Landry M, Hökfelt T
Department of Neuroscience/Histology, Karolinska Institutet, Stockholm, Sweden.
Neuroscience. 1998 Jun;84(3):897-912. doi: 10.1016/s0306-4522(97)00567-8.
The subcellular compartmentalization and axonal transport of oxytocin and vasopressin messenger RNAs have recently been reported in the rat hypothalamo-posthypophyseal system using in situ hybridization. So far, no data are available concerning the intracellular distribution of co-localized peptide transcripts, for example of galanin, which is synthesized in the vasopressinergic magnocellular neurons of the rat and which is up-regulated in these neurons under different conditions, including salt loading and colchicine injection. In the present study, using non-radioactive in situ hybridization and immunohistochemistry at the light and electron microscope levels, preprogalanin messenger RNA and galanin-like immunoreactivity were localized in the hypothalamo-posthypophyseal system. After salt loading, preprogalanin transcripts were found throughout the perikaryal cytoplasm, especially in the peripheral cytoplasm and in the perinuclear area. Since immunohistochemistry also showed galanin-like immunoreactivity preferentially in the perinuclear area of control rats, galanin synthesis may occur mainly in this cytoplasmic domain. Preprogalanin messenger RNA was also clustered in dendrites containing rough endoplasmic reticulum. The use of a new in situ hybridization method involving tyramide signal amplification, based on catalysed reporter deposition, allowed visualization of preprogalanin messenger RNA in axonal projections running through the internal layer of the median eminence after salt loading, but not in control or in colchicine-injected animals. The negative results obtained after colchicine injection indicate that the mechanism of messenger RNA transport may require an intact cytoskeleton. The labelling was found in non-dilated axon segments as well as in a subset of axonal swellings in the rostral aspect of the median eminence, but was restricted to a few swellings in its caudal part, with no labelling in the posterior pituitary. Thus, preprogalanin messenger RNA was segregated in the axons. The functional significance of messenger RNAs' exportation into axons is not known, but our results suggest that this phenomenon may not be limited to the two principal magnocellular hormone messenger RNAs, but may also involve co-existing peptide messenger RNAs.
最近，利用原位杂交技术在大鼠下丘脑 - 垂体后叶系统中报道了催产素和加压素信使核糖核酸的亚细胞区室化及轴突运输情况。到目前为止，尚无关于共定位肽转录本细胞内分布的数据，例如甘丙肽，它在大鼠的加压素能大细胞神经元中合成，并且在包括盐负荷和秋水仙碱注射在内的不同条件下，这些神经元中的甘丙肽会上调。在本研究中，利用光镜和电镜水平的非放射性原位杂交和免疫组织化学技术，对前甘丙肽信使核糖核酸和甘丙肽样免疫反应性在下丘脑 - 垂体后叶系统中进行了定位。盐负荷后，前甘丙肽转录本在整个核周细胞质中都有发现，尤其是在周边细胞质和核周区域。由于免疫组织化学也显示对照大鼠的甘丙肽样免疫反应性优先出现在核周区域，因此甘丙肽的合成可能主要发生在这个细胞质区域。前甘丙肽信使核糖核酸也聚集在含有粗面内质网的树突中。使用基于催化报告沉积的酪胺信号放大的新原位杂交方法，使得在盐负荷后能够观察到穿过正中隆起内层的轴突投射中的前甘丙肽信使核糖核酸，但在对照动物或秋水仙碱注射的动物中未观察到。秋水仙碱注射后得到的阴性结果表明，信使核糖核酸运输机制可能需要完整的细胞骨架。在正中隆起头侧的非扩张轴突段以及一部分轴突膨体中发现了标记，但在其尾侧部分仅限于少数膨体有标记，而在垂体后叶未发现标记。因此，前甘丙肽信使核糖核酸在轴突中是分离的。信使核糖核酸输出到轴突中的功能意义尚不清楚，但我们的结果表明，这种现象可能不仅限于两种主要的大细胞激素信使核糖核酸，还可能涉及共存的肽信使核糖核酸。
