Anderson Daniel, Baker Matthew, Grignol George, Hu Walter, Merchenthaler Istvan, Dudas Bertalan
Neuroendocrine Organization Laboratory (NEO), Lake Erie College of Osteopathic Medicine (LECOM), 1858 West Grandview Blvd, Erie, PA 16509, USA.
Growth Horm IGF Res. 2010 Oct;20(5):356-9. doi: 10.1016/j.ghir.2010.06.002. Epub 2010 Jul 31.
Previous studies revealed that growth hormone-releasing hormone (GHRH)-immunoreactive (IR) neurons form a circumscribed cell group in the basal infundibulum/median eminence of the human hypothalamus. GHRH from these neurons is released into the hypothalamo-hypophyseal portal circulatory system in a pulsatile manner. It is a common consensus that the pulsatile release of GHRH is the main driving force behind the pulsatile release of growth hormone (GH) and may contribute to the regulation of other hypothalamic functions. The pulsatile release of GHRH requires synchronized activity of GHRH-IR neurons. However, the morphological basis of this synchronization between the GHRH-IR neural elements has not been elucidated yet. Since the utilization of electron microscopy combined with immunohistochemistry is virtually impossible in the human brain due to the long post mortem period, immunohistochemistry, evaluated with oil immersion light microscopy, was used in order to reveal the associations between the GHRH elements. Numerous GHRH-GHRH juxtapositions have been detected in the infundibular area/median eminence, where GHRH-IR axonal varicosities often formed multiple contacts with GHRH-IR perikarya. Examination of these associations with high magnification oil immersion light microscopy revealed (1) axonal swellings at the site of the contacts and (2) no gaps between the contacting elements suggesting that these juxtapositions may be functional synapses. The large number of GHRH-GHRH juxtapositions in the infundibular area/median eminence suggests that these synapse-like structures may represent the morphological substrate of the synchronized activity of GHRH neurons that in turn may result in the pulsatile release of GHRH in human.
先前的研究表明，生长激素释放激素（GHRH）免疫反应性（IR）神经元在下丘脑底部漏斗/正中隆起处形成一个界限分明的细胞群。这些神经元分泌的GHRH以脉冲方式释放到下丘脑-垂体门脉循环系统中。人们普遍认为，GHRH的脉冲式释放是生长激素（GH）脉冲式释放的主要驱动力，并且可能有助于调节其他下丘脑功能。GHRH的脉冲式释放需要GHRH-IR神经元的同步活动。然而，GHRH-IR神经元之间这种同步的形态学基础尚未阐明。由于人脑死后间隔时间长，几乎不可能将电子显微镜与免疫组织化学结合使用，因此使用油浸光学显微镜评估的免疫组织化学来揭示GHRH神经元之间的联系。在漏斗区/正中隆起处检测到大量GHRH-GHRH并列，其中GHRH-IR轴突膨体经常与GHRH-IR胞体形成多个接触点。用高倍油浸光学显微镜检查这些联系发现：（1）接触部位有轴突肿胀；（2）接触元件之间没有间隙，这表明这些并列可能是功能性突触。漏斗区/正中隆起处大量的GHRH-GHRH并列表明，这些突触样结构可能代表了GHRH神经元同步活动的形态学基础，进而可能导致人类GHRH的脉冲式释放。
