Running exercise shows anti-depressive effect in mice through PV⁺ interneurons in medial prefrontal cortex

To investigate the effect of running exercise on depression-like behaviors in chronic unpredictable stress（CUS）-induced depression mice and GABAergic interneurons, PV⁺ interneurons and ratio of GAD67⁺/PV⁺ cells in medial prefrontal cortex（mPFC）.

After mouse model of depression was successfully established through CUS, these male C57BL/6 mice aged 4~6 weeks were randomly divided into control group, CUS control group and CUS+running group according to the results of sucrose preference test. The behaviors of the 3 groups were evaluated with sucrose preference test, forced swimming test and tail suspension test. The mRNA expression levels of GAD1, GAD2, PV and CCK in mPFC of mice were detected using qRT-PCR. The number of GABAergic interneurons and PV⁺ interneurons in mPFC of mice were quantified using immunohistochemical assay and unbiased stereological technique, and the ratio of PV⁺/GAD67⁺ cells was calculated.

Compared with those in CUS control group, the mice from the CUS+running and control groups showed a significantly higher percentage of sucrose preference（P<0.05）, shorter forced swimming immobility time（P<0.05）, and decreased tail suspension immobility time（P<0.05）. There were no obvious differences in mRNA expression levels of GAD1, GAD2 and CCK and number of GABAergic interneurons in mPFC in the 3 groups（P>0.05）. The mRNA level of PV, number of PV⁺ interneurons and ratio of PV⁺/GAD67⁺ cells in mPFC were remarkably lower in the CUS group than the CUS +running group and control group（P<0.05）.

Running exercise may exert anti-depressive effects through regulating the number and gene expression of PV⁺ interneurons.