Synaptic calcium transients in single spines indicate that NMDA receptors are not saturated
Synaptic calcium transients in single spines indicate that NMDA receptors are not saturated
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DOI：
10.1038/20187
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发表时间：
1999-05-13
期刊：
影响因子：
64.8
通讯作者：
Svoboda, K
中科院分区：
文献类型：
--
作者：
Mainen, ZF;Malinow, R;Svoboda, K
在中枢神经系统的兴奋性突触中，从囊泡中释放的谷氨酸分子的数量远远大于突触后受体的数量。但是单个囊泡的释放是否正常地使这些受体饱和呢？回答这个问题对于理解突触传递的幅度和可变性是如何设定和调节的至关重要。在这里，我们描述了使用双光子显微镜(1)来成像海马切片中CAI锥体神经元单个树突棘中NMDA （n -甲基- d -天冬氨酸）受体介导的Ca2+浓度的瞬时增加。为了测试nmda受体的饱和度，我们比较了单脉冲和双脉冲刺激的反应。我们发现单次释放事件不会使脊柱NMDA受体饱和；10毫秒后发生的第二次释放会使nmda受体的激活率提高80%。因此，脊柱nmda受体介导的[Ca2+]瞬态的振幅（以及依赖于此的突触可塑性）可能对动作电位爆发释放的量子数和突触间隙中谷氨酸浓度谱的变化敏感。
At excitatory synapses in the central nervous system, the number of glutamate molecules released from a vesicle is much larger than the number of postsynaptic receptors. But does release of a single vesicle normally saturate these receptors? Answering this question is critical to understanding how the amplitude and variability of synaptic transmission are set and regulated. Here we describe the use of two-photon microscopy(1) to image transient increases in Ca2+ concentration mediated by NMDA (N-methyl-D-aspartate) receptors in single dendritic spines of CAI pyramidal neurons in hippocampal slices. To test for NMDA-receptor saturation, we compared responses to stimulation with single and double pulses. We find that a single release event does not saturate spine NMDA receptors; a second release occurring 10 ms later produces similar to 80% more NMDA-receptor activation. The amplitude of spine NMDA-receptor-mediated [Ca2+] transients (and the synaptic plasticity which depends on this) may thus be sensitive to the number of quanta released by a burst of action potentials and to changes in the concentration profile of glutamate in the synaptic cleft.