Quantitative Relationship between Transmitter Release and Calcium Current at the Calyx of Held Synapse
Quantitative Relationship between Transmitter Release and Calcium Current at the Calyx of Held Synapse
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DOI：
10.1523/jneurosci.21-02-00462.2001
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发表时间：
2001-01
期刊：
影响因子：
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通讯作者：
T. Sakaba;E. Neher
中科院分区：
文献类型：
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作者：
T. Sakaba;E. Neher
一种新开发的去卷积方法（Neher和Sakaba，2001年）使我们能够解决的时间过程中的神经递质释放在萼的Held突触和量化的一些基本方面的递质释放。首先，我们确定了一个容易释放池（RRP）的突触囊泡。我们发现，RRP的大小，当测试与列车的强刺激，是恒定的，无论确切的刺激模式，如果刺激被限制在一个时间间隔为1.60毫秒。对于更持久的刺激模式，招聘新的囊泡的RRP作出了重大贡献的总释放。其次，作为Ca 2+电流的函数的递质释放的协同性估计为3-4，这证实了先前的结果（Borst和Sakmann，1999; Wu等人，1999年）。第三，最初的小Ca 2+内流增加的效率Ca 2+电流在随后的发射器释放。这种类型的促进被阻断了高浓度的EGTA（0.5毫米）。第四，突触囊泡在这个突触的释放率原来是异质性的：一旦一个高度钙敏感的囊泡人口被消耗，其余的囊泡以较低的速度释放。在0.5 mm EGTA存在下，这些释放组分更清楚地分离，这防止了残留Ca 2+的积累。相反，提高细胞外Ca 2+浓度促进了较慢的人口，使其释放特性变得更相似的标准条件下的快速人口。预计异质性释放概率将支持在高频刺激期间维持突触传递。
A newly developed deconvolution method (Neher and Sakaba, 2001) allowed us to resolve the time course of neurotransmitter release at the calyx of Held synapse and to quantify some basic aspects of transmitter release. First, we identified a readily releasable pool (RRP) of synaptic vesicles. We found that the size of the RRP, when tested with trains of strong stimuli, was constant regardless of the exact stimulus patterns, if stimuli were confined to a time interval of ∼60 msec. For longer-lasting stimulus patterns, recruitment of new vesicles to the RRP made a substantial contribution to the total release. Second, the cooperativity of transmitter release as a function of Ca2+ current was estimated to be 3–4, which confirmed previous results (Borst and Sakmann, 1999; Wu et al., 1999). Third, an initial small Ca2+ influx increased the efficiency of Ca2+ currents in subsequent transmitter release. This type of facilitation was blocked by a high concentration of EGTA (0.5 mm). Fourth, the release rates of synaptic vesicles at this synapse turned out to be heterogeneous: once a highly Ca2+-sensitive population of vesicles was consumed, the remaining vesicles released at lower rates. These components of release were more clearly separated in the presence of 0.5 mm EGTA, which prevented the buildup of residual Ca2+. Conversely, raising the extracellular Ca2+ concentration facilitated the slower population such that its release characteristics became more similar to those of the faster population under standard conditions. Heterogeneous release probabilities are expected to support the maintenance of synaptic transmission during high-frequency stimulation.