Horn J P, Stofer W D
Department of Physiology, University of Pittsburgh School of Medicine, Pennsylvania 15261.
J Neurosci. 1989 Jul;9(7):2543-61. doi: 10.1523/JNEUROSCI.09-07-02543.1989.
These experiments further define the organization of peptidergic pathways in the paravertebral sympathetic system of the bullfrog. Populations of axons and synaptic boutons in sympathetic ganglia 9 and 10 were found to express calcitonin gene-related peptide-like immunoreactivity (CGRP-IR) and substance P-like immunoreactivity (SP-IR). CGRP-IR is present in fibers that run through the ganglia and in boutons that make contact with almost half of the principal neurons. SP-IR is also present in fibers within the ganglia and in a rare class of synaptic boutons that are found on less than 1% of the principal neurons. Both forms of immunoreactivity are coexpressed in some nerve fibers and in the rare synaptic boutons that contain SP-IR. Neuropeptide Y-like immunoreactivity (NPY-IR), a marker for C-type postganglionic neurons, was used to identify the postsynaptic targets of boutons containing CGRP-IR and SP-IR. Ninety-five percent of the ganglion cells contacted by CGRP-IR boutons were negative for NPY-IR and are therefore likely to be B-type postganglionic neurons. Similarly, 100% of the ganglion cells contacted by boutons containing SP-IR were negative for NPY-IR. Lesions of the sympathetic chain demonstrated that synaptic boutons containing CGRP-IR arise from neurons whose axons enter the chain rostral to ganglion 7. Cutting the chain between ganglia 8 and 9 eliminates all preganglionic B and C inputs to ganglia 9 and 10. The destruction of the preganglionic C pathway by this lesion was verified by staining ganglia 9 and 10 for luteinizing hormone releasing hormone (LHRH). This lesion also eliminated boutons containing CGRP-IR and drastically reduced the number of ganglionic fibers that stained for CGRP-IR and SP-IR. By contrast, cutting the sympathetic chain between ganglia 6 and 7 spared LHRH-IR in the preganglionic C pathway but still eliminated the boutons that normally express CGRP-IR and reduced the amount of staining for SP-IR. CGRP-IR in the sympathetic ganglia arises from preganglionic and sensory neurons whereas ganglionic SP-IR is purely sensory in origin. In the spinal cord, the preganglionic B and C neurons that innervate ganglia 9 and 10 are located in different segments. In segments that contain preganglionic B cells, but not those that contain C cells, there were 243 +/- 37 (mean +/- SD) neurons in the intermediolateral cell column that express CGRP-IR. However, no cell bodies containing SP-IR were found in this region of the spinal cord.(ABSTRACT TRUNCATED AT 400 WORDS)
这些实验进一步明确了牛蛙椎旁交感神经系统中肽能通路的组织结构。研究发现，交感神经节9和10中的轴突和突触小体群体表达降钙素基因相关肽样免疫反应性（CGRP-IR）和P物质样免疫反应性（SP-IR）。CGRP-IR存在于贯穿神经节的纤维以及与近一半主神经元形成接触的突触小体中。SP-IR也存在于神经节内的纤维以及一类罕见的突触小体中，这类突触小体在不到1%的主神经元上被发现。两种免疫反应性在一些神经纤维以及含有SP-IR的罕见突触小体中共同表达。神经肽Y样免疫反应性（NPY-IR），一种C型节后神经元的标志物，被用于识别含有CGRP-IR和SP-IR的突触小体的突触后靶点。与含有CGRP-IR的突触小体接触的神经节细胞中有95%对NPY-IR呈阴性，因此很可能是B型节后神经元。同样，与含有SP-IR的突触小体接触的神经节细胞中有100%对NPY-IR呈阴性。交感神经链损伤表明，含有CGRP-IR的突触小体起源于其轴突进入神经节7前方神经链的神经元。在神经节8和9之间切断神经链，消除了对神经节9和10的所有节前B和C输入。通过对神经节9和10进行促黄体生成素释放激素（LHRH）染色，证实了该损伤对节前C通路的破坏。该损伤还消除了含有CGRP-IR的突触小体，并大幅减少了对CGRP-IR和SP-IR染色的神经节纤维数量。相比之下，在神经节6和7之间切断交感神经链，保留了节前C通路中的LHRH-IR，但仍消除了正常表达CGRP-IR的突触小体，并减少了SP-IR的染色量。交感神经节中的CGRP-IR起源于节前神经元和感觉神经元，而神经节中的SP-IR纯粹起源于感觉神经元。在脊髓中，支配神经节9和10的节前B和C神经元位于不同节段。在含有节前B细胞的节段中，但不包括含有C细胞的节段，中间外侧细胞柱中有243±37（平均值±标准差）个表达CGRP-IR的神经元。然而，在脊髓的这个区域未发现含有SP-IR的细胞体。（摘要截取自400字）
