Figure 4. Effects of ATP on ONH astrocytes. A: Ca²⁺ traces were initiated by 1 mM ATP in ONH astrocytes. Cells were conditioned in serum-free medium containing Ca²⁺. Removal of extracellular Ca²⁺ had no effect on the transients, suggesting that ATP was acting at receptors coupled to G-protein mediated release of Ca²⁺ from intracellular stores. AA and CA astrocytes gave comparable responses. B: Peak areas were calculated from transients obtained from multiple cells (10–15) from three different donor lines. There was no significant difference in peak areas. C: Shown in this panel are representative western blots of p-CREB (Ser-133) phosphorylation in AA and CA astrocytes after treatment with ATP for 0, 0.5, 1, and 3 h. D: ATP stimulated more CREB phosphorylation in CA astrocytes compared to AA astrocytes treated for 1 h (p<0.01, double asterisk, n=3). Error bars indicate SEM.