Genetics of alcoholism: Simultaneous presentation of a chocolate drink diminishes alcohol preference in high drinking HAD rats

Abstract

Through selective crossbreeding of the N/Nih heterogeneous stock of rats, two genetic lines of rats have been developed that are categorized by their preference for ethyl alcohol as high alcohol drinking (HAD) and low alcohol drinking (LAD) animals. Corresponding to other strains of rat bred for alcohol selection or rejection, they were subdivided on the basis of their intake of a solution of 10% alcohol vs. water. The present experiments were designed to determine whether the HAD-1 and LAD-1 lines are similar to the P and NP rats in their profile of alcohol consumption. Five successive three-bottle preference tests for alcohol drinking in the presence of water were undertaken in both HAD ( n = 9) and LAD ( n = 10) rats as follows: 10% alcohol for 5 days; 3–30% concentrations of alcohol increased over 11 days; the maximally preferred concentration of alcohol for 5 days; this maximally preferred concentration of alcohol plus either chocolate Slender for 5 days, or an aspartame solution for 5 days. The intake of alcohol of the LAD rats during the 10% test was 0.4 g/kg/day, whereas during the 3–30% test, the maximum intake was 1.7 g/kg/day; their maximally preferred concentrations ranged between 7% and 9% alcohol. In contrast, the intake of 10% alcohol of the HAD rats was 6.5 g/kg/day, whereas during the 3–30% test the mean daily intake was 6.6 g/kg/day; the maximally preferred solutions of the HAD rats ranged between 13 to 20%, with the mean maximum intake of 10.57 g/kg/day reached at the 20% concentration. Thus, the use of a single concentration of alcohol such as 10% to ascertain preference for alcohol for these lines of rat is not an optimal procedure. In the presence of both the chocolate drink and aspartame, the intakes of the preferred concentration of alcohol of the HAD rats declined markedly, whereas the limited drinking of the LAD rats was unaffected by either palatable fluid. These results differ with those of the P line of rats which sustained their high preference for alcohol even in the presence of the same palatable solutions. Therefore, gustatory factors associated with the sensory quality of the fluids overrode the characteristic preference of the HAD rats for a pharmacologically efficacious solution of alcohol.