Distribution of a Persistent Sodium Current Across the Ventricular Wall in Guinea Pigs

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Abstract
—A tetrodotoxin-sensitive persistent sodium current, IpNa, 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 (PIpNa than subendocardial and subepicardial myocytes. There was no significant difference in IpNa 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.