FoxOs subfamily proteins are involved in the development of MDD [19]. Our findings also indicate that PPD female mice also showed decreased FoxO1 expression in the mPFC but not in the hippocampus and a significant correlation of FoxO1 expression with depression-related behaviors. Additionally, a study using a FoxO1 knockout mouse model suggested that FoxO1 KO mice displayed depression-like behaviors as indicated by behavioral despair in the FST and TST [18]. All of these facts indicate that the inhibitory expression of FoxO1 is associated with depression. The correlation between BDNF and FoxO1 in PPD female mice shows that FoxO1 may be an underlying functional target gene of BDNF. The transcriptional activity of FoxO genes usually can be regulated by BDNF through activation of TrkB and downstream kinases [37, 52]. However, BDNF showed no effect on the phosphorylation of FoxO1 protein and its translocation in PC12 cells [53], which indicates that the regulatory mechanism of BDNF on the activity of FoxO1 may not be associated with protein modification level. Our results also demonstrated that specific BDNF knockout can reduce FoxO1 expression, showing
