Research ArticleNeuroscience

Astrocytes Modulate Neural Network Activity by Ca2+-Dependent Uptake of Extracellular K+

Sci. Signal.  03 Apr 2012:
Vol. 5, Issue 218, pp. ra26
DOI: 10.1126/scisignal.2002334

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Increasing Synaptic Fidelity

Although astrocytes have long been implicated in maintenance of extracellular K+ homeostasis and in the mediation of propagated Ca2+ signals, the relationship between these two properties has been unclear. Here, Wang et al. show that increases in astrocyte cytosolic Ca2+ secondary to activation of G protein–coupled receptors (GPCRs) lead to increased Na+ influx through the Na+/Ca2+ exchanger, which, in turn, stimulates astrocyte Na+,K+-ATPase activity and K+ uptake and consequently decreases the local extracellular K+ concentration. Decreased K+ increased neuronal hyperpolarization, with a consequent suppression of basal—but not evoked—synaptic activity, and enhanced synaptic fidelity. The authors thus conclude that Ca2+-dependent activation of the astrocyte Na+,K+-ATPase through GPCR-activated signaling pathways enables astrocytes to dynamically regulate the extracellular K+ concentration and thereby modulate neuronal function.