Abstract
A mutant strain of rats, the congenital aganglionosis rat (Spotting Lethal), was originally described by Ikadai as showing a congenital aganglionic bowel. Thus, this mutant seemed to be a proper model of Hirschsprung's disease in man. In the present study, the whole bowel of this mutant from the duodenum to the rectum was examined using acetylcholinesterase and immunohistochemical staining for tyrosine hydroxylase and substance P in whole mount preparation, routine staining in sectioned preparation, scanning electron microscopy and transmission electron microscopy.
All examined mutant rats had a constricted bowel region following a dilated bowel region. In 33 cases, the constricted segments extended from the rectum to the distal ileum; in three cases, from the rectum to the middle colon.
In controls, the Auerbach's plexus appeared as a meshwork consisting of ganglion strands and internodal strands, showing a rather regular ladder-like pattern from the duodenum to the rectum.
The Auerbach's plexus of mutants was very different from that of controls, showing conspicuous regional differences. Even in the duodemun, which appeared to be normal macroscopically, the Auerbach's plexus showed an irregular pattern, the meshes varying greatly in size and shape. Ganglion strands were shorter than in controls. The plexus in the enlarged segment gradually decreased in density, finally disappearing above the proximal terminal of the constricted segment. In some areas below this transition, that is, the anal portion of the enlarged segment and the oral portion of the constricted segment in 33 cases (long constricted segment type only), there were few nerve fibers and no ganglion cells.
In the distal part of the upper colon, some fine nerve bundles appeared to run irregularly. These nerve bundles gradually increased in number and mixed with thicker nerve bundles in the lower portion of the colon. Finally, at the rectum, nerve bundles of verious sizes interlaced irregularly with one another to make a kind of network. However, this network was free from ganglion cells.
