Lidocaine inhibition of T220A. (A) Representative current traces of T220A. The application of increasing concentrations of lidocaine to the control trace (bottom) significantly reduced the peak currents. Lidocaine was applied by a fast perfusion while applying depolarizing pulses from −120 to −20 mV for 500 ms with 3-s intervals. The dashed line indicates the zero current level. Bar, 100 ms. (B) The representative lidocaine concentration response curve describing the effects of lidocaine on T220A was generated with the mean of I_drug/I_control obtained from the peak currents after exposing cells to 100 µM, 300 µM, 1 mM, and 3 mM lidocaine. The mean IC₅₀ for lidocaine is 765 ± 76.3 µM, with a mean slope of 0.92 ± 0.1 (n = 4). Error bars represent SEM.