Ontogenesis of endocrine cells in the chicken intestine: an immunohistochemical study

The authors report the time of appearance, morphology and topographic distribution of gastrin/cholecystochinin- (G/CCK-), somatostatin- (SRIF-), neurotensin- (NT-), motilin- (MO-) and substance P-like immunoreactive (SP-LI) elements during embryonic and postnatal development, in ileum, caeca and colon of chick embryos (from 8 days of incubation to hatching), newborn chicks (up to 15-days old) and adult chickens. In the ileum, G/CCK-LI and SP-LI cells appeared on day 11, the others on about day 13. In the caeca the first cells of all types were seen from about day 17. In the colon, NT-LI cells appeared early, on day 9, SP-LI and occasional SRIF-LI cells from day 13 on and MO-LI and G/CCK-LI only from day 17. In the ileum all the cells studied were present, in the caeca and colon they were extremely scarce, apart from NT-LI cells which were more numerous. In the prenatal stages, SP-LI was found only in epithelial cells; after hatching, it was also present in metasympathetic nerve elements.