The orthograde labeling of postganglionic sympathetic cardiac nerves in the dog and cat as demonstrated by autoradiography

Sympathetic innervation of the young canine heart using antero- and retrograde axonal tracer methods

The present study was performed to determine the origin of cardiac sympathetic postganglionic fibers and to demonstrate their distribution in the heart. Young dogs were used in this study. Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was injected into various regions of the heart, and cholera toxin B subunit (CTB) and WGA-HRP were injected into the middle cervical ganglion or the stellate ganglion. In our retrograde axonal transport study, a large number of WGA-HRP-labeled cells were observed in the middle cervical and stellate ganglia bilaterally. Only a small number of the labeled cells were observed in the superior cervical ganglia bilaterally. In the anterograde axonal transport study, CTB and WGA-HRP labels showed terminal-like structures in the intrinsic ganglia located in the sinoatrial node, left atrium, and the origin of the ascending aorta. The labeled fibers were also observed around the coronary arteries.

Horseradish peroxidase localization of the sympathetic postganglionic neurons innervating the cat heart

The localization of the sympathetic postganglionic neurons innervating the cat heart has been investigated by using retrograde axonal transport of horseradish peroxidase (HRP). HRP was injected into the subepicardial layers of 4 different cardiac regions. The animals were sacrificed 72-96 h later and fixed by perfusion via the left ventricle. The paravertebral sympathetic ganglia from the superior cervical, middle cervical and stellate ganglia to T10 ganglia were removed and processed for HRP identification. Following injections of HRP into the apex of the heart, the sinoatrial (SA) nodal region and the ventral wall of the right ventricle, we observed that HRP-labeled sympathetic neurons were localized predominantly in the right stellate ganglia, and to a lesser extent, in the right superior and middle cervical ganglia, and left stellate ganglia. Fewer labeled cells were found in the right T4-T6. T8 and T9. After HRP injection into the dorsal wall of the left ventricle, HRP-labeled cells were present mainly in the left stellate ganglia.

Localization of sympathetic postganglionic neurons of physiologically identified cardiac nerves in the dog

Cardiac nerves were identified physiologically and injected with horseradish peroxidase in 38 dogs. Retrogradely labeled neurons were present in the greatest number in the middle cervical ganglion, whereas fewer labeled neurons were present in the stellate ganglion. Only occasional neurons in the superior cervical ganglion were labeled, and no labelphysiologically and injected with horseradish peroxidase in 38 dogs. Retrogradely labeled neurons were present in the greatest number in the middle cervical ganglion, whereas fewer labeled neurons were present in the stellate ganglion. Only occasional neurons in the superior cervical ganglion were labeled, and no labelphysiologically and injected with horseradish peroxidase in 38 dogs. Retrogradely labeled neurons were present in the greatest number in the middle cervical ganglion, whereas fewer labeled neurons were present in the stellate ganglion. Only occasional neurons in the superior cervical ganglion were labeled, and no labeled cells were found in the T3 to T6 paravertebral ganglia or in the ganglia contralateral to the nerve injected. following injections into specific cardiac nerves, retrograde labeling was widespread within the middle cervical ganglion, and the distributions of labeled neurons from different nerves overlapped considerably. In the middle cervical ganglion there was little or no regional grouping of cells projecting to specific cardiac nerves. within the stellate ganglion, however, te cardiac-sympathetic cells were clustered primarily at the cranial pole near toe origin of the ventral and dorsal ansae. Mediastinal ganglia and ganglia located in cardiac nerves were frequently as heavily labeled as the ipsilateral stellate ganglion. The occurrence of heavy labeling in mediastinal and cardiac nerve ganglia indicates that these hitherto unreported ganglia play a significant role in cardiac neural regulation. These data imply that the organization of sympathetic neurons controlling the heart is much more complex than has previously been considered.

Autoradiographic study of the right stellate ganglionic fibers to the cat heart

Autoradiographic techniques have been employed to demonstrate the distribution of the postganglionic sympathetic cardiac fibers originating from the right stellate ganglion in 3 cats. After exposing the ganglion through a right thoracotomy, a total of 500 muCi of tritiated leucine was injected into the right stellate ganglion of each cat. After 3 days the animals were sacrificed by vascular perfusion. The injected ganglia, the heart and great vessels were processed for autoradiography. The majority of the right stellate ganglionic fibers travelled between the trachea and aortic arch, and entered the cardiac fibers travelled between the trachea and aortic arch, and entered the cardiac plexus. Continuing through the plexus, these fibers coursed between the ascending aorta and the pulmonary arterial trunk to form a periarterial plexus around the left coronary artery and its branches. Most of the fibers followed the distribution of the ventral descending branch of the left coronary artery; a few followed the circumflex artery. A conspicuous subepicardial plexus was derived from the periarterial plexus and was most prominent in the cranial half of the left ventricle. Other fibers arising from the right stellate ganglion descended between the cranial vena cava and the right branch of the pulmonary artery. These ramified on the dorsolateral surface of the right atrium, and also formed a large bundle which passed caudally through the interatrial septum.