Distribution of peripheral nerve terminals in the small and large intestine of congenital aganglionosis rats (Hirschsprung's disease rats)

The congenital aganglionosis rat is considered to be an animal model of Hir schsprung's disease. The mutants had a long constricted segment (from dista l ileum to rectum) below the dilated distal ileum. In the dilated region, s ynaptophysin-immunoreactivity (IR) was almost preserved in all layers of th e intestinal wall. In the constricted distal ileum and oral proximal colon, synaptophysin-IR was scarce in all layers, including the circular and long itudinal muscle layers. In the anal proximal and distal colon, synaptophysi n-IR was almost scarce in the circular muscle layer (CML). An ultrastructur al study confirmed that almost no terminals were found in the CML of any re gions of constricted intestine. Therefore, the CML in any region of a const ricted segment, is presumed to be poor innervation. However, a few synaptop hysin-IR were found in the longitudinal muscle layer (LML) of an anal part of a constricted segment. An ultrastructural study also confirmed that some terminals were observed in the LML of this segment. The present study sugg ested that denervated CML is related to the production of constricted segme nt, irrespective of the presence or absence of terminals in the LML.