Conditioned Place Preference of Mice Selectively Bred for High Voluntary Wheel Running

Abstract

Running acts as a natural reward and shares features with other rewarding behaviors, such as eating or taking drugs of abuse. Exercise is even proposed to have addictive properties, as humans and rodents have shown signs of “withdrawal,” including 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 a specific floor texture) several times and are then tested for preference of the conditioned environment as compared with a different environment in which they had not received a reward (e.g., saline injection). We studied CPP in a unique exercise model of 4 replicate lines of mice selectively bred for high voluntary wheel running (High Runner or HR lines) and 4 non‐selected control (C) lines. HR mice run ~3‐times as much as C mice on a daily basis, partly because of 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 minutes. Preliminary results show no significant conditioning by either HR or C mice. In a recent experiment 3, mice were tested for CPP with Ritalin as the reward, following the same protocol as experiment 1. Functioning as a dopamine transporter blocker, the drug Ritalin has been shown to decrease wheel running of HR mice while increasing running by C mice. Thus, we hypothesize a significant difference in the degree of conditioning between HR and C mice with Ritalin.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.