Astrocytes orchestrate neuronal synchrony

Astroctyes are known to modulate synaptic communication between neurons. Now, Olivier Pascual (University of Pennsylvania, Philadelphia, PA), Tommaso Fellin, Giorgio Carmignoto (University of Padova, Italy), and colleagues report that astrocytes can elicit slow inward currents outside of synapses and thus activate synchronous responses in multiple neurons.

During periods of intense neural activity, calcium oscillations are triggered in astrocytes, inducing the cells to release glutamate. Fellin et al. find that this glutamate release stimulates neuronal activity in hippocampal slices. Photolysis of caged Ca²⁺ in single astrocytes almost exclusively activates the extrasynaptic NMDA receptors in CA1 pyramidal neurons. Thus, the astrocytes are triggering neural activity by turning on receptors outside of the synaptic junction itself—receptors that are abundant but whose role has been unknown.

Based on electrical activity and fluorescent probes,...