Figure 3. Analysis of the effect SKF-96365 on the mean open and closed times within a single opening. Histograms of open and closed times measured from records of single-channel activity recorded in the presence of either 50 µM (A) or 100 µM (B) SKF-96365. The histograms of open and closed times were fit with a single exponential function. (C) Plot of the reciprocal of the mean open time obtained from the single exponential fit to the open time distribution as a function of the concentration of SKF-96365 in the electrode. The data were fit with a straight line with slope = 13.3 and y-intercept –363.5, r² = 0.9. The fit was not constrained to go through zero, so the negative y-intercept is an artifact of the variability of the resolution of the open time measurements. (D) Plot of the reciprocal of the mean blocked times obtained from the single exponential fit of the closed time histogram. Data points obtained in the presence of 25 µM SKF-96365 were omitted from the plot, since at low concentrations of blocker the number of true channel closures far exceeds the number of blockages. The data were fit with a straight line with slope = -5.4 and y-intercept of 1608.7, r² = 0.3, indicating little dependence of blocked time on blocker concentration.