Xenbase Image ID: 121167

Figure 13. . IgOFF components. (A) OFF gating currents recorded at −80 mV in 70 μM Ca2+ following pulses of different duration (0.11–20 ms) to 120 mV decay more slowly as pulse duration increases. IgOFF traces were integrated to obtain QOFF time courses in B. QOFF saturates for pulses of 5 ms or greater duration. (C) OFF kinetics following brief (0.11 ms) or prolonged (5–20 ms) pulses are compared by plotting the quantity QOFF(t)-QOFFSS on a log scale versus time where QOFFSS is the mean value of QOFF(t) for t = 4–5 ms. The 5–20 ms trace is the average of 5, 7, 10, and 20 ms records and is fit by a double exponential function (solid line, qMED = 14.1 fC, τMED = 200 μs, qSLOW = 7.4 fC, τSLOW = 810 μs) with dashed lines representing the two components. The 0.11-ms trace is fit by a triple exponential function (solid line, qFAST = 4.9; fC, τFAST = 25 μs, qMED = 0.6 fC, τMED = 200 μs, qSLOW = 0.4 fC, τSLOW = 810 μs) with a dashed line indicating the fast component. (D) The Ca2+-saturated gating scheme (sub-Scheme IIB*) indicates the origin of the three OFF components which are determined by voltage sensor deactivation when channels are closed (Fast) or open (Medium), or by channel closing (Slow). (E) OFF kinetics for all pulse durations are plotted as in C using the data in B. Dashed lines are triple exponential fits (τFast = 25 μs, τMED = 200 μs, τSLOW = 810 μs). (F) The amplitude of the three OFF components are plotted versus pulse duration and fit by exponential functions with 1.4-ms time constants representing the time course of channel opening. Image published in: Horrigan FT and Aldrich RW (2002) Copyright © 2002, The Rockefeller University Press. Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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