Neural control of left ventricular contractility in the dog heart: synaptic interactions of negative inotropic vagal preganglionic neurons in the nucleus ambiguus with tyrosine hydroxylase immunoreactive terminals

• Published in: Brain research Vol. 802; no. 1; pp. 205 - 220
• Main Authors: Massari, V.John, Dickerson, Linda W., Gray, Alrich L., Lauenstein, Jean-Marie, Blinder, Karen J., Newsome, Joseph T., Rodak, David J., Fleming, Terry J., Gatti, Philip J., Gillis, Richard A.
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 17.08.1998; Amsterdam Elsevier; New York, NY
• Subjects: Animals; Biological and medical sciences; Brain Mapping; Catecholamine; Dogs; Female; Fundamental and applied biological sciences. Psychology; Heart; Heart Conduction System - physiology; Histochemistry; Immunocytochemistry; Intrinsic cardiac ganglion; Isolated neuron and nerve. Neuroglia; Male; Medulla Oblongata - cytology; Medulla Oblongata - physiology; Microscopy, Electron; Myocardial Contraction - physiology; Neurons - physiology; Synapse; Synapses - physiology; Transganglionic transport; Tyrosine 3-Monooxygenase - metabolism; Ultrastructure; Vagus nerve; Vagus Nerve - cytology; Vagus Nerve - physiology; Ventricular Function, Left - physiology; Vertebrates: nervous system and sense organs; Heart; Synapse; Immunocytochemistry; Ultrastructure; Vagus nerve; Catecholamine; Intrinsic cardiac ganglion; Histochemistry; Transganglionic transport; Fissipedia; Preganglionic neuron; Carnivora; Nervous control; Enzyme; Central nervous system; Contractility; Tyrosine 3-monooxygenase; Left ventricle; Vertebrata; Mammalia; Nucleus ambiguus; Circulatory system; Oxidoreductases; Dog; Brain (vertebrata)
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(98)00613-1

Recent physiological evidence indicates that vagal postganglionic control of left ventricular contractility is mediated by neurons found in a ventricular epicardial fat pad ganglion. In the dog this region has been referred to as the cranial medial ventricular (CMV) ganglion [J.L. Ardell, Structure and function of mammalian intrinsic cardiac neurons, in: J.A. Armour, J.L. Ardell (Eds.), Neurocardiology, Oxford Univ. Press, New York, 1994, pp. 95–114; B.X. Yuan, J.L. Ardell, D.A. Hopkins, A.M. Losier, J.A. Armour, Gross and microscopic anatomy of the canine intrinsic cardiac nervous system, Anat. Rec., 239 (1994) 75–87]. Since activation of the vagal neuronal input to the CMV ganglion reduces left ventricular contractility without influencing cardiac rate or AV conduction, this ganglion contains a functionally selective pool of negative inotropic parasympathetic postganglionic neurons. In the present report we have defined the light microscopic distribution of preganglionic negative inotropic neurons in the CNS which are retrogradely labeled from the CMV ganglion. Some tissues were also processed for the simultaneous immunocytochemical visualization of tyrosine hydroxylase (TH: a marker for catecholaminergic neurons) and examined with both light microscopic and electron microscopic methods. Histochemically visualized neurons were observed in a long slender column in the ventrolateral nucleus ambiguus (NA-VL). The greatest number of retrogradely labeled neurons were observed just rostral to the level of the area postrema. TH perikarya and dendrites were commonly observed interspersed with vagal motoneurons in the NA-VL. TH nerve terminals formed axo-dendritic synapses upon negative inotropic vagal motoneurons, however the origin of these terminals remains to be determined. We conclude that synaptic interactions exist which would permit the parasympathetic preganglionic vagal control of left ventricular contractility to be modulated monosynaptically by catecholaminergic afferents to the NA-VL.