Chronic ethanol administration decreases 5-HT and increases 5-HIAA concentration in rat brain

The effect of acute and chronic ethanol administration on cerebral 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations of male Sprague-Dawley and Wistar rats was studied. Acute HIAA concentration one hour after administration. In chronically treated rats the whole brain 5-HT concentration was decreased by 9% during ethanol intoxication. This fall was significant in the part of brain containing diencephalon, mesencephalon and telencephalon except cortex (by 23%; P less than 0.01) and in that containing pons and medulla oblongata (by 37%; P less than 0.001) but not in cerebral cortex. The cerebral 5-HIAA concentrations of chronically treated Wistar and Sprague-Dawley rats were increased during intoxication (4--6 hrs after last ethanol administration) and even more during withdrawal (16--18 hrs after last ethanol administration, by 24--58%; P less than 0.05--0.01). The increase was observed in all three parts into which the brain of Wistar rats were dissected. Because ethanol did not further increase the probenecid induced elevation of cerebral 5-HIAA concentration, our results suggest that ethanol increases the cerebral 5-HIAA concentration by attenuating its removal from the brain.