Received April 24, 2004
Revised June 18, 2004
Accepted after revision October 1, 2004
Comparison of Effects of Acetylcholine on Electromechanical Characteristics in Guinea Pig Atrium and Ventricle
Wei-Jin Zang 1*,
Li-Na Chen 1,
Xiao-Jiang Yu 1,
Ping Fang 2,
Jun Lv 1,
Qiang Sun 2
1 Xi'an Jiaotong University
2 Xi'an Jiaotong Universit
* To whom correspondence should be addressed. E-mail: zwj{at}mail.xjtu.edu.cn.
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Abstract |
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The direct negative effects of acetylcholine (ACh) on guinea pig atria and ventricles were investigated using standard microelectrodes, a force transducer and a video edge-detection system. It was found that (1) ACh (at 0.001 " C100 µM) decreased the force of contraction and shortened the action potential duration (APD) in both atria and ventricles in a concentration-dependent manner, and that the atria was more sensitive to ACh than the ventricles; and (2) the direct negative inotropic effect of ACh (1 µM) on an isolated cardiac cell was similar to that on the isolated myocardium. But this effect was not present in all isolated ventricular cells, while all the atrial cells responded to ACh. In conclusion, ACh had direct inhibitory effects on both atrial and ventricular tissue and myocytes, although the effects were greater in atria than in ventricles; and the negative inotropic effect of ACh was closely related to the shortening of the APD.
Key Words:
Acetylcholine, Action potential, Contraction
