Acute ethanol exposure increases norepinephrine (NE) turnover both centrally and peripherally. One of the mechanisms by which ethanol could increase NE turnover is by increasing spontaneous NE release. The effect of ethanol on spontaneous NE release was investigated using tritium release from l-[3H]NE-labeled vasa deferentia as an index of NE release. Ethanol, 65 mM, increased spontaneous tritium release by 8% and pargyline, 100 mg/kg b.wt., pretreatment increased the ethanol effect by 63%. Ethanol alone (22 mM) had no effect on tritium release; however, with pargyline pretreatment tritium release increased by 13%. Combined reserpine, 5 mg/kg, and pargyline, 100 mg/kg, abolished these ethanol effects. Preincubation with tyramine, 1.8 microM, and omitting calcium from Krebs-bicarbonate buffer also abolished the ethanol effect. Butanol and propanol were more potent and methanol less potent than ethanol in increasing spontaneous tritium release. The mechanism consistent with all the above observations is that ethanol increases spontaneous exocytosis due to a nonspecific effect on presynaptic and vesicular membranes.