Comparison of effects of acetylcholine on electromechanical characteristics in guinea-pig atrium and ventricle.
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 0.001-100 microm) 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 were more sensitive to ACh than the ventricles; and (2) the direct negative inotropic effect of ACh (1 microm) 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.
School of Medicine, Department of Pharmacology, Division of Cardiovascular Physiology and Pharmacology, Ki'an Jiaotong University, Xi'an, 710061, China. zwj@mail.xjtu.edu.cn
W J
WJ
Zang
L N
LN
Chen
X J
XJ
Yu
P
P
Fang
J
J
Lu
Q
Q
Sun
D000109:Acetylcholine / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D016275:Atrial Function / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D032342:Muscle Cells / Q000187:drug effects / Q000502:physiology*; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D013314:Stress, Mechanical; D016276:Ventricular Function
D000109:Acetylcholine