[Comparison of distribution of cholinergic nerves and M2 receptors between rat atria and ventricles].
OBJECTIVE
To investigate the general pattern of cholinergic nerve distribution and M(2) receptors in adult rat heart.


METHODS
Karnovsky-Roots histochemical staining combining point counting method and immunochemical SABC method with image analysis were used to identify the cholinergic nerves and M(2) receptors, respectively, in adult rat heart.


RESULTS
Positive staining of cholinergic nerves and M(2) receptors was found in all regions of the rat heart, and the point count of cholinergic nerves in the atria was 4.6 times as much as that in ventricles, and the area of immunoreactive substance for M(2) receptors two-fold higher in the atria than in the ventricles. The point counts of the cholinergic nerves in the medial-layer myocardium were fewer than that in subepicardial and endocardial tissues of the left ventricular free wall. However, M(2) receptors were comparable among the 3 layers of the left free ventricular wall.


CONCLUSIONS
Cholinergic nerves and M(2) receptors are located in both rat atria and ventricles, but their density is much higher in the atria than in the ventricles. Transmural heterogeneity characterizes cholinergic nerve innervation in the left ventricular free wall without significant differences in M(2) receptor density.
Xu
Xiao-li
XL
Department of Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an 710061, China. xxl_happy@163.com
Zang
Wei-jin
WJ
Kang
Xin-qin
XQ
Li
Ming
M
Yu
Xiao-jiang
XJ
Chen
Li-na
LN
Luo
Hong-li
HL
D000818:Animals; D002799:Cholinergic Fibers / Q000378:metabolism*; D005260:Female; D006321:Heart / Q000294:innervation*; D006325:Heart Atria / Q000294:innervation / Q000378:metabolism; D006352:Heart Ventricles / Q000294:innervation / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043585:Receptor, Muscarinic M2 / Q000032:analysis*
D043585:Receptor, Muscarinic M2