Regulation of galanin by dexamethasone in the rat anterior pituitary and the uterus.

Galanin is a 29 amino acid neuropeptide widely distributed throughout the mammalian nervous and endocrine system. We have previously reported that estrogen dramatically increases galanin gene expression and protein synthesis in the anterior pituitary (AP), while the expression in the uterus (UT) of the same animals is transient and similar to the induction of protooncogenes (c-fos, c-jun, c-myc). In order to examine if this pattern of induction is specific to estrogen administration, we investigated the effect of glucocorticoids, another steroid, on the gene expression of galanin in the AP and in the UT of ovariectomized female rats and in the AP of male rats. Using Northern blot analysis, the AP and the UT showed almost undetectable levels of galanin mRNA, but in vivo treatment of female rats with 1 mg/kg body weight of dexamethasone (DEX) led to a significant increase of galanin mRNA levels in both AP and UT. Similarly, DEX (0.1-5 mg/kg i.p.) significantly stimulated galanin mRNA levels in the AP of the male rats. In both males and females the peak of induction was at 9 h after injection that is different from the 3-hour peak after estrogen administration. Daily injection of DEX for up to 7 days sustained the levels of galanin mRNA in both the AP and the UT, in contrast to the transient induction of galanin in the UT after estrogen administration. No change was noted in the galanin protein content of AP (control = 30 +/- 3.5 ng/mg protein; DEX treated = 38 +/- 4.2 ng/mg protein). Interestingly, in the UT of ovariectomized rats the combination of DEX and DES (diethylstilbestrol) treatment for 2 days resulted in a synergistic stimulation of galanin mRNA. In summary, these data demonstrate a tissue- and steroid-specific regulation of the galanin gene in AP and UT and suggest that DEX regulates the galanin gene possibly through a pathway different from estrogen.