NMDA receptor subtypes at autaptic synapses of cerebellar granule neurons
NMDA receptor subtypes at autaptic synapses of cerebellar granule neurons
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DOI：
10.1152/jn.00078.2006
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发表时间：
2006-11-01
影响因子：
2.5
通讯作者：
Vicini, Stefano
中科院分区：
文献类型：
--
作者：
Lu, Congyi;Fu, Zhanyan;Vicini, Stefano
我们研究了动作电位诱发的autaptic N-甲基-D-天冬氨酸受体介导的兴奋性突触后电流（NMDA-EPSC）使用孤立的小脑神经元培养在微岛从野生型（+/+），NR 2A亚基敲除（NR 2A-/-），和NR 2C亚基敲除（NR 2C-/-）小鼠。在体外第8天（DIV 8）和DIV 13之间，所有基因型的自发性NMDA-EPSC的峰值幅度均增加。与DIV 13时的+/+细胞相比，NR 2A-/-细胞具有较小的NMDA-EPSC，而NR 2C-/-细胞具有较大的NMDA-EPSC。这些电流的衰减时间都出乎意料地快，除了在NR 2A-/-神经元，并显示小，但显着缩短与发展。发育过程中的量子参数的比较表明，在所有基因型的量子含量增加。使用MK-801阻断剂测量的NMDA受体的突触部分在DIV 8时在所有基因型中大约为50%，并且在DIV 12时，该百分比在NR 2A-/-和NR 2C-/-神经元中略微变大。NR 2B-选择性拮抗剂Conantokin G和CP 101，606在其阻断作用中随发育而不同，表明存在异源二聚体NR 1/NR 2B和异源三聚体NR 1/NR 2A/NR 2B受体。我们获得的最显著的结果是NR 2C-/-小鼠的NMDA-EPSC峰幅度和电荷转移显著增加。这主要是量子尺寸增加的结果，如从微型NMDA-EPSC估计的。NR 2C-/-细胞在DIV 13时NMDA受体对Mg ~（2+）敏感性的降低支持了NR 2C亚基受体的表达。因此，小脑颗粒神经元的孤束核为研究NMDA受体亚型在突触发育变化中的作用提供了一个新的模型。
We studied the action potential-evoked autaptic N-methyl-D-aspartate receptor-mediated excitatory postsynaptic currents (NMDA-EPSCs) using solitary cerebellar neurons cultured in microislands from wild-type (+/+), NR2A subunit knockout (NR2A-/-), and NR2C subunit knockout (NR2C-/-) mice. The peak amplitude of autaptic NMDA-EPSCs increased for all genotypes between days in vitro 8 (DIV8) and DIV13. Compared with +/+ cells at DIV13, NR2A-/- cells had smaller and NR2C-/- cells had larger NMDA-EPSCs. The decay time of these currents were all unexpectedly fast, except in NR2A-/- neurons, and showed small but significant shortening with development. Comparison of quantal parameters during development indicated an increase in quantal content in all genotypes. The synaptic portion of NMDA receptors measured using MK-801 blockade was roughly 50% in all genotypes at DIV8, and this percentage became slightly larger in NR2A-/- and NR2C-/- neurons at DIV12. The NR2B-selective antagonists Conantokin G and CP101,606 differed in their blocking actions with development, suggesting the presence of both heterodimeric NR1/NR2B and heterotrimeric NR1/NR2A/NR2B receptors. The most striking result we obtained was the significant increase of NMDA-EPSC peak amplitude and charge transfer in NR2C-/- mice. This was mainly the result of an increase in quantal size as estimated from miniature NMDA-EPSCs. The expression of NR2C subunit containing receptors was supported by the decreased Mg2+ sensitivity of NMDA receptors at DIV13 in +/+ but not in NR2C-/- cells. Thus solitary cerebellar granule neurons provide a novel model to investigate the role of receptor subtypes in the developmental changes of synaptic NMDA receptors.