The present study investigated the cellular localization of 3 catecholamine 
biosynthetic enzymes, tyrosine hydroxylase (TH), dopamine beta-hydroxylase 
(DBH), and phenylethanolamine N-methyltransferase (PNMT) to identify and analyze 
the localization of norepinephrine (NE) and epinephrine (E) cells in the adrenal 
gland in the chicken using peroxidase-antiperoxidase immunohistochemical 
techniques. Tyrosine hydroxylase immunoreactivity (IR) was observed in almost 
all adrenal medullary cells of the adult chicken. Dopamine beta-hydroxylase IR 
coincided with that of TH. Many medullary cells also exhibited PNMT IR, but 
PNMT-immunonegative cells were also observed. Tyrosine hydroxylase IR was 
localized in the E- and NE-containing cells, but PNMT IR was localized only in 
the E-containing cells. Approximately 69% of medullary cells were E-containing, 
and the remaining were NE-containing cells. The ratio of E- and NE-containing 
cells between the subcapsular and central zone was statistically significant (P 
< 0.01). Although cortical cells of the adrenal gland did not show TH-, DBH-, or 
PNMT-positive reactions, ganglia close to the adrenal gland showed TH, DBH, and 
PNMT immunoreactivities. These findings indicated the cellular localization of 3 
catecholamine-biosynthesizing enzymes in chicken adrenal medulla and suggest 
that the majority of medullary cell are E-containing cells. The ratio of E cells 
to NE cells varies among the 3 zones in the adrenal glands of the chicken.