Merkley C M, Coolen L M, Goodman R L, Lehman M N
Neuroscience Graduate Program, University of Western Ontario, London, Ontario, Canada.
Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA.
J Neuroendocrinol. 2015 Jul;27(7):624-35. doi: 10.1111/jne.12293.
Kisspeptin neurones located in the arcuate nucleus (ARC) and preoptic area (POA) are critical mediators of gonadal steroid feedback onto gonadotrophin-releasing hormone (GnRH) neurones. ARC kisspeptin cells that co-localise neurokinin B (NKB) and dynorphin (Dyn), are collectively referred to as KNDy (Kisspeptin/NKB/Dyn) neurones, and have been shown in mice to also co-express the vesicular glutamate transporter, vGlut2, an established glutamatergic marker. The ARC in rodents has long been known as a site of hormone-induced neuroplasticity, and changes in synaptic inputs to ARC neurones in rodents occur over the oestrous cycle. Based on this evidence, the the present study aimed to examine possible changes across the ovine oestrous cycle in synaptic inputs onto kisspeptin cells in the ARC (KNDy) and POA, and inputs onto GnRH neurones. Gonadal-intact breeding season ewes were perfused using 4% paraformaldehyde during either the luteal or follicular phase of the oestrous cycle, with the latter group killed at the time of the luteinising hormone (LH) surge. Hypothalamic sections were processed for triple-label immunodetection of kisspeptin/vGlut2/synaptophysin or kisspeptin/vGlut2/GnRH. The total numbers of synaptophysin- and vGlut2-positive inputs to ARC KNDy neurones were significantly increased at the time of the LH surge compared to the luteal phase; because these did not contain kisspeptin, they do not arise from KNDy neurones. By contrast to the ARC, the total number of synaptophysin-positive inputs onto POA kisspeptin neurones did not differ between luteal phase and surge animals. The total number of kisspeptin and vGlut2 inputs onto GnRH neurones in the mediobasal hypothalamus (MBH) was also increased during the LH surge, and could be attributed to an increase in the number of KNDy (double-labelled kisspeptin + vGlut2) inputs. Taken together, these results provide novel evidence of synaptic plasticity at the level of inputs onto KNDy and GnRH neurones during the ovine oestrous cycle. Such changes may contribute to the generation of the preovulatory GnRH/LH surge.
位于弓状核(ARC)和视前区(POA)的 kisspeptin 神经元是性腺类固醇对促性腺激素释放激素(GnRH)神经元进行反馈的关键介质。共定位神经激肽 B(NKB)和强啡肽(Dyn)的ARC kisspeptin 细胞统称为 KNDy(Kisspeptin/NKB/Dyn)神经元,并且在小鼠中已显示它们还共同表达囊泡谷氨酸转运体 vGlut2,这是一种公认的谷氨酸能标记物。长期以来,啮齿动物的ARC一直被认为是激素诱导神经可塑性的部位,并且啮齿动物ARC神经元的突触输入在发情周期中会发生变化。基于这些证据,本研究旨在研究绵羊发情周期中ARC(KNDy)和POA中 kisspeptin 细胞的突触输入以及GnRH神经元的突触输入可能发生的变化。在发情周期的黄体期或卵泡期,使用4%多聚甲醛对性腺完整的繁殖季节母羊进行灌注,后一组在促黄体生成素(LH)高峰时处死。对下丘脑切片进行 kisspeptin/vGlut2/突触素或 kisspeptin/vGlut2/GnRH 的三重标记免疫检测。与黄体期相比,LH高峰时ARC KNDy神经元的突触素和vGlut2阳性输入总数显著增加;因为这些不包含 kisspeptin,所以它们不是来自KNDy神经元。与ARC相反,黄体期和高峰动物之间POA kisspeptin神经元上突触素阳性输入的总数没有差异。在LH高峰期间,中基底部下丘脑(MBH)中GnRH神经元上的 kisspeptin 和 vGlut2 输入总数也增加了,这可能归因于KNDy(双标记 kisspeptin + vGlut2)输入数量的增加。综上所述,这些结果为绵羊发情周期中KNDy和GnRH神经元输入水平的突触可塑性提供了新的证据。这种变化可能有助于排卵前GnRH/LH高峰的产生。