High frequency stimulation induces Ca2+ release from cultures astrocytes. (A) High frequency stimulation induced calcium increases as indicated by the fluorescent dye, fluo-4. (B) The fluorescence intensity for several individual cells, designated in (A), was monitored following HFS and demonstrates transient increases in a unique cell-specific pattern. (C) Mean calcium increase monitored from multiple cells. Note HFS was applied for 10s beginning at 15s with the following parameters: 100Hz, 100μs pulse width, 300μA. (D) HFS-induced glutamate release was significantly decreased (**P<0.01 vs. control) following chelation of calcium with BAPTA-AM (50μM, 45min) suggesting a calcium-dependent mechanism of release.