The present article reviews the immunohistochemical findings on the localization of
biogenic amines and neuropeptides in adrenal medullary cells of birds. In the chicken,
about 70% of medullary cells are adrenaline-containing cells and the rest of cells
seem to be noradrenaline-containing cells. The ratio of adrenaline-cells to noradrenaline-cells
extremely varies among avian species. Besides adrenaline and noradrenaline, medullary
cells of birds contain many kinds of biogenic amines and neuropeptides: serotonin,
galanin, cholecystokinin, somatostatin, enkephalin, neuropeptide tyrosine and atrial
natriuretic peptide. The existence of these bioactive substances in medullary cells
also exhibits interspecies heterogeneity. In the chicken, serotonin and galanin are
contained in both adrenaline- and noradrenaline-cells of the adrenal gland. Cholecystokinin-
and somatostatin-immunoreactivity is restricted to adrenaline-containing cells. Enkephalin-immunoreactivity
is seen in both adrenaline- and noradrenaline-cells, but in about half of medullary
cells. Neuropeptide tyrosine-immunoreactivity is found in the adrenal gland of the
chick embryo and newly hatched chick, but not in the adult chicken. Serotonin and
these neuropeptides may be selectively coreleased with adrenaline and/or noradrenaline
from adrenal medullary cells of the chicken.
Key words
Bioactive Substances - Colocalization - Adrenaline Cells - Noradrenaline Cells - Adrenal
Gland - Birds
