[Psychiatric disorders from a perspective of glia]

Glia is a collective term for cell types other than neurons, including large glial (astrocyte, oligodendrocyte) and small glial cells (microglia). The human brain consists of the same number of glial cells as neurons. Recent evidence suggests that the active brain should no longer be regarded solely as a network of neuronal contacts, rather as a circuit of integrated, interactive neurons and glial cells. Researchers have proposed that glial cells should receive much greater attention when attempting to understand the underlying biological mechanism of psychiatric disorders because the hypothesis of a monoamine neuron system could partially explain this phenomenon. Postmortem and imaging evidence for reductions in glial cell numbers and glia-related gene expressions and for abnormal hyperactivity of specific glia exist in the brain of psychiatric patients. Further, psychotropic drugs, such as antidepressants and antipsychotics, are reported to have a direct action on astrocyte and microglia through the expression of neurotrophic factors and inhibition of excess cytokines, which suggests these medication themselves could regulate mental function via the interaction between neuron and glia. Therefore, a perspective of glia contributes to a novel strategy for resolution of the biological mechanism in psychiatric disorders.