Date of Award

2010

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Cell Biology, Neurobiology and Anatomy

Abstract

The hypothalamic-pituitary- gonadal axis is intrinsic in regulating reproductive function. Each part orchestrates the synthesis and release of a key hormone. At the level of the hypothalamus, Gonadotropin- releasing hormone (GnRH) is released and it is the

most upstream regulator of sexual maturation. GnRH neurons express a type of estrogen receptor, ERbeta, which suggests that estradiol (E2) plays a direct role in modulating GnRH function (Herbison and Pape 2001). The objective of this study was to determine if gonadal steroid hormones regulate the expression of ERbeta and GnRH mRNA in the male brain during pubertal development. In-situ hybridization was used to detect ERbeta and

GnRH mRNA in the organum vasculosum of the lamina terminalis, diagonal band of broca and medial preoptic area, which are the main brain regions involved in regulating reproduction. Pre- pubertal (PND 30) and post-pubertal (PND 70) gonad intact male rats were studied to determine baseline information about pre-pubertal and adult hormone levels and the expression of ERbeta and GnRH mRNA. Another group of animals was bilaterally gonadectomized at PND 30 and sacrificed at PND 70 in order determine GnRH mRNA levels in the absence of hormones. Testosterone (T) implants were also used to imitate circulating T levels in gonadectomized animals. The following study detected no significant changes in GnRH signal per cell via in-situ hybridization in all groups compared to juveniles indicating that gonadal hormones do not affect GnRH message levels. Also, the number of cells expressing ERbeta message and the average number of grains per region show no significant changes pre- and post-puberty, suggesting that ERbeta gene expression is also independent of circulating hormone levels during puberty. However, these conclusions are made with some reservation due to a small sample size. The lack of changes in ERbeta message levels may suggest that ERbeta is able to function independent of ligand.

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Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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