Microinjection of sulpiride into the nucleus accumbens increases ethanol drinking in alcohol-preferring (P) rats

The effects of dopamine antagonists microinjected into the nucleus accumbens (Acb) on alcohol-drinking behavior were studied in the selectively bred alcohol-preferring (P) line of rats. P female rats (N = 8) were given access to food and water ad lib, while availability of a 10% (v/v) ethanol solution was limited to 1 hr/day. After implantation of guide cannulas bilaterally into the Acb and recovery from surgery, the rats were microinjected with either the D1 antagonist SCH 23390 (0.1 to 2.0 micrograms/side), the D2 antagonist sulpiride (0.1 to 2.0 micrograms/side) or vehicle, and ethanol intake was monitored. The D1 antagonist SCH 23390 had little effect on alcohol intake although the 0.5 ug/side dose produced a small increase which was not statistically significant. The D2 antagonist sulpiride increased, in a dose dependent manner, the intake of ethanol to as high as 215% of control values (F(4,28) = 39.9; p < 0.001). Additional experiments indicated that the 2.0 micrograms/side dose of sulpiride did not alter the consumption of a 14% glucose nor a 0.25% saccharin solution. These data suggest that D2 receptors in the Acb are important in the regulation of alcohol drinking by the P line of rats.