Site independence of EPSP time course is mediated by dendritic <i>I</i>_h in neocortical pyramidal neurons

作     者：Williams, SR Stuart, GJ 

作者机构：Australian Natl Univ John Curtin Sch Med Res Div Neurosci Canberra ACT 0200 Australia 

出 版 物：《JOURNAL OF NEUROPHYSIOLOGY》 (神经生理学杂志)

年 卷 期：2000年第83卷第5期

页      面：3177-3182页

核心收录：

学科分类：0710[理学-生物学] 1001[医学-基础医学(可授医学、理学学位)] 07[理学] 071003[理学-生理学] 

主　　题：轴突/代谢 心血管药物/药理学 环核苷酸门控阳离子通道 树突/药物作用 树突/代谢 电刺激 兴奋性突触后电位/药物作用 兴奋性突触后电位/生理学 离子通道/拮抗剂和抑制剂 离子通道/代谢 膜电位/药物作用 膜电位/生理学 新皮质/细胞学 新皮质/药物作用 新皮质/代谢 膜片钳术 钾通道 锥体细胞/药物作用 锥体细胞/代谢 嘧啶类/药理学 大鼠 Wistar 钠通道阻滞剂 河豚毒素/药理学 动物 大鼠 

摘      要：Neocortical layer 5 pyramidal neurons possess long apical dendrites that receive a significant portion of the neurons excitatory synaptic input. Passive neuronal models indicate that the time course of excitatory postsynaptic potentials (EPSPs) generated in the apical dendrite will be prolonged as they propagate toward the soma. EPSP propagation may, however, be influenced by the recruitment of dendritic voltage-activated channels. Here we investigate the properties and distribution of I-h channels in the axon, soma, and apical dendrites of neocortical layer 5 pyramidal neurons, acid their effect on EPSP time course. We find a linear increase (9 pA/100 mu m) in the density of dendritic I-h, channels with distance from soma. This nonuniform distribution of I-h channels generates site independence of EPSP time course, such that the half-width at the soma of distally generated EPSPs (up to 435 mu m from soma) was similar to somatically generated EPSPs. As a corollary, a normalization of temporal summation of EPSPs was observed. The site independence of somatic EPSP time course was found to collapse after pharmacological blockade of I-h channels, revealing pronounced temporal summation of distally generated EPSPs, which could be further enhanced by TTX-sensitive sodium channels. These data indicate that an increasing density of apical dendritic I-h channels mitigates the influence of cable filtering on somatic EPSP time course and temporal summation in neocortical layer 5 pyramidal neurons.