MKI67 and major depressive disorder: 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.