Figure 2. ATP-induced calcium transients are reversibly inhibited by low concentrations of manganese.

(a) Application of 1 μM ATP resulted in robust Ca²⁺ transients in striatal astrocytes that persisted for greater than 30 sec. (b) Addition of Mn²⁺ to the imaging media at concentrations as low as 10 μM acutely suppressed ATP-induced Ca²⁺ transients. (c) Representative traces of the astrocytic response to 1 μM ATP (black arrowhead indicates time of ATP addition) in the presence of increasing concentrations of Mn²⁺ (1 - 1000 μM) indicate a dose-dependent suppression of intracellular Ca²⁺ transients. (d) Quantitation of the maximum astrocytic Ca²⁺ response to 1 μM ATP in the presence of increasing concentrations of Mn²⁺. (e) Repeated additions of 1 μM ATP to striatal astrocytes using a flow chamber induce multiple Ca²⁺ transients that are reversibly inhibited by acute addition (f) of 10 μM Mn²⁺ to the flow cell. Vertical bars denote 1 relative fluorescent unit; horizontal bars denote 10 sec (n= 50-60 cells group; *** p<0.001).