Zhang X, Aman K, Hökfelt T
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
J Comp Neurol. 1995 Feb 20;352(4):481-500. doi: 10.1002/cne.903520402.
Using immunocytochemistry combined with confocal and electron microscopy, the secretory pathways related to substance P (SP), calcitonin gene-related peptide (CGRP), galanin (GAL), and neuropeptide Y (NPY) were investigated in neurons in rat lumbar (L) 4 and L5 dorsal root ganglia (DRGs) before and after peripheral axotomy. All four peptides were processed through the regulated secretory pathway in many small neurons in normal DRGs, and CGRP through this pathway also in some large neurons. In many small neurons, two neuropeptides could be sorted into the same or separate large dense-core vesicles (LDCVs). The LDCVs had a significantly larger diameter in small as compared to large DRG neurons. Fourteen days after sciatic nerve cut, the levels of SP- and CGRP-like immunoreactivities (-LIs) and the number of LDCVs containing these peptides were markedly reduced, but SP- and CGRP-LIs were still seen in the regulated pathway. GAL-LI was markedly increased in many small neurons and some large neurons and NPY-LI mainly in large neurons. Both peptides were particularly abundant in the Golgi region. In small neurons, the number of LDCVs containing GAL- or NPY-LI was increased, but did not appear to reach the numbers containing SP- or CGRP-LI in normal DRG neurons. After axotomy, CGRP-LI and GAL-LI were often in separate LDCVs. One type of NPY-positive large neurons showed budding off of LDCVs after axotomy, but also some "scattered" labeling in the cytoplasm. In the second type, NPY-LI was mainly found in multivesicular bodies. In several myelinated nerve fibers a "diffuse" distribution of NPY was seen together with some LDCVs containing NPY-LI. In contrast, in unmyelinated nerve fibers, NPY-, GAL-, SP-, and CGRP-LIs were always observed in LDCVs. Thus, both in normal and axotomized DRG neurons, peptides are processed through the regulated pathway. However, in some large neurons, NPY is, in addition, secreted through the constitutive pathway, perhaps as a consequence of limited sorting mechanisms for NPY, i.e., the plasticity of the secretory mechanisms does not match the rate of peptide synthesis after axotomy.
运用免疫细胞化学技术结合共聚焦显微镜和电子显微镜，研究了大鼠腰4和腰5背根神经节（DRG）神经元在周围轴突切断前后与P物质（SP）、降钙素基因相关肽（CGRP）、甘丙肽（GAL）和神经肽Y（NPY）相关的分泌途径。在正常DRG的许多小神经元中，所有四种肽均通过调节性分泌途径进行加工，在一些大神经元中CGRP也通过该途径加工。在许多小神经元中，两种神经肽可被分选到相同或不同的大致密核心囊泡（LDCV）中。与大DRG神经元相比，小神经元中的LDCV直径明显更大。坐骨神经切断14天后，SP和CGRP样免疫反应性（-LI）水平以及含有这些肽的LDCV数量显著减少，但在调节途径中仍可见到SP和CGRP-LI。许多小神经元和一些大神经元中的GAL-LI显著增加，而NPY-LI主要在大神经元中增加。这两种肽在高尔基体区域特别丰富。在小神经元中，含有GAL或NPY-LI的LDCV数量增加，但似乎未达到正常DRG神经元中含有SP或CGRP-LI的LDCV数量。轴突切断后，CGRP-LI和GAL-LI常存在于不同的LDCV中。一种NPY阳性大神经元在轴突切断后显示出LDCV的芽生，但在细胞质中也有一些“散在”标记。在第二种类型中，NPY-LI主要存在于多囊泡体中。在几条有髓神经纤维中，观察到NPY呈“弥散”分布，同时还有一些含有NPY-LI的LDCV。相反，在无髓神经纤维中，NPY、GAL、SP和CGRP-LI总是在LDCV中观察到。因此，在正常和轴突切断的DRG神经元中，肽均通过调节途径进行加工。然而，在一些大神经元中，NPY此外还通过组成型途径分泌，这可能是由于NPY的分选机制有限所致，即轴突切断后分泌机制的可塑性与肽合成速率不匹配。
