Meeting Abstract
Animals tend to seek activities that are rewarding, either psychologically or physically, and avoid those that are not. Although much is known about the reward system in mammals, questions remain, especially concerning the comparison of behavioral rewards. To what extent can one rewarding behavior substitute for another? How does the strength of a reward influence its ability to substitute for another reward? In humans and rodents, some rewarding substances have been shown to partially substitute for other rewarding substances or behaviors, but this substitution is not always reciprocal. To explore whether physical activity can be subject to “reward substitution,” female mice from a selective breeding experiment for high voluntary wheel-running (HR mice) and their control counterparts (C) were allowed access to wheels along with sweet solutions as a potentially competing reward (saccharin, Sweet ‘N Low, Equal, Splenda, sucrose). Fluid consumption and wheel running were measured daily. Home-cage activity (without access to wheels) was measured for a different generation of mice that had access to the same sweeteners (analyses are in progress). Wheel running was not statistically affected by exposure to the artificial sweeteners. Sucrose significantly elevated wheel running in C but not HR mice. Fluid consumption increased in a dose-dependent manner with saccharin, sucrose, Sweet ‘N Low, Equal, and Splenda. HR mice had a significantly smaller increase in fluid consumption with the artificial sweetener blends as compared with C mice, despite running ~2.6-fold more than C. These results suggest that HR mice have a reduced incentive salience for artificial sweeteners and this is likely attributable to the stronger competing reward of wheel running that has evolved in these lines.
