乙酰胆碱对心脏作用的脱敏研究

Studying on the phenomenon of desensitization to acetylcholine in the heart

目的 :观察副交感神经递质乙酰胆碱 ( acetylcholine,Ach)对单个豚鼠心房肌细胞、豚鼠心房肌毒蕈碱钾型通道 ( IK,Ach)、动作电位 ( action potential)及其对心房肌收缩力脱敏 ( desensitization)的影响。方法 :采用全细胞膜片钳记录技术、标准玻璃微电极细胞内记录技术及肌力换能器等分别研究 Ach对单个豚鼠心房肌细胞或心房肌组织的心肌收缩力、动作电位及 IK,Ach离子流不同层次的脱敏作用。结果 :( 1) Ach对心房肌组织有降低收缩力的作用 ,且随时间延长 Ach作用逐渐降低 ,即出现脱敏现象 ,并呈时间依赖性。 ( 2 ) Ach可使心房肌细胞动作电位时程缩短 ,亦出现脱敏。 ( 3) Ach可以激活一种内向整流的钾通道 (即 IK,Ach) ,IK,Ach离子流的脱敏分为快、慢两个时相。结论 :Ach降低心房肌组织收缩力的作用有脱敏现象 ,脱敏的发生可能与心房肌细胞APD的脱敏及 Ik。

Objective:To observe the phenomenon of desensitization to parasympathetic transmitter acetylcholine (Ach) on the muscarinic potassium current (I K,Ach ),action potential and force contraction in single atrial myocytes and atrial muscles of guinea pig hearts.Methods:The whole cell patch clamp,standard microelectrodes and force transducer were used to record the different level desensitization to Ach on I K,Ach ,action potentials and force contraction in single atrial cells or atrial muscles from guinea pig hearts.Results:(1)It was showed that Ach resulted in a decrease in contraction of atrial muscles.During an exposure to Ach the negative inotropic effect of Ach faded with time as result of desensitization.It showed a timedependent manner. (2) Ach shortened the action potential duration (APD),and the desensitization of APD after exposure to Ach also occurred.(3) Ach activated an inward rectifying potassium current (I K,Ach ),which faded in the continuous presence of Ach as well.There were fast and slow phases of desensitization of I K,Ach .Conclusions:Decrease in contraction of the atrial muscles by Ach showed desensitization phenomenon.This might be the result of fade of action potential shortening caused by fade (desensitization) of the muscarinic potassium current,I K,Ach .