Fig. 4.

Depletion of internal Ca²⁺ stores after exposure of astrocytes to an external calcium-free solution. The effect of a calcium-free external solution containing EGTA (2 mm) on the filling of internal Ca²⁺ stores was tested by using 30–60 sec applications of ionomycin (20 μm). At the beginning of the perfusion, ionomycin indicated the amount of filling of the internal stores in control conditions. With time, Ca²⁺ pools were reduced progressively by the lack of external Ca²⁺ and were emptied completely after 10 min. Note that depletion of internal Ca²⁺ stores started after 5 min of treatment. Data are pooled from 25 experiments in which each measurement was performed independently on seven different cells.