Meeting Abstract
Running acts as a natural reward and shares features with other rewarding behaviors, such as eating or taking drugs of abuse. Although exercise can attenuate withdrawal symptoms of chemical addiction, exercise itself is proposed to have addictive properties, as humans and rodents have shown signs of anxiety and depression after being denied exercise. Conditioned place preference (CPP) is a neuro-behavioral test of reward and reinforcement, widely used in studies of addictive processes in rodents. In typical protocols, individuals receive a reward (e.g., cocaine injection) paired with a specific environment (usually different floor textures) several times and are then tested for preference of the conditioned environment. We studied CPP in a unique exercise model of 4 replicate lines of mice selectively bred for high voluntary wheel running (HR) and 4 non-selected control (C) lines. HR mice run 3-times as much as C mice, in part based on evolutionary changes in their reward and motivational systems. We hypothesized that HR mice would differ from C in the extent to which they show a CPP following conditioning with rewarding drugs and/or wheel running. In experiment 1, HR and C mice were tested for CPP with cocaine as the reward. Both HR and C mice were significantly conditioned by cocaine, with no statistical difference between groups in the degree of conditioning. In experiment 2, mice were tested for CPP with wheel access as the reward. Specifically, mice were granted or not granted wheel access for 10 days, and each day removed from wheels or standard cages during peak wheel running and placed in CPP chambers for 30 min. Preliminary results show no significant conditioning by either HR or C mice. An upcoming third experiment will use Ritalin as the reward, a drug that has been shown to decrease wheel running of HR mice while increasing running by C mice.
