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| Factors Influencing the Modulation of Psychomotor Stimulants Effects on Operant Behavior |
| Monday, May 26, 2008 |
| 3:30 PM–4:50 PM |
| Inspiration Studio |
| Area: BPH/EAB; Domain: Basic Research |
| Chair: Matthew T Weaver (University of Florida) |
| Abstract: Stimulus and procedural conditions can impact the effect a particular drug has on operant behavior. In some cases these important features of an experiment are not taken into consideration either because there is a lack of information on the topic or because of variation across laboratories in conducting experiments. The results from various areas of research that use drugs in the investigation of behavior, such as choice, timing, and tolerance, could be affected by these various procedural differences across experiments. This symposium will review four experiments that investigate how various procedural or stimulus control conditions modulate the effect of drug on behavior. Delay between drug dosing and behavioral testing, stimulus control variations, and locomotion will be the focus of three studies conducting research with d-amphetamine. A fourth study investigates how the capacity to eat effects the development of tolerance with cocaine. |
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| Modulation of d-Amphetamine’s Effects on Behavior Based on Delay of Administration. |
| KATHRYN A. SAULSGIVER (University of Florida), Erin A. McClure (University of Florida), Clive D. L. Wynne (University of Florida) |
| Abstract: The time between drug administration and behavioral testing can have a large impact on the effect of drug. Varying delays between administration and testing can be imposed directly (a set delay between injection and testing) or indirectly (allowing session time to vary or examining behavior over an extended period of time). In order to investigate how these delays influence results we measured the acute effects of d-amphetamine on a concurrent peak interval (PI) random ratio (RR) schedule was examined across several directly programmed delays (0, 30, 60, and 90 minutes). Sessions were terminated after a minimum of 50 PI trials and 40 minutes or a maximum of 60 minutes, which ever came first, in order to hold the behavioral testing interval constant. The effect of d-amphetamine varied across each delay. When there was no delay behavior under the PI schedule was more affected than behavior under the RR schedule. When the delay was extended to 90 minutes responding under the RR schedule was suppressed at the highest doses for most subjects while responding under the PI schedule was less effected. The behavioral effect at each delay for all subjects will be discussed. |
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| Evaluation of IRT > t Performance Following the Recovery from Amphetamine-Induced Focused Stereotypy. |
| JONATHAN W. PINKSTON (University of Kansas), Stephen Fowler (University of Kansas) |
| Abstract: Acute 5.0 mg/kg d-amphetamine induces a reliable sequence of behavioral effects. For the first two hours after administration, rats display stereotypy. When the stereotypy subsides, rats are hyperactive. The period of hyperactivity has some interesting behavioral consequences that have received little experimental attention. The present experiment sought to examine the impact of the hyperactivity phase on operant behavior. Three groups of rats were trained to respond on one of three interrresponse time (IRT) > t schedules (8-, 24-, or 72-s) prior to tests with amphetamine. For the first two hours after amphetamine, rats displayed focused stereotypy, and operant behavior was suppressed. Once the stereotypies subsided, operant responding recovered, but there were differences across groups. Performance of animals trained on the DRL 8-s recovered to baseline levels of performance. Animals trained on the DRL 72-s schedule, on the other hand, revealed the emission of many more short inter-response times (IRT’s). Previous research has offered varied interpretations for disrupted DRL performance, such as increased impulsivity or errors in timing. The different interpretations will be discussed. Additionally, we put forth the idea that the hyperactivity following focused stereotypy may be a previously unexplored test bed for antipsychotic action. Supported by MH042429. |
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| Effects of d-Amphetamine on Delay Discounting: Role of Delay Signals. |
| CHRISTINE E. HUGHES (University of North Carolina, Wilmington), Raymond C. Pitts (University of North Carolina, Wilmington) |
| Abstract: In laboratory “self-control” procedures, individuals choose between a smaller, more immediate reinforcer and a larger, more delayed reinforcer. As the delay to the larger reinforcer increases, choices for that reinforcer decrease. Delay-discounting functions can be obtained within individual sessions. In such procedures, stimulants, such as amphetamines, have been shown to increase choices of the larger, more delayed reinforcer (increase “self-control”). It has been shown that this effect can be modulated by the stimulus conditions present during the delay. In this presentation, I will review some of the data on the effects of amphetamine under self-control procedures and will describe some of our work investigating the potential role of delay signals in drug-induced shifts in the delay-discounting functions. |
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| Capacity and Initial Sensitivity to Cocaine. |
| MATTHEW T WEAVER (University of Florida), Jonathan E. Friedel (University of North Texas), Marc N. Branch (University of Florida) |
| Abstract: It is assumed that multiple factors affect an animal’s sensitivity to cocaine. The current discussion focuses on the value of measuring an animal’s capacity to eat as a predictor of between-subject variability in the sensitivity to cocaine’s effects. First the capacity of eight White Carneaux pigeons was determined. Capacity assessments were conducted once a week for eight consecutive weeks. Assessment sessions entailed the animal having free access to 200 g of mixed grains. The weight difference in the grain following the 65 minute session served as the measure of capacity. Following the capacity assessment, seven of the eight subjects were trained to peck a key for 3-s access to mixed grain under a fixed-ratio 20 schedule. Once a stable baseline was established the effects of cocaine on responding were determined. This included doses of cocaine ranging from 1.0 to 13.0 mg/kg. Following dose-effect determinations the results were correlated with the capacity measures. The results revealed a weak correlation between capacity and the initial effects of cocaine. To conclude, it would be dubious to advise the use of capacity alone as a predictor of cocaine sensitivity, however, it may be one of a number of factors contributing to between subject variability. |
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