Seminatural housing increases subsequent ethanol intake in male Maudsley reactive rats

Objective: Previous studies of ethanol (EtOH) intake under spontaneous choice conditions in Maudsley Reactive (MR) rats have demonstrated marked variability in EtOH preference. The present study investigated whether the social housing environment during the juvenile and early adult period would influence subsequent EtOH intake in male MR rats. Method: Rats were assigned to isolation, group housing in typical laboratory cages, or to a seminatural enclosure setting (1 x 2 m) at approximately 42 days of age and were maintained there for 16 weeks. Rats were then singly housed and exposed to a 2-bottle choice of 10% (v/v) EtOH versus tap water for 8 weeks. Results: MRs housed in the seminatural setting drank some three times the level of EtOH consumed by isolate or group housed rats with regard to both preference ratio and intake of pure EtOH relative to body weight. Conclusions: A number of factors are hypothesized to account for the increased consumption of EtOH in rats housed in the seminatural setting, including differences in social dynamics across settings, and switching from a large physical space to a smaller isolated space. The results demonstrate that environmental factors can significantly modify the tendency to drink excessive amounts of EtOH in an inbred strain showing some preference for EtOH.