Localization of the cells of origin for primary afferent fibers supplying the gallbladder of the cat

Neurochemical characterization of nerve fibers in the porcine gallbladder wall under physiological conditions and after the administration of Salmonella enteritidis lipopolysaccharides (LPS)

Lipopolysaccharides (LPS, bacterial endotoxin) are a component of the cellular membrane of Gram-negative bacteria, which is known as an important pathological factor. In spite of many previous studies describing multidirectional negative effects of LPS on living organisms, the knowledge concerning the influence of bacterial endotoxins on the gallbladder innervation is extremely scarce. The present study, based on the immunofluorescence technique, describes the changes in the neurochemical characterization of nerves within various parts of the porcine gallbladder (neck, body and fundus) after the administration of low doses of LPS. The obtained results show that even low doses of bacterial endotoxins affect the nerve structures within the gallbladder wall and the intensity of fluctuations in immunoreactivity to particular substances clearly depends on the part of the investigated organ. The most evident changes were observed in the case of fibers exhibiting the presence of neuropeptide Y (an increase from 7.84 ± 0.17 to 14.66 ± 0.37) in the neck, substance P (an increase from 0.88 ± 0.1 to 8.4 ± 0.3) in the body and the vesicular acetylocholine transporter in the gallbladder's fundus (an increase from 4.29 ± 0.18 to 11.01 ± 0.26). The mechanisms of the observed changes still remain unclear, but probably they are connected with the pro-inflammatory and/or neurodegenerative activity of LPS.

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.

Identification of dorsal root ganglion neurons that innervate the common bile duct of rats

Pain originating in the bile duct is common and many patients who have suffered from it report that it is one of the most intense forms of pain that they have experienced. Many uncertainties remain about the mechanisms underlying pain originating in the bile duct. For example, the dorsal root ganglion (DRG) neurons that give rise to the sensory innervation of the common bile duct (CBD) have not been identified and examined in any species. The goal of the present study was to determine the number, distribution, and size of DRG neurons that innervate the CBD in rats. Injections of WGA-HRP or CTB-HRP were restricted to the lumen of the bile duct. Injections of WGA-HRP labeled a mean number of about 500 DRG neurons bilaterally throughout all thoracic and upper lumbar levels. Injections of CTB-HRP labeled smaller numbers of DRG neurons. Application of colchicine onto the surface of the CBD reduced the number of cells labeled following injections of WGA-HRP into the lumen of the CBD by roughly 86%, suggesting that tracer had not spread in large amounts out of the CBD and labeled afferent fibers in other tissues. Approximately 85% of the neurons labeled with WGA-HRP had cell bodies that were classified as small; the remainder were medium in size. Injections of CTB-HRP labeled cell bodies of varying sizes, including a few large diameter cell bodies. These results indicate that a large number of primarily small DRG cells, located bilaterally at many segmental levels, provide a rich innervation of the common bile duct.

Afferent innervation of the gallbladder in the cat, studied by the horseradish peroxidase method

Following injection of horseradish peroxidase (HRP) into the wall of the gallbladder of cats, HRP-positive cells were found bilaterally in dorsal root ganglia T2-L3 (T2-L2, and T3-L2/L3 also observed in a few cats) and nodose ganglia. In about 33% of animals labelled cells were also distributed in cervical dorsal root ganglia C5-C7. Labelled cells were more frequently localized on the right side than the left. There was no apparent change in numbers of labelled cells in the nodose ganglion (NG) on either side following greater and lesser splanchnicotomy or section of the right phrenic nerve or removal of the celiac ganglion. After severing both the greater and lesser splanchnic nerves unilaterally, numbers of labelled afferent cells from the gallbladder in dorsal root ganglia (DRGs) significantly decreased on the ipsilateral side but there was no change in the pattern of distribution contralaterally. After section of the right phrenic nerve, labelled cells were not found in ipsilateral cervical ganglia. That some afferent fibers from the gallbladder travel via the phrenic nerves, particularly on the right side, may be a supplementary mechanism in the generation of referred pain in gallbladder disease. The splanchnic nerves are the main, but not the only pathway for afferent fibers from the gallbladder.

Visceral pain: a review of experimental studies

This paper reviews clinical and basic science research reports and is directed toward an understanding of visceral pain, with emphasis on studies related to spinal processing. Four main types of visceral stimuli have been employed in experimental studies of visceral nociception: (1) electrical, (2) mechanical, (3) ischemic, and (4) chemical. Studies of visceral pain are discussed in relation to the use and 'adequacy' of these stimuli and the responses produced (e.g., behavioral, pseudoaffective, neuronal, etc.). We propose a definition of an adequate noxious visceral stimulus and speculate on spinal mechanisms of visceral pain.

Distribution of cell bodies for primary afferent fibers from the stomach of the cat

The distribution of primary afferent cell bodies supplying the stomach of the cat was localized using lectin-conjugated horseradish peroxidase. Labelled cells were found in the nodose ganglia and dorsal root ganglia T4-L2 or T4-L1. The spinal entry levels of the stomach afferents do not overlap extensively with those of the cardiac afferents.

Activation of visceral thin-fiber afferents increases respiratory output in cats

Respiratory responses to chemical activation of thin-fiber afferents from the stomach and the gallbladder were measured in anesthetized cats. Capsaicin or bradykinin applied to the serosal surface of either the stomach or the gallbladder elicited increases in breathing and phrenic nerve activity. Transection of the cervical vagi or the carotid sinus nerves had no effect on these responses. However, the respiratory responses to visceral stimulation were abolished by bilateral transection of the splanchnic nerves. We conclude that activation of thin-fiber afferents from the stomach and gallbladder causes a reflex increase in respiratory output. The initial afferent limb of this reflex is via the splanchnic nerves.