Objective To investigate the changes of cardiac sinus node connexin 45 (Cx45), connexin 31.9(Cx31.9) of gap junction in rabbits'' sinus bradycardia model caused by dexmedetomidine, and to discuss whether the negative frequency and negative conduction caused by Dexmedetomidine are related to the expression changes of connexin.Methods Forty-eight healthy adult New Zealand rabbits were divided into three groups (n=16).Sinus bradycardia rabbits were prepared by intravenous injecting Dexmedetomidine through ear vein.After rabbits were anesthetized by sodium pentobarbital, basic procedures were quickly completed in order to monitor MAP and ECG.Rabbits in group C were injected with normal saline.Rabbits in group D1 were injected a loading dose of dexmedetomidine 10 μg/kg for 10 min, and then continuously pumped 5 μg·kg-1·h-1 for 50 min.Rabbits in group D2 were pumped a loading dose of dexmedetomidine 60 μg/kg for 10 min, and then continuously pumped 30 μg·kg-1·h-1 for 50 min.After observation hearts were quickly removed and sinus node tissue was dissected.The average optical density of sinus node Cx45, Cx31.9 were detected by immunohistochemistry, and the genes expression were detected by real-time quantitative.Results Cx45 gene expression of group D2 showed remarkable increase than groups C and D1(P<0.05), there were no significant differences between groups D1 and C, Cx45 average optical density change were consistent with the gene expression.Cx31.9 gene expression of group D1 showed a more remarkable increase than group C(P<0.05), there were no significant differences between groups D2 and C,D1 and D2, Cx31.9 average optical density changes were consistent with the gene expression.Conclusion Dexmedetomidine increases the expression of low electrical conductivity Cx45, Cx31.9 of gap junction on rabbits'' sinus node, which is one of the possibly reasons that slow down cardiac conduction velocity in sinus node.