Early social isolation increases persistence of alcohol-seeking behavior in alcohol-related contexts.

Social conditions during rearing are well known to affect adult alcohol consumption, but few experiments have explored the effects of social conditions on behaviors that are related to alcohol dependence, such as the persistence of alcohol seeking. This study compared the effects of isolation (ISO) and interaction (INT) rearing on the persistence of alcohol-seeking behavior. Rats were trained to lever press for a solution of 10% alcohol diluted in water. They were then exposed to a two-component multiple schedule of reinforcement (baseline). Responses in one component were reinforced by a higher rate of alcohol delivery (rich component, variable interval 15 s) and responses in the other component were reinforced by a lower rate of delivery (lean component, variable interval 45 s). The persistence of lever pressing in the presence of each stimulus was then assessed during extinction. The results from baseline showed that response rates in rats in both groups were higher in the rich component than in the lean component, but ISO rats responded significantly more than INT rats in both components. The persistence of responding during extinction in ISO rats in both components was also higher than that in INT rats. The results show that effects of ISO are not restricted to alcohol consumption, but also affect persistence of alcohol-seeking behavior, which may reflect differences in the value of drug-related stimuli.