Galanin is a brain-gut peptide that is present in the central and periphera
l nervous systems. In the gut, it is contained exclusively in intrinsic and
extrinsic nerve supplies, and it is involved overall in the regulation of
gut motility. To obtain information about the ontogeny of galanin, we under
took an immunohistochemical study of chicken embryos.
The time of first appearance and the distribution patterns of galanin were
investigated with fluorescence and streptavidin-biotin-peroxidase (ABC) imm
unohistochemical protocols by using a galanin polyclonal antiserum. The var
ious regions of the gut and the pancreas were obtained from chicken embryos
aged from 3 days of incubation to hatching. All specimens were fixed in bu
ffered picric acid-paraformaldehyde, frozen, and cut with a cryostat.
Galanin-immunoreactive neuroblasts were first detected at 4 days in the mes
enchyme of the proventriculus/gizzard primordium and within the Remak gangl
ion. They then extended cranially and caudally, reaching all of the other g
ut regions at 6.5 days. Galanin-immunoreactive nerve elements mainly occupi
ed the sites of myenteric and submucous plexuses. From day 15, galanin-immu
noreactive nerve fibers tended to invade the circular muscular layer and pa
rt of the lamina propria of the mucosa. In the pancreas, weak galanin-immun
oreactive nerve elements were detected at 5.5 days. They tended to be distr
ibuted among the glandular lobules according to the organ differentiation.
The widespread distribution during the earlier embryonic stages represents
evidence indicating that the neuropeptide galanin may have a role as a diff
erentiating or growth factor. From late embryonic life, its predominant pre
sence in sympathetic nerves and in muscular layers fits with the functions
demonstrated previously in adults of other vertebrates for galanin as a mod
ulator of intestinal motility. Anat Rec 254:28-38, 1999. (C) 1999 Wiley-Lis
s, Inc.