Alterations of the intramural nervous distributions in a chick intestinal atresia model

The postoperative intestinal dysmotility seen in intestinal atresia (IA) is usually found in association with a dilatation of the proximal intestinal segment, but the etiology of this disorder is not yet fully understood. A chick IA model was made by cutting the postumbilical midgut on d II in ovo. The operated chicks were euthanized 2 d after hatching. The samples were divided into two groups according to the extent of the dilatation of proximal ileal segments. Cryostat sections were processed for immunohistochemistry by the use of antisera to protein gene product 9.5, vasoactive intestinal polypeptide, substance-P, and alpha-smooth muscle actin and were also stained by NADPH-diaphorase. In highly dilated proximal segments, a decreased number of protein gene product 9.5-positive fibers was found in both the circular muscle and submucous layers. The number of nerve fibers positive for vasoactive intestinal polypeptide, substance-P, and NADPH-diaphorase also decreased in the circular muscle layer, particularly in the deep muscular plexus. Hypertrophy and an alteration of the staining intensities in the circular muscle layer were also revealed by at-smooth muscle actin staining. The nerve distribution of the distal segments was indistinguishable from that of the age-matched controls and the sham-operated group. Abnormalities in the intramural nerves are only found in the proximal ileal segment of the IA models. The abnormal nerve distribution of the proximal segment might thus be implicated in the postoperative dysmotility of the intestine in IA.