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Sex‐Steroid Control of Galanin in the Rat Hypothalamic‐Pituitary Axis
Author(s) -
Selvais Philippe L.,
Denef JeanFrançois,
Adam Evelyne,
Maiter Dominique M.
Publication year - 1995
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1995.tb00775.x
Subject(s) - medicine , endocrinology , galanin , hypothalamus , testosterone (patch) , chemistry , pituitary gland , biology , hormone , neuropeptide , receptor
Abstract To further investigate how sex steroids regulate galanin (GAL) in the rat pituitary and hypothalamus, we examined the effects of prepubertal gonadectomy (Gx) and long‐term (9 weeks) replacement with estradiol (E 2 ) or testosterone (T) on pituitary and hypothalamic GAL concentrations in Wistar rats (5–6/group). Sham‐operated animals served as controls (CTR). Pituitary GAL concentration was markedly higher in random‐cycling CTR‐females than in CTR‐males (1391 ± 247 vs 39 ± 5 pg/mg protein, P<0.01) and decreased after Gx only in females (20 ± 3 pg/mg protein, P<0.01). E 2 strongly increased pituitary GAL in Gx‐females and Gx‐males (4470 ± 365 and 3853 ± 347 pg/mg protein, P<0.01), whereas T had no effect. Inversely, hypothalamic GAL was higher in CTR males than in CTR females (5.4 ± 0.3 vs 4.0 ± 0.5 ng/mg protein, P<0.05), and decreased significantly after gonadectomy in males (3.7 ± 0.2 ng/mg protein, P<0.01). The only steroid treatment that significantly modified hypothalamic GAL in Gx animals was administration of E 2 to females (5.7 ± 0.4 ng/mg protein, P<0.01 vs non‐treated Gx). We also studied in hypophysectomized (Hx) rats (8/group) the effects of sex steroids on hypothalamic GAL concentration and distribution. The low hypothalamic GAL concentration observed in male and female Hx rats (1.0 ± 0.1 ng/mg protein) was significantly increased by T in males and in females (respectively, by 40% and by 50%, P<0.02) and by E 2 in males (by 60%, P<0.02). Immunohistochemistry showed that both E 2 and T increased GAL labeling in fibers restricted to the lateral regions of the median eminence of male and female Hx rats, a distribution corresponding to that of GnRH‐immunoreactive fibers. In conclusion, in addition to the marked stimulatory effect of estradiol on pituitary GAL, endogenous and exogenous sex steroids also modulate hypothalamic GAL in male and female rats. Both E 2 and T may exert a stimulatory influence on hypothalamic GAL concentration and histochemical analysis shows that sex steroids enhance GAL immunoreactivity in a subset of neurons that closely overlaps the distribution of GnRH neurons.