Microglia regulate neuronal and behavioral functions under physiological and pathological conditions


 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 signaling 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 signaling in the striatum underlies this behavioral 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.