Behavioral mechanisms of oxycodone's effects in female and male rats: Reinforcement delay and impulsive choice.

µ-Opioid agonists (e.g., morphine) typically increase impulsive choice, which has been interpreted as an opioid-induced increase in sensitivity to reinforcement delay. Relatively little research has been done with opioids other than morphine (e.g., oxycodone), or on sex differences in opioid effects, on impulsive choice. The present study investigated the effects of acute (0.1-1.0 mg/kg) and chronic (1.0 mg/kg twice/day) administration of oxycodone on choice controlled by reinforcement delay, a primary mechanism implicated in impulsive choice, in female and male rats. Rats responded under a concurrent-chains procedure designed to quantify the effects of reinforcement delay on choice within each session. For both sexes, choice was sensitive to delay under this procedure. Sensitivity to delay under baseline was slightly higher for males than females, suggesting more impulsive choice with males. When given acutely, intermediate and higher doses of oxycodone decreased sensitivity to delay; this effect was larger and more reliable in males than females. When given chronically, sex differences were also observed: tolerance developed to the sensitivity-decreasing effects in females, whereas sensitization developed in males. These data suggest that reinforcement delay may play an important role in sex differences in impulsive choice, as well as in the effects of acute and chronic administration of opioids in impulsive choice. However, drug-induced changes in impulsive choice could be related to at least two potential behavioral mechanisms: reinforcement delay and/or reinforcement magnitude. Effects of oxycodone on sensitivity to reinforcement magnitude remain to be fully characterized. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Escalating schedules of incentives increase physical activity with no differences between deposit and no-deposit groups: A systematic replication.

Physical inactivity has increasingly affected public health in the United States during the COVID-19 pandemic as it is associated with chronic diseases such as arthritis, cancer, and heart disease. Contingency management has been shown to increase physical activity. Therefore, the present study sought to evaluate the effects of an escalating schedule of monetary reinforcement with a reset contingency on physical activity, as compared between 2 counterbalanced groups in which a monetary deposit of $25 was either required (deposit group) or not (no-deposit group). Twenty-five adults wore Fitbit accelerometers to monitor step counts. An ABA reversal design was used; in the 2 baseline phases, no programmed contingencies were in place for step counts. During intervention, step goals were set using a modified 70th percentile schedule with a 7-day window: Reaching the first goal would result in $0.25, and incentives increased by $0.25 for each subsequent day in which the goal was met. Failure to reach a goal resulted in a reset of the monetary incentive value to $0.25. Ten out of 12 participants from the deposit group were determined to be responders to intervention, whereas 8 out of 13 participants from the no-deposit group were determined to be responders to intervention. Overall, there were no significant differences between the groups' step counts. However, the deposit group's intervention was cheaper to implement, which suggests that deposit contracts are a viable modification for physical activity interventions.

A method for studying reinforcement factors controlling impulsive choice for use in behavioral neuroscience.

Although procedures originating within the experimental analysis of behavior commonly are used in behavioral neuroscience to produce behavioral endpoints, they are used less often to analyze the behavioral processes involved, particularly at the level of individual organisms (see Soto, 2020). Concurrent-chains procedures have been used extensively to study choice and to quantify relations between various dimensions of reinforcement and preference. Unfortunately, parametric analysis of those relations using traditional steady-state, single-subject experimental designs can be time-consuming, often rendering these procedures impractical for use in behavioral neuroscience. The purpose of this paper is to describe how concurrent-chains procedures can be adapted to allow for parametric examination of effects of the reinforcement dimensions involved in impulsive choice (magnitude and delay) within experimental sessions in rats. Data are presented indicating that this procedure can produce relatively consistent within-session estimates of sensitivity to reinforcement in individual subjects, and that these estimates can be modified by neurobiological manipulation (drug administration). These data suggest that this type of procedure offers a promising approach to the study of neurobiological mechanisms of complex behavior in individual organisms, which could facilitate a more fruitful relationship between behavior analysis and behavioral neuroscience.