Fig. 1.

Use-dependent block of the Na⁺ channel by ranolazine (25 μM) is unaffected by test pulse duration. A train of 40 pulses was applied after a 15-s rest. The diastolic interval was kept constant at 150 ms, and pulse durations were 5, 20, or 200 ms. A: atrial myocytes (n = 6). B: ventricular myocytes (n = 5 cells) C: human embryonic kidney (HEK)-293 cells expressing SCN5A outward Na⁺ current (I_Na; n = 6). D: HEK-293 cells expressing SCN5A inward I_Na (n = 6). Insets in A–D show typical current traces during 200-ms test pulses. Data are means ± SD.