Siegel S J, Janssen W G, Tullai J W, Rogers S W, Moran T, Heinemann S F, Morrison J H
Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
J Neurosci. 1995 Apr;15(4):2707-19. doi: 10.1523/JNEUROSCI.15-04-02707.1995.
Ionotropic excitatory amino acid (EAA) receptors are divided pharmacologically into three categories termed NMDA, AMPA/kainate, and high affinity kainate receptors. Each of these receptor subtypes is composed of a specific subset of subunits termed GluR1-4 (AMPA/kainate), GluR5-7, KA1-2 (high affinity kainate), and NMDAR1, 2 A-D (NMDA). Although colocalization of NMDA and non-NMDA receptors has been previously demonstrated electrophysiologically in rat, comprehensive analyses of subunit specific colocalization patterns have not been possible until the advent of appropriate antibodies. The present study investigates such immunocytochemical colocalization of several EAA receptor subunits within individual cells as well as dendritic spines in the monkey hippocampus. Double-label immunohistochemical experiments using antibodies which are specific for GluR2(4), GluR5-7, and NMDAR1 demonstrated that virtually all projection neurons in each subfield of the hippocampus contain subunits from the AMPA/kainate, kainate, and NMDA receptor families. In addition, confocal microscopy has demonstrated that individual spines may contain subunits representative of multiple EAA receptor families. Furthermore, detailed regional, cellular, and ultrastructural distribution patterns of the EAA receptor subunits GluR2 and GluR4 in monkey hippocampus are presented based on the use of a monoclonal antibody (mAb), 3A11, which was generated against the putative extracellular N-terminal domain of GluR2. Since this antibody recognizes only GluR2 in Western blots, and GluR2 as well as GluR4 in fixed transiently transfected cells, it has been designated anti-GluR2(4). Immunocytochemical labeling with mAb 3A11 revealed pyramidal cell somata and dendrites in each field of the hippocampus, as well as granule cells and polymorphic hilar cells in the dentate gyrus. Small cells with the morphologic characteristics of astroglia were also immunolabeled for GluR2(4) within the alveus and fimbria. Immunoreactivity at the ultrastructural level was localized to postsynaptic densities on dendritic spines and shafts and within the somatodendritic cytoplasm in all major hippocampal regions, as well as in a subset of dentate granule cell axons within the mossy fiber projection.
离子型兴奋性氨基酸（EAA）受体在药理学上可分为三类，即NMDA、AMPA/海人酸和高亲和力海人酸受体。这些受体亚型中的每一种都由特定的亚基子集组成，分别称为GluR1 - 4（AMPA/海人酸）、GluR5 - 7、KA1 - 2（高亲和力海人酸）以及NMDAR1、2 A - D（NMDA）。尽管此前已通过电生理学方法在大鼠中证明了NMDA和非NMDA受体的共定位，但在合适的抗体出现之前，对亚基特异性共定位模式进行全面分析是不可能的。本研究调查了猴海马体中单个细胞以及树突棘内几种EAA受体亚基的免疫细胞化学共定位情况。使用针对GluR2(4)、GluR5 - 7和NMDAR1的特异性抗体进行的双标记免疫组织化学实验表明，海马体每个亚区中几乎所有投射神经元都含有AMPA/海人酸、海人酸和NMDA受体家族的亚基。此外，共聚焦显微镜显示单个树突棘可能含有代表多个EAA受体家族的亚基。此外，基于使用针对GluR2假定的细胞外N端结构域产生的单克隆抗体（mAb）3A11，展示了猴海马体中EAA受体亚基GluR2和GluR4详细的区域、细胞和超微结构分布模式。由于该抗体在蛋白质印迹中仅识别GluR2，而在固定的瞬时转染细胞中识别GluR2和GluR4，因此它被命名为抗GluR2(4)。用mAb 3A11进行免疫细胞化学标记显示了海马体各个区域的锥体细胞胞体和树突，以及齿状回中的颗粒细胞和多形性门区细胞。在海马槽和伞内具有星形胶质细胞形态特征的小细胞也被标记为GluR2(4)。在超微结构水平上，免疫反应性定位于所有主要海马区域树突棘和树突干上的突触后致密物以及胞体 - 树突细胞质内，以及苔藓纤维投射内齿状颗粒细胞轴突的一个子集中。
