Functional significance of passive and active dendritic properties in the synaptic integration by an identified nonspiking interneuron of crayfish.
Functional significance of passive and active dendritic properties in the synaptic integration by an identified nonspiking interneuron of crayfish.
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DOI：
10.1152/jn.00680.2006
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发表时间：
2006-12
影响因子：
2.5
通讯作者：
A. Takashima;R. Hikosaka;M. Takahata
中科院分区：
文献类型：
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作者：
A. Takashima;R. Hikosaka;M. Takahata
非尖峰中间神经元通过突触活动引起的膜电位变化直接控制其突触输出。虽然这些中间神经元不产生尖峰，但它们的树突膜具有多种电压依赖性电导，其在突触整合中的功能意义尚不清楚。利用基于电生理测量和三维形态测量的小龙虾多室模型，通过计算机模拟，定量研究了被动和主动树突特性如何影响小龙虾非尖峰中间神经元的突触整合。静息电位水平下，单一突触电位从树突末端（V(s)）向其他末端（V(t)）传播过程中的衰减因子(V（s)/V(t)）范围为4.42 ~ 6.30，超极化和去极化电位之间无显著差异。对强机械感觉刺激的复合突触反应只能作为衰减电位的空间求和结果在计算中再现，而不能作为任何单一的大电位再现。通过假设活动电导仅分布在进行突触求和的树突区域，可以再现特征响应。细胞其他部分的活跃电导既不影响复合突触反应的形状，也不影响突触电位的树突分布。这些发现表明，活跃的膜电导不影响突触电位在树突上的空间分布，但在塑造突触总电位方面起作用，以增强非尖峰中间神经元突触输出的时间分辨率。
Nonspiking interneurons control their synaptic output directly by membrane potential changes caused by synaptic activities. Although these interneurons do not generate spikes, their dendritic membrane is endowed with a variety of voltage-dependent conductances whose functional significance in synaptic integration remains unknown. We quantitatively investigated how the passive and active dendritic properties affect the synaptic integration in an identified nonspiking interneuron of crayfish by computer simulation using its multicompartment model based on electrophysiological measurements and three-dimensional morphometry. At the resting potential level, the attenuation factor (V(s)/V(t)) of a unitary synaptic potential in the course of its spread from a dendritic terminal (V(s)) to other terminals (V(t)) ranged from 4.42 to 6.30 with no substantial difference between hyperpolarizing and depolarizing potentials. The compound synaptic responses to strong mechanosensory stimulation could be reproduced in calculation only as the result of spatial summation of attenuated potentials, not as any single large potential. The characteristic response could be reproduced by assuming that the active conductances were distributed only in the dendritic region where the synaptic summation was carried out. The active conductances in other parts of the cell affected neither the shape of the compound synaptic response nor the dendritic spread of synaptic potentials. These findings suggest that the active membrane conductances do not affect the spatial distribution of synaptic potentials over dendrites but function in sculpting the summed synaptic potential to enhance temporal resolution in the synaptic output of the nonspiking interneuron.