Effects of serotonin depletion on the volitional alcohol intake of rats during a condition of psychological stress

Non-preferred solutions of ethyl alcohol, that were slightly above preference threshold, were offered together with water to rats which were trained to avoid foot shock by pressing a lever. Intake of alcohol increased significantly when the rats were stressed by intermittent, random unavoidable shock. When levels of brain serotonin were lowered by p-chlorophenylalanine (pCPA), a potent inhibitor of tryptophan hydroxylase, the selection of alcohol declined during the period of random punishment to the pre-stress baseline intakes. The depletion of serotonin during the stress period reduced alcohol preference particularly in those rats which drank the largest amounts of alcohol. These findings extend those of an earlier report that pCPA lowers alcohol intake in non-stressed rats which drank alcohol solutions within the normal range of preference.