Figure 4. Nicorandil shortens rat atrial action potential duration. (A) Representative spontaneous rat electrocardiogram (ECG) and atrial action potential duration (APD) tracings of before (left panel) and after (middle panel) nicorandil stimulation (1 mg/kg) are shown. Arrows denote P waves that correspond to atrial APDs. (B) Overlap of representative action potentials before (black) and after (red) nicorandil stimulation. (C) Summary data of the mean APD50 and APD70 before and after nicorandil stimulation (1 mg/kg) are shown (n = 7). The mean APD50 and APD70 are shorter after nicorandil stimulation (1 mg/kg). Data represent mean ± SD; p < 0.05 before versus after nicorandil stimulation.