Date of Graduation
Davis College of Agriculture, Natural Resources and Design
Animal and Nutritional Sciences
Robert L Goodman
Stanley M Hileman
Michael W Vernon
Robert A Dailey
Steven L Hardy
Neurokinin B (NKB) and kisspeptin are critical for fertility and potent stimulators of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion in sheep. We previously demonstrated that administration of NKB receptor (NK3R) agonist, senktide, within the retrochiasmatic area (RCh) resulted in surge-like release of LH and increased expression of kisspeptin neurons in the arcuate nucleus (ARC) of female lambs. We concluded that NKB-responsive neurons in the RCh stimulate GnRH secretion by inducing kisspeptin release from neurons in the ARC.
We have demonstrated morphological and functional evidence of sexual dimorphism in NKB-NK3R signaling in ovine RCh. RCh senktide administration resulted in prolonged, surge-like LH release in female, but not male sheep. This was associated with fewer NK3R-positive cells and NKB contacts onto NK3R-containing cells in the RCh, and fewer NKB and kisspeptin cells in the ARC of males. This led us to conclude that deficiencies in NKB inputs to the RCh, response to NKB in the RCh, and ability of KNDy neurons to respond to a stimulus from the RCh contribute to sex-dependent expression of the GnRH/LH surge in sheep. Additionally, we provide evidence for existence of galanin/NK3R colocalization in the RCh in females and support a role for galanin as a possible candidate for the neurotransmitter in NK3R-containing cells needed for the LH surge in this region. Based on the observation that galanin and CTβ colocalize in the RCh, NKB may stimulate NK3R-containing galanin neurons in the RCh that project to the ARC to stimulate kisspeptin release from KNDy neurons.
Lopez, Justin A., "Morphological and Functional Evidence of Sexual Dimorphism in the Retrochiasmatic Area Population of NK3R-containing Neurons in Sheep" (2019). Graduate Theses, Dissertations, and Problem Reports. 3861.