Enhanced NR2A subunit expression and decreased NMDA receptor decay time at the onset of ocular dominance plasticity in the ferret.
Enhanced NR2A subunit expression and decreased NMDA receptor decay time at the onset of ocular dominance plasticity in the ferret.
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DOI：
10.1152/jn.1999.81.5.2587
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发表时间：
1999-05
影响因子：
2.5
通讯作者：
Elizabeth B. Roberts;A. S. Ramoa
中科院分区：
文献类型：
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作者：
Elizabeth B. Roberts;A. S. Ramoa
雪貂眼优势可塑性开始时NR2A亚基表达增强，NMDA受体衰减时间缩短。已知谷氨酸受体的NMDA亚型在神经发育过程中表现出亚基组成和功能特性的显著变化。目前流行的观点是NMDA受体介导的突触反应在啮齿动物皮层可塑性达到峰值后持续时间减少。因此，认为NMDA受体介导的电流的缩短是眼优势可塑性发育降低的基础。然而，一些先前的证据实际上表明，NMDA受体电流的持续时间在可塑性达到峰值之前减少。在本研究中，我们研究了NMDA受体的变化的时间过程，以及它们如何与高度双目动物，雪貂的视觉皮层中的眼优势可塑性的关键时期。NMDA受体亚单位NR1，NR2A，和NR2B的表达进行了检查，在动物的年龄范围从出生后第16天到成人使用Western印迹。在雪貂初级视皮层离体切片上，用全细胞膜片钳技术研究了皮层第IV层神经元NMDA受体的功能特性。我们观察到NR1和NR2A的显着增加，但不是NR2B，表达睁眼后。NMDA受体介导的突触电流的衰减时间突然减少，同时NR2A亚基表达的增加。重要的是，这些变化发生在平行增加眼睛优势可塑性的雪貂报告。总之，导致NMDA受体兴奋性突触后电流持续时间减少的分子变化可能是眼优势可塑性关键期开始的要求，而不是结束。
Enhanced NR2A subunit expression and decreased NMDA receptor decay time at the onset of ocular dominance plasticity in the ferret. The NMDA subtype of glutamate receptor is known to exhibit marked changes in subunit composition and functional properties during neural development. The prevailing idea is that NMDA receptor-mediated synaptic responses decrease in duration after the peak of cortical plasticity in rodents. Accordingly, it is believed that shortening of the NMDA receptor-mediated current underlies the developmental reduction of ocular dominance plasticity. However, some previous evidence actually suggests that the duration of NMDA receptor currents decreases before the peak of plasticity. In the present study, we have examined the time course of NMDA receptor changes and how they correlate with the critical period of ocular dominance plasticity in the visual cortex of a highly binocular animal, the ferret. The expression of NMDA receptor subunits NR1, NR2A, and NR2B was examined in animals ranging in age from postnatal day 16 to adult using Western blotting. Functional properties of NMDA receptors in layer IV cortical neurons were studied using whole cell patch-clamp techniques in an in vitro slice preparation of ferret primary visual cortex. We observed a remarkable increase in NR1 and NR2A, but not NR2B, expression after eye opening. The NMDA receptor-mediated synaptic currents showed an abrupt decrease in decay time concurrent with the increase in NR2A subunit expression. Importantly, these changes occurred in parallel with increased ocular dominance plasticity reported in the ferret. In conclusion, molecular changes leading to decreased duration of the NMDA receptor excitatory postsynaptic current may be a requirement for the onset, rather than the end, of the critical period of ocular dominance plasticity.