Figure 2

Effects of 1 µM GS967 (A) and 40 µM mexiletine (B) on the voltage dependence of steady-state inactivation of I_NaL, determined using a conventional prepulse-protocol presented in the insets. 2 s long prepulses, ranging from –130 to −40 mV were followed by a test pulse clamped to −20 mV for 2 s. Each I_NaL amplitude (I_test) was normalized to the peak current measured after the −130 mV prepulse (I_max) and these I_test/I_max ratios were plotted as a function of the corresponding prepulse-potential. Finally, data were fitted to a Boltzmann function and the results are given below the stead-state inactivation curves. Symbols and bars are mean ± SEM values, numbers in parentheses indicate the number of myocytes studied, asterisks denote significant differences between data of the pre-drug control and the GS967- or mexiletine-treated groups.