Sabatini B L, Svoboda K
Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724, USA.
Nature. 2000 Nov 30;408(6812):589-93. doi: 10.1038/35046076.
Most synapses form on small, specialized postsynaptic structures known as dendritic spines. The influx of Ca2+ ions into such spines--through synaptic receptors and voltage-sensitive Ca2+ channels (VSCCs)--triggers diverse processes that underlie synaptic plasticity. Using two-photon laser scanning microscopy, we imaged action-potential-induced transient changes in Ca2+ concentration in spines and dendrites of CA1 pyramidal neurons in rat hippocampal slices. Through analysis of the large trial-to-trial fluctuations in these transients, we have determined the number and properties of VSCCs in single spines. Here we report that each spine contains 1-20 VSCCs, and that this number increases with spine volume. We are able to detect the opening of a single VSCC on a spine. In spines located on the proximal dendritic tree, VSCCs normally open with high probability (approximately 0.5) following dendritic action potentials. Activation of GABA(B) receptors reduced this probability in apical spines to approximately 0.3 but had no effect on VSCCs in dendrites or basal spines. Our studies show that the spatial distribution of VSCC subtypes and their modulatory potential is regulated with submicrometre precision.
大多数突触形成于称为树突棘的小型特化突触后结构上。钙离子通过突触受体和电压敏感性钙离子通道（VSCCs）流入这些树突棘，触发了构成突触可塑性的各种过程。我们使用双光子激光扫描显微镜，对大鼠海马切片中CA1锥体神经元树突棘和树突中动作电位诱导的钙离子浓度瞬变进行成像。通过分析这些瞬变中大量的试验间波动，我们确定了单个树突棘中VSCCs的数量和特性。在此我们报告，每个树突棘含有1至20个VSCCs，且这个数量随树突棘体积增加。我们能够检测到单个树突棘上VSCC的开放。在位于近端树突树的树突棘中，VSCCs通常在树突动作电位后以高概率（约0.5）开放。GABA(B)受体的激活将顶端树突棘中的这种概率降低至约0.3，但对树突或基底树突棘中的VSCCs没有影响。我们的研究表明，VSCC亚型的空间分布及其调节潜力以亚微米精度受到调控。
