Associative factors in drug pretreatment effects on gustatory conditioning: cross-drug effects

The pretreatment effect (PE) in gustatory avoidance conditioning refers to the fact that pretreatment with a variety of pharmacological agents subsequently reduces the ability of the same agents to induce gustatory aversion. Explanations of this phenomenon emphasize either tolerance or associative interference. Any explanation of the phenomenon must also account for the present findings which demonstrate the PE when agents of pretreatment and conditioning were pharmacologically dissimilar. Rats were pretreated with d-amphetamine and tested for acquisition of an aversion to saccharin conditioned by amphetamine or morphine. The PE was obtained regardless of the drug used in conditioning. An associative manipulation involving nonreinforced presentation of the drug administration cues (i.e., injections followed by saline instead of drug), that attenuated the PE when pretreatment and conditioning were with amphetamine, was also effective when the pretreatment agent was amphetamine and the conditioning agent was morphine. The findings were interpreted within a framework of compensatory conditioning of a general physiological mechanism common to all gustatory avoidance.