Individual differences in novelty-induced activity and the rewarding effects of novelty and amphetamine in rats.

Previous work has shown that individual differences in locomotor behavior in an inescapable novel environment predict the locomotor-stimulant effect of amphetamine. Experiment 1 of the present study assessed if novelty-seeking behavior in a free choice situation also predicts the locomotor-stimulant effect of amphetamine. Rats were first assessed for their locomotor response to an inescapable novel environment and then were allowed to choose between this environment (familiar) and a novel environment. Activity in the inescapable novel environment was found to predict subsequent locomotor response to amphetamine, but approach to novelty in the free choice situation did not. In experiment 2, rats were assessed for their approach to novelty in the free choice situation and then assessed for amphetamine-induced conditioned place preference. It was found that rats who spent more time in a novel environment also showed a higher magnitude of amphetamine-induced conditioned place preference. These findings are consistent with the hypothesis that the rewarding properties of novelty and amphetamine may be mediated by a similar brain mechanism.