[Microglial regulation of brain function and pathological changes].

Microglia are the only immune cells in the central nervous system. It has been shown that microglia actively regulate the number of neurons by participating in the cell death of neural stem cells during development and maturation. In addition, recent optical techniques have enabled in vivo imaging, which has revealed the function of microglia on synapses. Microglia regularly monitor synaptic activity and remove synapses that show abnormal activity in the event of brain infarction or other disorders. During development, microglia contribute to the formation of immature synapses by contacting dendrites during early synapse formation, and they are also involved in the de-synaptic process by selectively removing weakly active synapses through the use of classical complement cascade signaling. Furthermore, these abnormalities are known to contribute to the development of autism during development and to the development of Alzheimer's disease during maturation. In addition to this, microglia also contribute to plastic changes in synapses during the learning process in maturation. Furthermore, by modifying synaptic activity, microglia are known to be involved in changes in the activity of neuronal circuits. In addition to these synaptic functions, microglia are also known to be involved in the permeability of the blood-brain barrier. In this chapter, these functions will be summarized and discussed.