Peptidergic innervation of the human gallbladder

Surgical anatomy of innervation of the gallbladder in humans and Suncus murinus with special reference to morphological understanding of gallstone formation after gastrectomy

AIM: To clarify the innervation of human gallbladder, with special reference to morphological understanding of gallstone formation after gastrectomy.

METHODS: The liver, gallbladder and surrounding structures were immersed in a 10 mg/L solution of alizarin red S in ethanol to stain the peripheral nerves in cadavers (n = 10). Innervation in the areas was completely dissected under a binocular microscope. Similarly, innervation in the same areas of 10 Suncus murinus (S. murinus) was examined employing whole mount immunohistochemistry.

RESULTS: Innervation of the gallbladder occurred predominantly through two routes. One was from the anterior hepatic plexus, the innervation occurred along the cystic arteries and duct. Invariably this route passed through the hepatoduodenal ligament. The other route was from the posterior hepatic plexus, the innervation occurred along the cystic duct ventrally. This route also passed through the hepatoduodenal ligament dorsally. Similar results were obtained in S. murinus.

CONCLUSION: The route from the anterior hepatic plexus via the cystic artery and/or duct is crucial for preserving gallbladder innervation. Lymph node dissection specifically in the hepatoduodenal ligament may affect the incidence of gallstones after gastrectomy. Furthermore, the route from the posterior hepatic plexus via the common bile duct and the cystic duct to the gallbladder should not be disregarded. Preservation of the plexus may attenuate the incidence of gallstone formation after gastrectomy.

Innervation of the extrahepatic biliary tract

The extrahepatic biliary tract is innervated by dense networks of extrinsic and intrinsic nerves that regulates smooth muscle tone and epithelial cell function of extrahepatic biliary tree. Although these ganglia are derived from the same set of precursor neural crest cells that colonize the gut, they exhibit structural, neurochemical, and physiological characteristics that are distinct from the neurons of the enteric nervous system. Gallbladder neurons are relatively inexcitable, and their output is driven by vagal inputs and modulated by hormones, peptides released from sensory fibers, and inflammatory mediators. Gallbladder neurons are cholinergic and they can express a number of other neural active compounds, including substance P, galanin, nitric oxide, and vasoactive intestinal peptide. Sphincter of Oddi (SO) ganglia, which are connected to ganglia of the duodenum, appear to be comprised of distinct populations of excitatory and inhibitory neurons, based on their expression of choline acetyltransferase and substance P or nitric oxide synthase, respectively. While SO neurons likely receive vagal input and their activity is modulated by release of neuropeptides from sensory fibers, a significant source of excitatory synaptic input to these cells arise from the duodenum. This duodenum-SO circuit is likely to play an important role in the coordination of SO tone with gallbladder motility in the process of gallbladder emptying. Now that we have gained a relatively thorough understanding of the innervation of the biliary tree under healthy conditions, the way is paved for future studies of altered neural function in biliary disease.

Gallbladder motility in children with Down syndrome

OBJECTIVE

The aim of this study was to investigate gallbladder motility in children with Down syndrome by measuring gall-bladder volume and contraction index.

METHODS

This study, performed between January 2001 and December 2002 at the Ondokuz Mayis University, School of Medicine, Department of Paediatric Neurology, Samsun, Turkey, included 21 patients with Down syndrome (study group) and 22 healthy children (control group). After an 8-hour fast, gallbladder diameters in both groups were measured in length, width, and height by ultrasonography before and 30 minutes after a test meal. The volume of gallbladder before and after a test meal was determined, and the contraction index was calculated. Blood triglyceride and cholesterol levels were measured, and 5-hydroxyindoleacetic acid (5-HIAA) levels in urine were determined.

RESULTS

Mean gallbladder volume before test meal in the study group and controls was 8,412.4 +/- 5,174 mm and 16,516.8 +/- 6,796.1 mm (P < 0.001), respectively. The mean contraction index of the study group was 41.2% +/- 19.4% and of controls, 75.0% +/- 12.3% (P < 0.001). The mean triglyceride level of the study group was significantly higher than controls (P < 0.05). The mean urine 5-HIAA level of the study group was lower than controls (P < 0.05).

CONCLUSION

CI was lower in patients with Down syndrome, suggesting gallbladder hypomotility. Hypomotility may be a feature associated with the high prevalence of gallstones in Down syndrome.

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.

Somatostatin stimulates the brush-tailed possum sphincter of Oddi in vitro and in vivo

BACKGROUND & AIMS

Somatostatin, a neuropeptide and hormone, is found in the biliary tract of several species. The aim of this study was to map the distribution of somatostatin-like immunoreactive nerve fibers in the extrahepatic biliary tract of the Australian possum and to determine the pharmacological effects of somatostatin 1-14 on sphincter of Oddi activity in vitro and in vivo.

METHODS

Tissue was harvested for immunohistochemistry and sphincter of Oddi for circular or longitudinal muscle contractility. In anesthetized possums, sphincter of Oddi motility was measured by manometry, and transsphincteric flow was measured gravimetrically.

RESULTS

Somatostatin immunoreactivity was evident in gallbladder ganglia nerve cell bodies and in nerve fibers of the common bile duct and sphincter of Oddi. Somatostatin 1-14 increased circular and longitudinal muscle contraction amplitude 3-4-fold (P < 0.05), but only the longitudinal muscle contraction amplitude was tetrodotoxin sensitive. Somatostatin 1-14 stimulated spontaneous sphincter of Oddi motility in a tetrodotoxin-insensitive manner, increasing basal pressure, contraction frequency, and amplitude 2-4-fold (P < 0.05) and reducing transsphincteric flow to 25% of control (P < 0.0001).

CONCLUSIONS

Somatostatin-like immunoreactivity is present in the extrahepatic biliary tree, and somatostatin 1-14 stimulates sphincter of Oddi smooth muscle and nerves. The major action is direct stimulation of sphincter of Oddi circular muscle, which reduces transsphincteric flow.

Substance P stimulates sphincter of Oddi motility and inhibits trans-sphincteric flow in the Australian brush-tailed possum

Substance P containing nerves are widely distributed throughout the gastrointestinal tract. The aims of this study were to determine the distribution of substance P containing nerves in the extrahepatic biliary tree of the Australian brush-tailed possum and to characterize the effect of exogenous substance P on the sphincter of Oddi (SO) motility and transphincteric flow in vivo. Immunohistochemical staining of fixed specimens (n = 8) found moderate numbers of substance P containing nerve cell bodies and fibres throughout the neural plexuses of the SO, in particular in the serosal and intraluminal nerve trunks of the SO and gallbladder. Synthetic porcine substance P (1-2000 ng kg-1), administered by close intra-arterial injection (i.a.; n = 7), produced a dose-dependent elevation in basal pressure [P < 0.01] and an associated dose-dependent reduction in trans-sphincteric flow [P < 0.0001]. Substance P had no significant dose-dependent effect on SO phasic contraction amplitude or frequency. Tetrodotoxin (9 micrograms kg-1, i.a.) did not inhibit the effect of substance P on SO motility and trans-sphincteric flow (n = 5). In conclusion, substance P containing nerves are found throughout the possum extrahepatic biliary tree. Exogenous substance P stimulates SO motility and reduces trans-sphincteric flow in vivo by acting directly on the sphincter smooth muscle.