PYRAMIDAL NEURONS IN LAYER-5 OF THE RAT VISUAL-CORTEX .1. CORRELATION AMONG CELL MORPHOLOGY, INTRINSIC ELECTROPHYSIOLOGICAL PROPERTIES, AND AXON TARGETS
PYRAMIDAL NEURONS IN LAYER-5 OF THE RAT VISUAL-CORTEX .1. CORRELATION AMONG CELL MORPHOLOGY, INTRINSIC ELECTROPHYSIOLOGICAL PROPERTIES, AND AXON TARGETS
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DOI：
10.1002/cne.903390402
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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;LARKMAN, AU;BLAKEMORE, C
以前的工作已经建立了两个结构/功能的相关性，大鼠初级视皮层的第5层锥体神经元。首先，投射到上级丘的细胞在第1层中具有厚的顶端树突，其具有华丽的末端树枝状结构，而投射到相对半球的视觉皮层的细胞具有较薄的顶端树突，其终止于第1层下方，没有末端簇（例如，Hallman等人：J Comp Neurol 272：149，'90）。第二，细胞内记录结合染料注射揭示了两类细胞：第一类细胞具有厚的、簇状的顶端树突，并响应于电流注射而发射两个或更多个脉冲的独特的初始爆发，其具有几乎固定的、短的峰间间隔;另一种具有细长的顶端树枝状突起，缺乏末端簇，往往具有更长的膜时间常数和更高的输入电阻，并且不发射特征突发（例如，Larkman和Mason：J Neurosci 10：1407，'90）。本研究结合细胞内记录在大鼠视皮层和注射羧基荧光素，以揭示体树突的形态，与前注射罗丹明共轭微球到上级或对侧视皮层标记神经元，根据其轴突的目标。这允许一个完整的相关性的形态，内在的电生理特性，和身份的投影目标为个人锥体细胞。逆行标记的神经元从对面的视觉皮层被发现在所有层，除了第1层，而那些标记的上级丘只躺在第5层。在第5层内，纵裂细胞更多地集中在该层的下半部分，但广泛地与皮质顶盖细胞的分布重叠。投射到上级丘的细胞均为爆裂型，顶端树突粗，末端有一簇。在这项研究中，每个细胞投射到对面的视觉皮层是一个“nonburster”，并有一个细长的顶端树突，较少的斜分支，结束时没有一个终端簇，通常在2/3层的上部。纵裂细胞也有圆，少圆锥形的胞体，一般有较少的基底树突比皮质顶盖神经元。许多具有半球间细胞的生理和形态特征的细胞没有从相反的视觉皮层反向标记，这意味着这种类型的锥体细胞可以具有其他投射目标（例如，同侧半球中的其它皮质部位）。另一方面，少数“厚/簇状”爆裂类细胞没有被上级丘的反向标记，这意味着大多数这样的细胞投射到该靶点。
Previous work has established two structure/function correlations for pyramidal neurons of layer 5 of the primary visual cortex of the rat. First, cells projecting to the superior colliculus have thick apical dendrites with a florid terminal arborization in layer 1, whereas those projecting to the visual cortex of the opposite hemisphere have thinner apical dendrites that terminate below layer 1, without a terminal tuft (e.g., Hallman et al.: J Comp Neurol 272:149, '90). Second, intracellular recording combined with dye injection has revealed two classes of cells: the first has a thick, tufted apical dendrite and fires a distinctive initial burst of two or more impulses, of virtually fixed, short interspike interval, in response to current injection; and the other, with a slender apical dendrite lacking a terminal tuft, tends to have a longer membrane time constant and higher input resistance, and does not fire characteristic bursts (e.g., Larkman and Mason: J Neurosci 10:1407, '90). The present study combined intracellular recording in isolated slices of rat visual cortex and injection of carboxyfluorescein, to reveal soma-dendritic morphology, with prior injection of rhodamine-conjugated microspheres into the superior colliculus or contralateral visual cortex to label neurons according to the target of their axons. This permitted a complete correlation of morphology, intrinsic electrophysiological properties, and identity of the projection target for individual pyramidal cells. Neurons retrogradely labeled from the opposite visual cortex were found in all layers except layer 1 while those labeled from the superior colliculus lay exclusively in layer 5. Within layer 5 interhemispheric cells were more concentrated in the lower half of the layer but extensively overlapped the distribution of corticotectal cells. Every cell studied that projected to the superior colliculus was of the bursting type and had a thick apical dendrite with a terminal tuft. Every cell in this study projecting to the opposite visual cortex was a ''nonburster'' and had a slender apical dendrite with fewer oblique branches that ended without a terminal tuft, usually in the upper part of layer 2/3. Interhemispheric cells also had rounder, less conical somata and generally had fewer basal dendrites than corticotectal neurons. Many cells with the physiological and morphological characteristics of interhemispheric cells were not back-labeled from the opposite visual cortex, implying that pyramidal cells of this type can have other projection targets (e.g., other cortical sites in the ipsilateral hemisphere). On the other hand, few cells of the ''thick/tufted,'' bursting class were found that were not back-labeled from the superior colliculus, implying that the majority of such cells project to that target.