HTR5A and major depressive disorder: To verify whether XPF works in treating CHD with depression by intervening in the cAMP-PKA-CREB-BDNF signaling pathway and cell apoptosis process, the expression of 5-HT, Ang-II, cAMP, PKA, CREB, BDNF, Bcl-2, Bax, Cyt-c, and caspase-3 in the myocardial and hippocampal tissues were detected.