ИСТИНА

Introduction: Orchestrated activation of different cell types and their interactions within the brain active milieu provide the cellular basis for brain functions. We investigated and compared how the astrocytic and neuronal calcium activity patterns are organized and change while head-fixed mice were moving around an airlifted platform. Methods: The genetically encoded calcium indicator, GCaMP6f, was expressed under the astrocyte- or neuron-specific promoter in C57BL/6 mice. Two-photon calcium imaging was performed on the somatosensory cortex of awake head-fixed mice navigating Mobile HomeCage (Neurotar, Finland). Results and discussion: Ca2+ activity in astrocytes was low at periods of animal quiescence but significantly increased during locomotion. Ca2+ signals first appeared in the distal processes and then propagated to astrocytic somata where exhibited oscillatory behavior, suggesting that astrocytic soma operates as both signal integrator and amplifier. In contrast to astrocytes, profound Ca2+ activity was detected in neurons in quiescent periods and it further increased during locomotion. Neuronal Ca2+ rose almost immediately following the onset of locomotion, whereas astrocytic Ca2+ signals emerged with a time lag of several seconds. Neurons reliably responded to each episode of locomotion, while Ca2+ elevations in astrocytes were significantly diminished in response to the second locomotion in each pair of sequential locomotion episodes. Thus, neuronal Ca2+ response is primary and reflects sensory input routed by neurons. Astrocytic Ca2+ dynamics is secondary and likely to provide metabolic and homeostatic support of intercellular communication and plasticity within the brain active milieu. Research support: The work is supported by the Russian Science Foundation (grant 22-14- 00033).