Department of Agroforestry Sciences, University of Huelva, Carretera de Palos de la Frontera s/n, Palos de la Frontera, 21819 Huelva, Spain.
J Endocrinol. 2011 Dec;211(3):263-72. doi: 10.1530/JOE-11-0225. Epub 2011 Sep 8.
This research examines which neural mechanisms among the endogenous opioid, dopaminergic, serotonergic and excitatory amino acid systems are involved in the stimulation of LH secretion by melatonin implantation and their modulation by nutritional level. Female goats were distributed to two experimental groups that received either 1.1 (group H; n=24) or 0.7 (group L; n=24) times their nutritional maintenance requirements. Half of each group was implanted with melatonin after a long-day period. Plasma LH concentrations were measured twice per week. The effects of i.v. injections of naloxone, pimozide, cyproheptadine and N-methyl-d,l-aspartate (NMDA) on LH secretion were assessed the day before melatonin implantation and again on days 30 and 45. The functioning of all but the dopaminergic systems was clearly modified by the level of nutrition, melatonin implantation and time elapsed since implantation. Thirty days after implantation, naloxone increased LH concentrations irrespective of the level of nutrition (P<0.05), similar to NMDA in the melatonin-implanted H goats (HM; P<0.01). On day 45, naloxone increased LH concentrations in the HM animals (P<0.05), similar to cyproheptadine in both the non-implanted H (HC) and the HM animals (P<0.01). Finally, at 45 days, NMDA increased the LH concentration in all subgroups (P<0.01). These results provide evidence that the effects of different neural systems on LH secretion are modified by nutritional level and melatonin implantation. Endogenous opioids seem to be most strongly involved in the inhibition of LH secretion on days 30 and 45 after melatonin implantation. However, the serotonergic mechanism appears to be most influenced by nutritional level.
本研究旨在探讨内源性阿片、多巴胺能、5-羟色胺能和兴奋性氨基酸系统中的哪些神经机制参与了褪黑素植入刺激 LH 分泌，并研究其受营养水平的调节情况。将雌性山羊分为两组进行实验，一组接受 1.1 倍（组 H；n=24），另一组接受 0.7 倍（组 L；n=24）的营养维持需求。每组的一半在长日周期后接受褪黑素植入。每两周测量两次血浆 LH 浓度。在褪黑素植入前一天以及第 30 天和第 45 天，评估静脉注射纳洛酮、匹莫齐特、赛庚啶和 N-甲基-d,l-天冬氨酸（NMDA）对 LH 分泌的影响。除了多巴胺能系统之外，所有系统的功能都明显受到营养水平、褪黑素植入和植入后时间的影响。植入后 30 天，纳洛酮增加了 LH 浓度，而不论营养水平如何（P<0.05），与植入 H 组的 NMDA 相似（HM；P<0.01）。第 45 天，纳洛酮增加了 HM 动物的 LH 浓度（P<0.05），与未植入 H 组（HC）和 HM 动物的赛庚啶相似（P<0.01）。最后，在第 45 天，NMDA 增加了所有亚组的 LH 浓度（P<0.01）。这些结果表明，不同神经系统对 LH 分泌的影响受营养水平和褪黑素植入的调节。内源性阿片似乎在植入褪黑素后第 30 天和第 45 天对 LH 分泌的抑制作用最强。然而，5-羟色胺能机制似乎最受营养水平的影响。
