An immunohistochemical study of somatostatin-containing nerves in the aganglionic colon of human and rat.

The distribution of somatostatin-like immunoreactive (SOM-LI) nerves was elucidated immunohistochemically in the gut tissues from patients with Hirschsprung's disease and congenital aganglionosis rats. In the normoganglionic human colon, SOM-LI nerve cell bodies were found to a greater extent in the submucous plexus and to a lesser extent in the myenteric plexus. However, they were rarely observed in both the plexuses of the oligoganglionic segment. SOM-LI nerve fibres were widely distributed in the aganglionic bowel. The circular muscle layer of the distal aganglionic segment was densely innervated by SOM-LI nerve fibres which are probably derived from the extrinsic, hypertrophic nerve bundles. A decreased number of the intramuscular nerves fibres were seen in the proximal aganglionic segment. In the colon and rectum from adult and 21-day-old rats, SOM-LI cell bodies were numerous in both plexuses. On the other hand, enteric neurons were completely lacking from the colon and rectum of congenital aganglionosis rats of 21 days old. No neuronal elements staining for SOM were disclosed in these aganglionic segments of mutant rats. A possible origin and pathophysiological role of the extrinsic nerve fibres containing SOM in the diseased bowel are discussed. It is concluded that SOM-LI nerves in the human distal colon comprise both intrinsic and extrinsic elements, while SOM nerves in the rat colon and rectum are of only intrinsic origin.