The onset of reproduction is an important event in the life of any organism.  It begins with the activation of the hypothalamic-pituitary-gonadal (HPG) axis.  While there has been extensive study of the HPG during the latter half of the 20th century and into the 21st, the research has mainly focused on the details at or below the level of the hypothalamus.  More recent work has begun to focus on control of reproduction above the level of the hypothalamus, shedding light into the mechanisms for control of the onset and end of reproduction.  Gonadotropin-inhibiting hormone (GnIH) is a neuropeptide that has been suggested to control the cessation of reproduction in seasonally breeding animals, such as most temperate-breeding birds.  Kisspeptin (KiSS), a peptide originally discovered in relation to metastasis suppression, has been recently suggested to have a role in the onset of puberty and seasonal reproduction.  KiSS, along with its cognate G-protein coupled receptor, GPR54, has been shown to interact with GnRH neurons, initiating release of GnRH and subsequently leutinizing hormone (LH) and testosterone (T).  To date, all studies involving KiSS have been performed in mammals such as primates, sheep, mice, and rats.  
    My research seeks to examine the role of KiSS in the reproductive cycle of a temperate-breeding passerine bird, the dark-eyed junco (Junco hyemalis).  To do this, I am asking the following questions:

1. Are there seasonal, sex, and/or age differences in KiSS distribution in the brains of dark-eyed juncos?
2. Are there seasonal, sex, and/or age differences in the LH response to KiSS injections?
3. Is there a population-level difference in KiSS distribution in the brain and/or in the LH response to KiSS injections when examining populations with very different breeding season lengths?  In other words, could KiSS be a mechanism for creating the differences seen?
4. Is the basis of any population-level difference due to the environment in which the juncos live or is it due to genetic differences of the populations?

    The answers to these questions will provide us with a better understanding of the control of seasonal breeding as well as a clearer picture of the nuances of the HPG axis in the dark-eyed junco.  Currently, the actions of the HPG above the hypothalamus are poorly understood; this proposed study will shed light into this “black box” view of the axis.   In addition, understanding the mechanism behind the onset of seasonal reproduction is important when considering the effect that global warming could have on breeding time and offspring survival.