Figure 5.
Quantitative analysis of SV channel block by neomycin. (A) Dose–response of block in the voltage range from +60 to +100 mV; normalized stationary currents for six neomycin concentrations derived from three to five experiments were averaged, corrected for current increase due to neomycin-induced channel activation, as described in MATERIALS AND METHODS, and resulting Gneo/Gcontrol(block) values were plotted as a function of neomycin concentration. For all potentials under investigation, a global curve fit was performed, which allowed the fit of all data sets with the same Hill coefficient and a series of Hill functions. Values of Ir, the fraction of the residual current at saturating neomycin concentrations, were as follows: 0.21 ± 0.04 at +60 mV, 0.17 ± 0.03 at +70 mV, 0.15 ± 0.03 at +80 mV, 0.11 ± 0.03 at +90 mV, 0.06 ± 0.03 at +100 mV. (B) Kh values derived from the Hill global fit shown in A are plotted against the applied membrane potential. The line represents the best fit with a monoexponential function.