Distribution of a persistent sodium current across the ventricular wall in guinea pigs

A tetrodotoxin-sensitive persistent sodium current, I-pNa, was found in guinea pig ventricular myocytes by whole-cell patch clamping: This current was characterized in cells derived from the basal left ventricular subendocardium, midmyocardium, and subepicardium. Midmyocardial cells show a statistically significant (P<0.05) smaller I-pNa than subendocardial and subepicardial myocytes. There was no significant difference in I-pNa current density between subepicardial and subendocardial cells. Computer modeling studies support a role of this current in the dispersion of action potential duration across the ventricular wall.