Miyazaki Kenichi, Ross William N
Department of Physiology, New York Medical College, Valhalla, New York 10595, and.
Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
J Neurosci. 2017 Oct 11;37(41):9964-9976. doi: 10.1523/JNEUROSCI.1758-17.2017. Epub 2017 Sep 13.
Dendritic spines are key elements underlying synaptic integration and cellular plasticity, but many features of these important structures are not known or are controversial. We examined these properties using newly developed simultaneous sodium and calcium imaging with single-spine resolution in pyramidal neurons in rat hippocampal slices from either sex. Indicators for both ions were loaded through the somatic patch pipette, which also recorded electrical responses. Fluorescence changes were detected with a high-speed, low-noise CCD camera. Following subthreshold electrical stimulation, postsynaptic sodium entry is almost entirely through AMPA receptors with little contribution from entry through NMDA receptors or voltage-gated sodium channels. Sodium removal from the spine head is through rapid diffusion out to the dendrite through the spine neck with a half-removal time of ∼16 ms, which suggests the neck has low resistance. Peak [Na] changes during single EPSPs are ∼5 mm Stronger electrical stimulation evoked small plateau potentials that had significant longer-lasting localized [Na] increases mediated through NMDA receptors. Dendritic spines, small structures that are difficult to investigate, are important elements in the fundamental processes of synaptic integration and plasticity. The main tool for examining these structures has been calcium imaging. However, the kinds of information that calcium imaging reveals is limited. We used newly developed, high-speed, simultaneous sodium and calcium imaging to examine ion dynamics in spines in hippocampal pyramidal neurons. We found that following single subthreshold synaptic activation most sodium entry was through AMPA receptors and not through NMDA receptors or through voltage-gated sodium channels and that the spine neck is not a significant resistance barrier. Most spine mechanisms are linear. However, regenerative NMDA conductances can be activated with stronger stimulation.
树突棘是突触整合和细胞可塑性的关键要素，但这些重要结构的许多特征尚不清楚或存在争议。我们使用新开发的具有单棘分辨率的钠钙同步成像技术，对来自不同性别的大鼠海马切片中的锥体神经元进行了研究。两种离子的指示剂通过体细胞膜片钳电极加载，该电极同时记录电反应。荧光变化通过高速、低噪声的电荷耦合器件（CCD）相机进行检测。在阈下电刺激后，突触后钠的进入几乎完全通过AMPA受体，通过NMDA受体或电压门控钠通道进入的贡献很小。棘突头部的钠清除是通过快速扩散经棘突颈部到达树突，半清除时间约为16毫秒，这表明颈部电阻较低。单个兴奋性突触后电位（EPSP）期间的峰值[Na]变化约为5 mM。更强的电刺激诱发了小的平台电位，这些电位通过NMDA受体介导产生了持续时间更长的局部[Na]增加。树突棘是难以研究的小结构，是突触整合和可塑性基本过程中的重要元素。研究这些结构的主要工具一直是钙成像。然而，钙成像所揭示的信息种类有限。我们使用新开发的高速钠钙同步成像技术来研究海马锥体神经元棘突中的离子动力学。我们发现，在单个阈下突触激活后，大多数钠的进入是通过AMPA受体，而不是通过NMDA受体或电压门控钠通道，并且棘突颈部不是一个显著的电阻屏障。大多数棘突机制是线性的。然而，更强的刺激可以激活再生性NMDA电导。
