title: Locally synchronized astrocytes.
abstract: Astrocytes exhibit spontaneous calcium fluctuations. These activities have not been captured by large-scale recordings, and little is known about their collective dynamics. In situ and in vivo calcium imaging from hundreds (up to 2195) of astrocytes in the mouse hippocampus and neocortex revealed that neighboring astrocytes spontaneously exhibited synchronous calcium elevations and formed locally correlated cell groups ("clusters" of 2 to 5 astrocytes within a diameter of 81 ± 45 μm). Cluster activity accounted for approximately 10% of the astrocytic calcium events, and 44% of the clusters appeared repetitively during our observation period of 60 min. Astrocytic clusters emerged through metabotropic glutamate receptor activation, independently of neuronal activity. Neurons were depolarized by 1.5 mV when clusters appeared near their dendrites. This depolarization was mediated by non-N-methyl-D-aspartate (NMDA) glutamate receptor channels and was replicated by calcium uncaging activation of multiple astrocytes. Importantly, the activation of single astrocytes alone could not depolarize neurons but readily elicited NMDA-dependent slow inward currents in depolarized neurons. Thus, these novel ensemble dynamics of astrocytes, which cannot be captured by conventional small-scale imaging techniques, play a different role in neuronal modulation than does the sporadic activity of single astrocytes.
authors.affiliation: Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Sasaki
authors.forename: Nahoko
authors.initials: N
authors.lastname: Kuga
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Namiki
authors.forename: Norio
authors.initials: N
authors.lastname: Matsuki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ikegaya
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology; D002449:Cell Aggregation / Q000502:physiology*; D003344:Cortical Synchronization / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D019579:Neocortex / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D009924:Organ Culture Techniques; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000502:physiology
chemical_list: D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D002118:Calcium