FIGURE 3.

[Ca²⁺]_c responses to dopamine are dependent on intracellular Ca²⁺ stores in astrocytes. A, removal of external Ca²⁺ (Ca²⁺-free HBSS with 0.5 mm EDTA) delays the onset of the DA-induced Ca²⁺ responses in astrocytes, but does not abolish it. B, depletion of the intracellular Ca²⁺ pool by application of the inhibitor of ER Ca²⁺ pump, thapsigargin (0.5 μm), abolishes the DA-induced Ca²⁺ signal in astrocytes. C, changes in [Ca²⁺]_c in response to DA are dependent on the presence of the inhibitor of phospholipase C U73122 (5 μm). D, application of the inhibitor of IP₃ receptor and capacitive calcium entrance 2-APB (20 μm) blocked the effect of DA in astrocytes. E, in the presence of external 100 μm Mn²⁺, the fura-2 response excited at 360 nm showed no change during the [Ca²⁺]_c transients in astrocytes, demonstrating that this is close to the isosbestic [Ca²⁺]_c-independent excitation wavelength for fura-2, confirming that the DA-induced Ca²⁺ signal in astrocytes is independent of external Ca²⁺.