Structural studies on the connectivity of the inferior mesenteric ganglion of the guinea pig.

After injection of horseradish peroxidase (HRP) into the inferior mesenteric ganglion (IMG) of the guinea pig, labeled cell bodies were found in the solar plexus ganglia, the ganglia of the pelvic plexus and in the nodose ganglia as well as in the spinal cord and dorsal root ganglia at the T13-L4 levels. By using the fluorescent tracer True blue, labeled cell bodies could also be detected in the myenteric and submucosa ganglia of the distal colon. Application and uptake of HRP by the colonic nerves resulted in labeling of cell bodies in the dorsal root ganglia, the IMG and in the solar plexus ganglion complex indicating that the latter neurons send their axons in the intermesenteric nerve through the IMG to continue in the colonic nerves to the distal colon. When HRP was applied and diffused into the hypogastric nerves labeled cell bodies were seen in the IMG, the dorsal root ganglia and in the preganglionic nuclei of the lumbar spinal cord with 50% of the labeled neurons located dorsal and dorsolateral to the central canal. The finding of such a diversity in the nerve supply to the IMG, supports the view that the ganglion plays an important role in the integration of visceral reflexes.