FIGURE 4.

Effects of delayed rectifier K⁺ current blockade on APs measured with constant and I_K1 current injection. (A) Typical APs of one atrial myocyte in absence (baseline) and presence of low dose 4-aminopyridine (4-AP) to block the ultra-rapid delayed rectifier K⁺ current. (B) Average AP parameters measured in five cells in presence of 4-AP. AP parameters are normalized to the AP parameters measured under baseline conditions in the same cell. (C) Typical APs of one atrial myocyte in absence (baseline) and presence of E-4031 to block the rapid delayed rectifier K⁺ current. (D) Average AP parameters measured in five cells in presence of E-4031. AP parameters are normalized to the AP parameters measured under baseline conditions in the same cell. *p < 0.05, drug vs. baseline (paired t-test); ^# p < 0.05, drug effects observed with constant current, Bett current, and Kir2.1 current (ANOVA with follow-up test).