Fig. 4. Differential block of two components of the Na⁺current by droperidol. (A ) Na⁺currents recorded in an isolated soma  in control and in the presence of 10, 30, 100, and 300 μm droperidol. Inactivation kinetics of the currents were fitted with two exponentials using . The time constants of inactivation of fast and slow components are indicated near the control recording. The amplitudes of the total current (I⁰) and of fast (I^F) and slow (I^S= I⁰− I^F) components are given below the corresponding traces. (B ) Concentration dependence of suppression of fast (filled symbols) and slow (open symbols) components by droperidol (eight somata ). The data points for the fast component were best fitted with : IC⁵⁰= 8.3 ± 1.1 μm, Res = 0. Fitting the data points for the slow component under the assumption that Res = 0 resulted in an IC⁵⁰value of 809 ± 247 μm.