Fig. 1.

Voltage-Dependent Characteristics of ether-a-go-go–Related Gene (ERG) K⁺ Channels. Upper Panel: Cartoon schematic illustrating the 3 conductance states of ERG K⁺ channels. Lower Panel: Macroscopic current corresponding to the conductance states as illustrated in the upper panel. At hyperpolarized membrane potentials, ERG channels are closed (C). Depolarizing the membrane potential from −80 to 0 mV (lower trace) slowly opens the channels (C→O) resulting in an initial outward current as K⁺ ions diffuse out of the cell. However, ERG channels rapidly inactivate (O→I) by entering a second nonconductive state that limits the outward current produced by the initial depolarization. Partial repolarization of the membrane potential induces a rapid transition from an inactive to an open conformation (I→O). Because the rate of deinactivation (I→O) exceeds the rate at which the channels can close, a large resurgent current is generated as the membrane potential repolarizes.