CHARACTERISTICS OF EARLY AFTERDEPOLARIZATION IN MOUSE ATRIAL FIBERS

Early after depolarization (EAD) in mouse atrial fibers was investigat ed under the treatment with aconitine, 3.0 mmol/L K+, quinidine, ryano dine or Bay k 8644. All of these EADs possessed the following common c haracteristics:all the parameters of EAD showed cycle length-dependenc e; take-off potential of the first triggered burst played an important role in the generation of the other parameters; hyperpolarization of the triggered brust enhanced the end of EAD; and the second plateau re sponse might be used as an indicator of the capability of EAD generati on of myocardiac cell. All those EADs were inhibited or abolished by n ifedipine, tetrodotoxin or lidocaine. Potassium channel activators, le makalim, thalium ion, acetyl-choline or high potassium could also inhi bit or abolish the EADs. It is suggested that the EADs induced by diff erent agents may base on a common mechanism; all currents contributing to the plateau phase of the action potential play an important role i n the generation of EAD.