Figure 6.

Extracellular La³⁺ (10 µM) slows activation of T449V channels but causes no inactivation. I_K is compared in 10KCa2K (black traces) and in 10Ca2K + La³⁺ (10 µM La³⁺; blue traces). Sampling was interrupted at each of the vertical dashed lines for 100 ms and then resumed. Total sweep duration was 850 ms. On return to −80 mV, there was a clear inward I_K tail without La³⁺(bottom arrow), but none in the presence of La³⁺, which blocks K⁺ channels at negative voltage (top arrow). The tail is shown at slightly higher gain in inset a.