Evidence that pubertal status impacts kisspeptin/neurokinin B/dynorphin neurons in the gilt

Authors: HARLOW, KALYNN - North Carolina State University; RENWICK, ALLISON - North Carolina State University; SHUPING, SYDNEY - North Carolina State University; SOMMER, JEFFREY - North Carolina State University; Lents, Clay; KNAUER, MARK - North Carolina State University; NESTOR, CASEY - North Carolina State University

Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2021
Publication Date: 10/13/2021
Citation: Harlow, K., Renwick, A.N., Shuping, S.L., Sommer, J.R., Lents, C.A., Knauer, M.T., Nestor, C.C. 2021. Evidence that pubertal status impacts kisspeptin/neurokinin B/dynorphin neurons in the gilt. Biology of Reproduction. 105(6):1533-1544. https://doi.org/10.1093/biolre/ioab189.
DOI: https://doi.org/10.1093/biolre/ioab189

Interpretive Summary: Gilts that reach puberty earlier are more fertile and produce more pigs over their reproductive lifetime. Pork producers do not know which gilts will reach puberty first and this impairs their ability to select the most fertile gilts to use as mothers. To better understand what causes differences in age at puberty in pigs, ARS scientists at Clay Center, Nebraska, in collaboration with researchers at North Carolina State University studied two different genetic lines of pigs that reach puberty at different ages. Scientists looked at specialized neurons which produce two hormones called neurokinin B and dynorphin. When scientists looked in a particular part of the brain called the hypothalamus, that controls reproduction, they found that the amount of neurokinin B was increased and the amount of dynorphin was decreased when gilts became pubertal. Scientists think these two hormones act as a trigger and a brake, respectively, on attainment of puberty. This information is an important step toward understanding how reproduction in pigs is controlled and will allow researchers to develop new methods that help pork producers select the most fertile gilts for their breeding herd.

Technical Abstract: Puberty onset is a complex physiological process, which enables the capacity for reproduction through increased gonadotropin-releasing hormone and subsequently luteinizing hormone secretion. While cells that coexpress kisspeptin, neurokinin B (NKB), and dynorphin in the hypothalamic arcuate nucleus are believed to govern the timing of puberty, the degree to which kisspeptin/NKB/dynorphin (KNDy) neurons exist and are regulated by pubertal status remains to be determined in the gilt. Hypothalamic tissue from prepubertal and postpubertal, early follicular phase gilts was used to determine the expression of kisspeptin, NKB, and dynorphin within the arcuate nucleus. Fluorescent in situ hybridization revealed that the majority (>74%) of arcuate nucleus neurons that express mRNA for kisspeptin coexpressed mRNA for NKB and dynorphin. There were fewer arcuate nucleus cells that expressed mRNA for dynorphin in postpubertal gilts compared to prepubertal gilts (P < 0.05), but the number of arcuate nucleus cells expressing mRNA for kisspeptin or NKB was not different between groups. Within KNDy neurons, mRNA abundance for kisspeptin, NKB, and dynorphin of postpubertal gilts was the same as, less than, and greater than, respectively, prepubertal gilts. Immunostaining for kisspeptin did not differ between prepubertal and postpubertal gilts, but there were fewer NKB immunoreactive fibers in postpubertal gilts compared to prepubertal gilts (P < 0.05). Together, these data reveal novel information about KNDy neurons in gilts and support the idea that NKB and dynorphin play a role in puberty onset in the female pig.