Comparison of early afterdepolarization induced by cesium chloride in mouse atrial and ventricular fibers

Abstract

Aim: To study the similarities and the differences in the induction of early afterdepolarization (EAD) by CsCl, a blocker of potassium channels, between mouse atrial and ventricular fibers.

Methods: Papillary muscle from left ventricle or a small piece of right atrium of Swiss Albino mouse was isolated. Transmembrane action potential (AP) and EAD were recorded using the conventional microelectrode method.

Results: CsCl induced EAD directly in the mouse atrial and ventricular fibers on the basis of elongation of action potential duration (APD). In both preparations EAD appeared after 5-15 min exposure to CsCl and the take-off potentials (TOP) were in the same range (-30 to -60 mV). But the inducing concentration in ventricular fibers (3 mmol.L-1) was lower than that in atrial fibers (5 mmol.L-1), and most of the EAD induced in atrium belonged to the triggered burst type (6/9) which demonstrated the property of cycle length (CL)-dependence while the EAD occurred in ventricle mainly belonged to the second plateau type (14/17) which showed no definite relation with the CL.

Conclusion: Low concentration of CsCl induced EAD more easily in mouse ventricular fibers than in atrial fibers, and the types of EAD were also different from each other. These suggested that there might be some differences in potassium channels between mouse atrial and ventricular fibers.