Reid C A, Fabian-Fine R, Fine A
Division of Neurophysiology, National Institute for Medical Research, London NW7 1AA, United Kingdom.
J Neurosci. 2001 Apr 1;21(7):2206-14. doi: 10.1523/JNEUROSCI.21-07-02206.2001.
Control of Ca(2+) within dendritic spines is critical for excitatory synaptic function and plasticity, but little is known about Ca(2+) dynamics at thorny excrescences, the complex spines on hippocampal CA3 pyramidal cells contacted by mossy fiber terminals of dentate granule cell axons. We have monitored subthreshold stimulus-dependent postsynaptic Ca(2+) transients in optically and ultrastructurally characterized complex spines and find that such spines can act as discrete units of Ca(2+) response. In contrast to the more common "simple" spines, synaptically evoked Ca(2+) transients at complex spines have only a small NMDA receptor-dependent component and do not involve release of calcium from internal stores. Instead, they result mainly from AMPA receptor-gated Ca(2+) influx through voltage-activated calcium channels on the spine; these channels provide graded amplification of the response of thorny excrescences to individual mossy fiber synaptic events.
树突棘内钙离子（Ca(2+)）的调控对于兴奋性突触功能和可塑性至关重要，但对于棘状赘生物（即齿状颗粒细胞轴突的苔藓纤维终末所接触的海马CA3锥体细胞上的复杂树突棘）处的钙离子动态变化，我们却知之甚少。我们对光学和超微结构特征明确的复杂树突棘中阈下刺激依赖性突触后钙瞬变进行了监测，发现此类树突棘可作为钙离子反应的离散单元。与更为常见的“简单”树突棘不同，复杂树突棘处突触诱发的钙瞬变仅具有一小部分NMDA受体依赖性成分，且不涉及从内部储存库释放钙离子。相反，它们主要源于AMPA受体门控的钙离子通过树突棘上的电压激活钙通道内流；这些通道为棘状赘生物对单个苔藓纤维突触事件的反应提供了分级放大作用。
