Chronic Ethanol Administration Decreases 5‐HT and Increases 5‐HIAA Concentration in Rat Brain

Abstract

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 ethanol administration caused a slight fall (by 13%) in 5-HT concentration and a slight increase (by 10%) in 5-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<0.01) and in that containing pons and medulla oblongata (by 37%; P<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<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.