COMPARISON OF EARLY AFTERDEPOLARIZATION INDUCED BY CESIUM-CHLORIDE INMOUSE ATRIAL AND VENTRICULAR FIBERS

AIM: To study the similarities and the differences in the induction of early afterdepolarization (EAD) by CsCl, a blocker of potassium chann els, between mouse atrial and ventricular fibers. METHODS: Papillary m uscle from left ventricle or a small piece of right atrium of Swiss Al bino mouse was isolated. Transmembrane action potential (AP) and EAD w ere recorded using the conventional microelectrode method. RESULTS: Cs Cl induced EAD directly in the mouse atrial and ventricular fibers on the basis of elongation of action potential duration (APD). In both pr eparations EAD appeared after 5-15 min exposure to CsCl and the take-o ff potentials (TOP) were in the same range (-30 to -60 mV). But the in ducing concentration in ventricular fibers (3 mmol . L(-1)) was lower than that in atrial fibers (5 mmol . L(-1)), and most of the EAD induc ed in atrium belonged to the triggered burst type (6/9) which demonstr ated the property of cycle length (CL)dependence while the EAD occurre d in ventricle mainly belonged to the second plateau type (14/17) whic h showed no definite relation with the CL. CONCLUSION: Low concentrati on of CsCl induced EAD more easily in mouse ventricular fibers than in atrial fibers, and the types of EAD were also different from each oth er. These suggested that there might be some differences in potassium channels between mouse atrial and ventricular fibers.