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目的：研究组织胺Ｈ２受体阻断剂－西米替丁（ＣＭＴ）对离体豚鼠心房肌动作电位和收缩活动的影响。方法：应用微电极技术和机械收缩描记方法。结果：１００μｍｏｌ／Ｌ以上浓度ＣＭＴ可明显降低豚鼠心房肌动作电位幅度、减慢０期最大除极速率、延长动作电位时程和有效不应期，其作用呈明显浓度依赖性；ＣＭＴ浓度依赖性地抑制豚鼠右心房肌收缩，使最大收缩幅度降至正常值的５４％，但对左心房肌收缩无明显影响。结论：ＣＭＴ对豚鼠右心房肌有明显抑制作用，其机制可能是通过Ｈ２受体，阻断Ｎａ＋、Ｋ＋、Ｃａ２＋通道所实现的。
Objective: To investigate the effect of histamine H2 receptor antagonist - cimetidine (CMT) on the action potential and contractile activity of isolated atrial myocardium in guinea pigs. Methods: Microelectrode technique and mechanical contractility method were used. Results: CMT at a concentration above 100 μmol / L could significantly decrease the amplitude of action potential of atrial myocardium in guinea pigs, slow down the maximum depolarization rate in period 0, prolong the action potential duration and the effective refractory period, and the effect was significant in a concentration dependent manner. CMT concentration - dependent To inhibit guinea pig right atrial muscle contraction, the maximum contraction amplitude reduced to 54% of normal, but no significant effect on left atrial muscle contraction. CONCLUSION: CMT can significantly inhibit right atrial myocardium in guinea pigs, which may be mediated by H2 receptors and block Na +, K + and Ca2 + channels.