Watson A H, Burrows M
Department of Zoology, University of Cambridge, England.
J Comp Neurol. 1988 Jun 22;272(4):605-16. doi: 10.1002/cne.902720411.
The structure and distribution of synapses on nonspiking local interneurones in the metathoracic ganglion of the locust was revealed by electron microscopy following intracellular injection of horseradish peroxidase (HRP). Before staining, each interneurone was characterized physiologically as nonspiking and its output effects on motor neurones innervating muscles in a hindleg were investigated. Three nonspiking interneurones of different morphologies, each typical of a previously described population, were selected for detailed study. The first has a dorsal soma and ipsilateral neuropilar branches, the second a ventral soma and ipsilateral branches, and the third a ventral soma and contralateral branches. The somata have few trophospongial invaginations, and most of their volume is occupied by the nucleus. The initial parts of the primary neurites are either wrapped in glia or isolated in tracts from the neuropile and thus do not participate in synaptic interactions. Some of the larger secondary neurites are also wrapped in glia, but others both make and receive synaptic contacts. Output synapses have an array of some 500-1,600 round, agranular vesicles (diameter 47.0 +/- 5.7 nm; mean +/- S.D., n = 97) associated with a bar-shaped presynaptic density up to 0.3 micron long. Two postsynaptic processes, whose diameter can vary greatly, are usually associated with each presynaptic density. Processes making input synapses onto nonspiking local interneurones typically contain round, agranular vesicles and often make several contacts within a few microns. Serial reconstructions from one of the interneurones revealed input and output synapses intermingled on the larger processes with outputs dominating by a factor of 3:1, whereas on some of the thinner processes only input synapses are present. In the other two interneurones, however, both input and output synapses are present on the fine branches. No feature of the structure or distribution of synapses observed here on the nonspiking local interneurones distinguishes them from spiking neurones in the same ganglia.
通过细胞内注射辣根过氧化物酶（HRP）后进行电子显微镜观察，揭示了蝗虫后胸神经节中无峰电位局部中间神经元上突触的结构和分布。在染色之前，每个中间神经元在生理上被表征为无峰电位，并研究了其对支配后肢肌肉的运动神经元的输出效应。选择了三种形态不同的无峰电位中间神经元，每种都是先前描述的群体中的典型代表，进行详细研究。第一种具有背侧胞体和同侧神经纤维分支，第二种具有腹侧胞体和同侧分支，第三种具有腹侧胞体和对侧分支。胞体几乎没有营养海绵状内陷，其大部分体积被细胞核占据。初级神经突的起始部分要么被神经胶质包裹，要么在神经纤维网的束中孤立，因此不参与突触相互作用。一些较大的次级神经突也被神经胶质包裹，但其他一些既形成突触联系又接受突触联系。输出突触有一系列约500 - 1600个圆形、无颗粒小泡（直径47.0 +/- 5.7纳米；平均值 +/- 标准差，n = 97），与长达0.3微米的条形突触前致密物相关。通常每个突触前致密物有两个直径变化很大的突触后突起。在无峰电位局部中间神经元上形成输入突触的突起通常含有圆形、无颗粒小泡，并且常常在几微米内形成多个接触点。对其中一个中间神经元的连续重建显示，输入和输出突触在较大的突起上相互交织，输出突触占主导，比例为3:1，而在一些较细的突起上只存在输入突触。然而，在另外两个中间神经元中，输入和输出突触都存在于细分支上。在这里观察到的无峰电位局部中间神经元上突触的结构或分布特征，与同一神经节中的有峰电位神经元并无区别。
