Accumulating evidence shows astrocytic contribution to brain function and diseases, however, the function of astrocytes remains to be uncovered. Dynamic changes in the intracellular Ca2+ level in astrocytes are one of the outstanding indexes of ongoing astrocytic activity. Therefore, we tried to uncover astrocytic function using approaches combined with Ca2+ imaging. We showed that astrocytes promote neuronal growth and survival after injury via Ca2+-dependent regulation of a cell adhesion protein, N-cadherin. Furthermore, we developed a method for the monitoring of astrocytic Ca2+ signals in living mouse brain, and found a previously unidentified pattern of spontaneous Ca2+ signals, which are preferably displayed in astrocytic fine processes. These findings and methods are promising to provide further information of astrocytic function, which can contribute to development of pharmacology.