Horch H L, Sargent P B
Department of Stomatology, University of California, San Francisco 94143, USA.
J Neurosci. 1995 Dec;15(12):7778-95. doi: 10.1523/JNEUROSCI.15-12-07778.1995.
Most nicotinic ACh receptors (AChRs) studied to date in the embryonic chicken ciliary ganglion are recognized either by monoclonal antibody (mAb) 35 or by alpha-bungarotoxin (alpha-Bgt). Previous studies found that mAb 35-AChRs are found at both synaptic and extrasynaptic sites, while alpha-Bgt-AChRs are found exclusively at extrasynaptic sites. To gain a three-dimensional understanding of the distribution of these two AChR classes and their spatial relationship to synaptic sites, we have visualized mAb 35-AChRs and alpha-Bgt-AChRs immunofluorescently using laser scanning confocal microscopy and have compared their distribution with that of the synaptic vesicle antigen SV2. Both mAb 35-AChR and alpha-Bgt-AChRs are found in clusters that are widely distributed over the surface of embryonic chicken ciliary ganglion neurons. Some mAb 35-AChRs are located at synaptic sites, but the bulk of them are located extrasynaptically in well-defined patches measuring 1-4 micron in diameter. alpha-Bgt-AChRs are found almost exclusively in these extrasynaptic sites, which thus contain both AChR types. These sites are often surrounded by elements of the synaptic calyx but are themselves largely free of SV2 antigen. In 14 week chickens the relationship between mAb 35-AChRs, alpha-Bgt-AChRs, and synaptic sites is similar to that in embryos except that in this instance individual synaptic boutons are often surrounded by AChR-containing patches. These results suggest that most surface AChRs in both embryonic and mature chicken ciliary neurons are perisynaptic, which raises questions about the function of these AChRs.
迄今为止，在胚胎期鸡睫状神经节中研究的大多数烟碱型乙酰胆碱受体（AChRs）可被单克隆抗体（mAb）35或α-银环蛇毒素（α-Bgt）识别。先前的研究发现，mAb 35-AChRs存在于突触和突触外位点，而α-Bgt-AChRs仅存在于突触外位点。为了从三维角度了解这两类AChR的分布及其与突触位点的空间关系，我们使用激光扫描共聚焦显微镜对mAb 35-AChRs和α-Bgt-AChRs进行了免疫荧光可视化，并将它们的分布与突触囊泡抗原SV2的分布进行了比较。mAb 35-AChR和α-Bgt-AChRs都以簇状形式存在，广泛分布于胚胎期鸡睫状神经节神经元的表面。一些mAb 35-AChRs位于突触位点，但它们中的大部分位于突触外，形成直径为1-4微米的明确斑块。α-Bgt-AChRs几乎只存在于这些突触外位点，因此这些位点同时包含这两种AChR类型。这些位点通常被突触杯的成分所包围，但它们本身基本不含SV2抗原。在14周龄的鸡中，mAb 35-AChRs、α-Bgt-AChRs与突触位点之间的关系与胚胎期相似，只是在这种情况下，单个突触小体通常被含有AChR的斑块所包围。这些结果表明，胚胎期和成熟鸡睫状神经元中的大多数表面AChRs都位于突触周围，这引发了关于这些AChRs功能的问题。
