ABSTRACT
Recently it has been shown that, in parallel with its uptake into the astrocyte, glutamate is released in association with Ca2+ waves (Pasti, Zonta, Pozzan, Vicini, & Carmignoto 2001, Schipke, Boucsein, Ohlemeyer, Kirkhoff, & Kettenmann 2002)„ which represent a formofmulticellular bidirectional communication with neurons. Astrocytes can communicate with each other by the propagation of Ca2+ elevation. Astrocytes can also generate Na+ waves whose behavior is driven by the Ca2+ waves. It has been observed that inhibiting Na+/glutamate transporters blocks the Na+ waves without affecting the Ca2+ waves (Bernardinelli, Magistretti, & J. 2004). On the contrary each process that inhibits Ca2+ also inhibits the Na+ waves. Since the glutamate released in the synaptic cleft during neuronal activity is rapidly taken up by astrocyte with three Na+ ions, the uptake of glutamate results in an increase of the astrocytic Na+ concentration. Glutamate is thus involved in the generation of the Na+ wave, as the inhibition of glutamate transporter TOBA causes a strong inhibition of the wave without affecting the Ca2+ wave. Recent experiments proved that glutamate release and its subsequent Na+ dependent uptake mediate the regenerative Na+ wave (Bernardinelli, Magistretti, & J. 2004).
