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Social and Environmental Control of the Reproductive Axis

  • Author(s): Jennings, Kimberly J.
  • Advisor(s): Kriegsfeld, Lance J
  • et al.
Abstract

In order to survive and reproduce, animals must be exquisitely sensitive to their environment. Factors such as season and social setting can have powerful influence on reproductive outcomes by determining availability of mates, food, safety, or housing. Therefore, many species have evolved mechanisms to detect changes in environmental context and modify reproductive physiology accordingly. This dissertation examines the neural substrates mediating social and environmental control of reproductive physiology and behavior. The studies presented here focus on the hypothalamic neuropeptides kisspeptin and RFamide-related peptide (RFRP). These neuropeptides regulate the reproduction by modulating release of gonadotropin releasing hormone (GnRH) and downstream luteinizing hormone (LH), which in turn regulates gonadal function and sex steroid production. Chapter 2 explores the impact of aggressive encounters on kisspeptin and RFRP neuronal systems. Chapter 3 investigates how chemosensory information about a potential mate is conveyed to the reproductive axis, and how processing of this information differs across breeding and non-breeding conditions. Chapter 4 examines in detail how expression of kisspeptin and RFRP changes as males and females transition from breeding to non-breeding back to breeding condition in response to changes in photoperiod (proportion of light:dark in a 24 h day). These studies, utilizing a variety of rodent species, indicate that RFRP but not kisspeptin is sensitive to social information, whereas both neuropeptide systems integrate information about photoperiod, although in different ways. These findings inform our understanding of the complex circuitry mediating social and environmental control of physiology and behavior.

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