Projections of nerve cells from the duodenum to the sphincter of Oddi and gallbladder of the Australian possum

Abstract

Background: This study investigated the existence of direct neural connections between the duodenum and the biliary tract in the Australian possum.

Methods: Retrogradely transported neuronal dyes, Fast Blue and Dil, were injected into the wall of the gallbladder and the sphincter of Oddi. The duodenum, biliary tract, and sympathetic and sensory ganglia were examined for the presence of labeled cell bodies.

Results: Two to 3 weeks after gallbladder injection, labeled nerve cell bodies were found in the myenteric plexus of the proximal duodenum but were rare in the duodenum distal to the sphincter of Oddi. No neurons were found in the submucous plexus. Labeled nerve cells were also found in the sphincter of Oddi. After injection of the sphincter, labeled neurons were in both the submucous and myenteric plexuses of the duodenum, on either side. Approximately one third of labeled myenteric neurons were immunoreactive for enkephalin. Labeled cell bodies were also in the coeliaco-mesenteric, nodose, and dorsal root ganglia after both gallbladder and sphincter injection. After a myotomy on the proximal duodenum, no neurons were labeled on the pyloric side of the lesion by subsequent sphincter injection of dye.

Conclusions: Direct neural pathways connect the duodenum with the gallbladder and the sphincter of Oddi, and the sphincter with the gallbladder; this implies that enteric nerve circuits participate in coordinating duodenal and biliary functions.