BDNF and major depressive disorder: In a rat model of depression, Shuganjieyu capsules increased phosphorylation levels of the phosphorylation cyclic adenosine monophosphate response element binding protein and brain-derived neurotrophic factor (BDNF) expression in the medial prefrontal cortex and hippocampal CA3 area, which is believed to be the major mechanism of its antidepressant effect (36).