Drug-induced conditioned suppression: specificity due to drug employed as UCS.

The classical conditioning potential of several drugs was tested in rats by pairing a light CS with the drug UCSs; these stimuli were superimposed in a variable-interval 30 sec schedule for water reinforcement. Conditioning (suppression of bar-pressing in the presence of the CS) was definitely demonstrated with psilocybin (2.0 mg/kg), was suggested but not clearly shown with LSD (0.13 MG/kg), and was not evident with methyl atropine nitrate (50 mg/kg) or pentobarbital (25 mg/kg). These results indicate that previously demonstrated drug-induced conditioned suppression is not a nonspecific effect of unconditioned suppression but depends on the type of drug employed.