Morphology and topography of nucleus ambiguus projections to cardiac ganglia in rats and mice

    Authors

    J. Al; P. N. Epstein; D. Gozal; B. Yang; R. Wurster;Z. J. Cheng

    Comments

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    Abbreviated Journal Title

    Neuroscience

    Keywords

    brainstem; nucleus ambiguus; vagal efferent; cardiac ganglia; heart; baroreflex; VAGAL AFFERENT INNERVATION; CARDIOVASCULAR AUTONOMIC NEUROPATHY; DORSAL; MOTOR NUCLEUS; PARASYMPATHETIC CONTROL; MYENTERIC PLEXUS; ATRIOVENTRICULAR-CONDUCTION; INTRACARDIAC GANGLION; TRANSGENIC MICE; FISCHER-344 RAT; SMOOTH-MUSCLE; Neurosciences

    Abstract

    Vagal efferent axons from the nucleus ambiguus (NA) innervate ganglionated plexuses in the dorsal surface of cardiac atria, which in turn, may have different functional roles in cardiac regulation. However, the morphology and topography of vagal efferent projections to these ganglionated plexuses in rats and mice have not been well delineated. In the present study, we injected the tracer 1,1'-dioctadecyl-3,3,3',3'tetramethylindocarbocyanine methanesulfonate (Dil) into the left NA to label vagal efferent axons and terminals in cardiac ganglia and administered Fluoro-Gold (FG) i.p. to stain cardiac ganglia. Then, we used confocal microscopy and a Neurolucida 3-D Digitization System to qualitatively and quantitatively examine the distribution and structure of cardiac ganglia, and NA efferent projections to cardiac ganglia in the whole-mounts of Sprague-Dawley (SD) rats and FVB mice. Our observations were: 1) Cardiac ganglia of different shapes and sizes were distributed in the sinoatrial (SA) node, atrioventricular (AV) node, and lower pulmonary vein (LPV) regions on the dorsal surface of the atria. In each region, several ganglia formed a ganglionated plexus. The plexuses at different locations were interconnected by nerves. 2) Vagal efferent fibers ramified within cardiac ganglia, formed a complex network of axons, and innervated cardiac ganglia with very dense basket endings around individual cardiac principal neurons (PNs). 3) The percent of the PNs in cardiac ganglia which were innervated by Dil-labeled axons was 54.3 +/- 3.2% in mice vs. 53.2.+/- 3.2% in rats (P > 0.10). 4) The density of axonal putative-synaptic varicosities on the surface of PNs was 0.15 +/- 0.02/ mu m(2) in mice vs. 0.16 +/- 0.02/mu m(2) in rats (P > 0.10). Thus, the distributions of cardiac ganglia and vagal efferent projections to cardiac ganglia in mice and rats were quite similar both qualitatively and quantitatively. Our study provides the structural foundation for future investigation of functional differentiation of ganglionated plexuses and the brain-heart circuitry in rodent models of human disease. (c) 2007 IBRO. Published by Elsevier Ltd. All rights reserved.

    Journal Title

    Neuroscience

    Volume

    149

    Issue/Number

    4

    Publication Date

    1-1-2007

    Document Type

    Article

    Language

    English

    First Page

    845

    Last Page

    860

    WOS Identifier

    WOS:000251501700012

    ISSN

    0306-4522

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