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目的:研究M受体亚型阻断剂对粉防己碱(Tet)减慢心率,抑制窦房结功能的影响并探讨其离子机制。方法:在离体右心房标本及毁脊髓大鼠模型观察粉防己碱减慢心率的作用,用标准微电极及膜片箝全细胞记录技术观察Tet对窦房结动作电位及L型钙电流(I_(Ca-L))的影响。结果:Tet浓度依赖性抑制离体右心房自发收缩频率并减慢毁脊髓大鼠心率。Tet抑制窦房结自律性,降低V_(max、SP_4、并延长SCL,在分离单个心肌细胞Te抑制I_(Ca-L)的峰值电流。阿托品和M_2受体亚型阻断剂AF-DX 116能竞争性抑制Tet的上述作用。结论:粉防己碱的心肌负性变时作用是由于其对I_(Ca-L)的抑制,而M受体阻断剂对Tet阻滞钙通道作用的调节是其影响Tet作用的离子机制。
AIM: To investigate the effects of M receptor subtype blockers on the heart rate and inhibit the sinus node function of tetrandrine (Tet) and to explore its ionic mechanism. Methods: The effects of tetrandrine on heart rate reduction were observed in isolated right atrium and spinal cord injured rats. The effect of Tet on the action potentials and L-type calcium current of sinoatrial node was observed by using standard microelectrode and patch-clamp whole cell recording I_ (Ca-L)). Results: Tet concentration-dependently inhibited the spontaneous contraction frequency of isolated right atrium and the heart rate of destructed spinal cord rats. Tet suppressed the sinus node autonomic activity, decreased the V_ (max, SP_4, and prolonged SCL, and inhibited the peak current I_ (Ca-L) in isolated cardiomyocytes.) Atropine and the M_2 receptor subtype blocker AF- Can competitively inhibit the above-mentioned effects of Tet.Conclusion: The anti-apoptotic effect of tetrandrine on myocardium is due to its inhibition of I_ (Ca-L), and the modulation of M blocker on Tet blockade of calcium channel Is its ion mechanism that affects the action of Tet.