Figure 5.

Lack of inward ionic tail currents under the recording conditions used to measure Q_off. Representative data collected from a SkEIIIK-expressing dysgenic myotube obtained under both ionic (10 mM Ca²⁺, ○) and gating current recording conditions (8 mM Ca²⁺, 2.0 mM Cd²⁺, and 0.2 mM La³⁺, •). Cells were depolarized for 200 ms to +60 mV (to fully activate SkEIIIK channels) and subsequently repolarized to the potentials indicated on the abscissa. Currents during the repolarization period (20 ms) were subsequently integrated and plotted against the repolarization potential. Outward ionic currents through SkEIIIK (seen as positive integrals at potentials >0 mV) were significantly attenuated by Cd²⁺ and La³⁺. At potentials hyperpolarized to −20 mV (inset), negative integrals were not largely affected by either the Cd²⁺ and La³⁺ solution or by the increase in driving force, indicating a lack of inward ionic currents through SkEIIIK channels. Similar results were obtained from four separate experiments.