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.