5-HT-like immunoreactive cells in chicken intestine: ontogenesis, morphology and topography.

The indirect immunoperoxidase method was used to describe time of appearance, morphology and topography of 5-hydroxy- tryptamine-like immunoreactive (5-HT-LI) cells in the gut of chick embryos, newborn and adult chickens. The earliest cells were seen in the ileum at 11 days, in the caeca at 14 and in the colon at 9 days. At first appearance they were ovoid or pyramidal but later became more irregular because of the numerous apical and basal processes. The peak of cell concentration at hatching, was in the ileal samples, whereas in the colon these cells were also abundant in adults both throughout the villi and the glands. In sections of adult ileum, on the contrary, they could be found mainly in the glands.