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

Abstract

We have previously demonstrated that rat type-1 cerebellar astrocytes express a very active Na + /Ca 2+ exchanger which accounts for most of the total plasma membrane Ca 2+ fl uxes 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 + /Ca 2+ exchange is involved in agonistinduced Ca 2+ signalling in rat cerebellar astrocytes. Laser-scanning confocal microscopy experiments using immuno fl uorescence labelling of Na + /Ca 2+ exchanger and RyRs demonstrated that they are highly co-localized. The most important fi nding presented in this chapter is that L -glutamate activates the reverse mode of the Na + /Ca 2+ exchange by inducing a Na + entry through the electrogenic Na + -glutamate co-transporter and not through the ionophoric L -glutamate receptors as con fi rmed by pharmacological experiments with speci fi c blockers of ionophoric L -glutamate receptors, electrogenic glutamate transporters and the Na/Ca exchange.