Ar. Bello et al., SEXUAL DIMORPHISM IN THE DISTRIBUTION OF ALPHA-NEOENDORPHIN-LIKE IMMUNOREACTIVITY IN THE ANTERIOR-PITUITARY OF THE RAT, Journal of neuroendocrinology, 5(3), 1993, pp. 315-322
The localization of the opioid peptide alpha-neoendorphin (alpha-Neo-E
) was studied in the anterior pituitary of normal and castrated male a
nd normal female rats. Immunoreactive (ir) cells were noted in both se
xes. These alpha-Neo-E-ir cells were further characterized using doubl
e immunostaining with an elution-restaining procedure. It was seen tha
t in males, alpha-Neo-E-ir cells corresponded mainly to luteinizing ho
rmone/follicle-stimulating hormone cells and a few thyroid-stimulating
hormone (TSH) cells, whereas in females, virtually all alpha-Neo-E-ir
cells corresponded to TSH cells. Castration of male rats caused, with
in 3 to 5 days, a dramatic decrease in the number of alpha-Neo-E-ir go
nadotrophs, whereas the number of alpha-Neo-E-ir TSH cells tended to i
ncrease. Two weeks after castration, however, most alpha-Neo-E-ir cell
s were also follicle-stimulating hormone-ir. This study demonstrates t
hat in the anterior lobe of the rat, alpha-Neo-E-ir is located within
gonadotrophs and/or thyrotrophs, depending on the sex. In addition, re
sults obtained following castration suggest that the expression of thi
s peptide in the anterior pituitary depends upon the steroid environme
nt, possibly indicating that alpha-Neo-E is implicated in the regulati
on of the pituitary-gonadal axis.