Effect of Ethanol, Propanol, Butanol, and Catalase Enzyme Blockers on β‐Endorphin Secretion from Primary Cultures of Hypothalamic Neurons: Evidence for a Mediatory Role of Acetaldehyde in Ethanol Stimulation of β‐Endorphin Release

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Abstract
Previously, we have shown that low closes of ethanol (12.5–100 mm) and acetaldehyde (12.5–50 μm), but not salsolinol, enhanced immunoreactive β‐endorphin (IR‐β‐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‐β‐EP secretion were studied in vitro to determine the role of membrane fluidization and ethanol metabolism on ethanol‐induced IR‐β‐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‐β‐EP from the cultures revealed that only 50 mm ethanol caused stimulation of IR‐β‐EP secretion, whereas propanol and butanol did not alter IR‐β‐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‐stim‐ulated IR‐β‐EP secretion, but did not inhibit dibutyryl cAMP (dcAMP)‐stimulated IR‐β‐EP secretion. Another catalase inhibitor, sodium azide (5 mm), also inhibited ethanol‐stimulated IR‐β‐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 μm) that are known to evoke IR‐β‐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‐β‐EP secretion via conversion of alcohol to acetaldehyde.