Abstract
Emerging lines of evidence show that glial cells are not simply supportive, but rather are functional, controling various brain functions. Thus, their dysfunction seems to be closely related to several brain diseases. Although glial cells are non-excitable cells and do not evoke action potentials, they have various receptors for chemical transmitters, respond to them, and release chemical transmitters, so called "gliotransmitters". Using these gliotransmitters, glial cells communicate with adjacent cells including neurons, vascular cells and glial cells themselves. Glial cells, especially astrocytes, enwrap almost all synapses and release gliotransmitter in response to neuronal activities or even spontaneously. As a gliotransmitter, extracellular ATP has a central role. Astrocytic ATP acts on the P2 receptors on astrocytes to produce a spreading Ca^<2+> wave, which induces further ATP release from astrocytes to control neuronal activities. Almost 10 years have passed since the first report of such dynamic glial activities in vitro, and we now understand that astrocytes are active even in vivo. Here, we show that astrocytic ATP dynamically regulates neuronal excitability, i.e., synaptic transmission.
