Zhu J J
Abteilung Zellphysiologie, Max-Planck-Institut fur medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg, Germany.
J Physiol. 2000 Aug 1;526 Pt 3(Pt 3):571-87. doi: 10.1111/j.1469-7793.2000.00571.x.
Changes in the arborization and electrical excitability of the apical dendritic tufts of pyramidal cells of cortical layer 5 were examined during the first 2 months (postnatal days (P)2-56) of postnatal development in rats. Reconstructions of biocytin-filled neurons showed that the apical dendritic trunk was continually growing, becoming longer and thicker and that the distance between the tuft and soma increased more than 5-fold. In P2 animals, both the tuft and soma had a high input resistance (> 500 MOmega) and the tuft was electrotonically close to the soma. In contrast, the apical tuft and soma of P56 neurons had a low input resistance (< 50 MOmega) and they were electrotonically isolated from each other. Depolarizing current pulses injected into the tuft of P2 cells generated mostly Na+-dependent regenerative dendritic potentials of short duration ( approximately 15 ms) while in the tuft of P56 animals, complex regenerative potentials were generated which had a longer duration ( approximately 55 ms) and were Na+ and Ca2+ dependent. In young and juvenile animals (P14-28) dendritic regenerative potentials could be restricted to the apical dendritic tuft whereas in adult animals (> P42), the complex regenerative potentials frequently occurred simultaneously with somatic action potentials. The main developmental change in layer 5 pyramidal neurons, as assayed with square pulse current injections and synaptic stimulations, is the progressive electrotonic isolation of the dendritic tuft from the soma. This change is concomitant with the appearance of complex, mostly Na+- and Ca2+-dependent, regenerative dendritic potentials initiated partly in the tuft and partly in the axon. The coupling of the dendritic tuft and axonal initiation zones for regenerative potentials by active dendritic Na+ and Ca2+ conductances enables mature layer 5 pyramidal neurons to detect selectively the salient distal synaptic inputs and coincident synaptic inputs arriving at different cortical layers.
在大鼠出生后发育的前2个月（出生后第（P）2 - 56天），研究了皮层第5层锥体细胞顶端树突簇的分支和电兴奋性变化。生物胞素填充神经元的重建显示，顶端树突干持续生长，变得更长更粗，树突簇与胞体之间的距离增加了5倍多。在出生后第2天的动物中，树突簇和胞体都具有高输入电阻（> 500 MΩ），并且树突簇在电紧张方面与胞体接近。相比之下，出生后第56天神经元的顶端树突簇和胞体具有低输入电阻（< 50 MΩ），并且它们在电紧张方面相互隔离。注入出生后第2天细胞树突簇的去极化电流脉冲主要产生短持续时间（约15毫秒）的依赖于Na +的再生性树突电位，而在出生后第56天动物的树突簇中，产生了复杂的再生性电位，其持续时间更长（约55毫秒），并且依赖于Na +和Ca2 +。在幼年和少年动物（出生后第14 - 28天）中，树突再生性电位可能局限于顶端树突簇，而在成年动物（>出生后第42天）中，复杂的再生性电位经常与体细胞动作电位同时出现。用方波电流注入和突触刺激测定，第5层锥体细胞的主要发育变化是树突簇与胞体的逐渐电紧张隔离。这种变化伴随着复杂的、主要依赖于Na +和Ca2 +的再生性树突电位的出现，这些电位部分在树突簇中引发，部分在轴突中引发。活跃的树突Na +和Ca2 +电导使树突簇与再生性电位的轴突起始区耦合，使成熟的第5层锥体细胞能够选择性地检测到达不同皮层层的显著远端突触输入和同时发生的突触输入。
