Local Resting Ca 2+ Controls the Scale of Astroglial Ca 2+ Signals.

Astroglia regulate neurovascular coupling while engaging in signal exchange with neurons. The underlying cellular machinery is thought to rely on astrocytic Ca ²⁺ signals, but what controls their amplitude and waveform is poorly understood. Here, we employ time-resolved two-photon excitation fluorescence imaging in acute hippocampal slices and in cortex in vivo to find that resting [Ca ²⁺ ] predicts the scale (amplitude) and the maximum (peak) of astroglial Ca ²⁺ elevations. We bidirectionally manipulate resting [Ca ²⁺ ] by uncaging intracellular Ca ²⁺ or Ca ²⁺ buffers and use ratiometric imaging of a genetically encoded Ca ²⁺ indicator to establish that alterations in resting [Ca ²⁺ ] change co-directionally the peak level and anti-directionally the amplitude of local Ca ²⁺ transients. This relationship holds for spontaneous and for induced (for instance by locomotion) Ca ²⁺ signals. Our findings uncover a basic generic rule of Ca ²⁺ signal formation in astrocytes, thus also associating the resting Ca ²⁺ level with the physiological "excitability" state of astroglia.
Competing Interests: Declaration of Interests The authors declare no competing interests.
(Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)