Castel M N, Beaudet A, Laduron P M
Laboratoire de Génétique Moléculaire de la Neurotransmission et des Processus Neurodégénératifs, (LGN), CNRS, Gif-sur-Yvette, France.
Biochem Pharmacol. 1994 Jan 13;47(1):53-62. doi: 10.1016/0006-2952(94)90437-5.
Biochemical and anatomical data are reported which demonstrate for the first time the existence of a retrograde axonal transport process for a neuropeptide, neurotensin, in rat brain. Neurotensin receptors are mainly located in the striatum on nerve terminals of the nigrostriatal dopaminergic pathway. Thus, the association of specific neurotensin receptors on a well defined pathway provides an excellent model to investigate the existence of such a process. Two hours after the intrastriatal injection of iodinated neurotensin, radioactivity started to accumulate in the ipsilateral substantia nigra. The levels were maximal during the fourth hour. The appearance of this labelling was prevented by injection of a large excess of unlabelled neurotensin or of neurotensin 8-13, an active neurotensin fragment, but not by neurotensin 1-8 which had no affinity for neurotensin receptors. These results suggest that the appearance of radioactivity in the ipsilateral substantia nigra was dependent on the initial binding of this peptide to its receptors in the striatum. HPLC studies demonstrated that the radioactivity found in the substantia nigra corresponded to intact neurotensin and to degradation products of this peptide. Moreover, it has been shown that this retrograde transport was microtubule-dependent and occurred in dopaminergic nigrostriatal neurons. Light and electron microscopic data confirmed and extended the present results. Four and a half hours after intrastriatal injection of iodinated neurotensin, silver grains were mainly detected in dopaminergic perikarya of the substantia nigra pars compacta. The vast majority were associated with neuronal elements and their localization within cell bodies suggests that retrogradely transported neurotensin may be processed along a variety of intracellular pathways including those mediating recycling in the rough endoplasmic reticulum and degradation in lysosomes. However, the presence of silver grains over the nucleus, as well as the increase in tyrosine-hydroxylase mRNA expression in the ipsilateral substantia nigra 4 hr after intrastriatal injection of neurotensin support the concept that neurotensin alone, or associated with its receptor, might be involved in the regulation of gene expression. Finally, we have demonstrated that in old rats the quantity of retrogradely transported neurotensin was significantly decreased as compared to that observed in young adult rats. This retrograde axonal transport of a neuropeptide may represent, as already suggested for growth factors, an important dynamic process conveying information from nerve terminals to the cell body.
本文报道了生化和解剖学数据，首次证明大鼠脑中神经肽神经降压素存在逆行轴突运输过程。神经降压素受体主要位于黑质纹状体多巴胺能通路神经末梢所在的纹状体中。因此，在一条明确界定的通路上存在特定的神经降压素受体，为研究这一过程的存在提供了一个绝佳的模型。纹状体内注射碘化神经降压素两小时后，放射性开始在同侧黑质中积累，在第四小时达到最高水平。注射大量未标记的神经降压素或活性神经降压素片段神经降压素8 - 13可阻止这种标记的出现，但对神经降压素受体无亲和力的神经降压素1 - 8则不能。这些结果表明，同侧黑质中放射性的出现取决于该肽最初与纹状体中其受体的结合。高效液相色谱研究表明，在黑质中发现的放射性对应于完整的神经降压素及其降解产物。此外，已经表明这种逆行运输依赖于微管，且发生在多巴胺能黑质纹状体神经元中。光镜和电镜数据证实并扩展了目前的结果。纹状体内注射碘化神经降压素4.5小时后，银颗粒主要在黑质致密部的多巴胺能神经元胞体中被检测到。绝大多数银颗粒与神经元成分相关，它们在细胞体内的定位表明，逆行运输的神经降压素可能沿着多种细胞内途径进行处理，包括那些介导在粗面内质网中循环利用和在溶酶体中降解的途径。然而，细胞核上银颗粒的存在，以及纹状体内注射神经降压素4小时后同侧黑质中酪氨酸羟化酶mRNA表达的增加，支持了神经降压素单独或与其受体一起可能参与基因表达调控的观点。最后，我们已经证明，与年轻成年大鼠相比，老年大鼠中逆行运输的神经降压素数量显著减少。正如之前对生长因子所提出的那样，这种神经肽的逆行轴突运输可能代表了一个从神经末梢向细胞体传递信息的重要动态过程。
