Skip to main content
. 2010 Jun 14;588(Pt 15):2691–2706. doi: 10.1113/jphysiol.2010.193128

Figure 4. Effect of K+ and voltage on Qd block of Shab.

Figure 4

A, apparent Kd against membrane potential Vm. Kd was obtained from complete dose–response curves as in Fig. 3C. The line is the fit of the points with the Woodhul equation: Kd(Vm) =Kd(0)exp(zδFVm/RT), with z= 1, where Kd(0) (Kd at 0 mV) = 22.5 μm, and δ= 0.35; R, T and F have their usual meaning. B, fraction blocked (fb) vs. Vm; the points are the average block obtained with either 0.1 mm Qd plus 100 mmInline graphic (n= 5) or 0.035 mm Qd plus 40 mmInline graphic (n= 4) or 0.015 mm Qd plus 15 mmInline graphic (n= 4), as indicated. The lines are the fit of the points with the equation fb=[Qd]/(Kd(V) +[Qd]), with parameters,100 mmInline graphic: Kd(0) = 74 μm, δ= 0.49; 40 mmInline graphic: Kd(0) = 35 μm, δ= 0.40; 15 mmInline graphic: Kd(0) = 20.6 μm, δ= 0.35. C, Kd(0) vs.[K+]o. The line is the least-squares fit of the points with the equation: Kd(0) = (Ki/Kd,0)[K+]o+Kd,0, with Kd,0 (apparent Kd for Qd at 0 mV and 0 Inline graphic) = 12.2 μm, and Ki (inhibition constant of Inline graphic) = 20 mm, r= 0.998; Kd(0) was obtained as the parameter of the curves in either A (5 Inline graphic) or B (15, 40 and 100 Inline graphic). D, electrical distance δ at the indicated [K+]o; δ was obtained as the parameter of the curves in either A(5 Inline graphic) or B (15, 40 and 100 Inline graphic).