Glial calcium signaling and neuron-glia communication.

The existence of bidirectional signaling between astrocytes and neurons has revealed an important active role of astrocytes in the physiology of the nervous system. As a consequence, there is a new concept of the synaptic physiology-"the tripartite synapse", where astrocytes exchange information with the pre- and postsynaptic elements and participate as dynamic regulatory elements in neurotransmission. The control of the Ca2+ excitability in astrocytes is a key element in this loop of information exchange. The ability of astrocytes to respond to neuronal activity and discriminate between the activity of different synapses, the modulation of the astrocytic cellular excitability by the synaptic activity, and the expression of cellular intrinsic properties indicate that astrocytes are endowed with cellular computational characteristics that process synaptic information. Therefore, we propose that astrocytes can be considered as cellular elements involved in the information processing by the nervous system.