Excitatory synaptic integration in hippocampal pyramids and dentate granule cells.
Excitatory synaptic integration in hippocampal pyramids and dentate granule cells.
复制标题
海马锥体和齿状颗粒细胞中的兴奋性突触整合。
DOI：
10.1101/sqb.1990.055.01.010
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Johan F. Storm
中科院分区：
文献类型：
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作者：
P. Andersen;M. Raastad;Johan F. Storm
海马金字塔上的兴奋性突触专门位于树突棘上，通常比例为 1:1。棘的数量表明大鼠的每个 CA1 锥体细胞汇聚了多达 12,000 个兴奋性波顿。单个传入纤维的激活会产生约 150/xV 的单一兴奋性突触后电位 (EPSP)，可能由单个发射器量子产生。令人惊讶的是，鉴于大量的突触会聚，这些微电极实验表明只需要100-300个同步活动的兴奋性突触即可使细胞放电。更令人震惊的是，全细胞贴片记录给出了 1-4 mV 的单纤维 EPSP，这表明只需要大约 10 个共活动的突触前细胞即可使年轻的 CA1 细胞放电。释放概率通常较低，但可通过辅助流程提高。平均而言，每个传入纤维与给定的 CA1 金字塔接触的纽扣很少（大部分是 1 个，但最多 5 个）。树突树各个部分的突触几乎是等价的。相邻突触产生的兴奋性突触后电位线性相加，相互之间以及超极化抑制电位线性相加。电缆理论考虑表明，接触相同次级树突的突触的总和将大于接触更多分布的树突接触的突触的总和。三种类型的抑制性神经元提供不同类别的干扰。吊灯细胞终止于大量锥体细胞的初始轴突，因此能够产生广泛且有效的抑制。通过使较少数量的细胞的体体超极化，篮细胞抵消这些细胞的所有兴奋性输入，无论突触位置如何。与这两种形式的全局抑制相反，星状细胞可能在特定的树突位点引起分流形式的抑制。这种局部抑制有效地消除了位于同一树突分支上更远端的突触的影响，而它对更中心的输入没有影响，甚至有一定的促进影响。后超极化也会降低兴奋性突触驱动的效率，但仅限于神经元放电。最后，突触效率以及整合在很大程度上取决于几种依赖于活动的可塑性变化：促进、增强、强直后增强和长时程增强，按持续时间增加的顺序列出。影响突触相互作用的大量因素使得个体
Excitatory synapses on hippocampal pyramids are exclusively located to dendritic spines, usually in a 1: 1 proportion. The number of spines indicates a convergence of as many as 12,000 excitatory boutons per CA1 pyramidal cell in rats. Activation of a single afferent fiber produces a unitary excitatory postsynaptic potential (EPSP) of about 150/xV, probably produced by a single quantum of transmitter. Surprisingly, in view of the large synaptic convergence, these microelectrode experiments suggest that only 100-300 synchronously active excitatory synapses are necessary to make the cell discharge. Even more astounding, whole-cell patch recording gave single fiber EPSPs of 1-4 mV, suggesting that only about ten coactive presynaptic cells are required to discharge a young CA1 cell. The release probability is normally low but may be increased by facilitatory processes. On average, each afferent fiber has few boutons (mostly one but up to five) in contact with a given CA1 pyramid. Synapses in various parts of the dendritic tree are nearly equipotent. Excitatory postsynaptic potentials produced by neighboring synapses sum linearly, both with each other and with hyperpolarizing inhibitory potentials. Cable theoretical considerations suggest that the sum will be greater for synapses contacting the same secondary dendrite than for more distributed dendritic contacts.Three types of inhibitory neurons provide different classes of interference. The chandelier cells terminate on the initial axons of a large number of pyramidal ceils, thus capable of producing a widespread and effective inhibition. By hyperpolarizing the soma of a smaller number of cells, basket cells counteract all excitatory inputs with these cells, irrespective of synaptic location. In contrast with these two forms of global inhibition, stellate cells may cause a shunting form of inhibition at specific dendritic sites. Such local inhibition effectively removes the influence of synapses lying further distally on the same dendritic branch, whereas it has either no effect or even a certain facilitatory influence on more centrally placed inputs. After-hyperpolarization also reduces the efficiency of an excitatory synaptic drive but only for discharging neurons. Finally, synaptic efficiency, and thereby integration, depends heavily on several activity-dependent plastic changes: facilitation, augmentation, posttetanic potentiation, and long-term potentiation, listed in order of increasing duration. The large number of factors that influence the synaptic interplay makes an individual