Quantitative analysis of parasympathetic innervation of the porcine heart.
BACKGROUND
Parasympathetic control of the heart is an important component in the regulation of normal cardiac function. However, the anatomic course of parasympathetic innervation of the heart is unclear.


OBJECTIVE
The purpose of this study was to apply a gross parasympathetic nerve stain technique to reveal the details of the morphology of the cardiac parasympathetic nervous system.


METHODS
Ten whole pig hearts were stained using a histochemical method. Immediately after sacrifice, hearts were placed in a buffered solution containing acetylthiocholine, which precipitates with acetylcholinesterase, allowing identification of cholinergic nerves. The epicardial and endocardial surfaces of the atria and ventricles were examined for nerve thickness and density.


RESULTS
In both atria, nerve density was significantly greater on the endocardium, but nerve thickness was significantly greater on the epicardium. The right atrium (RA) was more densely innervated than the left atrium (LA) on the endocardium, whereas the LA was more densely innervated than the RA on the epicardium. In the ventricles, numerous thick cholinergic nerves were clearly identifiable across the epicardium, generally running parallel to the left anterior descending artery. The endocardial surfaces of the ventricles revealed a dense network of fine parasympathetic nerve fibers. As in the atria, nerve density was greater on the ventricular endocardium, but nerve thickness was greater on the epicardium. The right ventricle (RV) was more densely innervated than the left ventricle (LV), whereas the LV endocardium was more densely innervated than the RV endocardium.


CONCLUSIONS
The epicardial and endocardial surfaces of the atria and ventricles are richly innervated by parasympathetic nerves. The density of parasympathetic innervation is heterogeneous across both the epicardial and endocardial surfaces of the heart.
Ulphani
Joseph S
JS
Bluhm Cardiovascular Center and Division of Cardiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Cain
Jack H
JH
Inderyas
Firdous
F
Gordon
David
D
Gikas
Peter V
PV
Shade
Gregory
G
Mayor
David
D
Arora
Rishi
R
Kadish
Alan H
AH
Goldberger
Jeffrey J
JJ
D000818:Animals; D004396:Coloring Agents; D006321:Heart / Q000294:innervation*; D010275:Parasympathetic Nervous System / Q000033:anatomy & histology*; D013552:Swine
D004396:Coloring Agents