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 immunoreacti ve beta-endorphin (IR-beta-EP) secretion from fetal hypothalamic neuro ns 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 secr etion. The primary cultures of fetal hypothalamic neurons were maintai ned for 8-9 days in chemically defined medium and treated for 5 hr wit h 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 re vealed that only 50 mM ethanol caused stimulation of IR-beta-EP secret ion, whereas propanol and butanol did not alter IR-beta-EP response at any given concentration, Pretreatment of these cultures with the cata lase inhibitors, 3-amino-1,2,4,-triazole (3-AT; 1, 5, and 10 mM), caus ed a dose-dependent inhibition of ethanol-stimulated IR-beta-EP secret ion, but did not inhibit dibutyryl cAMP (dcAMP)-stimulated lR-beta-EP secretion. Another catalase inhibitor, sodium azide (5 mM), also inhib ited ethanol-stimulated IR-beta-EP secretion. Measurement of acetaldeh yde production in cultured cells and media after ethanol or dcAMP trea tments revealed that cultured cells produce acetaldehyde only after et hanol treatment and at levels of acetaldehyde (8-24 mu M) that are kno wn to evoke IR-beta-EP release. The catalase inhibitor 3-AT (10 mM) tr eatment 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.