Paired-pulse depression of unitary quantal amplitude at single hippocampal synapses
Paired-pulse depression of unitary quantal amplitude at single hippocampal synapses
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DOI：
10.1073/pnas.0307149101
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发表时间：
2004-01-27
影响因子：
11.1
通讯作者：
Tsien, RW
中科院分区：
文献类型：
--
作者：
Chen, G;Harata, NC;Tsien, RW
在中枢突触，量子大小通常被认为是围绕一个固定的平均值波动，在短期突触可塑性期间几乎没有变化。我们用fm1 -43染色对海马培养的单突触进行短暂电刺激，诱发量子释放。基于α -氨基-3-羟基-5-甲基-4-异恶唑丙酸受体介导的反应振幅分布的检测，单突触引起的量子事件大多数是单泡性的。与先前的研究结果一致，在配对脉冲促进（PPF）期间，量子大小没有改变，支持了诱发事件是单量子的概念。然而，在配对脉冲抑制（PPD）期间，单一量子大小显着减少，这不是由于突触后受体脱敏。这种量子调制在PPF和PPD期间的不对称性在不同细胞外钙浓度下的同一单个突触中得到证实。我们的研究结果表明，PPF可以完全由释放概率的增加来解释，而PPD可能是由释放概率和量大小的减少引起的。一种可能的解释是突触囊泡释放一定量的神经递质不是不变的，而是在短期突触可塑性期间受到快速的钙依赖性调节。
At central synapses, quantal size is generally regarded as fluctuating around a fixed mean with little change during short-term synaptic plasticity. We evoked quantal release by brief electric stimulation at single synapses visualized with FM 1-43 dye in hippocampal cultures. The majority of quantal events evoked at single synapses were monovesicular, based on examination of amplitude distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-receptor-mediated responses. Consistent with previous findings, the quantal size did not change during paired-pulse facilitation (PPF), supporting the notion that the evoked events were monoquantal. However, during paired-pulse depression (PPD), there was a significant decrease in unitary quantal size, which was not due to postsynaptic receptor desensitization. This asymmetry of quantal modulation during PPF and PPD was demonstrated at the same single synapse at different extracellular calcium concentrations. Our results indicate that PPF can be fully accounted for by an increase of release probability, whereas PPD may be caused by decreases in both release probability and quantal size. One possible explanation is that the release of a quantum of neurotransmitter from synaptic vesicles is not invariant but subject to rapid calcium-dependent modulation during short-term synaptic plasticity.