Differential densities of muscarinic acetylcholine receptor and I(K,ACh) in canine supraventricular tissues and the effect of amiodarone on cholinergic atrial fibrillation and I(K,ACh).
BACKGROUND
Vagal nerve plays an important role in the induction and maintenance of atrial fibrillation (AF). This study investigated the differential densities of M2 receptor and acetylcholine-induced inward rectifier K+ current (I(K,ACh)) in atrial appendage, atrium, pulmonary vein (PV) and super vena cava (SVC) to discuss the role of atrial appendage and PV in cholinergic AF.


RESULTS
In 10 dogs, action potential duration was determined at 24 sites during bilateral cervical vagal stimulation and amiodarone administration. AF could be induced at first in right atrial appendage (RAA) and right atrium (RA) without left atrial appendage (LAA) and left atrium (LA). Amiodarone decreased the initiation of AF in vivo. Western blot and patch clamp were used to determine M2 receptor and I(K,ACh) in RAA, LAA, RA, LA, PV and SVC. The densities of M2 receptor and I(K,ACh) in LAA, RAA and LA were higher than that in RA, PV and SVC (21.34 +/- 0.92 vs. 8.24 +/- 0.45 pA/pF, p < 0.05). Furthermore, the densities of the M2 receptor and I(K,ACh) in LAA and RAA were higher than that in LA (21.34 +/- 0.92 vs. 14.17 +/- 0.65 pA/pF, p < 0.05). After amiodarone administration, densities of I(K,ACh) in LA and RA were not different, but densities of I(K,ACh )were also less in atrium than in atrial appendage.


CONCLUSIONS
Densities of the M2 receptor and I(K,ACh) are higher in atrial appendage than other sites. Atrial appendage perhaps plays an important role in initiation of cholinergic AF. However, PV and SVC less often play an important role in vagotonic paroxysmal AF. Reduced dispersion of I(K,ACh) is the mechanism for amiodarone to therapy AF.
Huang
Cong-Xin
CX
Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, People's Republic of China. ruyan1971@yahoo.com.cn
Zhao
Qing-Yan
QY
Liang
Jin-Jun
JJ
Chen
Hui
H
Yang
Bo
B
Jiang
Hong
H
Li
Geng-Shan
GS
D000200:Action Potentials; D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D020517:Atrial Appendage; D001281:Atrial Fibrillation / Q000209:etiology / Q000503:physiopathology*; D004285:Dogs; D004558:Electric Stimulation; D006325:Heart Atria / Q000166:cytology / Q000503:physiopathology*; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000502:physiology*; D011667:Pulmonary Veins; D011976:Receptors, Muscarinic / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology; D014683:Vena Cava, Superior
D000889:Anti-Arrhythmia Agents; D024661:Potassium Channels, Inwardly Rectifying; D011976:Receptors, Muscarinic; D000638:Amiodarone