Figure 3.

Extracellular verapamil and quinine inhibited only the outward current. a, Single-channel trace of four NSC channels in the bilayer, showing the effect of verapamil at a range of membrane voltages (indicated in mV on the left). b, 1 mm quinine caused reversible blockade of the outward current. c, Rapid block of the NSC channel by 1 mm quinine produced an apparent decrease in unitary conductance of the single channel. All data were recorded in 100 mm NaCl:100 mm KCl plus 5 mm TES-BTP, pH 7.4, cis/trans.