Drug effects on multiple and alternating mixed-schedule performance

Abstract

The effects of d-amphetamine, pentobarbital, morphine, chlorpromazine and triflupromazine were determined on key pecking by pigeons maintained under multiple and alternating-mixed fixed-ratio 30, fixed-interval 5-min schedules of grain presentation. Similar schedule performances were maintained under both the multiple and alternating mixed schedules. The effects of d-amphetamine and pentobarbital were similar under the multiple and alternating mixed schedules. Low doses of d-amphetamine and pentobarbital increased relatively low rates of responding in the fixed-interval component and higher doses decreased rates of responding in both the fixed-interval and fixed-ratio components. The effects of morphine, chlorpromazine and triflupromazine on fixed-interval rates of responding did not differ between the multiple and alternating mixed schedules. However, morphine, chlorpromazine and triflupromazine decreased responding under the alternating mixed fixed-ratio without affecting responding under the multiple fixed-ratio component. This selective decrease in fixed-ratio responding under the alternating mixed schedule by morphine, chlorpromazine and triflupromazine appears to be functionally similar to the effects of these drugs to decrease avoidance responding without affecting escape responding.