Received 2001-12-10 Accepted 2002-04-03

This work was supported by grants from the National Natural Science Foundation of China (No.39870334, 39970273), Ph.D. Programs Foundation (20010698034) and Key Research Programs for Science and Technology of Education Ministry of China (No.01161). *Corresponding author. Tel: +86-29-5275150; E-mail: zwj@mail.xjtu.edu.cn

生理学报, Aug. 2002, 54 (4): 311~316

Acta Physiologica Sinica

研究论文

乙酰胆碱对豚鼠心房肌和心室肌的动作电位和收缩力的不同作用

方萍1, 臧伟进1, *, 于晓江1, 孙强1, 臧益民2, 吕军1

1西安交通大学医学院心血管生理药理研究室, 西安 710061; 2第四军医大学生理学教研室, 西安 710032

摘要: 实验采用标准玻璃微电极细胞内记录技术记录心肌细胞动作电位(action potential, AP)、肌力换能器记录心肌收缩力(force contraction, Fc), 研究乙酰胆碱(acetylcholine, ACh)对离体豚鼠心房肌、心室肌的作用。结果表明, 10 µmol/L ACh可缩短心房肌、心室肌动作电位的时程(action potential duration, APD)。心房肌APD在给药前后分别为208.57±36.05 ms及101.78±14.41 ms (n=6, P<0.01), 心室肌APD在给药前后分别为286.73±36.11 ms及265.16±30.06 ms (n=6, P<0.01)。心房肌动作电位的幅度 (action potential amplitude, APA)也降低, 给药前后分别为88.00±9.35 mV及62.62±20.50 mV (n=6, P<0.01), 而心室肌APA无明显变化。ACh还降低心房肌、心室肌的收缩力, 心房肌、心室肌Fc的抑制率分别为100% (n=6, P<0.01)和37.57±2.58% (n=6, P<0.01)。ACh对心房肌、心室肌APD和Fc的抑制作用在一定范围内(1 nmol/L~100 µmol/L)随ACh浓度的增高而增强。用Scott法求出ACh对心房肌、心室肌APD缩短作用的KD值, 分别为0.275和0.575 µmol/L, 对Fc抑制作用的KD值分别为0.135和0.676 µmol/L。各浓度下ACh对心房肌效应与心室肌效应作组间t检验, 从10 nmol/L到0.1 mmol/L均有显著的统计学差异。此外, 10 µmol/L阿托品及20 mmol/L CsCl可阻断10 µmol/L ACh对心室肌APD的缩短作用, 而0.1 mmol/L CdCl2对ACh所致心室肌APD的缩短作用影响不大。上述结果提示, ACh对心房肌、心室肌APD及Fc均有不同程度的直接抑制作用, 并随所用ACh浓度的增大而增大, 心房肌对ACh的反应较心室肌更为敏感。ACh对心室肌APD的缩短作用与毒蕈碱型胆碱受体(muscarinic receptor, MR)及K+电流关系较为密切, 而与Ca2+电流可能关系不大。

关键词: 乙酰胆碱; 心房肌; 心室肌; 动作电位; 收缩力

学科分类号: Q463

Different effects of acetylcholine on the action potential and force contraction in guinea pig atrial and ventricular myocardium

FANG Ping1, ZANG Wei-Jin1, *, YU Xiao-Jiang1, SUN Qiang1, ZANG Yi-Min2, LU Jun11Division of Cardiovascular Physiology & Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an 710061; 2Department of Physiology, Fourth Military Medical University, Xi'an 710032

Abstract: The purpose of this study was to investigate the different effects of ACh on the action potential and force contraction in guinea pig atrial and ventricular myocardium by using standard microelectrodes and force transducer. The results showed that the duration of the action potential (APD) of atrial myocardium was shortened from 208.57±36.05 to 101.78±14.41 ms (n=6, P<0.01), and the APD of the ventricular myocardium was shortened from 286.73±36.11 to 265.16±30.06 ms (n=6, P<0.01).The amplitude of the action potential (APA) of the atrial myocardium was decreased from 88.00±9.35 to 62.62±20.50 mV (n=6, P<0.01), while the APA of the ventricular myocardium did not change significantly.The force contraction of atrial myocardium was inhibited completely (n=6, P<0.01), while the force contraction of ventricular myocardium was inhibited by 37.57±2.58% (n=6, P<0.01). The ACh effects correlated with its concentration. The KD of the APD shortening effects in the atrial and ventricular myocardium were 0.275 and 0.575 µmol/L. The KD of the negative inotropic in the atrial and ventricular myocardium were 0.135 and 0.676 µmol/L, respectively. The corresponding data points were compared using t test between the atrial and ventricular myocardium, and the differences were significant when the ACh concentration was above 10 nmol/L. Furthermore, atropine (10 µmol/L) and CsCl (20 mmol/L) blocked the effects of 10 µmol/L ACh on the APD of ventricular myocardium, while CdCl2 (0.1 mmol/L) had no influence on these effects. In conclusion, ACh could shorten the action potential duration and inhibit the force contraction of atrial and ventricular myocardium in a concentration-dependent manner. There are differences in the effects of ACh on the atrial and ventricular myocardium. The atrial myocardium is more sensitive to ACh than the ventricular myocardium. It is probable that the muscarinic receptor and the potassium channel, but not the calcium channel, are involved in the ACh-induced shortening of the ventricular APD.

Key words: acetylcholine; atrial; ventricle; action potential; force contraction