Spontaneous astrocytic Ca super(2+) oscillations in situ drive NMDAR-mediated neuronal excitation

Astrocytes respond to chemical, electrical and mechanical stimuli with transient increases in intracellular calcium concentration ([Ca super(2+)] sub(i)). We now show that astrocytes in situ display intrinsic [Ca super(2+)] sub(i) oscillations that are not driven by neuronal activity. These spontaneous astrocytic oscillations can propagate as waves to neighboring astrocytes and trigger slowly decaying NMDA receptor-mediated inward currents in neurons located along the wave path. These findings show that astrocytes in situ can act as a primary source for generating neuronal activity in the mammalian central nervous system.