ENVIRONMENTAL INFLUENCES UPON DRUG-INDUCED SUPPRESSION OF OPERANT BEHAVIOR

¹ Departments of Pharmacology and Psychiatry, University of Minnesota, Minneapolis, Minnesota

Rats were trained to press a lever for food reinforcement and stabilized on a schedule which required 30 lever presses for each pellet. Injection of mescaline hydrochloride (10 mg/kg i.p.) just prior to placement into the operant conditioning chamber resulted in a disruption of lever pressing beginning 10 minutes later and lasting about 25 minutes. Removal of the rats from the chamber 2 minutes after the onset of drug action and replacement after 2.5 or 5.0 minutes resulted in resumption of bar pressing almost immediately. Leaving the animals in their home cages for 10 minutes after the injection (latency to onset of action) also resulted in attenuation of the disruptive effects of the drug. Manipulating the dose of mescaline hydrochloride and an examination of d-lysergic acid diethylamide interacting with this phenomenon indicated that the attenuation produced by the manipulation appears to conform to log dose-response relationships and that the behavioral effects of at least one other psychoactive drug can be shortened by the manipulation. The implications of these results are 2-fold: 1) The experimental procedure of injecting a drug and looking for behavioral effects at some predetermined time after administration of the drug should take into account environmental factors as mundane as when the animal is placed into the behavioral chamber. 2) The results described for rats may be analogous to the drug-setting interaction commonly reported for humans reacting to psychoactive agents.