Ca²⁺ signaling regulated by an ATP-dependent autocrine mechanism in astrocytes

Although the mechanisms of Ca²⁺ wave propagation in astrocytes induced by mechanical stimulation have been well studied, it is still not known how the [Ca²⁺]_i increases in the stimulated cells. Here, we have analyzed the mechanisms of [Ca²⁺]_i increase in single, isolated astrocytes. Our results showed that there was an autocrine mechanism of Ca²⁺ regulation mediated by ATP in mechanically stimulated astrocytes. This autocrine mechanism induced the activation of phospholipase C via a G-protein, resulting in Ca²⁺ release from intracellular Ca²⁺ stores. A second pathway mediating a [Ca²⁺]_i increase was via a Ca²⁺ influx from the extracellular space, which, interestingly, suppressed an intracellular Ca²⁺ oscillation. These two different Ca²⁺ cascades are involved in signal transduction and may function separately during intercellular communication.