Effects on the gating currents of the W434F Shaker KV channel. (A) Effect of 100 µM Cmpd 5 on the ON-gating currents at denoted voltages. Holding voltage, −80 mV; extracellular solution, 1K; black curves, control solution; red curves, compound solution. (B) Effect of 100 µM Cmpd 5 on the OFF-gating currents at −80 mV, after 500-ms prepulses between −100 and +10 mV in steps of 5 mV. Extracellular solution, 1K; black curves, control solution; red curves, compound solution. (C) Effect of 100 µM Cmpd 5 on gating charge versus voltage, Q(V), curve. Extracellular solution, 1K. The gating charges were calculated as the area under the curve in B from 1.5 to 100 ms. Black symbols and curves, control solution; red symbols and curves, compound solution. Data were fitted to Eq. 2 (with exponent n = 1). ΔV1/2 = −8.3 mV. (D) Same as in A but Cmpd 6. (E) Same as in B but Cmpd 6. (F) Same as in C but Cmpd 6. ΔV1/2 = −3.8 mV. (G–I) Effects of 100 µM Cmpd 5 and 6 on the activation time constant (G), the deactivation time constant (H), and the steady-state curves (I). Channel activation is measured as the opening in Fig. 4 (A and D) and as the single exponential relaxation phase (as recorded in Fig. 5 A at 0 mV). Channel closing is measured as the closing in Fig. 4 (B and E) and as the single exponential relaxation phase at −80 mV after a prepulse to 0 mV as recorded in Fig. 5 (B and E). Shifts of G(V) (from Fig. 2 C), and Q(V) as measured in Fig. 5 (C and F). Mean ± SEM. Number of experiments indicated in the figure. A two-tailed t test was used to compare effects to a hypothetical value of 1 in G and H and 0 in I. ns, P > 0.05; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.
