Immunohistochemical Study Of The Neuromuscular Junction Of The Colon In Hirschsprung's Disease

[Objective] :Although there are marked absence of ganglion cells and proliferation of nerve fibers in the aganglionic bowel of patients with Hirschsprung's disease, controversy exists as to not only whether these fibers terminate in the muscle cells of the bowel wall but also the mechanism of the occurrence of constricted segment in Hirschsprung's disease. In order to explain the occurrence of constricted segment in patients with Hirschsprung's disease, we studied the neuromuscular junctionin of the colon in patients with Hirschsprung's disease applying immunohistochemical methods.[Methods] :Twenty cases (male 13,female 7) aging from 3 months to 10 years of Hirschsprung's disease were reported. Of which short segment type was in 5 cases , common type in 12 , long segment 3. The distribution of the neuromuscular junctionin in the muscle layers of bowel from 10 normal controls and 20 Hirschsprung's disease patients was studied by synaptophysin and neurofilament immunohistochemistry. Antimouse synaptophysin and neurofilament serum was used for visualization of neuromuscular junctionin .[ Results ] : In the colon of the control cases synaptophysin- immunoreactivity and neurofilament-immunoreactivity was widely distributed in the circular muscle layer. In the dilated colon with Hirschsprung's disease cases, synaptophysin-immunoreactivity and neurofilament-immunoreactivity were moderate distributed with normal ganglion cell and were scarce in constricted segment withdegenerated ganglion cell. In contrasted to the high degree of synaptophysin-im munoreactivity and neurofilament-immunoreactivity in the controls and dilated colon ,the synaptophysin- immunoreactivity and neurofilament -immunoreactivity in the constricted segment were nil in the circular muscle layer.[Conclutions] :It is well known that many kinds of intrinsic myenteric neurons send their processes into the circular muscle layer to act as motor neurons in the intestine. These processes were named neuromuscular junction. The present study demonstrated that dense synaptophysin-im munoreactivity and neurofilament-immunoreactivity nerve endings were prominent in the circular muscle layer in the control. An ultrastructural study also confirmed the dense distribution of the terminals in the circular muscle layer in the control. However, it was evident that there was almost no synaptophysin-immunoreactivity and neurofilament-immunoreactivity in the circular muscle layer in the constricted segment.In addition ,electron microscopic studies have shown that very few nerve terminals were detected from the circular muscle layer in the constricted segment.therefore, the circular muscle layer from the constricted segment is confirmed to be a region with poor innervation including extrinsic and intrinsic nerve.Several hypotheses have been proposed for the occurrence of constricted segment in Hirschsprung's disease. Meier-Ruge considered that an increase Ach-E reactive fibers was related to the constricted segment. Another hypothese suggested that the absence of the myenteric plexus or ganglion cells was related to the production of the constricted segment. Ward concluded that lack of c-kit+ interstitial cells of Cajal, an intestinal pacemaker,may lead to the bowel spasm in Hirschsprung's disease. Okamoto and Ehrenpreis considered that Cannon's law offered an explanation of the constricted segment. Cannon's Law of Denervation describes the wide ranging effects of the complete loss of nerve inputs to a variety of bodily structures under experimental conditions. One of the many responses to nerves thatare sick or dysfunctional (now termed Disuse Supersensitivity) is that When a structure is denervated, its irritability to certain chemical agents is increased . the muscles that are supplied by these nerves shorten and tighten , resulting in muscle spasm and stiffness. Normal colon transmits co-ordinated peristaltic waves from above to below and thus propels the feces through the bowel. In the patients with Hirschsprung's disease,the constricted segment which was denervated, is incapable of transmitting normal propulsive peristaltic waves and therefore acts as a physiologic obstruction.