The orthograde labeling of postganglionic sympathetic cardiac nerves in the dog and cat as demonstrated by autoradiography.
Previous functional and anatomical techniques have characterized the cardiac nerves and plexuses. They cannot, however, determine the course of fibers arising from a specific ganglion. This study has found that the intraaxonal orthograde labeling of axons can be used to determine the course of postganglionic sympathetic cardiac fibers in the dog and cat. The canine left caudal cervical ganglion and the feline right stellate ganglion were exposed through appropriate thoracotomies. Each ganglion received multiple injections of tritiated leucine (500 muCi/animal). Following a 3--14-day survival period the anesthetized animals were sacrificed by vascular perfusion. The injected ganglia, extracardiac nerves and selected portions of the heart were processed for autoradiography. Autoradiographs from the dog demonstrated labeled postganglionic sympathetic nerves in the extracardiac plexus, left atrial epicardium and the epicardium beneath the coronary sulcus. Labeled nerves in the cat heart were found within the epicardial layers and associated with blood vessels in the left ventricular myocardium. Neither myelinated fibers traveling through the injection site nor intrinsic cardiac ganglion cells were labeled, although the latter were often closely approximated to heavily labeled fibers.
D000818:Animals; D001338:Autonomic Fibers, Postganglionic; D001345:Autoradiography / Q000379:methods; D002415:Cats; D004285:Dogs; D005728:Ganglia, Sympathetic / Q000033:anatomy & histology; D006321:Heart / Q000294:innervation*; D013045:Species Specificity; D013564:Sympathetic Nervous System / Q000033:anatomy & histology*