Characteristics of the action potentials and the underlying ionic mechanisms in the cardiomyocytes from rabbit pulmonary vein sleeves

To investigate the characteristics of action potentials and their ionic mechanism in cardiomyocytes from rabbit pulmonary vein sleeves (PVC), and to compare them with those in left atrial cardiomyocytes (LAC), the technique of whole-cell patch clamp was applied. We used current-clamp technique to record action potentials, and voltage-clamp technique to record ionic currents. PVC had longer action potential duration (APD) than LAC, and therefore a second plateau response could be induced easily, suggesting a strong tendency of early afterdepolarization (EAD) genesis in PVC. Non-selective cation current (I(NSCC)) was first recorded in both LAC and PVC. This I(NSCC)was permeable to K(+), Na(+) and Cs(+), sensitive to GdCl3 but not sensitive to 4-AP. The current densities of inward rectifier potassium current (I(K1)), transient outward potassium current (I(To)) and I(NSCC) were all significantly less in PVC than those in LAC. These differences in repolarizing ionic currents between PVC and LAC form a basis of the