Inconsistent with these studies, we did not find a significant change in the expression of hippocampal BDNF after OVX, but P. histicola significantly upregulate the level of BDNF, whereas the nerve proliferation marker Ki-67 is also highly expressed after treatment with P. histicola, indicating that P. histicola promoted nerve proliferation to alleviate depression by upregulating BDNF. This evidence concerns the gene BDNF and major depressive disorder.