Intrinsic innervation of the atrioventricular junction of the rat heart

Abstract

Alternate serial semithin and thin sections of the glutaraldehyde-fixed interatrial septum and atrioventricular junction of adult rat were examined in light and electron microscopes. The animals were pretreated with a false precursor of catecholamines, i.e., with 5-OH-dopamine, in order to differentiate the adrenergic component of the intrinsic nervous system. According to the light microscope data, two kinds of ganglia can be distinguished at the level of the interatrial septum. Those of the first kind are composed of large pale cells with voluminous nuclei. Those of the other kind resemble acinuslike clusters of small osmiophilic cells. Another small ganglion is invariably associated with the distal edge of the bundle of His. At the electron-microscope level, two types of ganglionic cells are found in the meshes of the peri- and intranodal plexus: 1) small neurons (10 microns) with richly developed neuropiles, and 2) large 5-OH-dopamine contrasted neurosecretory cells (up to 25 microns) containing electron-dense vesicles typical of sympathetic neurons. Numerous glomeruli with dendrodendritic and axodendritic connections are also found in the vicinity of the specialized tissue; and, in the nodal interstitium, several clusters of small chromaffin cells (5 microns) and a network of multipolar satellite cells similar to the interstitial cells of Cajal can be distinguished. Our data suggest that the microanatomical and cytological organization of the terminal innervation of the node of Aschoff-Tawara and of the bundle to His resembles that of the myenteric plexus. The physiological significance of these ultrastructural data for the local control of electrophysiological properties of the atrioventricular junction is briefly considered.

GFRα‐3, a protein related to GFRα‐1, is expressed in developing peripheral neurons and ensheathing cells

“…The ganglia of the heart, mainly distributed in the epicardium, constitutes a complex organization of neural crest‐derived neurons of different sizes and shapes as well as SIF cells (Moravec & Moravec 1984;Baptista & Kirby 1997) totalling some 4000 neurons in the rat (Pardini et al 1987). To the knowledge of this system, the expression of GFRα‐3 mRNA in neural‐like cells of the developing heart, located above the atrioventricular border, and associated with the auricles can now be added.…”

“…These labelled cells may correspond to chromaffin cells and/or other neuronal or neuron-like cells of the cardiac wall (cf. Moravec & Moravec, 1984). Ganglia in close proximity, presumably parasympathetic, were devoid of robust signals.…”

Development of a model of complete heart block in rats

“…Previous studies of the rat AV conduction axis have focused on the histology and ultrastructure of the specialized muscle and have not correlated the gross anatomy with the microscopic anatomy and electrophysiology (2,(12)(13)(14)17). In the present study, we documented histologically the extent of damage to the specialized muscle and correlated these findings with the electrophysiological data.…”

Potassium currents in adult rat intracardiac neurones.

“…sino-atrial cardiac tissues. Anatomical studies of the mammalian node or atrio-ventricular node, remain fairly constant heart have revealed plexuses of parasympathetic ganglia among different animals (Randall, 1984;Moravec & and interganglionic nerves located mainly in atrial sub -Moravec, 1984;Burkholder et al 1992). …”