BDNF and major depressive disorder: Figure 4 After intervening with CSS in depression model rats, it was found that compared to the model group, rats in the CSS group exhibited significantly increased expression of BDNF and its receptor TrkB in the hippocampus, prefrontal cortex, and amygdala, suggesting that the mechanism through which CSS alleviates depressive states might be related to the increased expression of BDNF and its receptor TrkB in these brain regions (Ying et al., 2011).