Fig. 3. Blockade of Na⁺ currents by Cn11 in crayfish neurons. (A) After 3 min of establishing the whole-cell configuration, inward Na⁺ currents were elicited by test depolarizations to 0 mV from –60 mV, each for 15 s. The first three traces were averaged and taken as the control value in the absence of toxin. Subsequent traces were obtained during perfusion of the preparation with 1 µmol l^–1 Cn11. The traces show how the current decreases over time. (B) Cn11 blocks the current without affecting its kinetics, as shown by superimposition of the time course of control Na⁺ currents and those in the presence of toxin (scaled up fourfold), which blocked 75 % of the control current (labelled I_m 4x).