Role of taste and calories in the selection of ethanol by C57BL/6NHsd and Hsd:ICR mice.

The C57BL/6 mouse (C57) is used as a model for the human consumption of ethanol. Previous studies on the taste preferences of the C57 mouse indicate that ethanol drinking by this animal is for calories and not for a pharmacological effect. The purpose of this study, therefore, was to further determine the role of calories and taste in the selection of ethanol by the C57 mouse. C57 and outbred Hsd:ICR (ICR or CD-1) mice were housed two per cage with three drinking tubes. A standard 10-day preference test of 3-30% ethanol (v/v) vs. water was performed: the mean maximally preferred concentrations of ethanol were 17.9% for C57 and 6.8% for ICR mice. Once drinking of the preferred concentration for each cage had stabilized at 13.2 and 0.9 g/kg/day, respectively, the third tube was filled with water, 0.5% aspartame, isocaloric dextrose, or diluted chocolate Ultra Slim-Fast plus dextrose. Five days of dextrose or chocolate drink reduced the amount of ethanol consumed by 41% and 44% by C57 mice, but aspartame did not affect their drinking. Additional groups of C57 and ICR mice were habituated to a 2-h limited access to water. When offered a 0.5 mM quinine solution as the only fluid, both strains consumed the same volumes as water. Presentation of a saccharin solution was followed by an i.p. injection of either 0.5 M LiCl or NaCl. When given the saccharin solution 48 h later, the LiCl-treated mice of both strains drank less saccharin. The C57 mouse did not exhibit a LiCl-induced taste aversion when ethanol was the novel solution. As a test of response to novelty, a cork stopper was placed in each cage. The ICR mice gnawed much more of the cork than did the C57 mice. Thus, both C57 and ICR mice learned a taste aversion, but the C57 mouse altered its large consumption of ethanol based on more palatable sources of calories. These data support the earlier concept that the consumption of ethanol represents a preferred source of calories for the C57 mouse. Extrapolation of genetic or biochemical differences between these mice to differences between the human alcoholic and the nonalcoholic should thus be made with caution.