Figure 3. Effect of Cd²⁺ on I_to in rat myocytes.

I_Ca,L was blocked by 0 mM Ca²⁺_o-5 mM Mg²⁺_o. A, decrease of I_to by Cd²⁺ (0.3 mM). Current activated by a step from a holding potential of -80 to 0 mV. Traces in the absence (□) and in the presence of Cd²⁺ (•) are superimposed. Inset, voltage-clamp protocol (20 ms prepulse to -40 mV to inactivate I_Na not shown). B, increase of I_to by Cd²⁺. Current activated by a step to +60 mV after a 1 s prepulse to -30 mV in the absence (□) and presence of Cd²⁺ (•). Only currents during the test pulse are shown. Inset, voltage-clamp protocol. C, effect of Cd²⁺ on steady-state activation and inactivation curves. □, control; •, Cd²⁺; ▵, second control. The effect of Cd²⁺ was reversible.