Effects of dopaminergic agonists and antagonists on the serum prolactin levels in alcoholized rats.

A single dose of ethanol (1 g/kg p.o.) significantly decreased, whereas higher doses of ethanol (2 or 3 g/kg p.o.) significantly increased the serum prolactin (PRL) concentration. Administration of ethanol at a dose of 2 g/kg p.o. for 4 weeks did not affect this parameter but the ethanol withdrawal syndrome caused a significant rise in the serum PRL level. Chronic studies showed that D1-dopaminergic agonist SKF 38390 (2.5 mg/kg) significantly raised serum PRL levels in rats. This effect was reversed by long-lasting treatment of rats with ethanol and ethanol withdrawal. Pimozide (1 mg/kg), D2 antagonist, increased PRL in those rats. On the other hand, D1-antagonist SCH 23390 (0.5 mg/kg) and D2-agonist PPHT (0.5 mg/kg) were without effect in rats administered ethanol for a long period of time. In rats with ethanol withdrawal syndrome, administration of D1-antagonist SCH 23390 (0.5 mg/kg) also did not affect the serum PRL concentrations. However, D1-agonist SKF 38393 (2.5 mg/kg) and D2-antagonist pimozide (1 mg/kg) increased the serum PRL level in rats with ethanol withdrawal syndrome, whereas D2 agonist PPHT (2 mg/kg) decreased PRL level in serum. Thus, the acute effect of ethanol on PRL level appears to be dose-dependent. It seems that chronic ethanol administration and its withdrawal especially affected D1 receptor.