title: Subtle modulation of ongoing calcium dynamics in astrocytic microdomains by sensory inputs.
abstract: Astrocytes communicate with neurons through their processes. In vitro experiments have demonstrated that astrocytic processes exhibit calcium activity both spontaneously and in response to external stimuli; however, it has not been fully determined whether and how astrocytic subcellular domains respond to sensory input in vivo. We visualized the calcium signals in astrocytes in the primary visual cortex of awake, head-fixed mice. Bias-free analyses of two-photon imaging data revealed that calcium activity prevailed in astrocytic subcellular domains, was coordinated with variable spot-like patterns, and was dominantly spontaneous. Indeed, visual stimuli did not affect the frequency of calcium domain activity, but it increased the domain size, whereas tetrodotoxin reduced the sizes of spontaneous calcium domains and abolished their visual responses. The "evoked" domain activity exhibited no apparent orientation tuning and was distributed unevenly within the cell, constituting multiple active hotspots that were often also recruited in spontaneous activity. The hotspots existed dominantly in the somata and endfeet of astrocytes. Thus, the patterns of astrocytic calcium dynamics are intrinsically constrained and are subject to minor but significant modulation by sensory input.
authors.affiliation: Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Asada
authors.affiliation: Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan.
authors.forename: Sakiko
authors.initials: S
authors.lastname: Ujita
authors.affiliation: Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Nakayama
authors.affiliation: Graduate School of Informatics Kyoto University, Kyoto, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Oba
authors.affiliation: Graduate School of Informatics Kyoto University, Kyoto, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Ishii
authors.affiliation: Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Matsuki
authors.affiliation: Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan Center for Information and Neural Networks, Suita City Osaka, Japan ikegaya@mol.f.u-tokyo.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ikegaya
keywords: Astrocyte; endfoot; map; orientation selectivity; visual cortex