Abstract
Squirrel monkeys responded under fixed-interval (FI) schedules (3, 5, or 10 minutes' duration) in which behavior was maintained either by food presentation or by presentation of a brief electric shock. In some subjects, food-presentation and shock-presentation components were alternately present under a multiple schedule in which the presence of a given schedule component was correlated with a distinctive visual stimulus. Characteristic FI patterns of responding, a pause followed by a gradual increase in responding. were maintained regardless of whether food or electric shock was presented for the first response to occur after the fixed period of time had elapsed. d-Amphetamine (0.01-1.0 mg/kg) increased responding under both the food-and shock-presentation schedules at intermediate doses and decreased responding under both schedules at the higher doses. Morphine (0.03-1.0 mg/kg) produced increases in responding under the FI schedules of shock presentation similar to those seen with d-amphetamine but only decreased responding under the FI schedules of food presentation. Chlorpromazine (0.01-0.17 mg/kg) generally decreased responding under both FI schedules, but decreases in responding were usually proportionately greater under schedules of shock presentation. The effects of d-amphetamine on FI performance were the same whether responding was maintained by food presentation or electric shock presentation. In contrast, the effects of morphine, and to a lesser extent chlorpromazine, did seem to depend on whether responding was maintained by food presentation or electric shock presentation.
Footnotes
- Received June 25, 1973.
- Accepted March 1, 1974.
- © 1974 by The Williams & Wilkins Company
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