Nonresolving low-grade inflammation is supposed to underly the basis of chronic disorders including cancer, type 2 diabetes, cardiovascular diseases, obesity and psychiatric disorders such as depression. There is increasing evidence suggesting that pathophysiology of psychiatric disorders is related to the inflammatory responses mediated by microglial cells. Elevation of intracellular Ca2+ is important in activation of microglial cell functions, including proliferation, release of NO, cytokines and BDNF. It has been shown that alteration of intracellular Ca2+ signaling underlies the pathophysiology of psychiatric disorders, including schizophrenia, depression and bipolar disorders. Microglial cells are able to respond to BDNF, which may be important for the regulation of inflammatory responses, and may also be involved in the pathophysiology and/or the treatment of psychiatric disorders.