Imaging neuronal and astrocytic Ca²⁺ transients and hemodynamic responses evoked by single stimulation in rodent cortex

As transient intracellular Ca²⁺ changes play an important role in many eßential proceßes including neuronal and astrocytic plasticity, tracking brain activity via Ca²⁺ is crucial. Unlike hemodynamics, Ca²⁺ change must be measured optically using an ionic fluorescent Ca²⁺ indicator. Here, we combine our highly sensitive multimodality optical imaging platform with genetically encoded Ca²⁺ indicator (GCaMP6f) expreßed in neurons or astrocytes in somatosensory cortex, which enables simultaneous tracking of single-stimulation-evoked neuronal, astrocytic Ca²⁺transients along with the corresponding hemodynamic responses at high spatiotemporal resolutions. We imaged neuronal and astrocytic Ca²⁺ transients from mouse cortex in response to a single electrical pulse (3mA, 0.3ms). Our results show that the neuronal Ca²⁺ responses were strong (ΔF/F_N=6.4±0.29%), fast (latency τ_N=6±2.7ms) and of short duration (Δt_N=537±34ms) whereas the astrocyte responses were weak, slow and long-lasting (i.e., ΔF/F_A=1.7±0.1%, τ_A=313±65ms, Δt_A =993±48ms). The synchronized activities among astrocytes were temporally leß correlated than those among neurons. These results demonstrate the capability of optical detection of cell-specific Ca²⁺ activities from synchronized neuronal, astrocyte ensembles concurrently with the hemodynamic responses within the neuro-glio-vascular network, which can facilitate the study of the roles of astrocytes in the neurovascular coupling proceß.