Specific involvement of postsynaptic GluRN2B-containing NMDA receptors in the developmental elimination of corticospinal synapses
Specific involvement of postsynaptic GluRN2B-containing NMDA receptors in the developmental elimination of corticospinal synapses
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突触后含有 GluRN2B 的 NMDA 受体特异性参与皮质脊髓突触的发育消除
DOI：
10.1073/pnas.0906551107
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
M
中科院分区：
文献类型：
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作者：
Ohno;T.;Maeda;H.;Murabe;N.;Kamiyama;T.;Yoshioka;N.;Mishina;M. and Sakurai;M
GluN2B （GluRε2/NR2B）和GluN2A (GluRε1/NR2A) NMDA受体（NMDAR）亚型在活动依赖性突触可塑性中存在差异。然而，关于这两种亚型各自对发育可塑性的贡献知之甚少，部分原因是GluN2B KO [Grin2b−/−(2b−/−)]小鼠的研究受到早期新生儿死亡率的阻碍。我们之前使用啮齿动物大脑皮层（Cx）和脊髓（SpC）的体外切片共培养来表明，皮质脊髓（CS）突触，一旦存在于整个SpC中，在发育过程中以nmdar依赖的方式从腹侧消除。为了研究NMDAR在这种发育可塑性中的亚型特异性，我们共培养了来自出生后0天（P0）动物的不同基因型[2b−/−，Grin2a−/−(2a−/−)或WT小鼠]的Cx和SpC切片。电生理学和电压敏感染料研究了CS突触的分布。腹侧的突触消除在WT(Cx)-2b−/−(SpC)对中被阻断，但在WT(Cx)-2a−/−(SpC)或2b−/−(Cx)-WT（SpC）对中未被阻断。通过体外电穿孔对增强黄色荧光蛋白（EYFP）标记的CS轴突进行实时成像，观察CS轴突退化。这些发现提示突触后GluN2B选择性参与CS突触消除。此外，在2a−/−SpC切片中，消除没有被阻断，其中通过GluN2B介导的CS突触电流的Ca2+进入减少到与在2b−/−切片中相同的水平，这表明GluN2B和GluN2A在CS突触消除中的差异作用可能不能仅仅基于通过含GluN2B通道的更多Ca2+进入来解释。
The GluN2B (GluRε2/NR2B) and GluN2A (GluRε1/NR2A) NMDA receptor (NMDAR) subtypes have been differentially implicated in activity-dependent synaptic plasticity. However, little is known about the respective contributions made by these two subtypes to developmental plasticity, in part because studies of GluN2B KO [Grin2b−/−(2b−/−)] mice are hampered by early neonatal mortality. We previously used in vitro slice cocultures of rodent cerebral cortex (Cx) and spinal cord (SpC) to show that corticospinal (CS) synapses, once present throughout the SpC, are eliminated from the ventral side during development in an NMDAR-dependent manner. To study subtype specificity of NMDAR in this developmental plasticity, we cocultured Cx and SpC slices derived from postnatal day 0 (P0) animals with different genotypes [2b−/−,Grin2a−/−(2a−/−), or WT mice]. The distribution of CS synapses was studied electrophysiologically and with a voltage-sensitive dye. Synapse elimination on the ventral side was blocked in WT(Cx)-2b−/−(SpC) pairs but not in WT(Cx)-2a−/−(SpC) or2b−/−(Cx)-WT(SpC) pairs. CS axonal regression was also observed through live imaging of CS axons labeled with enhanced yellow fluorescent protein (EYFP) through exo utero electroporation. These findings suggest that postsynaptic GluN2B is selectively involved in CS synapse elimination. In addition, the elimination was not blocked in2a−/−SpC slices, where Ca2+entry through GluN2B-mediated CS synaptic currents was reduced to the same level as in2b−/−slices, suggesting that the differential effect of GluN2B and GluN2A in CS synapse elimination might not be explained based solely on greater Ca2+entry through GluN2B-containing channels.