DEVELOPMENT OF GENICULOCORTICAL AXON ARBORS IN A PRIMATE
DEVELOPMENT OF GENICULOCORTICAL AXON ARBORS IN A PRIMATE
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DOI：
10.1017/s0952523800000365
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发表时间：
1990-09-01
影响因子：
1.9
通讯作者：
CASAGRANDE, VA
中科院分区：
文献类型：
--
作者：
FLORENCE, SL;CASAGRANDE, VA
本研究的主要目的是描述灵长类纹状体皮质内大细胞和小细胞LGN轴突的出生后发育。为了这个目的，我们散装标记的轴突在新生儿原猴（galagos）在体内或体外定期从出生（PO）到出生后12周注射辣根过氧化物酶（HRP）到白色物质前的纹状体皮质。我们对第四层内充满轴突的结构进行了重建、定量分析，并与之前描述的成年轴突群体进行了比较（佛罗伦萨& Casagrande，1987）。我们的结果表明，尽管轴突在出生时在形态上是不成熟的，但它们与成年人一样局限于纹状体皮质第四层的上层（IVα）和下层（IVβ）。在成人中，我们将终止于IVα的假定大细胞LGN轴突称为I型，将终止于IVβ的假定小细胞轴突称为II型。我们使用相同的惯例发展轴突。从出生到出生后3周，I型和II型轴突类在外观上比成人同行更易变，并且在形态上没有类别区分。随着轴突的成熟，母轴突轴的口径增加，乔木变得更小，更放射状，其他不成熟的特征（如尖峰，突起，生长锥）是不太明显。这两个乔木类成熟缓慢，有些仍然表现出不成熟的功能（如生长锥），迟至12周出生后。虽然乔木直到发展后期才显示出阶级区别的特征，但每个阶级都显示出一些独特的成熟趋势。I型乔木在出生时仅比成年对应物稍大，而II型乔木则大得多。I型乔木的分支复杂性随着年龄的增长而增加，而II型乔木的复杂性随着时间的推移而向乔木的中心逐渐减小。这些增长趋势表明，大细胞和小细胞途径皮质可能是差异脆弱的操纵出生后的视觉经验。
The main objective of the present study was to describe the postnatal development of magnocellular and parvocellular LGN axons within the primate striate cortex. For this purpose, we bulk labeled axons in neonatal prosimians (galagos) in vivo or in vitro at regular intervals from birth (PO) to 12 weeks after birth by injecting horseradish peroxidase (HRP) into white matter anterior to the striate cortex. Filled axons within layer IV were reconstructed, quantitatively analyzed, and compared to a population of adult axons described previously (Florence & Casagrande, 1987).Our results show that although axons are morphologically immature at birth, they are restricted to the upper (IVα) and lower (IVβ) tiers of layer IV of the striate cortex as in adults. In adults, we referred to the presumed magnocellular LGN axons terminating in IVα as type I and the presumed parvocellular axons terminating in IVβ as type II. We used the same convention for developing axons.From birth to 3 weeks postnatal, type I and II axon classes are more variable in appearance than adult counterparts, and are not morphologically class distinct. As axons mature, parent axon shafts increase in caliber, arbors become smaller and more radial, and other immature features (e.g. spikes, protrusions, growth cones) are less evident. Both arbor classes mature slowly and some still exhibit immature features (e.g. growth cones) as late as 12 weeks postnatally. Although arbors do not show class-distinctive features until late in development, each class does show some unique maturational trends. Type I arbors are only slightly larger than adult counterparts at birth, whereas type II arbors are dramatically larger. Type I arbors increase in branch complexity with age, whereas type II arbors simply show a shift in complexity toward the center of the arbor with decreasing size over time. These growth trends suggest that magnocellular and parvocellular pathways to cortex could be differentially vulnerable to the manipulation of postnatal visual experience.