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ORIGINAL RESEARCH ARTICLE

Expression of Estrogen Receptor in the Anteroventral Periventricular Nucleus of Hypogonadal Mice

Tandra R. Chakraborty^*, Gopalan Rajendren and Andrea C. Gore^*,,1

^* Department of Neuroscience, Mount Sinai School of Medicine, New York, New York 10029; Department of Medicine, Division of Endocrinology, Mount Sinai School of Medicine, New York, New York 10029; and Division of Pharmacology and Toxicology, College of Pharmacy, Institute for Neuroscience, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712

To whom requests for reprints should be addressed at ¹ University of Texas at Austin, Division of Pharmacology/Toxicology, Austin, TX 78712. E-mail: andrea.gore{at}mail.utexas.edu

Gonadotropin-releasing hormone-1 (GnRH-1) neurons play critical roles in the development and maintenance of reproductive function in all vertebrates. Due to a truncation in the GnRH-1 gene, hypogonadal (hpg) mice are unable to synthesize GnRH-1 and are infertile. These animals develop in the complete absence of exposure to gonadal steroid hormones, making them an interesting model for understanding brain sexual differentiation and dimorphism. We studied expression of the estrogen receptors (ERs) and ß in the medial anteroventral periventricular nucleus (mAVPV), an important reproductive neuroendocrine brain region, in wild-type and hpg mice of both sexes. Adult wild-type and hpg mice of the same genetic background were used to quantify numbers of ER and ERß immunoreactive cells in the mAVPV using a stereologic approach. Quantitative analyses showed that ER cell numbers were significantly higher in hpg than wild-type mice, irrespective of sex. Qualitatively, ER-immunoreactive cells were concentrated more densely along the ventricular zone of the AVPV of wild-type female mice compared with wild-type male mice or hpg male and female mice. No ERß-immunoreactive cells were detected in the mAVPV of any mice, a result that was surprising because ERß expression is abundant in the mAVPV of rats. These results on ER provide additional evidence that the female brain is not the "default" organizational pattern, because neither ER cell number nor its distribution in hpg mice, which develops with a deficiency of reproductive hormones, resembles that of the wild-type female mouse. Differences in ER expression may be due in part to the absence of gonadal steroid hormones, although they more likely to also involve other factors, potentially GnRH itself.

Key Words: estrogen receptor • hypothalamus • preoptic • AVPV • hypogonadal • GnRH • stereology

This article has been cited by other articles:

				C. Bodo, A. E. Kudwa, and E. F. Rissman Both Estrogen Receptor-{alpha} and -{beta} Are Required for Sexual Differentiation of the Anteroventral Periventricular Area in Mice Endocrinology, January 1, 2006; 147(1): 415 - 420. [Abstract] [Full Text] [PDF]