Appel N M, Elde R P
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
J Neurosci. 1988 May;8(5):1767-75. doi: 10.1523/JNEUROSCI.08-05-01767.1988.
In this study we examined the hypothesis that the intermediolateral cell column (IML) of the thoracic spinal cord, the nucleus from which preganglionic sympathetic neurons originate, provides an anatomical substrate through which selective regulation of sympathetic nervous system targets is accomplished. Preganglionic sympathetic neurons of rats were retrogradely labeled by the simultaneous exposure of the cervical sympathetic trunk (CST) and the adrenal medulla to Fluoro-Gold and True blue, contrasting fluorescent dyes. Retrograde labeling from these sites revealed 2 populations of sympathetic preganglionic neurons in IML whose distribution overlapped between segments T1 and T4. In regions where these 2 groups of retrogradely labeled neurons overlapped, sympathoadrenal preganglionic (SAP) neurons occupied the most lateral aspect of the nucleus. It was also determined whether individual retrogradely labeled neurons within these two groups sent axon collaterals to both the CST and adrenal medulla. Diamidino yellow, a fluorescent retrograde tracer dye that labels only nuclei, was substituted for Fluoro-Gold and used in combination with True blue to simultaneously label preganglionic sympathetic neurons projecting to either the CST or adrenal medulla. No double-labeled cell bodies were observed in spinal cords of rats treated in this manner. Thus it appeared that the efferent projections of these 2 cell populations in IML were target-specific. Immunohistochemical analysis of the relationship between nerve fibers in the IML and preganglionic sympathetic neurons was also undertaken in an attempt to classify further these 2 populations of sympathetic preganglionic neurons. Equal proportions of identified CST and SAP neurons appeared to be apposed by varicosities immunoreactive for either somatostatin or serotonin. On the other hand, when the comparison was based on whether oxytocin-immunoreactive varicosities appeared to appose these 2 populations of retrogradely labeled sympathetic neurons, a highly significant difference was revealed. That is, oxytocin-immunoreactive fibers and terminals appeared to avoid SAP neurons. Thus these data support the hypothesis that an anatomical substrate exists in spinal cord IML whereby selective regulation of sympathetic nervous system targets may be mediated. Moreover, the lack of oxytocin-immunoreactive varicosities apposing SAP neurons in IML suggests that if the paraventricular nucleus innervates SAP neurons in IML, it does so via a population of neurons that do not use oxytocin as a neurotransmitter.
在本研究中，我们检验了以下假说：胸段脊髓的中间外侧细胞柱（IML），即节前交感神经元起源的核团，提供了一种解剖学基础，通过该基础可实现对交感神经系统靶标的选择性调节。通过将颈交感干（CST）和肾上腺髓质同时暴露于荧光金和真蓝这两种对比荧光染料，对大鼠的节前交感神经元进行逆行标记。来自这些部位的逆行标记显示，IML中有两类交感节前神经元，其分布在T1至T4节段之间重叠。在这两组逆行标记神经元重叠的区域，交感肾上腺节前（SAP）神经元占据了核团的最外侧部分。还确定了这两组中单个逆行标记的神经元是否向CST和肾上腺髓质都发出轴突侧支。用仅标记细胞核的荧光逆行示踪染料双脒基黄替代荧光金，并与真蓝联合使用，以同时标记投射至CST或肾上腺髓质的节前交感神经元。用这种方式处理的大鼠脊髓中未观察到双标记的细胞体。因此，IML中这两类细胞群的传出投射似乎具有靶标特异性。我们还对IML中的神经纤维与节前交感神经元之间的关系进行了免疫组织化学分析，试图进一步对这两类交感节前神经元进行分类。已确定的CST神经元和SAP神经元中，似乎有相等比例的神经元与对生长抑素或5-羟色胺呈免疫反应的曲张体相邻。另一方面，当基于催产素免疫反应性曲张体是否似乎与这两类逆行标记的交感神经元相邻进行比较时，发现了高度显著的差异。也就是说，催产素免疫反应性纤维和终末似乎避开了SAP神经元。因此，这些数据支持了以下假说：脊髓IML中存在一种解剖学基础，通过该基础可介导对交感神经系统靶标的选择性调节。此外，IML中缺乏与SAP神经元相邻的催产素免疫反应性曲张体，这表明如果室旁核支配IML中的SAP神经元，那么它是通过一群不使用催产素作为神经递质的神经元来实现的。
