Parasympathetic neurons in the cranial medial ventricular fat pad on the dog heart selectively decrease ventricular contractility

• Published in: Journal of the autonomic nervous system Vol. 70; no. 1; pp. 129 - 141
• Main Authors: Dickerson, Linda W, Rodak, David J, Fleming, Terence J, Gatti, Philip J, Massari, V.John, McKenzie, James C, Gillis, Richard A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 28.05.1998; Elsevier Science
• Subjects: Adipose Tissue - drug effects; Adipose Tissue - innervation; Adipose Tissue - physiology; Animals; Atrioventricular conduction; Atrioventricular Node - drug effects; Atrioventricular Node - innervation; Atrioventricular Node - physiology; AV node; Biological and medical sciences; Blood Pressure - drug effects; Blood Pressure - physiology; Cholinergic Antagonists - administration & dosage; Cholinergic Antagonists - pharmacology; Contractility; Dogs; Electric Stimulation; Electrocardiography; Fundamental and applied biological sciences. Psychology; Ganglia, Parasympathetic - cytology; Ganglia, Parasympathetic - drug effects; Ganglia, Parasympathetic - physiology; Ganglionic blockade; Heart - drug effects; Heart - innervation; Heart Rate - drug effects; Heart Rate - physiology; Heart Ventricles - drug effects; Heart Ventricles - innervation; Left ventricle; Myocardial Contraction - drug effects; Myocardial Contraction - physiology; Neurons - drug effects; Neurons - physiology; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; SA node; Sinoatrial Node - drug effects; Sinoatrial Node - innervation; Sinoatrial Node - physiology; Sinus rate; Trimethaphan - administration & dosage; Trimethaphan - pharmacology; Vagus Nerve - drug effects; Vagus Nerve - physiology; Ventricular Function; Vertebrates: nervous system and sense organs; AV node; SA node; Ganglionic blockade; Contractility; Dogs; Atrioventricular conduction; Sinus rate; Left ventricle; Heart; Fissipedia; Carnivora; Sinus node; Right ventricle; Nerve conduction; Vertebrata; Mammalia; Autonomic nervous system; Atrioventricular node; Circulatory system; Dog; Parasympathetic nervous system
• ISSN: 0165-1838; 1872-7476
• DOI: 10.1016/S0165-1838(98)00048-4

We hypothesized that selective control of ventricular contractility might be mediated by postganglionic parasympathetic neurons in the cranial medial ventricular (CMV) ganglion plexus located in a fat pad at the base of the aorta. Sinus rate, atrioventricular (AV) conduction (ventricular rate during atrial pacing), and left ventricular contractile force (LV d P/d t during right ventricular pacing) were measured in eight chloralose-anesthetized dogs both before and during bilateral cervical vagus stimulation (20–30 V, 0.5 ms pulses, 15–20 Hz). Seven of these dogs were tested under beta-adrenergic blockade (propranolol, 0.8 mg kg −1 i.v.). Control responses included sinus node bradycardia or arrest during spontaneous rhythm, high grade AV block or complete heart block, and a 30% decrease in contractility from 2118±186 to 1526±187 mm Hg s −1 ( P<0.05). Next, the ganglionic blocker trimethaphan (0.3–1.0 ml of a 50 μg ml −1 solution) was injected into the CMV fat pad. Then vagal stimulation was repeated, which now produced a relatively small 5% (N.S., P>0.05) decrease in contractility but still elicited the same degree of sinus bradycardia and AV block ( N=8, P<0.05). Five dogs were re-tested 3 h after trimethaphan fat pad injection, at which time blockade of vagally-induced negative inotropy was partially reversed, as vagal stimulation decreased LV d P/d t by 19%. The same dose of trimethaphan given either locally into other fat pads (PVFP or IVC-ILA) or systemically (i.v.) had no effect on vagally-induced negative inotropy. Thus, parasympathetic ganglia located in the CMV fat pad mediated a decrease in ventricular contractility during vagal stimulation. Blockade of the CMV fat pad had no effect on vagally-mediated slowing of sinus rate or AV conduction.