Sodium-Calcium Exchanger Modulates the L-Glutamate Ca i 2+ Signalling in Type-1 Cerebellar Astrocytes

We have previously demonstrated that rat type-1 cerebellar astrocytes express a very active Na+/Ca2+ exchanger which accounts for most of the total plasma membrane Ca2+ fluxes and for the clearance of Ca i 2+ induced by physiological agonist. In this chapter, we have explored the mechanism by which the reverse Na+/Ca2+ exchange is involved in agonist-induced Ca2+ signalling in rat cerebellar astrocytes. Laser-scanning confocal microscopy experiments using immunofluorescence labelling of Na+/Ca2+ exchanger and RyRs demonstrated that they are highly co-localized. The most important finding presented in this chapter is that L-glutamate activates the reverse mode of the Na+/Ca2+ exchange by inducing a Na+ entry through the electrogenic Na+-glutamate co-transporter and not through the ionophoric L-glutamate receptors as confirmed by pharmacological experiments with specific blockers of ionophoric L-glutamate receptors, electrogenic glutamate transporters and the Na/Ca exchange.