Abstract: Objective To study the effect of L-arginine (L-Arg) on sinoatrial conduction time (SACT) and sinus node recovery time (SNRT) and atrioventricular nodal effective refractory period (AVERP) in the course of ischemia-reperfusion (IR) of the right coronary artery in rabbits. Methods Thirty-two rabbit models of ischemia-reperfusion of the right coronary artery were randomly divided into control group, IR+saline group, IR+L-Arg group and IR+ L-arginine-methyl ester (IR+L-NAME group, 8 rabits in each group. At different time points after ligation or loosening of the artery, SACT, SNRT and AVERP were measured respectively by fast pacing of the right atrium and programmed electrical stimulations. Results Compared with the control group, SACT, SNRT and AVERP of the other groups were all prolonged significantly(P<0.01). In comparison with IR+NS group, at each time point, SACT, SNRT and AVERP of IR+L-Arg group were decreased during ischemia and in the early phases of reperfusion, followed by elevation during the latter stages of the reperfusion, as were contrary to the changes in IR+L-NAME group. Conclusions The longer duration of ischemia persists, the severer are the functional damages of the sinoatrial node. Adequate supply of L-Arg to the tissues during ischemia and the early stages of the reperfusion may alleviate the damages, but its administration in the latter stages of reperfusion might contribute to the contrary result.