GROSS AND MICROSCOPIC ANATOMY OF THE CANINE INTRINSIC CARDIAC NERVOUS-SYSTEM

Background: A three-dimensional description of the distribution and or ganization of the canine intrinsic cardiac nervous system was develope d in order to characterize its full extent physiologically. Methods: T he anatomy of the canine intrinsic cardiac nervous system was investig ated in 67 mongrel dogs by means of visualization following methylene blue staining as well as by light and electron microscopic analyses. R esults: Collections of ganglia associated with nerves, i.e., gangliona ted plexuses, were identified in specific locations in epicardial fat and cardiac tissue. Distinct epicardial ganglionated plexuses were con sistently observed in four atrial and three ventricular regions, with occasional neurons being located throughout atrial and ventricular tis sues. One ganglionated plexus extended from the ventral to dorsal surf aces of the right atrium. Another ganglionated plexus, with three comp onents, was identified in fat on the left atrial ventral surface. A ga nglionated plexus was located on the mid-dorsal surface of the two atr ia, extending ventrally in the interatrial septum. A fourth atrial gan glionated plexus was located at the origin of the inferior vena cava e xtending to the dorsal caudal surface of the two atria. On the cranial surface of the ventricles a ganglionated plexus that surrounded the a ortic root was identified. This plexus extended to the right and left main coronary arteries and origins of the ventral descending and circu mflex coronary arteries. Two other ventricular ganglionated plexuses w ere identified adjacent to the origins of the right and left marginal coronary arteries. Intrinsic cardiac ganglia ranged in size from ones comprising one or a few neurons along the course of a nerve to ones as large as 1 x 3 mm estimated to contain a few hundred neurons. Intrins ic cardiac neuronal somata varied in size and shape, up to 36% contain ing multiple nucleoli. Electron microscopic examination demonstrated t ypical autonomic neurons and satellite cells in intrinsic cardiac gang lia. Many of their axon profiles contained large numbers of clear, rou nd, and dense-core vesicles. Asymmetrical axodendritic synapses were c ommon. Conclusions: The canine intrinsic cardiac nervous system contai ns a variety of neurons interconnected via plexuses of nerves, the dis tribution of which is wider than previously assumed. (C) 1994 Wiley-Li ss, Inc.