Prazosin reduces alcohol drinking throughout prolonged treatment and blocks the initiation of drinking in rats selectively bred for high alcohol intake.

BACKGROUND: This study examined whether prazosin reduces alcohol drinking over the course of prolonged treatment and whether it blocks the initiation of alcohol drinking in rats with a genetic predisposition toward high alcohol drinking, that is alcohol-preferring (P) rats. METHODS: In study one, alcohol-experienced P rats that had been drinking alcohol for 2 h/d for several months were treated daily with prazosin (0, 0.5, 1.0, or 2.0 mg/kg body weight [BW]) for 7 weeks. In study two, alcohol-naïve P rats were treated daily with prazosin (0, 1.0, or 2.0 mg/kg BW) for 2 weeks prior to, or concomitantly with, the initiation of alcohol access and throughout 3 weeks of alcohol availability. Prazosin treatment and alcohol access were then discontinued for 2 weeks followed by reinstatement of alcohol access without prazosin treatment for 4 weeks, followed by resumption of daily prazosin treatment (2.0 mg/kg BW) for 3 weeks. RESULTS: Prazosin reduced alcohol drinking throughout 7 weeks of treatment in P rats accustomed to drinking alcohol. Following termination of prazosin treatment, alcohol drinking slowly returned to pretreatment baseline. Reduced alcohol intake was accompanied by increased water intake. In alcohol-naïve P rats, prazosin administration prior to the first opportunity to drink alcohol and throughout 3 weeks of alcohol access retarded acquisition of alcohol drinking and reduced the amount of alcohol consumed. When prazosin was administered concomitantly with the first opportunity to drink alcohol, it abolished acquisition of alcohol drinking. Discontinuation of prazosin treatment allowed expression of a genetic predisposition toward high alcohol drinking to gradually emerge. Prazosin retained the ability to reduce alcohol intake with repeated treatments. CONCLUSIONS: Prazosin decreased alcohol drinking during prolonged treatment and may be useful for treating alcoholism and alcohol-use disorders. Prazosin may also be useful for deterring the initiation of drinking in individuals with a family history of alcoholism.