IL6 and major depressive disorder: Among these factors, this study also confirmed that the expression of pro‐inflammatory cytokines—IL‐1ß, IL‐6, TNF‐α, PGE2, and COX267, 68—was dramatically increased, but not those of the anti‐inflammatory cytokines, IL‐10, arginase‐1 (ARG1), fibroblast growth factor (FGF)‐2, synaptophysin (SYP), and brain‐derived neurotrophic factor (BDNF) in the rat depression models.