Effects of methamphetamine on probability discounting in rats using concurrent chains

• Published in: Behavioural processes 2024-01, Vol.214, p.104971-104971, Article 104971
• Main Authors: Bodeker, Rebecca Rose Hazel, Grace, Randolph C.
• Format: Article
• Language: English
• Subjects: Concurrent-chains; Magnitude-effect; Methamphetamine; Probability-discounting; Rapid-acquisition
• ISSN: 0376-6357; 1872-8308
• DOI: 10.1016/j.beproc.2023.104971

How stimulant drugs affect risky choice and the role of reinforcement magnitude has been an important question for research on impulsivity. This study investigated rats’ responding on a rapid acquisition, concurrent chains, probability discounting task under methamphetamine administration. In each block of four sessions, probability of reinforcement delivery was unequal (0.5/1.0, 1.0/0.5) or equal, (1.0/1.0, 0.5/0.5) while amount of reinforcement was constant and unequal. This allowed for an estimate of probability discounting and the magnitude effect (where larger reinforcers are discounted at a greater rate) in each block. Baseline, acute and chronic methamphetamine administration, and re-establish baseline phases were completed. Rats showed sensitivity to probability and magnitude in baseline, as well as a magnitude effect whereby preference for the larger reinforcement was greater with 100% than 50% reinforcement probability. Acute methamphetamine dose-dependently reduced the probability effect. There were no effects of chronic administration and only probability discounting was maintained in the re-establish baseline phase. This was the first procedure to find a magnitude effect with rats in a probability discounting procedure and demonstrates that acute methamphetamine reduces both the probability and magnitude effects which increases propensity for risky choice. •We used a novel rapid acquisition choice procedure to study probability discounting and the effect of reward magnitude.•After baseline training, acute and chronic methamphetamine administration phases were completed.•Methamphetamine decreased sensitivity to probability.•Methamphetamine increased propensity for risky choice indicating an increase in impulsivity.