Mechanism of the distance-dependent scaling of Schaffer collateral synapses in rat CA1 pyramidal neurons
Mechanism of the distance-dependent scaling of Schaffer collateral synapses in rat CA1 pyramidal neurons
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DOI：
10.1113/jphysiol.2002.036376
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发表时间：
2003-04-01
影响因子：
5.5
通讯作者：
Magee, JC
中科院分区：
文献类型：
--
作者：
Smith, MA;Ellis-Davies, GCR;Magee, JC
Schaffer侧支轴突形成兴奋性突触，其分布在海马CA 1锥体神经元的大部分树突分支上。值得注意的是，AMPA受体介导的微型EPSP振幅在索马是相对独立的突触位置，尽管有很大程度的树突过滤。突触电导随距离的逐渐增加被认为是产生这种幅度正常化的原因。在这项研究中，我们研究的机制（S）负责的空间缩放，从CA 1锥体神经元的顶树突的全细胞记录。我们没有发现任何证据表明，有任何位置依赖的范围内发现在谢弗侧支突触的谷氨酸盐浓度的间隙。此外，我们观察到释放概率（P-r），成对脉冲易化和容易释放的囊泡池的大小不依赖于突触的位置。因此，似乎没有任何变化的基本突触前特性的谢弗侧支突触，可以解释距离依赖的缩放。另一方面，4-甲氧基-7-硝基吲哚啉-笼状L-谷氨酸到分离的树突棘上的双光子释放显示，突触后AMPA受体的数量随着与索马的距离而增加。因此，我们的结论是，参与生产的距离依赖缩放的谢弗侧支突触的主要突触机制是突触后AMPA受体密度升高。
Schaffer collateral axons form excitatory synapses that are distributed across much of the dendritic arborization of hippocampal CA1 pyramidal neurons. Remarkably, AMPA-receptor-mediated miniature EPSP amplitudes at the soma are relatively independent of synapse location, despite widely different degrees of dendritic filtering. A progressive increase with distance in synaptic conductance is thought to produce this amplitude normalization. In this study we examined the mechanism(s) responsible for spatial scaling by making whole-cell recordings from the apical dendrites of CA1 pyramidal neurons. We found no evidence to suggest that there is any location dependence to the range of cleft glutamate concentrations found at Schaffer collateral synapses. Furthermore, we observed that release probability (P-r), paired-pulse facilitation and the size of the readily releasable vesicular pool are not dependent on synapse location. Thus, there do not appear to be any changes in the fundamental presynaptic properties of Schaffer collateral synapses that could account for distance-dependent scaling. On the other hand, two-photon uncaging of 4-methoxy-7-nitroindolinyl-caged L-glutamate onto isolated dendritic spines shows that the number of postsynaptic AMPA receptors per spine increases with distance from the soma. We conclude, therefore, that the main synaptic mechanism involved in the production of distance-dependent scaling of Schaffer collateral synapses is an elevated postsynaptic AMPA receptor density.