Astrocytes integrate and drive neural activity

Abstract

Many brain functions depend on the ability of neural networks to temporally integrate transient inputs to produce sustained discharges. This can occur through cell-autonomous mechanisms in individual neurons or through reverberating activity in recurrently connected neural networks. We report a third mechanism involving temporal integration of neural activity by a network of astrocytes. Previously, we showed that some types of interneurons can generate long-lasting trains of action potentials for tens of seconds (\"barrage firing\") following repeated depolarizing stimuli. Here, we show that calcium signaling in an astrocytic network correlates with barrage firing; that active depolarization of astrocyte networks by chemical or optogenetic stimulation enhances barrage firing; and that chelating internal calcium, inhibiting release from internal stores, or inhibiting GABA transporters or metabotropic glutamate receptors inhibited barrage firing. Thus, through complex molecular processes, networks of interconnected astrocytes influence the spatiotemporal dynamics of neural networks by directly integrating neural activity and driving long-lasting barrages of action potentials in some populations of inhibitory interneurons.