Anatomical and neuropeptidergic properties of the duodenal neurons projecting to the gallbladder in the golden hamster

This study investigated the anatomical and neuropeptidergic properties of the duodenal neurons projecting to the gallbladder in the golden hamster. Fast blue (FB) was injected into the subserosa of the gallbladder in order to identify by retrograde tracing the duodenal neurons that project to the gallbladder. Subsequently, immunofluorescence microscopy was employed to see whether these duodenal neurons contained putative peptidergic neurotransmitters such as calcitonin gene-related peptide (CGRP), galanin (GAL) and vasoactive intestinal polypeptide (VIP). The FB-labeled cells were only found in the duodenal region adjacent to the major duodenal papilla where the biliary duct opens. On the other hand, there was no difference within this duodenal region in the numbers of FB-labeled cells between the mesenteric and antimesenteric portions, suggesting that these two portions of the duodenum equally contribute neuronal projections to the gallbladder. Double-immunofluorescence microscopy clearly demonstrated that a small population of FB-positive duodenal neurons contained putative neurotransmitters CGRP, GAL and VIP. Our data suggest that duodenal neurons around the major duodenal papilla in the golden hamster project to the gallbladder and exert their influence on the gallbladder via neuropeptides such as CGRP, GAL and VIP.