Early Social Isolation in Male Long-Evans Rats Alters Both Appetitive and Consummatory Behaviors Expressed

Background: Postweaning social isolation in rats produces profound and long-lasting cognitive and behavioral deficits in adult animals. Importantly, this housing manipulation alters sensitivity to a number of drugs of abuse including ethanol. However, most studies with ethanol have utilized continuous or limited home-cage access to examine interactions between juvenile social experience and drinking. More recently, social isolation was shown to increased ethanol respond-ing in a ‘‘dipper’ ’ model of self-administration (Deehan et al., 2007). In the current study, we utilize a ‘‘sipper’ ’ operant self-administration model to distinguish the effects of isolation rearing on ethanol seeking- and drinking-related behaviors. Methods: Postweaning juvenile male Long-Evans rats were placed into 2 housing groups for 6 weeks: one group consisted of individually housed animals; the second group was housed 4 animals per cage. Following the isolation period, anxiety-like behavior was assessed to confirm the efficacy of the isolation procedure. In some animals, ethanol drinking in the home cage was assessed using a continuous access, 2-bottle choice paradigm. All animals were then individually housed and trained to lever-press for a sipper tube containing either an ethanol solution or a sucrose solution