Distribution and development of peptidergic nerves and gut endocrine cells in mice with congenital aganglionic colon, and their normal littermates

Studies were made of the distribution of gut hormones and neuropeptides in the gastrointestinal tract of mice with hereditary aganglionic colon (s1/s1) and their normal littermates. Antisera to substance P, vasoactive intestinal polypeptide, and enkephalins demonstrated markedly diminished numbers of immunofluorescent nerve fibers in the aganglionic segment of colon; in contrast, in proximal colon and small intestine the distribution of peptidergic nerve fibers was essentially normal. Mucosal endocrine cells were demonstrated in the colon by antisera to substance P, somatostatin, glucagon, and cholecystokinin; in each case there were similar numbers of cells in s1/s1 and normal mice. Radioimmunoassays for vasoactive intestinal polypeptide and bombesin showed diminished concentrations of immunoreactive material in the aganglionic segment of colon of 16-17-day-old animals. However, assays for CCK--which is predominantly located in endocrine cells--showed similar concentrations of immunoreactive material throughout the gut of s1/s1 and normal mice. It was of interest that the concentrations of immunoreactive substance P were lower than normal not only in the aganglionic segment of colon, but also in proximal colon and distal small intestine, and that at all ages the development of substance P in the intestine was delayed in the s1/s1 mice. The results are consistent with the idea that the constriction of the aganglionic segment of colon develops as a consequence of lack of intrinsic inhibitory neurons, possibly those containing vasoactive intestinal polypeptide. The presence of an aganglionic segment is attributable to delayed migration of the neuroblasts from the neural crest. Thus the findings of normal populations of gut endocrine cells in the aganglionic segment is further support for the view that the embryologic origin of gut endocrine cells is different to that of gut neurons.