Effects of D1 and D2 dopamine receptor agents on ethanol consumption in the high-alcohol-drinking (HAD) line of rats.

Dopamine receptor agonists and antagonists were tested for effects on alcohol drinking in female HAD rats (n = 10) given limited access (4 h/day) to a 10% (v/v) ethanol solution. Food and water were available ad libitum. Subcutaneous drug injections were given 30-60 min before the ethanol access periods. The D2 agonist quinpirole (0.04-2.0 mg/kg) caused a dose-dependent decrease in alcohol drinking throughout the 4-h period. Spiperone, a D2 antagonist, had no effect during the initial part of the session, but by the fourth hour, the 10 micrograms/kg dose tended to increase alcohol intake and the 30 micrograms/kg dose reduced intake. The D1 antagonist SCH-23390 (3-30 micrograms/kg) dose-dependently decreased ethanol drinking during the first hour of access. The D1 agonist SKF-38393 (2-6 mg/kg) also decreased alcohol intake, but it was less effective than SCH-23390. The findings implicate both D1 and D2 receptors in the reinforcing effects of alcohol drinking by the HAD line of rats.