Changes in gap junction proteins Connexin30.2 and Connexin40 expression in the sinoatrial node of rats with dexmedetomidine-induced sinus bradycardia

BACKGROUND: Dexmedetomidine (Dex) is widely used, and its most common side effect is bradycardia. The complete mechanism through which Dex induces bradycardia has not been elucidated. This research investigates the expression of gap junction proteins Connexin30.2 (Cx30.2) and Connexin40 (Cx40) within the sinoatrial node of rats with Dex-induced sinus bradycardia. METHODS: Eighty rats were randomly assigned to five groups. Saline was administered to rats in Group C. In the other four groups, the rats were administered Dex to induce bradycardia. In groups D(1) and D(2), the rats were administered Dex at a loading dose of 30 μg.kg(−1) and 100 μg.kg(−1) for 10 min, then at 15 μg.kg(−1).h(−1) and 50 μg.kg(−1).h(−1) for 120 min separately. The rats in group D(1)A and D(2)A were administered Dex in the same way as in group D(1) and D(2); however, immediately after the administration of the loading dose, 0.5 mg atropine was administered intravenously, and then at 0.5 mg.kg(−1).h(−1) for 120 min. The sinoatrial node was acquired after intravenous infusion was completed. Quantitative real-time polymerase chain reaction and western blot analyses were performed to measure mRNA and protein expression of Cx30.2 and Cx40, respectively. RESULTS: The expression of Cx30.2 increased, whereas the expression of Cx40 decreased within the sinoatrial node of rats with Dex-induced sinus bradycardia. Atropine reversed the effects of Dex on the expression of gap junction proteins. CONCLUSION: Dex possibly altered the expression of gap junction proteins to slow down cardiac conduction velocity in the sinoatrial node.