Immunohistochemical study was performed using monoclonal antibodies specific to neurofilament (NF) (clone NR4 and 2F11) and synaptophysin (SY) in the bowel of Hirschsprung's disease and related diseases. The following results were obtained. 1) The ganglionic bowel : NF-immunoreactivities by NR4 were localized in the plexuses but weak in distal axons, but those by 2F11 were localized in the plexuses and distal axons. SY-immunoreactivities were localized in the plexuses and muscle layers. 2) The aganglionic bowel : NF-immunoreactivities by NR4 and 2F11 were localized in hypertrophic axon bundles. NF-immunoreactive nerve fibers decreased from the rectum to the descending colon in long segment aganglionosis. SY-immunoreactivities were localized in muscle layers but decreased gradually in more proximal areas. 3) The bowel of hypoganglionosis : In the case 1, NF-immunoreactivities by NR4 were localized in the submucous plexuses but not in the myenteric plexuses, and those by 2F11 were localized in both plexuses. There were fewer SY-localizations in muscle layers. In the case 2, NF-immunoreactivities by NR4 and 2F11 were very weak in the myenteric plexuses but were seen in the submucous plexuses. SY-immunoreactivities were localized in both plexuses, but not in the muscle layers. Conclusion : NF was rich in both quantity and quality in hypertrophic axons of the aganglionic bowel. These axons might innervate smooth muscle layers but the density of innervation decreased in the proximal bowel as indicated by SY localizations. In the bowel of hypoganglionosis, the structure of NF was abnormal to various degrees in the myenteric plexuses of bowels with hypogan-gionosis. Innernation in smooth muscle layers was also abnormal in the case 2.
