Astrocytes exhibit specific form of excitability associated with spatio-temporally organised fluc-tuations of cytosolic concentration of two major cations,Ca2+ and Na+.Astrocytes possess sev-eral sets of plasmalemmal molecules that provide for rapid transport of Na+ across the plasma membrane:(i) ionotropic receptors,(ii) canonical transient receptor potential cation channels,(ii) neurotransmitter transporters,and (iv) sodium-calcium exchanger.Activation of these path-ways in response to neuronal activity results in an increase of[Na+]i in astrocytes and there is manifold evidence for diverse signalling functions of these[Na+]i transients.Thus,in addition to its established homeostatic functions,activity dependent fluctuations of astrocyte[Na+]i regulate signalling cascades by feeding back on Na+-dependent transporters.The Na+ signalling system may be ideally placed for fast coordinating signalling between neuronal activity and glial "ho-meostatic" Na+-dependent transporters.