FIGURE 3.

Role of serotonin (5HT) in depression. Dysregulation of brain renin–angiotensin system (RAS) triggers the development and progression of depression through the reduction of brain 5HT and expression of BDNF and the induction of mitochondrial dysfunction, oxidative stress, and neuroinflammation. Therefore, inhibition of central classical RAS by angiotensin‐ACEIs and ARBs and activation of non‐classical RAS prevent the development of depression by regulating 5HT, BDNF, mitochondrial dysfunction, oxidative stress, and neuroinflammation.