Depolarization-induced increases in intracellular free calcium detected in single cultured neuronal cells.

Microspectrofluorometry was used to examine intracellular free calcium changes in single NG108-15 neurons loaded with the Ca2+ sensitive probe, quin2. The changes in intracellular free Ca2+ were induced either by depolarizing cells with high K+ or veratridine or by the addition of ionomycin. Ca2+-free medium and various inorganic and organic calcium-channel blocking agents blocked changes in intracellular free Ca2+ levels, indicating that Ca2+ entry is most likely through voltage-sensitive calcium channels.