Figure 4.

(A) Representative hERG current traces recorded before (control) or after addition of 10 μmol/L mexiletine (10 min incubation), using the protocol shown in the lower panel. To verify the reproducibility of the experiments, each measurement was repeated n ≥ 5 times. (B) “Mexiletine sensitive” current obtained by subtracting traces “a” and “b” shown in (A). (C) Concentration–response relationship (mean ± SEM) for block by mexiletine of hERG tail current, induced by repolarization from +80 mV to −50 mV. A Hill equation fit yielded an IC₅₀ of 47.2 ± 5.3 μmol/L and a Hill slope of 1.13 ± 0.20 (n ≥ 5 per data point).