Immunohistochemical studies on the intramural nerve in the chicken intestine

The distribution in the chicken intestine of neuropeptide-immunoreactive (IR) ganglion cells and nerve fibres was investigated immunohistochemically. There were four kinds of ganglion cells: vasoactive intestinal polypeptide (VIP)-, substance P (SP)-, galanin (GAL)- and somatostatin (SOM)-IR cells in the submucous plexus (SMP) of the whole intestine and in the myenteric plexus (MYP) in the small intestine excluding VIP-IR ones. These peptide-containing fibres were found consistently but their distribution was variable in the mean areas in different regions of the intestinal wall. They seemed to be intrinsic. Comparing the jejunum and rectum in density and variation, the characteristics of innervation were as follows: villi in both intestines received more VIP-IR fibres than the other three which showed no significant difference. Crypts were surrounded with SP-IR fibres; these were denser than the other three in the jejunum compared with the rectum. The mean areas of SOM- and GAL-IR fibres were four and six times larger than those in the rectum, respectively. The SMP was supplied with the six kinds of neuropeptide-IR fibres, and VIP-IR fibres were dominant in both sides. Areas of VIP-, SP- and SOM-IR fibres were about two times greater than in the jejunum. The area of VIP-IR fibres in the circular muscle was significantly larger than that of the other four in both intestines; their density in the rectum was bout two times higher than in the jejunum. The mean area of SP-IR fibres in jejunal circular muscle was 14 times larger than that in the rectum. The MYP was supplied with seven kinds of neuropeptide-IR fibres except that methionine enkephalin-IR was absent from the rectum. Of these seven fibres, SP- and VIP-IR fibres in the jejunum had the largest areas. However, GAL-IR fibres in the jejunum were about four times denser than in the rectum. We conclude that the jejunum is characterized by the dense distribution of neuropeptide-IR fibres in crypts and MYP whereas in the rectum they occur in SMP and circular muscle. Fig. 15 summarizes the connections described in the present study.