Rodent lines selected for factors affecting alcohol consumption.

The selectively bred alcohol-preferring P and alcohol-nonpreferring NP lines of rats have been used to study the biology of alcohol-seeking behavior. The P rats satisfy all the perceived criteria for an animal model of alcoholism: free-fed animals voluntarily drink alcoholic solutions (10-30% v/v) to intoxication; they acquire metabolic and neuronal tolerance, and develop physical dependence; they work (bar-press) to obtain the alcohol and self-administer ethanol intragastrically. Drinking in the P rats ceases when blood alcohol concentrations (BACs) reach 50-70 mg%, but BACs subsequently rise to as high as 270 mg%. BACs, 15-70 mg%, elicit increased spontaneous motor activity in the P rats, but not in the NP rats. Acute tolerance to a single hypnotic dose of ethanol develops more rapidly and persists many days longer in the P than in the NP rats. These differences in the effects of ethanol may underlie the disparate alcohol drinking behaviors of the P and NP rats. The P rats also exhibit lowered serotonin levels in certain brain regions. Serotonin reuptake inhibitors curtail the alcohol drinking of the P rats, suggesting a role for serotonin in alcohol preference.