Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland.
Neuron. 2013 Mar 20;77(6):1109-21. doi: 10.1016/j.neuron.2013.01.021.
At synapses formed between dissociated neurons, about half of all synaptic vesicles are refractory to evoked release, forming the so-called "resting pool." Here, we use optical measurements of vesicular pH to study developmental changes in pool partitioning and vesicle cycling in cultured hippocampal slices. Two-photon imaging of a genetically encoded two-color release sensor (ratio-sypHy) allowed us to perform calibrated measurements at individual Schaffer collateral boutons. Mature boutons released a large fraction of their vesicles during simulated place field activity, and vesicle retrieval rates were 7-fold higher compared to immature boutons. Saturating stimulation mobilized essentially all vesicles at mature synapses. Resting pool formation and a concomitant reduction in evoked release was induced by chronic depolarization but not by acute inhibition of the protein phosphatase calcineurin. We conclude that synapses in CA1 undergo a prominent refinement of vesicle use during early postnatal development that is not recapitulated in dissociated neuronal culture.
在分离神经元形成的突触中，大约有一半的突触小泡对诱发释放具有不应性，形成所谓的“静息池”。在这里，我们使用囊泡 pH 值的光学测量来研究培养海马切片中池分区和囊泡循环的发育变化。双光子成像的遗传编码双色释放传感器（ratio-sypHy）允许我们在单个 Schaffer 侧枝末梢进行校准测量。成熟的末梢在模拟位置场活动期间释放了其囊泡的很大一部分，并且与不成熟的末梢相比，囊泡回收速率高 7 倍。饱和刺激可动员成熟突触处的几乎所有囊泡。静息池的形成以及随之而来的诱发释放减少是由慢性去极化引起的，但不是由蛋白磷酸酶钙调神经磷酸酶的急性抑制引起的。我们的结论是，CA1 中的突触在出生后早期发育过程中经历了囊泡利用的显著细化，而在分离的神经元培养中没有再现。
