Pentobarbital, promazine, d-amphetamine, and scopolamine effects on behavior under multiple and primed schedules of...

Pigeons responded under compound fixed-interval (FI) fixed-ratio (FR) schedules of food presentation. Distinctive discrimininative stimuli were either continuously present during each component schedule (multiple FI FR) or were present only for a brief period at the beginning of each component (primed FI FR). Similar rates and patterns of responding were maintained under the multiple and primed schedules. Pentobarbital, scopolamine, and d-amphetamine decreased FR responding, but promazine had little effect at the doses studied. d-Amphetamine and promazine increased FI responding at certain doses, pentobarbital had little effect, and scopolamine decreased responding. There were no systematic differences in the effects of drugs under the multiple and primed schedules, in spite of the differences in discriminative stimuli under the conditions.