RESUMEN
In the heart cells, ultrarapid delayed rectifier potassium current [IKur] is one of the important currents in action potential repolarization phase. Ultrarapid delayed rectifier potassium current is specifically blocked by low concentration of 4-Amino Pyrimidine [4-AP]. The aim of this study was to determine the effect of low concentration of 4-Amino Pyrimidine blocker on pacemaker activity of sinoatrial node [SAN] and atrioventricular node [AVN] of mouse heart. SAN and AVN were separated and the pacemaker activity of distinct intact SAN and AVN was recorded before and during 50 micro M 4-AP by two separate metal microelectrodes that were in contact with the endothelail surface of the nodes. Then the action potential cycle length [CL] was measured. 50 micro M 4-Amino Pyrimidine increased the action potential cycle length of SAN and AVN preparations respectively by 20.2 +/- 3.3% and 18 +/- 3%. These increases on the action potential cycle length were significant in both nodes. According to the results, IKur is present in both SAN and AVN nodes and the effect of 50 micro M 4-AP on action potential cycle length [CL] of the two nodes is the same