Beer consumption in rats: The influence of ethanol content, food deprivation, and cocaine

A series of experiments examined various aspects of beer consumption in mal e Wistar rats. In the First experiment, rats were given home cage access to either beer or ethanol solutions under free access conditions. It was foun d that rats consumed greater amounts of moderate strength beer (2.7% ethano l by volume) or regular strength beer (5.0% ethanol) than equivalent dilute ethanol solutions in water. Consumption of 2.7% beer was greater than 5.0% beer and access to either beer, but not dilute ethanol, solutions caused s ubstantial increases in total fluid intake per day. In the second experimen t, individual rats given daily 30-min drink sessions consumed more 2.7% bee r than 3.85% beer and more 3.85% than 5.0% beer. A "hangover" effect was ev ident after the first day of consumption of 5.0% beer with subsequent intak e of this beer suppressed after high intake on first exposure. Intake of th e low-strength beer approached intake of isocaloric (8.6%) sucrose solution . In a third experiment, a lick-based progressive ratio paradigm was implem ented where rats had to emit progressively greater number of licks for a fi xed volume (0.1 ml) of 2.7% beer or 8.6% sucrose. Using this paradigm, it w as shown that food deprivation increased the motivation to consume beer and sucrose as shown by elevated break points (the highest ratio reached). Foo d deprivation also increased locomotor activity in the drinking environment . In contrast, cocaine (20 but not 18 mg/kg) caused a decrease in the break point for sucrose and beer, an effect probably mediated by the anorexic pr operties of the drug. It is concluded that rats will avidly consume beer, p articularly of moderate alcohol content, but that such consumption may be m ediated more by the nutritive and palatable characteristics of the beer rat her than by the psychoactive effects of the alcohol it contains. (C) 1998 E lsevier Science Inc.