ESTROGEN STIMULATION OF GALANIN GENE-EXPRESSION AND GALANIN-LIKE IMMUNOREACTIVITY IN THE RAT AND ITS BLOCKADE BY THE ESTROGEN ANTAGONIST KEOXIFENE (LY156758)

Rat galanin (rGAL) gene expression is stimulated potently by 17beta-es tradiol in the anterior pituitary. Neuroendocrine tissue extracts of w ere purified by chromatography and analyzed for rGAL-like (-LI) immuno reactivity. Greater than 90% of rGAL-LI eluted at the same position as the synthetic rGAL standard in untreated anterior pituitary, median e minence and neurointermediate lobe tissues. Additional immunoreactive forms were detected in the hypothalamus, anterior pituitary and MtT/W 15 adenoma tissues, particularly after 17beta-estradiol treatment. We examined rGAL and its encoding mRNA in the anterior pituitary of immat ure female rats after the injection of pregnant mare serum gonadotropi n (PMSG). One and two days after PMSG injection, serum 17beta-estradio l increased 3-fold and 4-fold, respectively. This resulted in a surge of endogenous gonadotropin 2 days after PMSG. At this time, rGAL-encod ing mRNA was increased 40-fold over controls. Three days after PMSG, t here was a 6-fold increase in anterior pituitary and a 41% increase in plasma rGAL-LI concentrations. Plasma 17beta-estradiol one day after injection of PMSG and the consequent anterior pituitary rGAL-LI concen trations 2 days later were positively correlated. This stimulation of rGAL and its encoding mRNA by PMSG was inhibited by treatment with the estrogen antagonist keoxifene (LY156758).