Figure 4. Effects of two different extracellular [K⁺] on deactivation of I_Kv4.3.

Experimental records of deactivation at [K⁺]_o concentrations of 2 mm (A) and 98 mm (B) are shown. A two-pulse protocol was used. Holding potential was −90 mV and the P1 pulse was set to +50 mV for 10 ms and followed by a second pulse that ranged between −120 to −40 mV for 50 ms in steps of 10 mV (inset in A). Capacitance transients were subtracted. Simulated traces of deactivation of I_Kv4.3 for different [K⁺]_o, 2 mm (C) and 98 mm (D), were obtained using the same voltage clamp protocol described in A and B, respectively. Depolarization pulses during simulations were applied at the end of a 20 ms holding potential at which time test depolarizations were initiated and designated as occurring at t = 0 ms. A 20 ms holding potential was used to allow the channel to reach equilibrium. Data shown in A and B in this figure were obtained using the cut-open oocyte voltage clamp technique.