Chronic Corticosterone Shifts Effort-Related Choice Behavior in Y-Maze

Abstract

Major depressive disorder (MDD) affects more than 16.1 million American adults (about 6.7% of the U.S. population age 18+) in a given year (ADAA). Understanding how chronic stress impacts decision-making may allow us to help people suffering from MDD receive the most suitable antidepressant treatment given their behavioral tendencies in reward and motivational processing. In these experiments, our objective is to characterize effort-related choice tasks using chronic stressors in mice. To study this topic, we take advantage of the well-validated homology between corticosterone (CORT) in rodents and cortisol in humans to induce mood disorders such as MDD and chronic stress in mice. Effort-related choice tasks have been characterized using stressors in rats, but the stressors have not been chronic and have not been characterized in mice. The results of these experiments would be a better foundation for research involving antidepressant treatment experiments on mice. The experimental group was administered CORT in their drinking water throughout all experiments. Then, both the control and experimental groups were tested in a Y-Maze barrier task to demonstrate the behavioral effects of CORT. The high reward (HR) arm of the Y-Maze contained a reward of four food pellets, which required high effort to obtain. The low reward (LR) arm of the Y-Maze contained a reward of two food pellets, which required less effort to obtain Animals chronically exposed to CORT displayed a stronger preference for low-effort, low-reward choices than control subjects. The results suggest that chronic CORT may reduce motivation to work for a highly rewarding reinforcer when a less rewarding reinforcer is available.