Figure 2.

A, ATP (1 μm to 1 mm) activated outward currents in a dose-dependent manner in PDGFRα⁺ cells at a holding potential of −40 mV. These responses were reproducible upon repetitive or continuous application of ATP. B, expanded time scales of current responses to ramp protocols from −80 mV to +80 mV denoted by a–e in A. C, concentration–response curve of ATP. Calculated EC₅₀ was 26 μm. D, continuous application of ATP generated reproducible outward currents. E, ATP (100 μm) induced hyperpolarization under current-clamp mode (I = 0) and activated outward currents in the same cell after switching to voltage-clamp mode (holding potential: HP = −40 mV). Dotted line denotes 0 pA under voltage clamp. Filled arrowheads denote ramp depolarizations before and during ATP application.