Origin and development of VIP and substance P containing neurons in the embryonic avian gut.

The development of substance P (SP) and VIP containing structures of the quail and chick guts was studied by immunocytochemistry. The appearance of VIP and substance P nerves follows a rostrocaudal pattern from day 9 in the quail and day 10 in the chick embryo. Immunoreactive fibres are first visible in the oesophagus and at 12 days they extend over the whole length of the intestine. VIP and substance P ganglionic cells are first localized in the foregut (day 9 for VIP containing neurons and day 13 for SP ones) and observed in the mid- and hind-gut just before hatching. Transplantation on the chorioallantoic membrane (CAM) of fragments of various parts of the digestive tract were carried out to see whether in such circumstances the pattern of VIP and SP containing nerves was comparable to normal. The explants contained numerous SP and VIP immunofluorescent nerve fibres. In addition, cell bodies with VIP and SP immunoreactivity appeared brightly fluorescent in the enteric ganglia of the graft showing that these peptidergic nerve cells belong to the intrinsic innervation of the gut.