Research ReportsEffects of food restriction on the conditioned reinforcing properties of an opioid-associated stimulusRobertson, Stephen H.; Jutkiewicz, Emily M. Author Information Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA Received 24 September 2020 Accepted as revised 16 June 2021 Correspondence to Emily M. Jutkiewicz, PhD, Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA, E-mail: [email protected] Behavioural Pharmacology: September 2021 - Volume 32 - Issue 6 - p 505-514 doi: 10.1097/FBP.0000000000000645 Buy Metrics Abstract Food restriction promotes drug self-administration; however, the effects of food restriction on the conditioned reinforcing properties of drug-associated stimuli are less clear. We tested the extent to which food restriction modified the conditioned reinforcing properties of a remifentanil-associated stimulus following conditioning with 3.2 or 1.0 μg/kg/infusion of remifentanil. First, we provided restricted (20 g/day standard chow) or ad libitum access to standard chow to rats. Second, within each feeding condition, we exposed rats to 20 intravenous infusions of remifentanil and 20 stimulus presentations that were delivered response independently each day for 5 days. For the experimental group (paired Pavlovian), the remifentanil infusions and stimulus presentations were delivered concurrently. The control group (random control) received the same number of infusions and stimulus presentations, but were not paired. For 28 sessions, we tested the extent to which the stimulus functioned as a conditioned reinforcer by allowing rats to freely respond for presentations of the remifentanil-associated stimulus. Following conditioning with 3.2 μg/kg/infusion of remifentanil, we found that rats that in the Paired Pavlovian group responded for the remifentanil-associated stimulus significantly more than rats in the Random control group, regardless of feeding condition. Following conditioning with 1.0 μg/kg/infusion of remifentanil, the remifentanil-associated stimulus was not associated with conditioned reinforcing properties, regardless of feeding condition. These findings confirm previous research demonstrating that a remifentanil-associated stimulus takes on conditioned reinforcing properties in a dose-dependent manner. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.