Both positive reinforcement and conditioned aversion from amphetamine and from apomorphine in rats.

Rats learned to press a lever for intravenous injections of amphetamine or apomorphine. They also learned to avoid the taste of saccharin which was associated with experimenter-administered amphetamine or with self-administered apomorphine. Thus these, and presumably other, self-administered drugs serve as compound pharmacological stimuli, having both positively reinforcing and aversive properties.