and with higher concentrations of ethanol inducing a less pronounced increase in the release of β-endorphin-like peptides, leading to an inverted U-shaped dose response relationship of ethanol and release of β-endorphin-like peptides from the rat hypothalamus.