Postnatal changes in the laminar and subcellular distribution of NMDA-R1 subunits in the cat visual cortex as revealed by immuno-electron microscopy
Postnatal changes in the laminar and subcellular distribution of NMDA-R1 subunits in the cat visual cortex as revealed by immuno-electron microscopy
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DOI：
10.1016/s0165-3806(96)00160-5
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发表时间：
1997-01-02
期刊：
影响因子：
--
通讯作者：
Aoki, C
中科院分区：
文献类型：
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作者：
Aoki, C
尽管人们认识到大脑皮层中几乎所有的突触都是在出生后形成的，但对于使这些突触发挥功能所必需的分子的出现却知之甚少。本研究通过免疫电镜标记发育中的猫视觉皮层中受体的必需亚基NMDA- r1，可视化了突触定位NMDA受体的出现。在睁眼之前（出生后2-10天），NMDA-R1免疫反应性已经存在于树突和轴突生长锥中，尽管这些特征缺乏突触特化。这表明NMDA-R1的合成和进入质膜是独立于形式视觉的。在接下来的2-3周内，即在眼优势可塑性关键期开始之前（约第四周），NMDA-R1免疫反应性从树突内弥漫性分布转变为轴棘连接突触后密度上更离散的聚集。NMDA-R1在突触上的聚集可能是在关键时期视觉刺激激活的突触稳定和加强的先决条件。此外，仅在最初几周内，颗粒内层和白质中存在强烈的nmda - r1免疫反应神经元。深层神经元中NMDA-R1的富集可能反映了神经元在皮质回路发育中的支持作用，作为圈状和皮质-皮质传入神经的短暂突触靶点，而这些传入神经在小颗粒层中“等待”其最终的、终身的目标神经元在上层接受。
Although it is recognized that nearly all synapses in the cerebral cortex form postnatally, little is known about the emergence of molecules necessary to render these synapses functional. This study visualized the emergence of synaptically localized NMDA receptors by immune-electron microscopic labeling of the receptor's obligatory subunit, NMDA-R1, in the developing cat visual cortex. Prior to eye-opening (postnatal day 2-10), NMDA-R1 immunoreactivity is already present within dendritic and axonal growth cones, even though these profiles are devoid of synaptic specializations. This indicates that synthesis and incorporation of NMDA-R1 into plasma membranes are independent of form vision. During the next 2-3 weeks, i.e., preceding the onset of the critical period for ocular dominance plasticity (around the fourth week), NMDA-R1 immunoreactivity changes from a diffuse distribution within dendrites to a more discrete aggregation over postsynaptic densities of axo-spinous junctions. Such clustering of NMDA-R1 at synapses may be a prerequisite for stabilization and strengthening of synapses activated by visual stimulation during the critical period. Furthermore, only during the first several weeks, intensely NMDA-R1-immunoreactive neurons are present in the infragranular layers and the white matter. Enrichment of NMDA-R1 in the deep-layer neurons may reflect the neurons' supportive role in the development of cortical circuitry, serving as transient synaptic targets for geniculate and cortico-cortical afferents while these afferents 'wait' in the infragranular layers for their ultimate, life-long target neurons to become receptive in the upper layers.