PYRAMIDAL NEURONS IN LAYER-5 OF THE RAT VISUAL-CORTEX .3. DIFFERENTIAL MATURATION OF AXON TARGETING, DENDRITIC MORPHOLOGY, AND ELECTROPHYSIOLOGICAL PROPERTIES
PYRAMIDAL NEURONS IN LAYER-5 OF THE RAT VISUAL-CORTEX .3. DIFFERENTIAL MATURATION OF AXON TARGETING, DENDRITIC MORPHOLOGY, AND ELECTROPHYSIOLOGICAL PROPERTIES
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DOI：
10.1002/cne.903390404
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发表时间：
1994-01-22
影响因子：
2.5
通讯作者：
BLAKEMORE, C
中科院分区：
文献类型：
--
作者：
KASPER, EM;LUBKE, J;BLAKEMORE, C
本文描述了大鼠视皮层第5层锥体神经元的早期形态和生理发育与其轴突所选择的靶点的关系。细胞从上丘或对侧视皮层逆行运输，并在固定切片或活切片记录后注入细胞内。在成体中，皮质顶盖细胞有粗大的顶端树突，具有延伸到第一层的广泛的末梢分枝，并且当注入去极化电流时，具有火特征的动作电位爆发；大脑间细胞有细长的顶端树突，终止时没有末端簇状，通常在第二/3层，并且它们显示出更规则的放电模式(Kasper等：J Comp Neurol，本期，339：459-474)。胚胎期E18和E21，皮质板区锥体样细胞均具有相似的胞体-树突形态，胞体呈纺锤形，基生树突较短，但顶端树突较少，均以簇状分布于边缘区。在出生后第3天，在两类细胞的轴突到达靶点后，第5层的所有锥体神经元在第1层仍有明显的终末分支，尽管它们的复杂程度和范围有所不同。体细胞现在更成熟(形状为圆形到卵圆形)，基树状突起已经延伸。早在P5，所有研究的细胞都可以清楚地分为簇状或非簇状(比以前报道的要早得多；Koester和O‘Leary：J Neurosci 12：1382，’92)，这些特征与投射目标精确相关，就像在成人中一样。测量表明，尽管大脑半球间细胞失去了它们的末梢簇，但总的来说，它们顶端树突的树干不会收缩，而是继续生长，生长速度与皮质顶盖细胞大致相同。这两类第5层锥体神经元的分化经历了三个不同的阶段：轴突的路径选择先于大脑半球间细胞的顶束消失，这些形态特征是在皮质顶盖细胞开始爆发放电的前10天建立的。这三个步骤可能由不同的分子信号引导。
This paper describes the early morphological and physiological development of pyramidal neurons in layer 5 of the rat visual cortex in relation to the targets chosen by their axons. Cells were prelabeled by retrograde transport from the superior colliculus or the contralateral visual cortex and intracellularly injected either in fixed slices or after recording in living slices. In the adult, corticotectal cells have thick apical dendrites with an extensive terminal arborization extending into layer 1, and fire characteristic bursts of action potentials when injected with a depolarizing current; interhemispheric cells have slender apical dendrites that terminate without a terminal tuft, usually in layer 2/3, and they display a more regular firing pattern (Kasper et al.: J Comp Neurol, this issue, 339:459-474). At embryonic day E18 (when axons of the two classes of cells are already taking different routes towards their targets) and E21, pyramidal-like cells throughout the cortical plate all have similar soma-dendritic morphology, with spindle-shaped cell bodies and few, short basal dendrites but apical dendrites that all end in distinct tufts in the marginal zone. At postnatal day P3, after the axons of both cell classes have reached their targets, all pyramidal neurons in layer 5 still have distinct terminal arborizations in layer 1, though they vary in complexity and extent. The somata are now more mature (round to ovoid in shape), and the basal dendritic tree has extended. As early as P5, all cells studied could be clearly classified as tufted or untufted (considerably earlier than previously reported; Koester and O'Leary: J Neurosci 12:1382, '92), and these features correlated precisely with the projection target, as in the adult. Measurement showed that although interhemispheric cells lose their terminal tufts, in general the trunks of their apical dendrites do not withdraw but continue to grow, at roughly the same rate as those of corticotectal cells. The two classes of layer 5 pyramidal neurons differentiate from each other in three distinct phases: pathway selection by axons precedes the loss of the apical tuft by interhemispheric cells, and these morphological characteristics are established 10 days before the onset of burst-firing in corticotectal cells. These three steps may be guided by different molecular signals.