Physical activity induces depression-like behavior in intact male rats

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Testosterone affects behavior. Whether regular physical training does influence these effects is unknown. The assumption that testosterone induces muscular hypertrophy if combined with physical training has not been confirmed experimentally. The aim of this study was to evaluate whether activity and/or testosterone treatment affects depression-like behavior and to observe the effects of activity and testosterone on muscle fiber diameter.

Forty-three male rats were divided into 4 groups: two groups (TST act and TST lazy) were treated with testosterone (5 mg/kg) and two groups were used as control (CTRL act and CTRL lazy). Two of the groups (CTRL act and TST act) underwent 2 weeks of exercise. The forced swim test was used as a test of depression-like behavior. Sex steroids were measured and the diameter of skeletal muscle fibers was evaluated.

Testosterone was significantly higher in both testosterone-treated groups (p<0.001). Physically active groups had higher immobility times in the forced swim test than inactive groups. Groups CTRL act and TST lazy showed significantly larger diameter of muscle fibers in comparison to the TST act group.

Our results suggest that physical activity induces depression-like behavior in rats. Controversial antagonistic effects of testosterone and physical activity on muscle fiber diameter were found.


▸ Physical activity induced depression-like behavior in the forced swim test. ▸ The effect of physical activity was potentiated by testosterone administration. ▸ Physical activity and testosterone seem to have an antagonistic effect on muscle fibers.

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