Imaging of Astrocytic Activity in Living Rodents

Mounting evidence from in vitro experiments supports bidirectional interactions between astrocytes and neurons, suggesting glial involvement in neuronal information processing in the brain. Elevation of the cytosolic calcium ion (Ca²⁺ ) concentration has been suggested to be important for gliotransmission; however, the study of Ca²⁺ dynamics in cerebral cortical astrocytes in vivo became possible only recently. Here, we describe a set of procedures to monitor Ca²⁺ concentration fluctuations in a population of astrocytes or in astrocytic processes using in vivo two-photon microscopy. Simultaneous recording of neuronal activity by electrodes and astrocytic activity by imaging is a promising way to reveal the nature of neuron–glia interactions in the brain of living rodents.