Figure 7. Inactivation of the ternary Kv4.1 channel complex prevents internal access of bTBuA to the pore.

(a) Schematic of experimental protocol. Current was evoked by a 5-s step depolarization from −100 to +50 mV to ensure complete steady-state inactivation. The intracellular side of the patch was exposed to 100 μM intracellular bTBuA for a total of 1.5 s (red bar). The application began once current inactivation had reached steady-state, and continued for 1 s at +50 mV. The exposure to bTBuA was then terminated 500 ms after repolarizing the membrane to −100 mV. To test whether bTBuA had any effect, the same pulse was subsequently repeated while the inside patch was bathed in control intracellular solution. (b) Overlay of macropatch currents before (black) and after (red) intracellular exposure to bTBuA. (c) Comparison of peak currents before (control) and after (bTBuA) exposure (20 iterations of the pulse sequence on the same macropatch). (d) Comparison of weighted time constant of decay from currents before (control) and after (bTBuA) exposure (same experiment, 20 iterations). Horizontal lines in (c,d) indicate mean values.