Evidences of the ultrarapid delayed rectifier potassium current (IKur) on pacemaker activity in sinoatrial and atrioventricular nodes of Rat

Sinoatrial node (SAN) is the primary pacemaker of the heart. If the SAN activity fails in any way, then the atrioventricular node (AVN) immediately starts to regulate the activities of the heart. The aim of this study was to assess the existence or non existence of ultrarapid delayed rectifier potassium current (Ikur) and its role on pacemaker activity of two intact SAN and AVN of rat. The pacemaker activities of distinct intact SAN and AVN by two separate metal microelectrodes that contact the endothelial surface of nodes were recorded and cycle length (CL) of action potential was measured. The recording was done before and during 50µM 4-Aminopyridine (4-AP) as an Ikur blocker. Compared to control condition, CL of action potentials of SAN and VAN preparations had increased by 17.60 +/-2.9% and 35.90 +/-2.9%, respectively (P<0.05). It is possible to conclude that the Ikur was present in AVN and SAN and the effect of 4-AP on CL of action potential nodes was significantly different.