Date of Award

4-2003

Degree Name

Doctor of Philosophy

Department

Psychology

Abstract

In the last 10 years, the use and abuse of the club drug gamma-hydroxybutyrate (GHB) has noticeably increased. Because GHB has only recently emerged as a drug of abuse, relatively little is known about the drug's behavioral effects, including its effects on learning. Therefore, the present study sought to characterize GHB's effects on rats' acquisition of a lever-press response using a two-lever, resetting/cancellation procedure. Under this procedure, responses on one ( reinforcement ) lever produced a single food pellet after a delay of 0, 20, or 40 s. Presses on the second ( cancellation ) lever during a delay interval initiated by a reinforcement-lever response canceled the scheduled reinforcer delivery, while presses on this lever at other times were recorded but had no programmed consequences. The present study used a 3 x 5 factorial design, with dose of GHB (0, 200, 400, 600, or 800 mg/kg) and reinforcement delay (0, 20, or 40 s) serving as the between-subject factors. Experimentally naive food-deprived rats ( N = 120) were randomly assigned to 1 of 15 experimental groups. In addition, eight rats were randomly assigned to a no-food, vehicle-control group. All rats received two magazine-training sessions, followed by a single 4-hour acquisition session. Responses by rats in the control group were recorded but had no programmed consequences. Consistent with previous studies, increasing the reinforcer delay decreased responding on the reinforcement lever. For all groups, very little responding occurred on the cancellation lever. With 0-s delays, GHB generally produced a dose-dependent suppression of responding early in the acquisition session, followed by a rapid increase in responding on the reinforcement lever. GHB substantially reduced, in a dose-dependent manner, responding under 20-s and 40-s delay conditions. The results of this study suggest that GHB impairs the acquisition of operant behavior and that GHB-induced learning impairment is greater when reinforcer delivery is delayed than when it is immediate. These results further confirm the utility of the resetting/cancellation procedure for assessing the effects of drugs on learning.

Access Setting

Dissertation-Open Access

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