Figure 2

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 p_o,max as the single channel current. p_o 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 p_o,max of 0.61.