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目的: 研究乙酰胆碱(ACh)对离体豚鼠心室肌的直接负性作用及机制。方法: 采用标准玻璃微电极细胞内记录技术记录动作电位(AP）及肌力换能器记录心肌收缩力（FC）的方法观察ACh对离体豚鼠心室肌的作用，并观察几种受体或通道水平的阻断剂阿托品、氯化铯(CsCl)、氯化镉(CdCl2)对ACh直接作用的影响。结果: 10-5mol/L ACh对心室肌动作电位持续时间(APD)及FC的抑制率分别为7.31%和37.57%（P<0.05），10-5 mol/L阿托品和20 mmol/L CsCl可阻断该作用，0.1 mmol/L CdCl2对该作用无影响。结论: 10-5mol/L ACh 对离体豚鼠心室肌有直接负性作用，ACh的作用与毒蕈碱型胆碱受体及K+电流有关，而与Ca2+电流的关系可能不大。“,”To investigate the mechanisms underlying the effects of ACh on isolated guinea-pig ventricular myocytes. METHODS: Using standard microelectrodes and force transducer we recorded the effects of ACh (10-5 mol/L) and various blockers such as atropine, CsCl and CdCl2 on the action potential and force contraction in isolated ventricular myocytes of guinea-pig. RESULTS: ACh(10-5 mol/L) reduced the duration of action potential and twitch tensions by 7.31% and 37.57% respectively (P<0.05),which could be blocked by atropine, CsCl, but not by CdCl2. CONCLUSION: ACh (10-5 mol/L) could cause a negative chronotropic and inotropic effects on guinea-pig ventricular myocytes. These effects are related to the muscarinic receptor and the potassium channel and may not related to the calcium channel.