XB-IMG-124590
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Figure 8. Voltage-dependent block by intracellular bis-QAC10. (A) Chemical structure of bis-QAC10. (B) Macroscopic current traces recorded from an inside-out patch containing CNGA1 channels in the absence or presence of 5 mM of intracellular bis-QAC10. Currents were elicited by first stepping the voltage from the 0-mV holding potential to −150 mV, and then testing voltages between −150 and 150 mV in 10-mV increments before returning to the holding potential. For clarity, only traces every 20 mV are shown. Dotted line indicates 0 current level. (C) I-V curves (mean ± SEM; n = 5) determined at the end of the test pulses in the absence or presence of 5 mM bis-QAC10. (D) Fraction of current not blocked (mean ± SEM; n = 5) by 5 mM bis-QAC10 is plotted against membrane voltage. The solid curve is a fit of Eq. 10 to the data from −150 to 90 mV (arrow) with KB1 = 3.17 ± 0.05 × 10−2 M, KB2 = 2.23 ± 0.14 × 10−2, KB2-Na = 2.67 ± 0.09 M−1, and Z = 1.11 ± 0.02. Dotted curve is a fit to the data from −150 to 90 mV (arrow) of a Boltzmann function (similar to Eq. 1, except for a nonunity asymptote at hyperpolarized potentials) with parameters appKd = 1.23 ± 0.08 × 10−2 M and Z = 0.83 ± 0.03. Image published in: Martínez-François JR and Lu Z (2010) © 2010 Martínez-François and Lu. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View |