Immunocytochemical and physiological evidence of a synapse between dopamine- and luteinizing hormone releasing hormone-containing neurons in the ewe median eminence.
Immunocytochemical and physiological evidence of a synapse between dopamine- and luteinizing hormone releasing hormone-containing neurons in the ewe median eminence.
复制标题
母羊正中隆起中含有多巴胺和黄体生成素释放激素的神经元之间存在突触的免疫细胞化学和生理学证据。
作者：
RO Kuljis;JP Advis
免疫细胞化学标记显示，绵羊下丘脑的弓状核(ARN)含有大量酪氨酸羟化酶(TH)阳性神经元，似乎缺乏多巴胺-β-羟基酶(DBH)样免疫反应。这些多巴胺能神经元的轴突汇聚在正中隆起(ME)，含有黄体生成素释放激素(LHRH)的轴突主要来自视前内侧区的神经元。电子显微镜双标记显示TH阳性突触前轮廓与含有LHRH的突触后成分之间存在突触接触。解剖下丘脑ME、ARN、弓状旁核和下丘脑外侧核标本，孵育后测定LHRH的释放和组织含量。只有ME-LHRH的释放在多巴胺(DA)存在时显著减少。所有其他地区在有无DA的情况下都释放了等量的二氧化碳。因此，在ME水平对含LHRH轴突的突触前多巴胺能抑制可能参与了LHRH向门脉血管释放的调节。
Immunocytochemical labeling revealed that the arcuate nucleus (ARN) of the ewe's hypothalamus contains numerous tyrosine hydroxylase (TH)-positive neurons, that appear to lack dopamine-beta-hydroxylase (DBH)-like immunoreactivity. Axons of these presumed dopaminergic neurons converge in the median eminence (ME) with Luteinizing Hormone Releasing Hormone (LHRH)-containing axons originating mostly from neurons situated in the medial preoptic area. Electron microscopic double labeling revealed synaptic contacts between TH-positive presynaptic profiles and LHRH-containing postsynaptic elements. Samples of ME, ARN, paraarcuate and lateral hypothalamus were dissected and incubated to assess LHRH release and tissue content. Only ME-LHRH release was significantly reduced in the presence of dopamine (DA). All other regions released equal amounts with and without DA. Thus, a presynaptic dopaminergic inhibition of LHRH-containing axons at the level of the ME might contribute to the regulation of LHRH release into the portal vessels.