|Choice Procedures in Behavioral Pharmacology
|Monday, May 26, 2008
|9:30 AM–10:50 AM
|Area: BPH/EAB; Domain: Basic Research
|Chair: Corina Jimenez-Gomez (Utah State University)
|Discussant: Karen G. Anderson (West Virginia University)
|Abstract: In choice procedures, the relative allocation of behavior between response alternatives serves as a measure of preference. This measure offers several advantages over simple schedules of reinforcement for the study of drug reinforcers. Choice procedures have been useful for the study of the reinforcing efficacy of drugs and the conditions under which drug consumption is chosen relative to other concurrently available non-drug sources of reinforcement. This symposium will focus on the effect of genetic strain and morphine on impulsive choices, application of quantitative models of choice to alcohol self-administration, and post-reinforcer response patterns on concurrent schedules.
|Effects of Acute and Repeated Morphine on Delay Discounting in Lewis and Fischer 344 Rats.
|NATALIE ROSE BRUNER (West Virginia University), Karen G. Anderson (West Virginia University)
|Abstract: High rates of delay discounting, the devaluing of a reinforcer as a result of its delay to presentation, has been suggested to underlie increased impulsive choice. Steeper delay-discounting functions have been observed in substance abusers relative to control subjects, suggesting a link between increased delay discounting and abuse of drugs, including opioids. The present study assessed effects of acute and repeated morphine on delay discounting in Lewis and Fischer 344 rat strains, which have been shown to differ in baseline rates of delay discounting. Subjects chose between one food pellet delivered immediately and three food pellets presented after an increasing delay. For all subjects, preference for the larger reinforcer decreased as the delay to its presentation increased. Mean indifference points at baseline indicated that Lewis rats had steeper discounting functions than Fischer 344 rats, which is consistent with previous literature. Following administration of acute morphine (1.0, 3.0, 5.6, 10.0 mg/kg, i.p.) mean indifference points and percent large reinforcer choice were dose-dependently decreased relative to saline for both groups. Effects of repeated morphine administration and subsequent withdrawal are discussed in terms of tolerance and effects of long-term drug exposure.
|Matching Law Analysis of Rats’ Alcohol Self-Administration in a Free-Operant Choice Procedure.
|CORINA JIMENEZ-GOMEZ (Utah State University), Timothy A. Shahan (Utah State University)
|Abstract: Research has shown that the generalized matching law adequately accounts for the allocation of drug-maintained behavior across two response alternatives. Previous studies applying matching-law analyses to alcohol-maintained choice behavior, however, have shown atypical findings, which likely were due to the procedures used (e.g., two-bottle choice procedure, volume consumed as dependent variable). In the present study, a free-operant choice procedure of concurrent variable-interval schedules of reinforcement was used. Across conditions, rates of alcohol deliveries on two response alternatives were varied to assess the adequacy of the matching law in accounting for alcohol-maintained choice behavior. Results show that the matching law adequately accounted for changes in the allocation of responding with changes in the relative rate of alcohol delivery. Therefore, the matching law may serve as a useful tool in the study of alcohol-related choice.
|Post-Reinforcer Response Patterning in Pigeons and Monkeys: Interaction between Response and Reinforcer Type.
|MIKHAIL KOFFARNUS (University of Michigan), Jonathan L. Katz (National Institute on Drug Abuse Intramural Research Program), James H. Woods (University of Michigan)
|Abstract: Allocation of behavior across two response options has been extensively demonstrated to match the relative amount or frequency of reinforcement contingent on response options. Recently, it has been proposed that this observation may be due to a perseverance of the response that most recently produced a reinforcer. This observation has primarily been observed in pigeons key-pecking, a behavior that is known to be affected by both respondent and operant conditioning processes. In the current set of experiments, we examined post-reinforcer response patterns on concurrent random-interval schedules across a variety of conditions, with both pigeons and rhesus monkeys. We examined different reinforcers (intravenous drug, food, conditioned stimuli, aspartame-sweetened water), responses (key-peck, treadle-press, lever-press, spout-lick), and various schedule conditions, including rapidity of schedule change, changeover delay, and random-interval values. Results indicate that the presence of post-reinforcer bursts of responding is not necessary for matching. While matching was observed in all conditions, preference pulses were only observed with monkeys licking spouts for aspartame-sweetened water and in some monkeys responding for drug or aspartame-sweetened water. We did not observe preference pulses in some monkeys lever-pressing or in pigeons key-pecking or treadle-pressing for grain. This research was supported by USPHS/NIDA grants DA00254, DA015449, and DA007267.