Figure 12.

Inhibition of hERG Na⁺ currents by external Na⁺ ions (Na⁺ _o). (A and B) hERG Na⁺ currents in the absence (A) and presence of 10 mM Na⁺ _o (B). The pipette solution contained 135 mM Na⁺. (C) The concentration-dependent block of hERG Na⁺ current by Na⁺ _o. The outward Na⁺ currents at 50 mV at each Na⁺ _o relative to the control value were plotted against the Na⁺ _o concentration, and the data were fitted to the Hill equation (n = 8).