EFFECT OF ETHANOL, PROPANOL, BUTANOL, AND CATALASE ENZYME BLOCKERS ON BETA-ENDORPHIN SECRETION FROM PRIMARY CULTURES OF HYPOTHALAMIC NEURONS - EVIDENCE FOR A MEDIATORY ROLE OF ACETALDEHYDE IN ETHANOL STIMULATION OF BETA-ENDORPHIN RELEASE

Previously, we have shown that low doses of ethanol (12.5-100 mM) and acetaldehyde (12.5-50 mu M), but not salsolinol, enhanced immunoreactive beta-endorphin (IR-beta-EP) secretion from fetal hypothalamic neurons in primary culture. In this study, the effects of ethanol, propanol, and butanol, as well as the effect of catalase inhibitors on IR-beta-EP secretion were studied in vitro to determine the role of membrane fluidization and ethanol metabolism on ethanol-induced IR-beta-EP secretion. The primary cultures of fetal hypothalamic neurons were maintained for 8-9 days in chemically defined medium and treated for 5 hr with ethanol (50 mM), propanol (25 and 50 mM), and butanol (25 and 50 mM). Determination of hourly secretion of IR-beta-EP from the cultures revealed that only 50 mM ethanol caused stimulation of IR-beta-EP secretion, whereas propanol and butanol did not alter IR-beta-EP response at any given concentration, Pretreatment of these cultures with the catalase inhibitors, 3-amino-1,2,4,-triazole (3-AT; 1, 5, and 10 mM), caused a dose-dependent inhibition of ethanol-stimulated IR-beta-EP secretion, but did not inhibit dibutyryl cAMP (dcAMP)-stimulated lR-beta-EP secretion. Another catalase inhibitor, sodium azide (5 mM), also inhibited ethanol-stimulated IR-beta-EP secretion. Measurement of acetaldehyde production in cultured cells and media after ethanol or dcAMP treatments revealed that cultured cells produce acetaldehyde only after ethanol treatment and at levels of acetaldehyde (8-24 mu M) that are known to evoke IR-beta-EP release. The catalase inhibitor 3-AT (10 mM) treatment reduced ethanol-evoked acetaldehyde production. These results suggest for the first time that the catalase-H2O2 system is functional in the cultured hypothalamic neurons and is involved in mediation of ethanol's effects on IR-beta-EP secretion via conversion of alcohol to acetaldehyde.