Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon.
Brain Health Research Institute, Kent State University, Kent, Ohio.
Endocrinology. 2020 Apr 1;161(4). doi: 10.1210/endocr/bqaa013.
Evidence suggests that the hypothalamic-pituitary-gonadal (HPG) axis is active during the critical period for sexual differentiation of the ovine sexually dimorphic nucleus, which occurs between gestational day (GD) 60 and 90. Two possible neuropeptides that could activate the fetal HPG axis are kisspeptin and neurokinin B (NKB). We used GD85 fetal lambs to determine whether intravenous administration of kisspeptin-10 (KP-10) or senktide (NKB agonist) could elicit luteinizing hormone (LH) release. Immunohistochemistry and fluorescent in situ hybridization (FISH) were employed to localize these peptides in brains of GD60 and GD85 lamb fetuses. In anesthetized fetuses, KP-10 elicited robust release of LH that was accompanied by a delayed rise in serum testosterone in males. Pretreatment with the GnRH receptor antagonist (acyline) abolished the LH response to KP-10, confirming a hypothalamic site of action. In unanesthetized fetuses, senktide, as well as KP-10, elicited LH release. The senktide response of females was greater than that of males, indicating a difference in NKB sensitivity between sexes. Gonadotropin-releasing hormone also induced a greater LH discharge in females than in males, indicating that testosterone negative feedback is mediated through pituitary gonadotrophs. Kisspeptin and NKB immunoreactive cells in the arcuate nucleus were more abundant in females than in males. Greater than 85% of arcuate kisspeptin cells costained for NKB. FISH revealed that the majority of these were kisspeptin/NKB/dynorphin (KNDy) neurons. These results support the hypothesis that kisspeptin-GnRH signaling regulates the reproductive axis of the ovine fetus during the prenatal critical period acting to maintain a stable androgen milieu necessary for brain masculinization.
有证据表明，在下丘脑-垂体-性腺 (HPG) 轴在绵羊性别二态性核的性分化的关键时期是活跃的，该时期发生在妊娠第 60 天至 90 天之间。两种可能激活胎儿 HPG 轴的神经肽是 kisspeptin 和神经激肽 B (NKB)。我们使用 GD85 胎儿羔羊来确定静脉内给予 kisspeptin-10 (KP-10) 或 senktide (NKB 激动剂) 是否可以引发促黄体生成素 (LH) 释放。免疫组织化学和荧光原位杂交 (FISH) 用于定位这些肽在 GD60 和 GD85 羔羊胎儿大脑中的位置。在麻醉的胎儿中，KP-10 引起了 LH 的强烈释放，雄性的血清睾酮水平随之升高。用 GnRH 受体拮抗剂 (acyline) 预处理可消除 KP-10 对 LH 的反应，证实了下丘脑的作用部位。在未麻醉的胎儿中，senktide 以及 KP-10 均可引发 LH 释放。雌性的 senktide 反应大于雄性，表明雌雄之间对 NKB 的敏感性存在差异。促性腺激素释放激素也引起雌性的 LH 释放大于雄性，表明睾酮的负反馈是通过垂体促性腺细胞介导的。弓状核中的促性腺激素释放激素和 NKB 免疫反应细胞在雌性中比在雄性中更为丰富。超过 85%的弓状核 kisspeptin 细胞与 NKB 共染色。FISH 显示，这些大多数都是 kisspeptin/NKB/dynorphin (KNDy) 神经元。这些结果支持这样的假设，即 kisspeptin-GnRH 信号在产前关键时期调节绵羊胎儿的生殖轴，以维持大脑男性化所需的稳定雄激素环境。
