The overall objective of this proposal is to investigate the regulation of gonadotropin-releasing hormone (GnRH) neurons in the non-human primate. GnRH is released from the hypothalamus and controls reproductive function through pituitary gonadotrophins. The proposed studies are designed to increase our understanding of estradiol (E2) regulation of GnRH release. Recently, the concept that E2 synthesized and released in the brain plays an important role in learning/memory as well as sexual behaviors has emerged. Although it is well known that circulating E2 from the ovary regulates hypothalamo-pituitray function via negative and positive feedback mechanisms, our preliminary data with a microdialysis method indicate that E2 synthesized and released in the hypothalamus appears to play a role in the regulation of GnRH release. That is, 1) a brief infusion of estradiol benzoate (EB) into the stalk-median eminence (S-ME) in vivo in ovariectomized (OVX) female monkeys stimulated GnRH release with a short latency (<10 min), 2) this rapid GnRH release is accompanied by E2 release, 3) electrical stimulation (ES) of the medial basal hypothalamus also stimulated both GnRH and E2 release, and 4) the aromatase inhibitor, letrozole, suppressed spontaneous and the EB-induced release of GnRH and E2. Remarkably, the source of E2 found in microdialysates must be of hypothalamic origin, as monkeys were OVX and analysis with a liquid chromatography-mass spectrometry (LC/MS/MS) method distinguishes E2 from EB. Therefore, in this R21 proposal we will test the hypothesis that neuroestrogens are important for control of GnRH release, hence reproductive function.
Aim 1 will test the hypothesis that the rapid action of E2 on GnRH release represents neuroestradiol action in the hypothalamus and neuroestradiol release in the S-ME contributes to regulation of GnRH/LH release. This will be accomplished by examining the effects of EB, ES, and letrozole on GnRH/LH release.
Aim 2 will test the hypothesis that the EB exposure period distingushes rapid stimulatory action from negative feedback inhibitory E2 action on GnRH/LH release. Experiments will be conducted in OVX adult female monkeys using an in vivo microdialysis method and serial blood sampling. GnRH in dialysates and LH in plasma samples will be assessed by RIA and E2 levels in dialysates by LC/MS/MS. Results from the proposed project in non-human primates will provide a basis for developing R01 projects leading to groundbreaking studies of the involvement of neuroestrogens in control of GnRH release. The PI believes that this will ultimately bring new insights into the neuroendocrine mechanism of reproductive function in humans.

Public Health Relevance

Understanding the control mechanism of GnRH release is fundamentally important for the onset of puberty during development, cyclic ovulations during adult life, and menopause after aging. The results from the proposed study of neuroestradiol in control of GnRH neurons in non-human primates will generate entirely new concepts on the role of E2 and neuroestrogens in control of GnRH release in mammals. Moreover, information obtained from this study will provide a basis for the development of new tools for clinical management of infertility and, conversely, alternative safe methods of fertility control.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21HD077447-01A1
Application #
8702755
Study Section
Integrative and Clinical Endocrinology and Reproduction Study Section (ICER)
Program Officer
Lamar, Charisee A
Project Start
2014-04-10
Project End
2016-03-31
Budget Start
2014-04-10
Budget End
2015-03-31
Support Year
1
Fiscal Year
2014
Total Cost
$225,750
Indirect Cost
$75,750
Name
University of Wisconsin Madison
Department
Pediatrics
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715