Individual differences in novelty-induced activity do not predict strength of amphetamine-induced place conditioning

A rat's level of activity while in a novel chamber has been shown to predict the likelihood that rat will learn to self-administer low doses of amphetamine (10). In a series of four experiments employing the place conditioning paradigm, a rat's level of activity when placed in a novel chamber was used to predict its sensitivity to the rewarding properties of low doses of amphetamine. In phase 1 of each experiment, rats were divided into high responders (HRs) and low responders (LRs) on the basis of activity level while in a novel chamber. In phase 2, rats were given place conditioning trials (one to four trials) with amphetamine (0.75-10 mg/kg). Although amphetamine-induced place preferences were consistently demonstrated, activity in a novel chamber did not predict the strength of a preference formed for an amphetamine-paired place. The failure of these experiments to support similar investigations using the self-administration paradigm [e.g., (10)], suggests that caution be used in generalizing between paradigms believed to measure similar processes.