Regional distribution of cholinergic nerves in rat parietal pericardium

The innervation pattern of parietal pericardium was studied in normal as well as chemically sympathectomized rats using the cholinesterase histochemical method. The existence of important regional variations in the distribution of cholinergic nerves within various portions of parietal pericardium studied was observed. The atria appear more richly innervated than ventricles, while the innervation of atria is characterized by the existence of thin and thick cholinergic nerve fibers not organized in plexuses and of elbow-shaped acetylcholinesterase cholinergic nerve fibers. Small blood vessels and islands of adipocytes receive a cholinergic innervation as well. The chemical sympathectomy does not alter the pattern of stained cholinergic nerve fibers. A possible afferent significance of the atrial innervation is discussed.