Ganeshina Olga, Berry Robert W, Petralia Ronald S, Nicholson Daniel A, Geinisman Yuri
Department of Cell and Molecular Biology, Northwestern University's Feinberg School of Medicine, Chicago, Illinois 60611, USA.
J Comp Neurol. 2004 Jan 1;468(1):86-95. doi: 10.1002/cne.10950.
Axospinous synapses are traditionally divided according to postsynaptic density (PSD) configuration into a perforated subtype characterized by a complex-shaped PSD and nonperforated subtype exhibiting a simple-shaped, disc-like PSD. It has been hypothesized that perforated synapses are especially important for synaptic plasticity because they have a higher efficacy of impulse transmission. The aim of the present study was to test this hypothesis. The number of postsynaptic AMPA receptors (AMPARs) is widely regarded as the major determinant of synaptic efficacy. Therefore, the expression of AMPARs was evaluated in the two synaptic subtypes and compared with that of NMDA receptors (NMDARs). Postembedding immunogold electron microscopy was used to quantify the immunoreactivity following single labeling of AMPARs or NMDARs in serial sections through the CA1 stratum radiatum of adult rats. The results showed that all perforated synapses examined were immunopositive for AMPARs. In contrast, only a proportion of nonperforated synapses (64% on average) contained immunogold particles for AMPARs. The number of immunogold particles for AMPARs was markedly and significantly higher in perforated synapses than in immunopositive nonperforated synapses. Although all synapses of both subtypes were NMDAR immunopositive perforated synapses contained significantly more immunogold particles for NMDARs than nonperforated ones. Multivariate analysis of variance revealed that the mode of AMPAR and NMDAR expression is related to the complexity of PSD configuration, not only to PSD size. These findings support the notion that perforated synapses may evoke larger postsynaptic responses relative to nonperforated synapses and, hence, contribute to an enhancement of synaptic transmission associated with some forms of synaptic plasticity.
轴棘突触传统上根据突触后致密物（PSD）的形态分为穿孔亚型，其特征是PSD形状复杂，以及非穿孔亚型，其PSD呈简单的盘状。据推测，穿孔突触对突触可塑性尤为重要，因为它们具有更高的冲动传递效率。本研究的目的是验证这一假设。突触后α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体（AMPARs）的数量被广泛认为是突触效能的主要决定因素。因此，对这两种突触亚型中AMPARs的表达进行了评估，并与N-甲基-D-天冬氨酸受体（NMDARs）的表达进行了比较。采用包埋后免疫金电子显微镜技术，对成年大鼠CA1辐射层连续切片中AMPARs或NMDARs单标记后的免疫反应性进行定量分析。结果显示，所有检测的穿孔突触对AMPARs均呈免疫阳性。相比之下，只有一部分非穿孔突触（平均64%）含有AMPARs的免疫金颗粒。穿孔突触中AMPARs的免疫金颗粒数量明显且显著高于免疫阳性的非穿孔突触。尽管两种亚型的所有突触对NMDARs均呈免疫阳性，但穿孔突触中NMDARs的免疫金颗粒明显多于非穿孔突触。多变量方差分析显示，AMPARs和NMDARs的表达模式与PSD形态的复杂性有关，而不仅与PSD大小有关。这些发现支持了这样一种观点，即相对于非穿孔突触，穿孔突触可能引发更大的突触后反应，因此有助于增强与某些形式的突触可塑性相关的突触传递。
