Author ORCID Identifier

https://orcid.org/0009-0001-8569-0674

Semester

Spring

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

School of Medicine

Department

Exercise Physiology

Committee Chair

Randall Bryner

Committee Member

Stanley Hileman

Committee Member

Paul Chantler

Abstract

The neural mechanisms that control the onset of puberty are not completely understood. In livestock, the onset of puberty relies on an increase in gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH). Kisspeptin, neurokinin B, and dynorphin neurons (KNDy) and their receptors, Kiss1r, NK3R, and KOR, respectively, are important regulators of puberty. Previous data from our laboratory has shown that KNDy neurons may be responding to other inputs, including the melanocortin system, that will affect the timing of puberty. Given this, we examined kisspeptin receptor (Kiss1r) mRNA expression in GnRH neurons as well as examining melanocortin 3 and 4 receptor (MC3R/MC4R) in kisspeptin neurons throughout pubertal development. Ewes were ovariectomized and a silastic estrogen implant was inserted two weeks before serial blood collection and sacrifice at 5 months (prepubertal), 8 months (peripubertal), and 10 months (postpubertal) of age. Hypothalamic tissue was perfused, obtained, and analyzed by RNAscope. We hypothesized that expression of Kiss1r mRNA in GnRH neurons, expression of MC3R/MC4R mRNA in kisspeptin neurons, and Kiss1r mRNA expression in the arcuate nucleus (ARC) would increase in association with puberty-related changes in LH secretion. We found that the percentage of GnRH neurons expressing Kiss1r increased throughout development. The percentage of ARC kisspeptin neurons expressing MC3R, but not MC4R, mRNA increased throughout development, but the area of MC3R, percent area of MC3R, and integrated density did not change. There were no significant changes in ARC Kiss1r throughout development. This work supports the idea that increased sensitivity to input by aMSH as well as responsiveness to kisspeptin input in GnRH neurons comprise part of the neurocircuitry involved in puberty.

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