Neuroendocrine mechanisms mediating differences in reproductive timing.

Portland State University, Portland OR

Investigators

Abstract

All animals use external cues from the environment throughout their lives to determine what behavior to do and not do. Ultimately it is the brain that must ?decide? what the cues mean and how to respond. The goal of this study is to understand how the brain integrates different types of environmental cues to regulate the timing of reproduction. The researcher will accomplish this using the garter snake to examine how temperature cues stimulate neural regulation of reproductive activity. Garter snakes are especially robust for these studies because its reproductive behavior is regulated exclusively by temperature. Furthermore, Thamnophis sirtalis has one of the most extensive ranges of any ectotherm in North America, from Canada to the Gulf of Mexico and from east to west coasts. Thus, garter snakes provide a relatively simple yet powerful framework for understanding why (and how) animals respond differently to the same environmental cues. Specifically this project uses a combination of molecular, physiological, and behavioral approaches to determine if temperature-induced reproductive behavior is regulated by changes in thyroid hormone metabolism within the brain. This project will broaden the participation of undergraduates in science education and outreach, with the ultimate goal of improving the scientific aptitude of the community. Additional broad impacts include training diverse students in integrative research, critical thinking, and community engagement. The project will test the hypothesis that temperature-induced activation of the reproductive axis is controlled by neural thyroid hormone metabolism. The research will use a combination of in situ hybridization, immunohistochemistry, pharmacological manipulation, radioimmunoassay, and behavioral testing to accomplish the following specific aims: (1) Identify the influence of low temperature dormancy on the neuroendocrine GnRH system; (2) Determine if temperature-induced reproductive behavior is regulated by changes in thyroid hormone metabolism within the hypothalamus; and (3) Determine if variation in the temperature sensitivity of reproductive regulatory mechanisms mediates differences in reproductive timing. This project will advance the understanding of the neurobiology underlying plasticity in reproductive timing, and should reveal mechanisms that may be impacted by climate change. Data from this project will be used to generate inquiry-based learning modules for the classroom, thereby providing students with hands-on practice in experimental design, data analysis and data interpretation.