Objective: To explore the expression of myocardial levels of connexin 43(Cx43), Cx40 in experimental dog model of sympathomimetic atrial fibrillation (AF). Methods: 15 mongrels dogs were randomly divided into 3 groups: Control group, Rapid atrium pacing (RAP) group and RAP+isoprenaline (ISO) perfusion group. n=5 in each group. The hearts were taken to establish in vitro langendorff cardiac perfusion model. Atrial effective refractory period (AERP) and AF inducing rate were tested;intracellular expression and distribution of nerve growth factor (NGF) and tyrosine hydroxylase (TH) were examined by immunohistochemistry, total protein contents of Cx43 and Cx40 were measured by Western blot analysis, mitochondria morphology was observed by transmission electron microscope and mitochondria reactive oxygen species (ROS) generation was detected by fluorescent colorimetric method. Results: AERP was similar between Control group and RAP group (166±5.1) ms vs (160±3.2) ms which cannot induce AF; while it was shortened in RAP+ISO group (148±3.7) ms, P<0.05 which may successfully induce AF.Compared with Control group, mitochondria was slightly swollen in RAP group and the matrix was intact, while mitochondria was obviously swollen in RAP+ISO group and part of matrix was transparent; total protein contents of Cx43 and Cx40 were lower in both RAP group and RAP+ISO group, P<0.05; in addition, they were even lower in RAP+ISO group than RAP group, P<0.05. Compared with Control group and RAP group, RAP+ISO group had increased expression and distribution of NGF, TH and mitochondria ROS generation, P<0.05; NGF, TH and ROS in RAP group were higher than Control group, P<0.05. Conclusion: Sympathetic AF has been related to the contents and changes of myocardial levels of CX43 and Cx40; sympathetic nerve might trigger AF by oxidative stress induced down-regulation of myocardial CX43 and Cx40 in experimental dog model.