Figure 4. Evolution of Ba²⁺ block of I_HERG during depolarization.

Top, original recordings during 2 s depolarizations to 0 mV (left) and 30 mV (right) before and after superfusion with 500 μm Ba²⁺. Capacitive transients have been removed. Horizontal bars indicate zero current levels for the adjacent traces. Bottom, evolution of fractional block (I_c–I_Ba)/I_c, where I_c and I_Ba are currents under control conditions and in the presence of 500 μm Ba²⁺, respectively, in the same experiment, upon depolarization to the 6 voltage levels indicated. Similar results were obtained in 4 other oocytes.