Research ReportsEffects of oxycodone on sensitivity to reinforcement magnitude: implications for effects of opioids on impulsive and risky choiceHunt, Katelyn H.; Hughes, Christine E.; Pitts, Raymond C. Author Information Department of Psychology, University of North Carolina Wilmington, Wilmington, North Carolina, USA Received 29 August 2019 Accepted as revised 10 December 2019 Correspondence to Raymond C. Pitts, PhD, Department of Psychology, University of North Carolina Wilmington, 601 S. College Rd, Wilmington, NC 28403-5612, USA, E-mail: [email protected] Behavioural Pharmacology: April 2020 - Volume 31 - Issue 2&3 - p 221-232 doi: 10.1097/FBP.0000000000000543 Buy Metrics Abstract Opioid addiction/dependence is associated with impulsive and risky behavior. Moreover, opioids can increase impulsive choice in preclinical studies with nonhumans. The objective of this study was to investigate a potential behavioral mechanism of opioids: a change in the impact of reinforcement magnitude on choice. Rats (n = 7) chose between smaller and larger reinforcers under a continuous-choice (concurrent-chains) procedure. The levers associated with the smaller and larger reinforcers alternated every five sessions. During baseline under this procedure, rats showed a reliable preference for the larger reinforcer. Effects of several doses (0.1–1.7 mg/kg, s.c.) of the prescription opioid, oxycodone, were examined on preference based upon reinforcement magnitude. Oxycodone dose-dependently decreased preference for the larger reinforcer (i.e. decreased sensitivity to reinforcement magnitude). The decrease in sensitivity to reinforcement magnitude was selective in that the intermediate doses did not affect, or had minimal impact on, other measures of performance (e.g. on general motivation to respond). These data suggest that a decrease in the sensitivity to reinforcement magnitude is a reliable outcome of μ-opioid administration, an effect that has important implications for the impact of these drugs on both impulsive and risky behavior. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.