Sodium homeostasis and signalling: The core and the hub of astrocyte function

Neuronal activity and neurochemical stimulation trigger spatio-temporal changes in the cytoplasmic concentration of Na⁺ ions in astrocytes. These changes constitute the substrate for Na⁺ signalling and are fundamental for astrocytic excitability. Astrocytic Na⁺ signals are generated by Na⁺ influx through neurotransmitter transporters, with primary contribution of glutamate transporters, and through cationic channels; whereas recovery from Na⁺ transients is mediated mainly by the plasmalemmal Na⁺/K⁺ ATPase. Astrocytic Na⁺ signals regulate the activity of plasmalemmal transporters critical for homeostatic function of astrocytes, thus providing real-time coordination between neuronal activity and astrocytic support.