Xu-Friedman M A, Regehr W G
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Neurosci. 2000 Jun 15;20(12):4414-22. doi: 10.1523/JNEUROSCI.20-12-04414.2000.
Strontium is capable of supporting synaptic transmission, but release is dramatically different from that evoked in calcium. By measuring presynaptic strontium levels, we gain insight into the actions of strontium, which has implications for the identification of molecules involved in different aspects of synaptic transmission. We examined presynaptic divalent levels and synaptic release at the granule cell to stellate cell synapse in mouse cerebellar slices. We find that the prolonged duration of release and paired-pulse facilitation in the presence of strontium can be accounted for by the slower removal of strontium from the presynaptic terminal. Phasic and delayed release are both driven by strontium less effectively than by calcium, indicating that a heightened sensitivity to strontium is not a feature of the binding sites involved in facilitation and delayed release. We also find that the cooperativity for phasic release is 1.7 for strontium compared with 3.2 for calcium, suggesting that differential binding may help to identify the calcium sensor involved in phasic release.
锶能够支持突触传递，但其释放情况与钙引发的释放显著不同。通过测量突触前的锶水平，我们深入了解了锶的作用，这对于识别参与突触传递不同方面的分子具有重要意义。我们检测了小鼠小脑切片中颗粒细胞到星状细胞突触处的突触前二价离子水平和突触释放情况。我们发现，在存在锶的情况下，释放持续时间延长和双脉冲易化现象可以用锶从突触前终末的清除较慢来解释。与钙相比，锶驱动的相位性释放和延迟释放的效率都较低，这表明对锶的更高敏感性并非参与易化和延迟释放的结合位点的特征。我们还发现，锶的相位性释放协同性为1.7，而钙为3.2，这表明差异结合可能有助于识别参与相位性释放的钙传感器。
