Role of afterhyperpolarization in termination of early afterdepolarization in mouse atrial fibers.

Afterhyperpolarization (AHP) following triggered burst in early afterdepolarization (EAD) was investigated in mouse atrial fiber treated with aconitine or ryanodine. In both cases, a long second plateau (SP) with or without intermittent trains of bursts could be observed in certain conditions. Repolarization potentials were measured both in normal EAD (cycle lengths of 1-5 sec) and in EAD with a long SP. The values of repolarization potentials were almost constant, around -61 mV, in both situations. AHP could be recorded at the end of the intermittent bursts or after a burst elicited by an electrical stimulation on the long lasting SP. When the voltage of AHP attained the repolarization potential, rapid repolarization started instantly leading to complete repolarization of the EAD. It is suggested that AHP in EAD or following a burst elicited by stimulation enhances the termination of EAD.