High Ih channel density in the distal apical dendrite of layer V pyramidal cells increases bidirectional attenuation of EPSPs
High Ih channel density in the distal apical dendrite of layer V pyramidal cells increases bidirectional attenuation of EPSPs
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DOI：
10.1152/jn.2001.85.2.855
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发表时间：
2001-02-01
影响因子：
2.5
通讯作者：
Lüscher, HR
中科院分区：
文献类型：
--
作者：
Berger, T;Larkum, ME;Lüscher, HR
尽管最近关于激活信号沿V层新皮质锥体神经元树突传播的研究很丰富，但关于阈值下突触信号的传输仍然知之甚少。我们提出了一项研究，用三个同步的全细胞记录在大鼠急性脑片上这些细胞的顶端树突上，以检测自发兴奋性突触后电位(SEPSP)的传播和衰减。在顶端树突上相隔约500微米的两个部位中的每个部位进行相等的电流注入，会导致另一个部位的电压瞬变相等(“互易性”)，从而揭示出神经元的线性行为。体顶和体细胞sEPSP顶端树突的平均表观长度常数分别为273和446微米。人工EPSP的序列没有显示时间总和。阻断超极化激活的阳离子电流(I-h)使体感诱发电位的衰减率降低17%，对体细胞的衰减率降低47%。可以看到EPSP列车的显著位置相关的时间总和。研究了i-h在细胞贴壁贴片中的亚细胞分布和生物物理性质。在胞体不到400um的范围内，在顶端远端树突中发现了类似于3pA/um(2)的低密度，增加到类似于40pA/um(2)的低密度。I-h表现为激活和失活的动力学过程，时间常数大于40ms，在-95 mV处呈现半最大激活。这些发现表明，突触输入到顶束和基底树突的整合在空间上是独立的。这是由于与被动树枝相比，顶端簇中的高I-h通道密度增加了这两个隔室之间的电张力距离。
Despite the wealth of recent research on active signal propagation along the dendrites of layer V neocortical pyramidal neurons, there is still little known regarding the traffic of subthreshold synaptic signals. We present a study using three simultaneous whole cell recordings on the apical dendrites of these cells in acute rat brain slices to examine the spread and attenuation of spontaneous excitatory postsynaptic potentials (sEPSPs). Equal current injections at each of a pair of sites separated by similar to 500 mum on the apical dendrite resulted in equal voltage transients at the other site ("reciprocity"), thus disclosing linear behavior of the neuron. The mean apparent "length constants" of the apical dendrite were 273 and 446 mum for somatopetal and somatofugal sEPSPs, respectively. Trains of artificial EPSPs did not show temporal summation. Blockade of the hyperpolarization-activated cation current (I-h) resulted in less attenuation by 17% for somatopetal and by 47% for somatofugal sEPSPs. A pronounced location-dependent temporal summation of EPSP trains was seen. The subcellular distribution and biophysical properties of I-h were studied in cell-attached patches. Within less than similar to 400 mum of the soma, a low density of similar to3 pA/mum(2) was found, which increased to similar to 40 pA/mum(2) in the apical distal dendrite. I-h showed activation and deactivation kinetics with time constants faster than 40 ms and half-maximal activation at -95 mV. These findings suggest that integration of synaptic input to the apical tuft and the basal dendrites occurs spatially independently. This is due to a high I-h channel density in the apical tuft that increases the electrotonic distance between these two compartments in comparison to a passive dendrite.