Ethanol preference in Maudsley and RXNRA recombinant inbred strains of rats

Abstract 

Male and female rats of the Maudsley Reactive (MR/Har) and the Maudsley Nonreactive (MNRA/Har substrain), as well as four of the RXNRA recombinant inbred (RI), strains were tested for ethanol intake and preference across 6 weeks of two-bottle choice between 10% ethanol (vol./vol.) and water. In Experiment 1, after exposure to 10% ethanol as their sole source of fluid for 4 days before the onset of the two-bottle choice, MR/Har rats showed a higher preference for ethanol than that observed for all other strains. Three of the RI strains of rats showed a preference intermediate between that for MR/Har and MNRA/Har rats, and one RI strain of rat (BD) drank reliably less than the amount consumed by other strains. In Experiment 2, ethanol-naive rats exhibited lower ethanol intake and preference than in Experiment 1, and strain differences were minimal, with the exception that BD rats drank less ethanol than that consumed by all other rat strains. In both experiments, female rats drank more ethanol than did male rats across nearly all strains. Marked differences in ethanol consumption between Experiments 1 and 2 support earlier work showing that forced exposure to ethanol increases later intake, but that this effect is strongly influenced by genotype and gender such that MR/Har rats exhibited this change, but MNRA/Har rats did not. The patterns of strain differences in ethanol consumption were consistent with their determination by a polygenic system.

Keywords:  Ethanol preference, Recombinant-inbreds, Sex differences, Maudsley rats, Ethanol experience