海马突触囊泡释放的时空相关性
Spatial and Temporal Correlates of Vesicular Release at Hippocampal Synapses
摘要：
我们开发了一个空间明确的生物物理模型的海马CA 3-CA 1突触前扣研究当地的钙动力学导致囊泡融合。一个动力学模型与两个钙传感器制定专门为CA 3-CA 1突触。该模型包括一个持续几十毫秒的快速同步释放传感器和一个持续几百毫秒的慢速异步释放传感器。我们发现，各种现存的数据CA 3-CA 1突触可以占一致时，只有一个不应期的顺序为几毫秒之间的释放被引入。包括第二个传感器的异步释放，有一个缓慢的解绑网站，因此嵌入式长记忆，被证明在短期可塑性中发挥作用，促进释放。对于由Synaptotagmin II介导的同步释放，除了快速和缓慢释放之外，还揭示了第三个时间尺度。这第三个时间尺度对应于“刺激相关的超快”神经递质释放。我们详细的空间模拟表明，所有三个时间尺度的神经递质释放的钙传感器和独立的突触超微结构的一个新兴的属性。此外，它使我们能够识别突触传递的特征，这些特征是普遍的，以及那些受结构调节的特征。
英文摘要：
We develop a spatially explicit biophysical model of the hippocampal CA3-CA1 presynaptic bouton to study local calcium dynamics leading to vesicle fusion. A kinetic model with two calcium sensors is formulated specifically for the CA3-CA1 synapse. The model includes a sensor for fast synchronous release that lasts a few tens of milliseconds and a sensor for slow asynchronous release that lasts a few hundred milliseconds. We show that a variety of extant data on CA3-CA1 synapse can be accounted for consistently only when a refractory period of the order of few milliseconds between releases is introduced. Including a second sensor for asynchronous release that has a slow unbinding site and therefore an embedded long memory, is shown to play a role in short-term plasticity by facilitating release. For synchronous release mediated by Synaptotagmin II a third time scale is revealed in addition to the fast and slow release. This third time scale corresponds to "stimulus-correlated super-fast" neurotransmitter release. Our detailed spatial simulation indicates that all three-time scales of neurotransmitter release are an emergent property of the calcium sensor and independent of synaptic ultrastructure. Furthermore, it allows us to identify features of synaptic transmission that are universal and those that are modulated by structure.
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