Estradiol Induces Galanin Gene Expression in the Pituitary of the Mouse in an Estrogen Receptor Alpha-Dependent Manner

Estradiol imprinting plays an important role in the regulation of galanin (GAL) gene expression in the rat. In the anterior pituitary gland, GAL gene expression is greatly induced by estrogen. The relative involvement that the two estrogen receptor subtypes, alpha and beta, have in regulating this induction is not known. We have utilized ER alpha-knock-out (ER alphaKO) mice to discriminate the roles of ER alpha and ER beta in the regulation of GAL gene expression in the anterior pituitary gland. Our goals were to measure the effects of estradiol on GAL gene expression by solution hybridization ribonuclease protection assay in wild-type mice and to determine the roles of ER alpha and, indirectly, ER beta by measuring the same response in the ER alphaKO mice. Estradiol treatment for one week elevated GAL gene expression 30-40 fold in the wild-type mouse pituitary. Evaluation of estrogen effects on GAL gene expression in the anterior pituitary of ER alphaKO animals revealed that ER alpha is essential, because no response to estrogen was observed in these animals. Since ER beta mRNA was identified in the anterior pituitary by RT-PCR, but estrogen had no effects on GAL gene expression in the ER alphaKO mice, the beta subtype of ER does not appear to participate in estrogen-evoked GAL gene expression in the mouse anterior pituitary.