Abstract: Obiectives:To discuss the effect of aerobic exercise on beta3-adrenoreceptor and nitric oxide synthase in left ventricular after myocardial infarction.Methods:48 male SpragueDawley rats were randomly assigned to four groups (n=12) :control group (C) , myocardial infarction group (MI) , moderate-intensity aerobic exercise with myocardial infarction group (ME1) , high-intensity aerobic interval exercise with myocardial infarction group (ME2) .MI was induced by ligation of the left anterior descending (LAD) coronary artery.ME1and ME2 group rats started exercising at 1week post-MI using a motorized rodent treadmill.Exercise in ME1group was initiated at 10 m/min, for 5 min.The speed were gradually increased to 16 m/min.Exercise in ME2group was initiated at 10m/min, for 10min.Exercise intervals alternated between 7min at 26m/min of speed and 3min at 15m/min of speed.total time was 60 min.The exercise was performed 5days per week for 8 weeks.After training, the following hemodynamic parameters were measured to detect cardiac function:LVSP, LVEDP, ±dp/dtmax.Then the heart was taken for histologic section and Masson dyeing.β3-AR in the left ventricle was examined by immunofluoresence staining and Western blot.eNOS and nNOS were examined by Western blot.Results:MI increased CVF and LVEDP (P<0.01) , but decreased LVSP and-dp/dtmax (P<0.05) .β3-AR-positive cells were identified in the LV, and expressed on the myocardial cell membranes.After MI, β3-AR protein expression in the LV did not differ but the trend was toward higher, nNOS expression was increased (P<0.01) , but eNOS was reduced.Compared with MI group, 8-weeks aerobic exercise significantly reduced CVF and LVEDP (P<0.01) , -dp/dtmax was increased in ME1group (P<0.05) , and LVSP was increased in ME2group (P<0.05) .β3-AR protein expression in the LV was increased in ME1group (P<0.05) , and did not differ but the trend was toward higher in ME2 group.eNOS, nNOS expression was increased in ME1and ME2group (P<0.05, P<0.01) .While no major differences were observed between ME1and ME2group.Conclusions:Moderate-intensity aerobic exercise and high-intensity aerobic interval exercise can increase eNOS and nNOS protein expression in the left ventricular through upregulation ofβ3-AR, then reduce myocardial interstitial fibrosis and promote cardiac function after MI.