Huntley G W, Vickers J C, Janssen W, Brose N, Heinemann S F, Morrison J H
Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029-6574.
J Neurosci. 1994 Jun;14(6):3603-19. doi: 10.1523/JNEUROSCI.14-06-03603.1994.
NMDA receptors are composed of multiple receptor subunit proteins, of which NMDAR1 appears to be a critical component for normal receptor function (Nakanishi, 1992). In this study, quantitative immunocytochemical methods were used at the light and electron microscopic levels to localize NMDAR1 subunits in the primary motor (M1) and somatic sensory (S1) cortex of monkeys, and in the primary visual cortices (V1) of monkey and human. Three principal features of NMDAR1 subunit organization were examined in detail in the monkey cortex: (1) the laminar and cellular distribution patterns, relying in part on double-labeling paradigms with the calcium-binding proteins parvalbumin (PV) and calretinin (CR) as markers for discrete subpopulations of GABAergic interneurons; (2) the codistribution of NMDAR1 subunits with non-NMDA ionotropic receptor subunits; (3) a quantitative assessment of the percentages of asymmetrical synapses in layers II/III, IV, and V/VI that were NMDAR1 immunoreactive. In monkey M1, S1, and V1, NMDAR 1 immunoreactivity was present in all layers, localized primarily to large numbers of pyramidal cell somata and proximal apical dendrites, to presumptive spiny stellate cells in layer IV of V1, and to the vast majority (approximately 80-90%) of PV-immunoreactive cells. By contrast, NMDAR1 immunoreactivity was present in only a very small percentage of the CR-immunoreactive cells (approximately 6-9%). Colocalization with non-NMDA receptor subunits showed that all cells (100%) that contained GluR2/3 subunits were also NMDAR1 immunoreactive. In addition, the complete codistribution of GluR5/6/7 subunits with GluR2/3 subunits suggests, indirectly, that all GluR5/6/7-immunoreactive cells are also NMDAR1 immunoreactive. The laminar and cellular distribution patterns of immunostaining in human V1 were very similar to those in monkey V1. Electron microscopy of monkey sections confirmed an extensive dendritic and synaptic localization of NMDAR1 subunits. Labeling of synapses was present on asymmetrical postsynaptic densities associated with both dendritic shafts and spines. In supragranular layers of V1, a greater percentage of asymmetrical synapses were NMDAR1 immunopositive (44%) in comparison to layer IVC beta (34%) or deep layers (19%). In contrast, in area 3b of S1, the percentage of labeled synapses was greatest in layer IV (45%) in comparison to superficial (26%) and deep (37%) layers, while in M1, the percentages of labeled synapses were similar between superficial (46%) and deep (40%) layers. Taken together, these data indicate that NMDAR1-immunoreactive cells in neocortex represent a morphologically, functionally, and neurochemically heterogeneous population.(ABSTRACT TRUNCATED AT 400 WORDS)
N-甲基-D-天冬氨酸（NMDA）受体由多种受体亚基蛋白组成，其中NMDAR1似乎是正常受体功能的关键组成部分（中谷，1992年）。在本研究中，运用定量免疫细胞化学方法，在光镜和电镜水平上对NMDAR1亚基在猴的初级运动（M1）和躯体感觉（S1）皮层以及猴和人的初级视皮层（V1）中进行定位。在猴皮层中详细研究了NMDAR1亚基组织的三个主要特征：（1）层状和细胞分布模式，部分依赖于以钙结合蛋白小白蛋白（PV）和钙视网膜蛋白（CR）作为GABA能中间神经元离散亚群标记的双重标记模式；（2）NMDAR1亚基与非NMDA离子型受体亚基的共分布；（3）对II/III层、IV层和V/VI层中具有NMDAR1免疫反应性的不对称突触百分比进行定量评估。在猴的M1、S1和V1中，NMDAR1免疫反应性存在于所有层中，主要定位于大量锥体细胞的胞体和近端顶树突、V1层IV中的推定棘状星形细胞以及绝大多数（约80 - 90%）PV免疫反应性细胞。相比之下，NMDAR1免疫反应性仅存在于极小比例的CR免疫反应性细胞中（约6 - 9%）。与非NMDA受体亚基的共定位显示，所有含有GluR2/3亚基的细胞（100%）也具有NMDAR1免疫反应性。此外，GluR5/6/7亚基与GluR2/3亚基的完全共分布间接表明，所有GluR5/6/7免疫反应性细胞也具有NMDAR1免疫反应性。人V1中免疫染色的层状和细胞分布模式与猴V1中的非常相似。猴切片的电子显微镜检查证实了NMDAR1亚基在树突和突触中的广泛定位。突触标记存在于与树突干和棘相关的不对称突触后致密物上。在V1的颗粒上层中，与IVCβ层（34%）或深层（19%）相比，更大比例的不对称突触是NMDAR1免疫阳性（44%）。相比之下，在S1的3b区，标记突触的百分比在IV层中最大（45%），而表层（26%）和深层（37%）较低，而在M1中，表层（46%）和深层（40%）的标记突触百分比相似。综上所述，这些数据表明新皮层中具有NMDARl免疫反应性的细胞代表了一个形态、功能和神经化学上异质的群体。（摘要截于400字）
