European Neuroscience Institute, Deutsche Forschungsgemeinschaft Center for Molecular Physiology of the Brain/Excellence Cluster 171, 37077 Göttingen, Germany.
Proc Natl Acad Sci U S A. 2011 Oct 11;108(41):17177-82. doi: 10.1073/pnas.1112688108. Epub 2011 Sep 8.
Chemical synapses contain substantial numbers of neurotransmitter-filled synaptic vesicles, ranging from approximately 100 to many thousands. The vesicles fuse with the plasma membrane to release neurotransmitter and are subsequently reformed and recycled. Stimulation of synapses in vitro generally causes the majority of the synaptic vesicles to release neurotransmitter, leading to the assumption that synapses contain numerous vesicles to sustain transmission during high activity. We tested this assumption by an approach we termed cellular ethology, monitoring vesicle function in behaving animals (10 animal models, nematodes to mammals). Using FM dye photooxidation, pHluorin imaging, and HRP uptake we found that only approximately 1-5% of the vesicles recycled over several hours, in both CNS synapses and neuromuscular junctions. These vesicles recycle repeatedly, intermixing slowly (over hours) with the reserve vesicles. The latter can eventually release when recycling is inhibited in vivo but do not seem to participate under normal activity. Vesicle recycling increased only to ≈ 5% in animals subjected to an extreme stress situation (frog predation on locusts). Synapsin, a molecule binding both vesicles and the cytoskeleton, may be a marker for the reserve vesicles: the proportion of vesicles recycling in vivo increased to 30% in synapsin-null Drosophila. We conclude that synapses do not require numerous reserve vesicles to sustain neurotransmitter release and thus may use them for other purposes, examined in the accompanying paper.
化学突触含有大量的神经递质填充的突触小泡，数量从大约 100 到成千上万不等。这些囊泡与质膜融合以释放神经递质，然后被重新形成和回收。体外刺激突触通常会导致大多数突触小泡释放神经递质，这导致人们假设突触含有大量的囊泡以在高活动期间维持传递。我们通过一种我们称之为细胞行为学的方法来检验这一假设，该方法监测行为动物（从线虫到哺乳动物的 10 种动物模型）中的囊泡功能。使用 FM 染料光氧化、pHluorin 成像和 HRP 摄取，我们发现，在中枢神经系统突触和神经肌肉接头中，只有大约 1-5%的囊泡在数小时内回收，这些囊泡反复回收，与储备囊泡缓慢混合（数小时）。后者最终可以在体内抑制回收时释放，但在正常活动下似乎不参与。当动物处于极端应激状态（青蛙捕食蝗虫）时，囊泡回收仅增加到约 5%。突触结合蛋白，一种结合囊泡和细胞骨架的分子，可能是储备囊泡的标志物：体内回收的囊泡比例在突触结合蛋白缺失的果蝇中增加到 30%。我们的结论是，突触不需要大量的储备囊泡来维持神经递质的释放，因此可能将它们用于其他目的，这在随附的论文中进行了探讨。
