NMDA Receptor Content of Synapses in Stratum Radiatum of the Hippocampal CA1 Area
NMDA Receptor Content of Synapses in Stratum Radiatum of the Hippocampal CA1 Area
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DOI：
10.1523/jneurosci.20-07-02512.2000
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发表时间：
2000-04
期刊：
影响因子：
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通讯作者：
C. Racca;F. A. Stephenson;P. Streit;J. Roberts;P. Somogyi
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文献类型：
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作者：
C. Racca;F. A. Stephenson;P. Streit;J. Roberts;P. Somogyi
由NMDA（NMDAR）或AMPA（AMPAR）激活的谷氨酸受体聚集在锥体细胞的树突棘上。AMPAR介导的突触后反应和突触AMPAR免疫反应性都显示出很大的突触间变异性。NMDAR介导的突触后反应表现出较小的变异性。为了评估NMDAR含量的变异性和它们与AMPAR在成年大鼠CA 1锥体细胞的Schaffer侧支连合突触中共存的程度，已使用受体的电子显微镜免疫金定位。NMDARs的免疫反应性检测几乎所有的突触的棘，但AMPAR检测不到，平均而言，在12%的突触。一部分突触的AMPAR含量相对于平均含量非常高，导致分布比NMDAR更偏向于更大的值。突触NMDAR含量的变异系数（CV）为0.64-0.70，远低于AMPAR含量的变异系数（CV）为1.17-1.45。与AMPAR含量不同，NMDAR含量与突触大小仅显示出弱相关性。正如先前对AMPAR的报道，NMDAR的免疫反应性也与脊柱内的脊柱器官相关。结果表明，大多数由CA 3锥体细胞到CA 1锥体棘上形成的突触都表达NMDAR和AMPAR，但比例不同。较少变化的NMDAR含量伴随着AMPAR含量的广泛变化，这表明两种受体的表达调节并不紧密相关。这些发现支持了一些报告，即这些突触的快速兴奋性传递主要由NMDAR的激活介导。
Glutamate receptors activated by NMDA (NMDARs) or AMPA (AMPARs) are clustered on dendritic spines of pyramidal cells. Both the AMPAR-mediated postsynaptic responses and the synaptic AMPAR immunoreactivity show a large intersynapse variability. Postsynaptic responses mediated by NMDARs show less variability. To assess the variability in NMDAR content and the extent of their coexistence with AMPARs in Schaffer collateral–commissural synapses of adult rat CA1 pyramidal cells, electron microscopic immunogold localization of receptors has been used. Immunoreactivity of NMDARs was detected in virtually all synapses on spines, but AMPARs were undetectable, on average, in 12% of synapses. A proportion of synapses had a very high AMPAR content relative to the mean content, resulting in a distribution more skewed toward larger values than that of NMDARs. The variability of synaptic NMDAR content [coefficient of variation (CV), 0.64–0.70] was much lower than that of the AMPAR content (CV, 1.17–1.45). Unlike the AMPAR content, the NMDAR content showed only a weak correlation with synapse size. As reported previously for AMPARs, the immunoreactivity of NMDARs was also associated with the spine apparatus within spines. The results demonstrate that the majority of the synapses made by CA3 pyramidal cells onto spines of CA1 pyramids express both NMDARs and AMPARs, but with variable ratios. A less-variable NMDAR content is accompanied by a wide variability of AMPAR content, indicating that the regulation of expression of the two receptors is not closely linked. These findings support reports that fast excitatory transmission at some of these synapses is mediated by activation mainly of NMDARs.