Voluntary beer drinking in rats.

Female Long-Evans rats (N = 30) were tested for individual preference for beer for a 24 h period and then assigned to beer (BR) (N = 15) or control (CT) (N = 15) groups according to preference. BR animals were allowed ad libitum access to beer, food and water; while CT animals were allowed ad libitum access to food and water for a 21 day period. Beer, food and water consumption levels were recorded daily. Animals were weighed every other day. Blood alcohol levels and pattern of drinking (comparison of beer consumption in light versus dark cycles) were measured in a separate set of animals. At the end of 21 days of drinking, beer was withdrawn from the BR group and all animals were observed for withdrawal symptomology. BR animals ate more food than CT animals days 2 through 13, and then ate less than CT on days 17 through 21. BR animals drank more "total water" (drinking water plus water in beer) than CT. Body weights were not affected. Changes in body temperatures and tail flick latency, and notation of hyperactivity, shivering and tremoring during 8 hours of withdrawal indicated that BR animals were dependent on alcohol.