Effect of Voluntary Exercise Training on Corticosterone Level and Immobility Behavior Induced by Chronic Stress in Rats

Background: Depression is a common mood disorder that in the long-term impairs thoughts, behavior, feelings, and health. Chronic unpredictable stress is one of the factors that can cause depression. Objectives: To investigate the effect of voluntary exercise training on immobility behavior (caused by chronic unpredictable stress) and serum corticosterone concentration. Materials & Methods: A total of 24 male rats were randomly and equally assigned to four groups of healthy-control, healthy-exercise, depressed-control, and depressed-exercise. Depressed-control and depressed-exercise groups were first exposed to three weeks of chronic unpredictable stress. After this period, the exercise groups performed four weeks of voluntary exercise training. Twentyfour hours after the last training session, a forced swim test was taken from the rats and their blood samples were taken 24 hours later. The obtained data were analyzed using a 2-way analysis of variance (significance level: P<0.05). The Pearson correlation coefficient was used to examine the relationship between study variables. All statistical analyses were performed in SPSS v. 22. Results: Chronic stress increased immobility behavior (P=0.001) and serum corticosterone concentration (P=0.001). In contrast, exercise training reduced immobility behavior (P=0.001) and serum corticosterone (P=0.001). The immobility time (P=0.001) and serum corticosterone concentration in the depressed-exercise group were higher than those in the healthy-exercise group (P=0.001). There was a positive correlation between immobility behavior and serum corticosterone concentration (r=0.85 and P=0.001). Conclusion: While the chronic stress increases the immobility behavior and serum corticosterone concentration, voluntary exercise training can reduce immobility behavior and serum corticosterone and adjust some depression symptoms.