Determinants of synaptic strength vary across an axon arbor.
Determinants of synaptic strength vary across an axon arbor.
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突触强度的决定因素在轴突轴上各不相同。
DOI：
10.1152/jn.00615.2011
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发表时间：
2012
影响因子：
2.5
通讯作者：
Balice-Gordon,RitaJ
中科院分区：
文献类型：
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作者：
Peng,Xiaoyu;Parsons,ThomasD;Balice-Gordon,RitaJ
我们使用突触泡蛋白-pHluorin在海马神经元中表达，以解决终端的功能特性，即，诱发释放，总囊泡池的大小，和释放分数，在空间上不同的个体轴突乔木。与以前的报道一致，在短的乔木距离（100 μm），诱发释放是空间异质性时，终端接触不同的突触后树突或神经元。无论突触后的配置，诱发释放和总囊泡池的大小空间共变，这表明突触囊泡可用于释放的分数（释放分数）是相似的短距离。诱发释放和总囊泡池的大小与NMDA受体和PSD-95在突触后特化中的数量高度相关。然而，当个别轴突在较长的距离（几百微米），诱发释放的显着增加，观察远端与增加的释放分数在远端终端。远端释放分数的增加可以通过单个囊泡释放概率以及易释放池大小的变化来解释。我们的研究结果表明，对于一个单一的轴突乔木，突触前强度表示诱发释放在短距离内与总囊泡池大小的异质性，而在较长的距离突触前强度与释放分数的空间调制。因此，决定突触强度的机制取决于空间尺度。
We used synaptophysin-pHluorin expressed in hippocampal neurons to address how functional properties of terminals, namely, evoked release, total vesicle pool size, and release fraction, vary spatially across individual axon arbors. Consistent with previous reports, over short arbor distances (∼100 μm), evoked release was spatially heterogeneous when terminals contacted different postsynaptic dendrites or neurons. Regardless of the postsynaptic configuration, the evoked release and total vesicle pool size spatially covaried, suggesting that the fraction of synaptic vesicles available for release (release fraction) was similar over short distances. Evoked release and total vesicle pool size were highly correlated with the amount of NMDA receptors and PSD-95 in postsynaptic specialization. However, when individual axons were followed over longer distances (several hundred micrometers), a significant increase in evoked release was observed distally that was associated with an increased release fraction in distal terminals. The increase in distal release fraction can be accounted for by changes in individual vesicle release probability as well as readily releasable pool size. Our results suggest that for a single axon arbor, presynaptic strength indicated by evoked release over short distances is correlated with heterogeneity in total vesicle pool size, whereas over longer distances presynaptic strength is correlated with the spatial modulation of release fraction. Thus the mechanisms that determine synaptic strength differ depending on spatial scale.