New Tools to Study Astrocyte Ca2+ Signal Dynamics in Brain Networks In Vivo

Gabriele Losi, Letizia Mariotti, Michele Sessolo, Giorgio Carmignoto

Sensory information processing is a fundamental operation in the brain that is based on dynamic interactions between different neuronal populations. Astrocytes, a type of glial cells, have been proposed to represent active elements of brain microcircuits that, through dynamic interactions with neurons, provide a modulatory control of neuronal network activity. Specifically, astrocytes in different brain regions have been described to respond to neuronal signals with intracellular Ca(2+) elevations that represent a key step in the functional recruitment of astrocytes to specific brain circuits. Accumulating evidence shows that Ca(2+) elevations regulate the release of gliotransmitters that, in turn, modulate synaptic transmission and neuronal excitability. Recent studies also provided new insights into the spatial and temporal features of astrocytic Ca(2+) elevations revealing a surprising complexity of Ca(2+) signal dynamics in astrocytes. Here we discuss how recently developed experimental tools such as the genetically encoded Ca(2+) indicators (GECI), optogenetics and chemogenetics can be applied to the study of astrocytic Ca(2+) signals in the living brain.