Voltage dependence of hEAG1 channel block by clofilium. (A) Control hEAG1 currents (bottom) elicited with voltage-pulse protocol shown in the top. V_h was −100 mV, and V_pre was 10 s in duration and ranged from −130 to +35 mV, applied in 15-mV increments. (B) Currents recorded from same oocyte after steady-state block by 0.5 µM clofilium. Note that the duration of V_pre was increased to 30 s. (C) Voltage dependence of hEAG1 activation (◆) and inactivation (■) in control, and inhibition by 0.5 µM clofilium (□). For inactivation and inhibition curves, normalized I_max was plotted as a function of V_pre. For the activation curve, I_pre normalized for electrical driving force was plotted as a function of V_pre. Data (n = 5) were fitted with a Boltzmann function (curves). For control inactivation, V_0.5 = −86.7 ± 4.5 mV and z = 3.12 ± 1.21; for control activation, V_0.5 = −12.4 ± 0.8 mV and z = 2.00 ± 0.02. For inactivation in the presence of clofilium, V_0.5 = −5.2 ± 1.7 mV and z = 2.13 ± 0.13. (D) Comparison of the voltage dependence of hEAG1 activation (dashed curve) and block by 0.5 µM clofilium (□).