Enhancement of conditioned preference for a place paired with amphetamine produced by blocking the association between place and amphetamine-induced sickness.

Rats learn to prefer a place that has been paired with the rewarding effect of amphetamine. Since amphetamine is also known to produce an aversive effect, called here sickness, pairings of a place with amphetamine should produce a place-sickness association as well as the place-reward association that underlies the conditioned place preference. The purpose of the present experiments was to enhance the conditioned place preference produced by place-amphetamine pairings by blocking the place-sickness association. In Experiments 1 and 2, the taste of saccharin was paired with sickness induced by amphetamine or by lithium, respectively. The saccharin taste was presented prior to each pairing of a white chamber with amphetamine to block the place-sickness association. In Experiment 3, a brief placement in a distinctive cage that had previously been paired with lithium-induced sickness preceded each pairing of the white chamber with amphetamine. Blocking of the place-sickness association occurred as evidenced by the reliable enhancement of conditioned place preference obtained in each of the three experiments.