Landry Marc, Vila-Porcile Evelyne, Hökfelt Tomas, Calas André
INSERM EPI 9914, Institut François Magendie, Université Victor Segalen, Bordeaux, France.
Eur J Neurosci. 2003 Jun;17(11):579-89. doi: 10.1046/j.1460-9568.2003.02472.x.
The functional implications of intraneuronal coexistence of different neuropeptides depend on their respective targeting to release sites. In the rat hypothalamic magnocellular neurons, we investigated a possible differential routing of the coexpressed galanin and vasopressin. The respective location of proteins and messengers was assessed with double immunogold and in situ hybridization combining confocal and electron microscope analysis. The various populations of labelled granules were quantitatively compared in three subcellular compartments: perikarya, local processes and posthypophyseal nerve endings. Three subpopulations of granules were detected in all three compartments, but their respective amount showed significant differences. Galanin alone was immunolocalized in some secretory granules, vasopressin alone in others, and both peptides in a third subpopulation of granules. The major part of the granules containing vasopressin, either alone or in association with galanin, is found in neurohypophyseal nerve endings. In contrast, galanin single-labelled granules represent the most abundant population in dendritic processes, while double-labelled granules are more numerous in perikarya. This indicates a preferential distribution of the two peptides in the different compartments of magnocellular neurons. Furthermore, galanin and vasopressin messenger RNAs were detected at different domains of the endoplasmic reticulum, suggesting that translation might also occur at different locations, thus leading to partial segregation of galanin and vasopressin cargoes between two populations of secretory granules. The present study provides, for the first time in mammals, evidence suggesting that galanin and vasopressin are only partly copackaged and undergo a preferential targeting toward dendrites or neurohypophysis, suggesting different functions, autocrine/paracrine and endocrine, respectively.
不同神经肽在神经元内共存的功能意义取决于它们各自靶向释放位点的情况。在大鼠下丘脑大细胞神经元中，我们研究了共表达的甘丙肽和加压素可能存在的差异转运途径。通过结合共聚焦显微镜和电子显微镜分析的双重免疫金标记和原位杂交技术，评估了蛋白质和信使分子的各自定位。在三个亚细胞区室（胞体、局部突起和垂体后叶神经末梢）中对不同标记颗粒群体进行了定量比较。在所有三个区室中均检测到三种颗粒亚群，但它们各自的数量存在显著差异。仅甘丙肽免疫定位在一些分泌颗粒中，仅加压素在其他颗粒中，而两种肽存在于第三种颗粒亚群中。含有加压素的颗粒，无论是单独存在还是与甘丙肽结合，其主要部分都存在于神经垂体神经末梢中。相比之下，单标记甘丙肽的颗粒在树突状突起中占最丰富的群体，而双标记颗粒在胞体中更多。这表明这两种肽在大细胞神经元的不同区室中存在优先分布。此外，在内质网的不同区域检测到了甘丙肽和加压素信使核糖核酸，这表明翻译也可能发生在不同位置，从而导致甘丙肽和加压素货物在两种分泌颗粒群体之间部分分离。本研究首次在哺乳动物中提供了证据，表明甘丙肽和加压素仅部分共包装，并分别优先靶向树突或神经垂体，提示它们分别具有自分泌/旁分泌和内分泌的不同功能。
