Discriminative stimulus effects and antipunishment effects of drugs measured during the same session

The effects of pentobarbital, diazepam, phencyclidine, buspirone and methamphetamine on drug discrimination and on responding under a variable-interval variable-interval with punishment schedule were studied in pigeons trained to discriminate 5.0 mg/kg pentobarbital from saline. Pentobarbital produced dose-dependent increases in the proportion of responses on the drug key and on rates of punished responding. Diazepam had very similar effects except that the dose-effect curve for punished responding turned over at the highest dose level. Phencyclidine produced only partial responding on the drug key and weakly increased punished responding. Buspirone produced small increases in punished responding, but in the drug discrimination experiments buspirone did not cause responding on the drug key. Methamphetamine did not produce responding on the drug key, nor did it increase rates of punished responding. These experiments are among the first to demonstrate that drug discrimination and other behaviors can be studied within single test sessions in the same animals and they suggest that there is a close correspondence between the discriminative stimulus effects of some drugs and their anti-punishment activity.