Astrocytes Integrate Behavioral State and Vascular Signals during Functional Hyperemia

Abstract

Dynamic changes in astrocyte free Ca²⁺ regulate synaptic signaling and local blood flow. Although astrocytes are poised to integrate signals from synapses and the vasculature to perform their functional roles, it remains unclear what dictates astrocyte responses during neurovascular coupling under realistic conditions. We examined peri-arteriole and peri-capillary astrocytes in the barrel cortex of active mice in response to sensory stimulation or volitional behaviors. We observed an AMPA and NMDA receptor-dependent elevation in astrocyte endfoot Ca²⁺ that followed functional hyperemia onset. This delayed astrocyte Ca²⁺ signal was dependent on the animal's action at the time of measurement as well as a neurovascular pathway that linked to endothelial-derived nitric oxide. A similar elevation in endfoot Ca²⁺ was evoked using vascular chemogenetics or optogenetics, and opto-stimulated dilation recruited the same nitric oxide pathway as functional hyperemia. These data show that behavioral state and microvasculature influence astrocyte Ca²⁺ in active mice. VIDEO ABSTRACT.

Keywords: active; arteriole; astrocyte; astroglia; awake; barrel cortex; calcium; conscious; in vivo; nitric oxide; two-photon.