Figure 11.

Absence of time-dependent block by β4_154–167 in BTX-modified wild-type or hNav1.5-CW mutant Na⁺ channels. Repetitive pulses (50 mV/20 ms at 2 Hz) were applied 2,000 times after the pipette break-in. The families of BTX-modified wild-type Na⁺ channels (A and B) or hNav1.5-CW mutant channels (C) were then recorded and superimposed. Current traces corresponding to 50 mV were labeled by arrows. Besides 4 μM BTX, the pipette solution also contained either 2 mM acetyl-KIFMK-amide (A) or 1 mM β4_154–167 (B and C). The time frame was recorded ∼50× slower in C than that in A and B. The bath solution contained 130 mM Na⁺ ions (A) or 65 mM Na⁺ ions (B and C). Holding potential was set at −140 mV. Experiments were repeated in five to six cells with similar results.