| In 1893, interstitial cells of Cajal (ICCs) were first described in the intestine of rabbit and guinea pig by a great Spanish neuroanatomist, Santiago Ramon y Cajal. On the basis of the staining characteristics of ICCs with methylene blue and silver chromste, Cajal believed ICCs were a type of terminal nerve of autonomic nerves. Over more than a century studies of morphology, ultrastructure, ontogeny and physiology, however, investigators have been certain that ICCs were a special interstitial cells forming cellular network in the gastrointestinal (GI) tract. They play an important role in the regulation of the GI motility by generating and propagating spontaneous electric slow-wave activity and mediating excitatory and inhibitory neurotransmission. Recent years, some studies showed that there are a group cells which are similar to ICCs in a certain spontaneous rhythmicity organs or tissues in non-enteric organs. They were named as interstitial Cajal-like cells (ICLC) and the research on ICLC have increasingly been given attention.When compared with GI smooth muscle cells (SMCs), the SMCs of biliary system also exhibit spontaneous rhythmic electric activites, but the underlying mechanisms are not clear. Recently, ICLC have been identified in gallbladder, carcinoma of gallbladder tissue, they might be responsible for the spontaneous rhythmic electric activity and play an important role in the regulation of the motor function of extrahepatic bile duct system, maintaining the normal pressure and preventing bile back flow from Sphincter of Oddi (SO). It is still unclear about the distribution detail, morphological character, function and the control factors of ICLC in the extrahepatic bile duct system. It is reported that nitric oxide (NO) can inhibit the movement of GI SMC by inhibiting the function of ICCs but if NO also inhibit the movement of SO via regulating the function of ICLC is still unclear. It has important guiding meaning on understanding the motility regulation of the extrahepatic bile duct system and related diseases. Gallstone is one of the common clinic diseases. Although the etiopathogenisis and the pathogenesis are still unclear, it is widely believed that the decreasing of gallbladder motor function is very important in gallstone formation. Therefoere, it is a very interesting question about the distribution and changes of the morphologies and function of ICLC.In the present study, using a special marker for c-Kit immunocytochemical staining and immunofluorescence and NADPH-d cytochemistry on whole mount preparations and cryo-sections and myoelectric activity record combined with, the morphological characteristic, distribution and the myoelectric activity of the extrahepatic bile duct system, hoping to provide new experimental evidences for understanding the regulation mechanism of spontaneous rhythmic motilities and a possible correlation with the gallstone formation.Results:â… . The morphological characters and distribution of ICLC in the EBDS of guinea-pigs1. Kit positive ICLC were observed throughout the EBDS. In hepatic duct, cystic duct and gallbladder, most of the ICLC were located within SMC bundles or layers. These cells appeared to be fusiform with short bipolar processes without branches on whole-mount preparations. From the upper portion to the the lower part of common bile duct, ICLC arrangement model changed from single circular direction to both circular and longitudinal direction and also appear between the circular and longitudinal SMC layers. At the same time, the numbers of ICLC were increased gradually, the processes became longer gradually. ICLC in SMC were long fusiform with two processes; Between SMC layers ICLC were star, where common bile duct was close to the ampulla, more ICLC appeared. Furthermore, a cellular network of ICLC showed up. The evidence of that ICLC distributed in allover the EBDS provided important morphological basis of the EBDS movement regulation.2. ICLC were observed both in exterior wall and in inner wall of the ampulla. In exterior wall of ampulla, ICLC had oval or triangle cell bodies projected long processes with branches, some processes had 1-3 branches or more than 3 branches. These cells, similar to ICC-MY of duodenum, formed a network by their processes. At the inner side of circular SMC layer of the exterior wall, ICLC were similar to ICC-DMP of small intestine. In inner wall of ampulla, a large amount of ICLC were distributed in the SMC layers or bundles and paralleled with them. At the opening point of the ampulla, a lot of ICLC were surrounding the bouche and forming a circle. Adjacent to debouch of the ampulla, the ICLC lay in the circular and longitudinal directions. The evidence about the numbers gradually increasing and the morphous gradually complex prompted that the complex regulation of physiological function in SO interrelated to ICLC.â…¡. The myoelectric activity of the gallbladder, common bile duct and SO of guinea-pigs1. We recorded the myoelectric activity of the SO, common bile duct and gallbladder. They displayed spike potential activity waves. These wave shapes had rather good concordance and most of them were bidirectional waves. In the different three position, their frequency of spike potential were conformity. oppositely, their wave amplitude were different, the wave amplitude of SO was the highest, common bile duct was the middle and gallbladder was the lowest.2. When added nitroprusside sodium which can provide NO into the Kreb-Ringer buffer, the wave amplitude and the frequency of spike potential decrease significantly and disappeared quickly. It prompted that NO could inhibit the activities of ICLC.â…¢. NOS innervation on ICLC in guinea-pigs EBDS1. By NADPH-d histochemistry examination, we found NOS neurons and nerve fiber distribute allover the EBDS. The NOS nerves scattered in hepatic duct, gallbladder, cystic duct and the upper portion of common bile duct. In the lower portion of common bile duct and SO, NOS nerves extensive distributed within myenteric plexus and in the SMC layers or bundles. And the NOS in myenteric plexus were the most abundant.2. Double labeling of NADPH-d and c-kit immunohistochemistry on whole-mount preparation and cryo-sections revealed a close distribution between NOS nerves and ICLC network surrounding myenteric plexus in SO and some varicosity-like endings around the ICLC cell bodies and their processes.â…£The morphological characters of ICLC and EBDS myoelectric activity of gallstone model guinea-pigs1. Compare with the control giunes-pigs, there were no apparent changes about the morphological characters and the numbers of ICLC in SO and gallbladder of gallstone giunes-pigs.2. The wave amplitude and the frequency of SO and gallbladder of gallstone giunes-pigs were lower than that of control giunes-pigs. In gallstone giunes-pigs, frequency of SO and gallbladder were no significant diference, but the wave amplitude were significant diference, SO still higher than gallbladder.
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