Poncer J C, Malinow R
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
Nat Neurosci. 2001 Oct;4(10):989-96. doi: 10.1038/nn719.
Synaptic transmission relies on both the gain and the dynamics of synapses. Activity-dependent changes in synaptic gain are well-documented at excitatory synapses and may represent a substrate for information storage in the brain. Here we examine the mechanisms of changes in transmission dynamics at excitatory synapses. We show that paired-pulse ratios (PPRs) of AMPAR and NMDAR EPSCs onto dentate gyrus granule cells are often different; this difference is reduced during LTP, reflecting PPR changes of AMPAR but not NMDAR EPSCs. Presynaptic manipulations, however, produce parallel changes in AMPAR and NMDAR EPSCs. LTP at these synapses reflects a reduction in the proportion of silent synapses lacking functional AMPARs. Changes in PPR during LTP therefore reflect the initial difference between PPRs of silent and functional synapses. Functional conversion of silent synapses permits postsynaptic sampling from additional release sites and thereby affects the dynamics and gain of signals conveyed between neurons.
突触传递依赖于突触的增益和动力学。兴奋性突触处与活动相关的突触增益变化已有充分记录，可能代表大脑中信息存储的一个基础。在此，我们研究兴奋性突触传递动力学变化的机制。我们发现，作用于齿状回颗粒细胞的AMPA受体和NMDA受体介导的兴奋性突触后电流（EPSCs）的配对脉冲比率（PPRs）通常不同；在长时程增强（LTP）期间这种差异减小，反映出AMPA受体介导的EPSCs的PPR变化，而不是NMDA受体介导的EPSCs的PPR变化。然而，突触前操作会使AMPA受体和NMDA受体介导的EPSCs产生平行变化。这些突触处的LTP反映了缺乏功能性AMPA受体的沉默突触比例的降低。因此，LTP期间PPR的变化反映了沉默突触和功能性突触PPR之间的初始差异。沉默突触的功能转换允许从额外的释放位点进行突触后采样，从而影响神经元之间传递信号的动力学和增益。
