Alcohol intake in the rat after lowering brain 5-hydroxtryptamine content by electrolytic midbrain raphé lesions, 5, 6-dihydroxytryptamine or p-chlorophenylalanine.

Voluntary alcohol consumption was measured in male albino rats after selectively lowering their brain 5-hydroxytryptamine concentration (an AA strain of rats was used, selectively outbred for its high alcohol consumption). The brain 5-hydroxytryptamine concentration was reduced using three different techniques: electrocoagulation of the dorsal and median raphé nuclei of the midbrain; injection of 75 mug of 5,6-dihydroxytryptamine into the lateral cerebral ventricle; and oral administration of 300 mg/kg/day p-chlorophenylalanine as a 0.5 per cent carboxymethylcellulose suspension, for 12 days. The first two methods did not markedly affect alcohol consumption despite a sizable decrease in the brain 5-hydroxytryptamine level: 69 per cent in the raphé-lesioned group and 31 per cent in the 5,6-dihydroxytryptamine-treated group. Intraperitoneal injection of 50 mg/kg L-5-hydroxytryptophan on five successive days resulted in a non-significant decrease in alcohol consumption by the 5,6-dihydroxytryptamine-treated rats. p-Chlorophenylalanine did reduce significantly alcohol drinking but it had a greater effect in increasing water intake, producing a net rise in total fluid consumption. The reduction in alcohol consumption, therefore, was probably an indirect result of the treatment. These findings raise doubts about the previously suggested relationships between brain serotonin depletion and alcohol drinking.