Effects of altering reinforcer magnitude and reinforcement schedule on phencyclidine (PCP) self-administration in monkeys using an adjusting delay task

Compared to nondrug reinforcers, few studies have examined delay discounting for drug reinforcers. The purpose of the present study was to examine delay discounting in rhesus monkeys using orally delivered phencyclidine (PCP) as the reinforcer and to examine the effects of manipulating reinforcer ma...

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Bibliographic Details
Published in:Pharmacology, biochemistry and behavior biochemistry and behavior, 2008-10, Vol.90 (4), p.778-786
Main Authors: Newman, Jennifer L., Perry, Jennifer L., Carroll, Marilyn E.
Format: Article
Language:English
Subjects:
Adjusting delay task
Animals
Biological and medical sciences
Conditioning, Operant - drug effects
Data Interpretation, Statistical
Delay discounting
Dose-Response Relationship, Drug
Excitatory Amino Acid Antagonists - pharmacology
Macaca mulatta
Magnitude of reinforcement
Medical sciences
Phencyclidine
Phencyclidine - pharmacology
Reinforcement Schedule
Reward
Rhesus monkeys
Self Administration
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Summary:Compared to nondrug reinforcers, few studies have examined delay discounting for drug reinforcers. The purpose of the present study was to examine delay discounting in rhesus monkeys using orally delivered phencyclidine (PCP) as the reinforcer and to examine the effects of manipulating reinforcer magnitude and cost on delay discounting for PCP using an adjusting delay task. Monkeys could choose between a single delivery of PCP available immediately or a bundle of PCP deliveries available following a titrated delay. The average of the delays, or the mean adjusted delay (MAD), served as the quantitative measure of delay discounting. In Experiment 1, reinforcer magnitude was manipulated by varying the PCP concentration and the size of the delayed reinforcer (6 or 12 deliveries). The concentration-effect curve for PCP deliveries assumed an inverted U-shaped function, but varying PCP concentration had little effect on MAD values or the choice between immediate and delayed reinforcers. Increasing the size of the delayed reinforcer produced an upward and leftward shift in the concentration-effect curve. In Experiment 2, the cost of reinforcers was manipulated by increasing the fixed ratio (FR) requirement for each choice. Increasing the FR led to increased MAD values and decreased PCP self-administration.
ISSN:0091-3057
1873-5177
DOI:10.1016/j.pbb.2008.05.022