THE EFFECTS OF CHRONIC ETHANOL EXPOSURE ON N-METHYL-D-ASPARTATE-STIMULATED OVERFLOW OF [H-3] CATECHOLAMINES FROM RAT-BRAIN

The effects of acute and chronic ethanol administration on N-methyl-D-aspartate-stimulated catecholamine overflow were examined. Three groups of male Sprague-Dawley rats were used. The first group received a chronic liquid diet containing ethanol (37%) for 3 weeks. The second group was pair-fed a liquid diet with dextrin substituted for ethanol isocalorically. The third group received Purina rat lab chow and water ad libitum. N-methyl-D-aspartate-stimulated [H-3]catecholamine overflow from brain tissue slices was determined. N-methyl-D-aspartate (50-2000-mu-M) produced a concentration-dependent increase in [H-3]norepinephrine overflow from cortical and hippocampal slices with no significant alteration of the response following chronic ethanol treatment. [H-3]Dopamine overflow from striatal slices of the chronic ethanol group was significantly different at 1000-mu-M N-methyl-D-aspartate. The response of the chronic ethanol-treated group at the 1000-mu-M N-methyl-D-aspartate concentration was 30% and 40% lower than the pair-fed and ad libitum controls, respectively. Ethanol when added in vitro (30-200 mM) produced a concentration-dependent inhibition of N-methyl-D-aspartate (150-mu-M) stimulated efflux in all brain regions, and chronic ethanol treatment did not alter the inhibitory response. These results indicate an apparent lack of adaptation in N-methyl-D-aspartate-stimulated transmitter release following chronic ethanol treatment in this particular paradigm.