SYNAPSES ON AXONS OF SYMPATHETIC PREGANGLIONIC NEURONS IN RAT AND RABBIT THORACIC SPINAL-CORD
SYNAPSES ON AXONS OF SYMPATHETIC PREGANGLIONIC NEURONS IN RAT AND RABBIT THORACIC SPINAL-CORD
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DOI：
10.1002/cne.903540204
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发表时间：
1995-04-03
影响因子：
2.5
通讯作者：
CHALMERS, J
中科院分区：
文献类型：
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作者：
LLEWELLYNSMITH, IJ;PILOWSKY, P;CHALMERS, J
交感神经节前神经元上存在轴体突触和轴树突突触，但尚不清楚它们的轴突是否接受突触输入，突触输入可能在调节交感神经流出方面特别有效。在这里，我们检查了逆行标记的交感节前轴突，看看它们是否接受突触。用霍乱毒素B亚单位(CTB)或辣根过氧化物酶标记的CTB-HRP标记向大鼠或兔颈上神经节、大鼠肾上腺髓质或兔星状神经节投射的神经元。在光镜水平上，少量CTB免疫反应轴突穿过腹角靠近其侧边界，偶尔轴突走更中间的路线。轴突穿过腹外侧索，在腹根发出。在矢状面旁，少数轴突在腹角内分支，向吻侧和向尾侧发出短距离突起，然后转向腹侧离开脊髓。在超微结构水平上，CTB免疫反应阳性的大鼠和兔的交感节前轴突几乎全部为无髓鞘。相反，CTB-HRP标记显示腹角、腹外侧白质和腹根既有有髓轴突，也有无髓轴突。CTB-HRP还可以检测到交感节前轴突的起始节段。在一些无髓鞘CTB免疫反应轴突上可见突触，突触前有囊泡聚集，突触后有膜特化。偶尔会有轴突接收到几个突触。突触最常见的是位于中间外侧细胞柱腹侧的含CTB的轴突。在距其起源2微米范围内的轴突上发现了一个突触，该突触来自近端的树突。在中间外侧细胞柱的腹侧数百微米处发现罕见的突触。一个分支轴突在主轴突和轴突分支的分支点的正下方有突触。这些发现表明，至少一些交感节前神经元的轴突有广泛的突触输入。这些轴突可能会对交感神经活动产生深远的影响。(C)1995年Wiley-Liss公司
Axosomatic and axodendritic synapses occur on sympathetic preganglionic neurons, but it is not yet known whether their axons receive synaptic input, which could be particularly effective at regulating sympathetic outflow. Here, we examined retrogradely labelled sympathetic preganglionic axons to see if they received synapses. Cholera toxin B subunit (CTB) or CTB conjugated to horseradish peroxidase (CTB-HRP) was used to label neurons projecting to the rat or rabbit superior cervical ganglion, the rat adrenal medulla, or the rabbit stellate ganglion. At the light microscopic level, small groups of CTB-immunoreactive axons travelled through the ventral horn near its lateral boundary, with occasional axons taking a more medial course. The axons passed through the ventrolateral funiculus to exit at the ventral roots. In parasagittal section, a few axons branched within the ventral horn, sending processes rostrally and caudally for short distances before they turned ventrally to exit the spinal cord. At the ultrastructural level, CTB-immunoreactive rat and rabbit sympathetic preganglionic axons were almost exclusively unmyelinated. In contrast, labelling with CTB-HRP revealed both myelinated and unmyelinated axons in the ventral horn, the ventrolateral white matter, and the ventral roots. CTB-HRP also allowed the detection of the initial segment of a sympathetic preganglionic axon. Synapses, with vesicles clustered presynaptically and membrane specializations postsynaptically, were found on some unmyelinated CTB-immunoreactive axons. Occasional axons received several synapses. Synapses were most common on CTB-containing axons just ventral to the intermediolateral cell column. One synapse was found on an axon within 2 mu m of its origin from a proximal dendrite. Rare synapses were found several hundred micrometers ventral to the intermediolateral cell column. One branching axon had synapses just below the branch point on both the main axon and the axonal branch. These findings indicate an extensive synaptic input to the axons of at least some sympathetic preganglionic neurons. These axoaxonic synapses could have a profound effect on sympathetic activity. (C) 1995 Wiley-Liss, Inc.