Sex-steroid control of galanin in the rat hypothalamic-pituitary axis

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 (E2) 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). E2 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 E2 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 E2 in males (by 60%, P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)