<正>Objective: To study the effect of simulated ischemia-reperfusion （I/R） on If of sinoatrial node （SAN） cells and the intervention of KATP channel opener Pinacidil. Methods: The SAN cells of the neonatal rats were detached and purified 2 d before the experiment. The experimental animals were randomly divided into the control group

group of simulated I/R

group intervened with KATP channel opener Pinacidil （P+ I/R） and group intervened with KATP channel blocking agent 5-HD （5-HD + P + I/R & 5-HD + I/R）. The If density of each group was measured by technique of routine whole cell patch clamp and multiple-catheter perfusion system and the If activated curve in each group was drawn. Results: ①Under different directive potentials

the If density of the SAN cells in I/R group increased significantly

compared with that in the control group （ P < 0.01）; that in P + I/R group decreased significantly

compared with that in I/R group （ P < 0.01）; the If density values in 5-HD + P + I/R group and 5-HD + I/R group i