Abstract
Moderate stress evokes adaptive stress responses. On the other hand, prolonged and excessive stress is a risk factor of psychiatric disorders. However, the mechanism underlying how stress induce emotional changes remains unknown. Since recent studies established the crucial roles of inflammation-like responses in stress-induced emotional changes, inflammation-like responses in both brain and periphery have been studied. In the brain, inflammation-related molecules is involved in repeated stress-induced suppression of dopaminergic system in the medial prefrontal cortex, and repeated stress activates microglia to produce inflammatory cytokines. In the periphery, stress-induced endocrine responses activate myeloid cells to produce inflammatory cytokines, whereas stress-induced sympathetic activation increases the number of neutrophils and monocytes in the blood. Furthermore, it is suggested that these peripheral changes affect microglial activation. These findings imply vicious cycle of inflammation between the brain and periphery and have led us to propose the development of novel anti-depressant drugs targeting on stress-induced inflammation.
