Ultrastructural localization of acetylcholinesterase activity in Hirschsprung's disease.

Localization of acetylcholinesterase activity in congenital megacolon was studied by light and electron microscopy. Acetylcholinesterase activity was strongly positive at the light microscopic level in the Auerbach's plexus of the normal segment and in proliferated nerve fibers of the aganglionic segment. The reaction product observed by electron microscopy was deposited in and between the plasma membranes of the ganglion cells, nerve fibers, and their terminals. The product was also observed in the rough endoplasmic reticulum, nuclear envelope, and Golgi apparatus of the ganglion cells. Acetylcholinesterase activity in the aganglionic segment was observed in and between the plasma membranes of nerve fibers and nerve terminals, which terminated in proximity to smooth muscle cells. Reaction deposits were also observed in the interspace between nerve terminals and smooth muscle cells, suggesting direct innervation of smooth muscles by extrinsic nerve fibers.