ESPE Abstracts

Introduction: Kisspeptin is well known gatekeeper of puberty onset to date. However, several neuroendocrine factors are also discovered to be associated with puberty onset and, especially neuropeptide Y (NPY) and neurokinin B, participate in the neuronal network integrating reproduction. However, the interactions between neuroendocrine factors and the reproductive axis have not yet been fully explored. We report herein the expression profile of NPY gene and neurokinin B gene in the rat at different developmental stages.

Methods: Spraque-Dawley (SD) strain female rats were used. To analysis expression of NPY mRNA, samples were obtained from hypothalamus in female rats at 4, 8, 14, 23, 27, 34, 38 and 40 days. At the same time, blood samples were collected for analysis serum level of kisspeptin and luteinizing hormone (LH). The expression of NPY mRNAs and neurokinin B mRNAs were assessed by RT-PCR and the serum levels of kisspeptin and LH were analyzed by ELISA.

Results: The expression of NPY mRNAs in hypothalamus was high in neonate and infant stages, while abruptly decreased prepubertal and pubertal stages (between day 23 and day 34). However, serum LH level was increased from prepubertal stage, especially day 23 and peak at pubertal stage (at day 38), reversely NPY mRNAs expression. In adult stage, both NPY mRNA expressions in hypothalamus and serum LH level were increased. Meanwhile, the expression of neurokinin B mRNA in hypothalamus was increased according to developmental stages as KiSS-1 gene mRNA expression and serum kisspeptin level and was peaked at adult stages.

Conclusion: The expressions of NPY mRNA were decreased in hypothalamus at prepubertal and pubertal stages in rat, while serum levels of LH were increased at those developmental stages. Although both NPY mRNA expression and serum LH level were high in adult stage, NPY may inhibit LH release in prepubertal and pubertal stages, and it can be one of the explanations why puberty is delayed in fasting or low BMI conditions. In addition, the expression of neurokinin B mRNA was increased in hypothalamus according to developmental stages, with similar pattern in the expression of KiSS-1 gene mRNA and serum kisspeptin level.