Biophysical properties of the slowly inactivating, late Na+ current (INaL) evaluated by whole cell patch clamp in human ventricular cardiomyocytes (A-E) and human cloned Nav1.5 expressed in tsA201 cells (F). A-B: INaL can be carried either by Na+ or Li+. B: I-V relation for INaL. C: examples of steady-state activation and availability curves, G(Vm) and A(Vp), respectively. D: Examples of original traces illustrating voltage-independent INaL decay. E: slow reactivation of INaL. F: INaL produced by Nav1.5 was assessed as difference current before application of a selective Na+ channel blocker tetrodotoxin (TTX, 30 μM) and after TTX. Voltage protocols are shown at the traces. Recording was performed at 24°C. Modified from [11] (A-E) and [65](F), used with permission.