Ontogeny of PACAP immunoreactivity in extrinsic and intrinsic innervation of chicken gut

An immunohistochemical study was conducted on the ontogeny of pituitary ade nylate cyclase-activating polypeptide-27 (PACAP) immunoreactive elements wi thin the extrinsic and intrinsic nerve supply of the chicken embryo gut. Th e first PACAP-immunoreactivity was detected in the extrinsic nerve supply a t E 4 within the pharyngeal region and the primary sympathetic chain. At E 5.5 it appeared in the vagus nerve, the spinal cord, the secondary sympathe tic chain, some perivascular plexuses and the Remak ganglion. In the intrin sic nerve supply, the first PACAP-immunoreactive elements were shown at E 4 .5-E 5 in the mesenchymal bud of the proventriculus/gizzard. Then they grad ually appeared also cranially and caudally both in myenteric and submucous plexuses. (C) 2000 Elsevier Science Inc. All rights reserved.