Voluntary wheel running ameliorates depression-like behaviors and brain blood oxygen level-dependent signals in chronic unpredictable mild stress mice

Background: Physical exercise has been long recognized for its therapeutic effects on depressive disorders, but the underlying mechanisms remain largely unknown. In the study, we investigated whether the physical exercise by voluntary wheel running (VWR) alters depression-like behaviors and its impact on brain blood oxygen level-dependent (BOLD) signals in mice. Methods: Adult male C57BL/6 mice were assigned to one of the following groups; (1) no exercise control (noEx), housed in a standard cage; (2) exercise (Ex), 2 h/day in a running wheel apparatus; (3) chronic unpredictable mild stress (CUMS), which was imitating adult stress; and (4) CUMS + Ex. The differences in functional brain changes were determined by BOLD functional magnetic resonance imaging (fMRI). Results: The results showed that VWR exercise significantly reversed the CUMS-induced behavioral abnormalities. Base on the fMRI amplitude of low-frequency fluctuation (ALFF) analysis, we found that VWR exercise could restore the CUMS-induced excessive BOLD activation in parts of limbic system, such as cortex, hippocampus and corpus callosum. Furthermore, CUMS-induced BOLD suppressive regions were also partially attenuated by VWR exercise, such as amygdala, cerebellum anterior lobe, thalamus, midbrain, and pontine. Most of these regions are involved in mood-regulating circuit, suggesting dysfunction of the circuit in CUMS model of depression, and VWR exercise could adjust the mood-regulating circuit. Conclusions: These results suggested that VWR exercise ameliorated depression-like behaviors and brain BOLD signals in CUMS induced depression mice.