Characterization and properties of Mg2+ uptake and release from guinea pig cerebral cortex synaptosomes

The transport of Mg2+ into and out of guinea pig cerebral cortex synaptosomes was studied. Experiments are reported showing that the influx of Mg2+ (at low synaptosomal ATP) specifically requires a physiologically oriented Na+ gradient across the plasma membrane. It is also shown that an outwardly directed energy dependent Mg2+ pump is present in the synaptosomal plasma membrane; this pump, which requires ATP, is inhibited at high synaptosomal (Na+).