BDNF and major depressive disorder: Additionally, increased numbers of apoptotic cells and necrotic cells were observed in chronic mild stress (CMS)-induced depression mice, and the expression of caspase-3, Bax, and proteins involved in the JAK2–STAT5 signaling pathway was decreased after PRLR silencing, along with increased expression of BDNF and Bcl-2 (Tian et al., 2019).