Chan R K, Peto C A, Sawchenko P E
Laboratory of Neuronal Structure and Function, Salk Institute for Biological Studies, La Jolla, California 92186.
J Comp Neurol. 1995 Jan 2;351(1):62-80. doi: 10.1002/cne.903510107.
Preembedding immunoperoxidase staining methods were used to characterize tyrosine hydroxylase-immunoreactive (TH-ir) elements in the caudal ventrolateral medulla, and to determine the extent to which neurons of the A1 cell group are directly innervated by projections of the nucleus of the solitary tract (NTS). TH-ir neurons in the A1 region were medium-sized and multipolar. They possessed rounded nuclei with infrequent invaginations, well-developed Golgi apparati, high cytoplasmic densities of mitochondria, and a low to moderate tendency for rough endoplasmic reticulum (RER) to align in parallel stacks. A1 cell bodies were commonly juxtaposed to TH-positive and TH-negative neurons, myelinated profiles, glia and/or vascular elements, but close membrane appositions were only seen with glial elements. Synaptic input to A1 neurons was predominantly asymmetric, provided virtually exclusively by non-TH-ir terminals, and directed principally to dendritic shafts; A1 somata are relatively sparsely innervated. In a second experiment, silver-intensified immunogold localization of TH-ir was combined with immunoperoxidase labeling for anterogradely transported Phaseolus vulgaris-leucoagglutinin (PHA-L), following tracer injections in the caudal aspect of the medial division of the NTS. These experiments revealed a small proportion of PHA-L-labeled axon terminals that made asymmetric contacts with dendritic shafts of TH-ir neurons. These results suggest that the fine structure and synaptic input of A1 neurons are somewhat distinct from that of rostrally situated C1 catecholamine cells. In addition, while they document a direct NTS-A1 projection that may participate in the interoceptive control of vasopressin secretion, the bulk of ventrolaterally directed projections from the caudomedial NTS contact noncatecholaminergic elements in the A1 region, some of which may correspond to so-called depressor neurons implicated in the baroreflex control of sympathetic outflow and vasopressin secretion.
采用包埋前免疫过氧化物酶染色方法来鉴定延髓尾端腹外侧区酪氨酸羟化酶免疫反应阳性（TH-ir）成分，并确定孤束核（NTS）的投射对A1细胞群神经元的直接支配程度。A1区的TH-ir神经元中等大小，呈多极。它们具有圆形细胞核，核内陷不常见，高尔基体发达，线粒体在细胞质中的密度高，粗面内质网（RER）平行排列的趋势低至中等。A1细胞体通常与TH阳性和TH阴性神经元、有髓轮廓、神经胶质和/或血管成分并列，但仅在与神经胶质成分接触时可见紧密的膜并置。对A1神经元的突触输入主要是不对称的，几乎完全由非TH-ir终末提供，主要指向树突干；A1细胞体的神经支配相对较少。在第二个实验中，在将示踪剂注射到NTS内侧部尾侧后，将TH-ir的银增强免疫金定位与用于顺行运输的菜豆白细胞凝集素（PHA-L）的免疫过氧化物酶标记相结合。这些实验揭示了一小部分PHA-L标记的轴突终末与TH-ir神经元的树突干形成不对称接触。这些结果表明，A1神经元的精细结构和突触输入与位于 Rostral的C1儿茶酚胺细胞有所不同。此外，虽然它们记录了可能参与血管加压素分泌的内感受控制的直接NTS-A1投射，但来自尾内侧NTS的大部分腹外侧投射与A1区的非儿茶酚胺能成分接触，其中一些可能对应于参与交感神经流出和血管加压素分泌的压力反射控制的所谓降压神经元。
