Figure 8.

GxTx reduces voltage dependence of gating-current activation and accelerates deactivation. (A) Control I_{g ON-fast} response to the following voltage steps: −20 mV, purple; 20 mV, blue; 60 mV, green; 100 mV, red. Holding potential was −100 mV. Lines are fits of Eq. 6, falling phase τ_ON: 20 mV = 1.91 ± 0.02 ms; 60 mV = 0.867 ± 0.007 ms; 100 mV = 0.42 ± 0.01 ms. (B) I_{g ON-fast} in 1 µM GxTx, same cell and fitting as in A. τ_ON: 20 mV = 1.55 ± 0.06 ms; 60 mV = 1.98 ± 0.06 ms; 100 mV = 2.81 ± 0.04 ms. (C) Voltage response of τ_on from individual control cells (n = 6). (D) Voltage response of τ_on from individual cells after application of 1 µM GxTx. Symbols mark same cells as in C (n = 5). (E) Geometric means of τ_ON from C and D. Control, black; 1 µM GxTx, red. Line is the fit of Eq. 8; control, τ_{ON 0mV} = 3.1 ± 0.1 ms, z = 0.50 ± 0.01 e₀. (F) I_{g OFF} control response to voltage steps down from +100 mV to the following potentials: −20 mV, purple; −60 mV, blue; −100 mV, green; −140 mV, red. Lines are fits of Eq. 4, τ_OFF: −100 mV = 14.6 ± 0.2 ms; −140 mV = 6.06 ± 0.6 ms. (G) I_{g OFF} with 1 µM GxTx, same cell, voltages, and fitting as F. τ_OFF: −20 mV = 4.0 ± 0.2 ms; −60 mV = 4.3 ± 0.1 ms; −100 mV = 2.93 ± 0.03 ms; −140 mV = 1.82 ± 0.01 ms. (H) Voltage dependence of τ_OFF from individual cells in vehicle (n = 4). (I) Voltage response of τ_OFF from individual cells after application of 1 µM GxTx. Symbols mark same cells as in H (n = 4). (J) Geometric means of τ_OFF from H and I. Lines are fits of Eq. 4: control, z = −0.50 ± 0.03 e₀, τ_{OFF 0mV} = 120 ± 20 ms; 1 µM GxTx, z = −0.28 ± 0.04 e₀, τ_{OFF 0mV} = 11 ± 2 ms.