Dose-response curves of currents from multiple- and single channel patches. (A) Multiple channel currents activated by different ATP concentrations at -120 mV. The data were sampled at 10 kHz and filtered at 5 kHz. The bar indicates the application of ATP. (B) The dose-response curve of multiple channel currents (Circles, n = 3) and single channel currents (Diamonds, n = 2) recorded from outside-out patches. The multiple channel currents were normalized to the peak value of currents activated by 100 μM ATP and rescaled to the same po,max as the single channel current. po of single channel currents (Diamonds) were calculated from the all-points histogram (see Figure 4). The solid line is a fit of the Hill equation of multiple channel currents with an EC50 of 9.8 ± 0.8 μM and a Hill coefficient of 1.91 ± 0.29. The dash-dot line is the fit of the Hill equation of single channel currents with an EC50 of 11.2 ± 1.0 μM, a Hill coefficient of 2.3 ± 0.44, and po,max of 0.61.