Effects of chronic ethanol intake at a low dose on the rat brain dopaminergic system

The effects of 8-week ethanol treatment (3% v/v in drinking water) on the rat brain dopaminergic system were investigated. Chronic ethanol consumption induced a significant increase in the number of dopamine D1 receptor sites in the caudate putamen. Conversely, no significant changes were observed in D2 receptor density or affinity. Biochemical results were in agreement with behavioral data, as amphetamine-induced locomotor hyperactivity was significantly higher in ethanol-treated rats in comparison to controls. Moreover, grooming behavior in response to SKF 38393, a selective agonist of D1 receptors was potentiated in ethanol-treated rats, whereas locomotor hyperactivity induced by LY 171555 (a selective agonist of D2 receptors) was not affected by ethanol treatment. The results indicate that changes in dopamine receptors may occur in the central nervous system at levels of ethanol intake that do not induce tolerance or dependence.