Microglia are immune cells in the central nervous system that engulf unnecessary synapses during development. In vivo imaging has substantially improved in recent years, besides the development of tools for manipulating microglia and neurons. These techniques reveal the novel functions of microglia. Microglia regulate neuronal activity to prevent synchronization. This neuron-microglia interaction is mediated by adenosine triphosphate-P2Y12 and adenosine-adenosine A1 receptor signalling in the striatum. Moreover, microglia release inflammation-related molecules that suppress neuronal activity, thus leading to lipopolysaccharide-induced aversion. Prostaglandin E2 (PGE2)-PGE receptor 1 signalling in the striatum underlies this behavioural alteration. Chronic stress activates microglia through toll-like receptor (TLR) 2 and TLR4 to release pro-inflammatory cytokines in the medial prefrontal cortex, thereby causing social avoidance. Microglia play multiple functions under physiological conditions, as well as pathological and psychological stress.
Keywords: behaviour; inflammation; microglia; neuron; stress.
© The Author(s) 2022. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.