RESUMEN
Objective To evaluate the effect of aminophylline on monophasic action potential (MAP) during remifentanil-induced negative chronotropic effect in the isolated rabbit hearts.Methods Eighteen healthy adult rabbits,weighing 2.0-2.5 kg,wereused in the study.Their hearts were excised and retrogradely perfused in a Langendorff apparatus.After 15 min of stabilization with K-H solution,the isolated hearts were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C),remifentanil group (R group),and remifentanil + aminophylline group (RA group).Group C was perfused with 37 ℃ K-H solution for 60 min.Group R was perfused with K-H solution containing remifentanil 12 ng/ml for 60 min.Group RA was perfused with K-H solution containing remifentanil 12 ng/ml and aminophylline 30 μg/ml for 60 min.At 15 min of stabilization and 15,30 and 60 min of perfusion,HR and MAP in the myardium of left ventricle were recorded:MAP duration at 90％ and 50％ repolarization (MAPD90,MAPD50) was calculated.The early after depolarization,delay after depolarization and arrhythmia were recorded.Results Compared with group C,HR was significantly decreased at 15,30 and 60 min of perfusion,and MAPD50 and MAPD90 were prolonged in goup R,and HR was increased in group RA.HR was significantly higher,and MAPD50 and MAPD90 were shorter in RA group than in group R.No early after depolarization,delay after depolarization or arrhythmia developed in each group.Conclusion Aminophylline antagonizes remifentanil-induced negative chronotropic effect through shortening monophasic action potential duration in the myocardium of left ventricle of the isolated rabbit hearts.