Localization of sympathetic postganglionic and parasympathetic preganglionic neurons which innervate different regions of the dog heart

Abstract

The locations of sympathetic postganglionic and parasympathetic preganglionic neurons projecting to the heart have not yet been clearly established. Therefore, aliquots of horseradish peroxidase (HRP) were injected into specific regions of the heart, intraventricular cavity, pericardial sac, aortic arch, and the skin in 27 dogs. Following injections into the heart, aorta, or pericardial sac, retrogradely labeled neurons were present in the greatest numbers in the middle cervical ganglia bilaterally. Labeled neurons were located in the cranial poles of the stellate ganglia bilaterally and occasionally in the superior cervical ganglia. Labeled cells were also found in small ganglia located along cardiopulmonary nerves. Injections of HRP into specific areas of the heart did not result in labeling of cells in specific loci of the thoracic or cervical sympathetic ganglia. When the ansae were cut on one side, no labeled cells were found in the ipsilateral stellate ganglion or upper thoracic chain. Following injections into the skin of the left elbow or left cranial nipple, labeled cells were found in the stellate ganglia and the sympathetic chain and in one case in the middle cervical ganglion as well. These data suggest that postganglionic sympathetic neurons which project efferent axons to a specific cardiac region are not located in a specific region of a sympathetic ganglion or a specific sympathetic ganglion. Rather, neurons in one region of a sympathetic ganglion project axons to widespread areas of the myocardium. Sympathetic postganglionic neurons in the stellate ganglion or sympathetic chain project their axons to the heart via the subclavian ansae or interganglionic nerves, not via nerves arising directly from the sympathetic chain. Small numbers of labeled neurons were found in the medulla oblongata, thus indicating that in comparison to sympathetic postganglionic neurons relatively few preganglionic parasympathetic neurons project directly to the heart. When labeled cells were present in the medulla, the majority were located in the ventrolateral nucleus ambiguus.

Dorsal spinal cord stimulation obtunds the capacity of intrathoracic extracardiac neurons to transduce myocardial ischemia

“…2). Considering the heterogeneous neuroanatomical organization of the extracardiac intrathoracic autonomic ganglia (24,25), including afferent, efferent, and local circuit neurons, it is not unexpected that the integrated reflex response to stressors is partially reflective of the characteristics of their imposed afferent and efferent neuronal inputs. As the vast majority (ϳ70%) of neurons in the middle cervical ganglia that respond to local epicardial mechanical deformation or chemical stimuli are local circuit in nature (5,6), presumably this population of polymodal neurons represented the principal neuronal population evaluated in this study.…”

Altered Atrial Electrical Restitution and Heterogeneous Sympathetic Hyperinnervation in Hearts With Chronic Left Ventricular Myocardial Infarction

“…22 The presence of increased atrial GAP43, a marker of nerve sprouting, 23 indicates that active nerve sprouting is occurring in the atria of dogs with chronic MI. Because postganglionic sympathetic neurons project to different areas of the heart, including the atria, 24 it is likely that some of the atrial neurons trafficking through the ventricle may be injured by the MI in the ventricle, promoting nerve sprouting in the atria. 22 Alternatively, atrial nerve sprouting might result from circulating cytokines and growth factors that become elevated during chronic MI.…”

Autonomic cardiac nerves: literature review

“…Hasan [22] presents similar data: as much as 92% of neurons determined retrospectively were found in the stellate ganglion. Hopkins and Armour [28] on the other hand, observed a large number of marked neurons in central cervical ganglia on both sides of the sympathetic trunk following injection into the heart, aorta, and cardiac sac in dogs. Cranial parts of bilateral stellate ganglia were the secondary location of neurons.…”

“…The results of studies by Hopkins et al [28] with the injection of horseradish peroxidase to specific areas of the heart in dogs suggest that postganglionic sympathetic neurons which project efferent axons to a specific cardiac region are not located in a specific region of a sympathetic ganglion or a specific sympathetic ganglion. Rather, neurons in one region of a sympathetic ganglion project axons to widespread areas of the myocardium.…”

“…Studies using retrograde tracing carried out on various animal species lead to the determination of neurons projecting axons to the heart (the conduction system, cardiomyocytes, and coronary vessels) and thus the identification of their location [28,35,42,52,64]. In cats, most cardiac neurons were located in the stellate ganglion (2679 cells, on average) and in the ipsilateral ganglions of segments C8-T9 (213 cells, on average) [35].…”