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

A series of experiments examined various aspects of beer consumption in male Wistar rats. In the first experiment, rats were given home cage access to either beer or ethanol solutions under free access conditions. It was found that rats consumed greater amounts of moderate strength beer (2.7% ethanol 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 substantial increases in total fluid intake per day. In the second experiment, individual rats given daily 30-min drink sessions consumed more 2.7% beer than 3.85% beer and more 3.85% than 5.0% beer. A "hangover" effect was evident after the first day of consumption of 5.0% beer with subsequent intake of this beer suppressed after high intake on first exposure. Intake of the low-strength beer approached intake of isocaloric (8.6%) sucrose solution. In a third experiment, a lick-based progressive ratio paradigm was implemented where rats had to emit progressively greater number of licks for a fixed volume (0.1 ml) of 2.7% beer or 8.6% sucrose. Using this paradigm, it was shown that food deprivation increased the motivation to consume beer and sucrose as shown by elevated break points (the highest ratio reached). Food deprivation also increased locomotor activity in the drinking environment. In contrast, cocaine (20 but not 10 mg/kg) caused a decrease in the break point for sucrose and beer, an effect probably mediated by the anorexic properties of the drug. It is concluded that rats will avidly consume beer, particularly of moderate alcohol content, but that such consumption may be mediated more by the nutritive and palatable characteristics of the beer rather than by the psychoactive effects of the alcohol it contains.