Lachica E A, Casagrande V A
Department of Psychology, Vanderbilt University, Nashville, TN 37232.
Vis Neurosci. 1988;1(1):103-23. doi: 10.1017/s095252380000105x.
In this study we examine the postnatal development of retinogeniculate axons projecting to the magnocellular (M axons), parvocellular (P axons), and koniocellular (K axons) layers of the lateral geniculate nucleus (LGN) in the prosimian primate, Galago crassicaudatus, in order to: (1) understand how individual retinogeniculate axons in primates mature postnatally, and (2) determine whether differences exist in the development of separate classes of axons that are known to be presynaptic to physiologically distinct cells in adults. In galagos, magnocellular, parvocellular, and koniocellular LGN layers contain Y-, X-, and W-like physiological cell classes, respectively (Norton & Casagrande, 1982). In vitro and in vivo optic tract bulk injections of horseradish peroxidase (HRP) were made in animals ranging in age from the day of birth (P0) to adulthood. Two hundred and fifty axonal arbors were completely reconstructed from serial sections and examined qualitatively for general features of maturity and compared quantitatively for changes in shape, arbor width, area, volume, bouton number, and bouton density. Our results confirm that in adult galagos M arbors are large and radially symmetric; P arbors are medium sized and elongated perpendicular to layer borders; K arbors are small and generally oriented parallel to layer borders. At birth, M, P, and K arbors, although still distinct and confined to layers, are qualitatively and quantitatively immature. Both the pattern and pace of maturation differ between classes. Overall, M arbors mature before P arbors which in turn mature before K arbors. Within classes, arbors representing central vision appear to develop about a week ahead of those representing peripheral vision; no differences are evident between the development of crossed and uncrossed arbors. In no case do arbors exhibit a period of postnatal exuberance, wherein arbors are larger than those of the adult as reported for cat X retinal axons. However, in width and bouton density P arbors are mature at P0 and thus occupy relatively more space in the nucleus compared to adult. All arbors mature rapidly and appear adult-like by the 4th or 5th postnatal week.
在本研究中，我们研究了原猴亚目灵长类粗尾婴猴外侧膝状核（LGN）的大细胞层（M轴突）、小细胞层（P轴突）和konio细胞层（K轴突）中视网膜膝状体轴突的出生后发育情况，目的是：（1）了解灵长类动物中单个视网膜膝状体轴突在出生后如何成熟，以及（2）确定已知在成体中与生理上不同的细胞形成突触前联系的不同类轴突的发育是否存在差异。在婴猴中，外侧膝状核的大细胞层、小细胞层和konio细胞层分别包含Y样、X样和W样生理细胞类别（诺顿和卡萨格兰德，1982）。对从出生当天（P0）到成年的动物进行了体外和体内视束大量辣根过氧化物酶（HRP）注射。从连续切片中完全重建了250个轴突分支，并对其成熟的一般特征进行了定性检查，并对形状、分支宽度、面积、体积、终扣数量和终扣密度的变化进行了定量比较。我们的结果证实，在成年婴猴中，M分支大且呈放射状对称；P分支中等大小且垂直于层边界拉长；K分支小且通常与层边界平行排列。出生时，M、P和K分支虽然仍然不同且局限于各层，但在质量和数量上都不成熟。不同类别的成熟模式和速度不同。总体而言，M分支比P分支先成熟，而P分支又比K分支先成熟。在同一类别中，代表中央视觉的分支似乎比代表周边视觉的分支提前约一周发育；交叉和未交叉分支的发育之间没有明显差异。在任何情况下，分支都没有表现出出生后旺盛生长的时期，即分支比猫X视网膜轴突报道的成年分支更大的时期。然而，在宽度和终扣密度方面，P分支在P0时成熟，因此与成年相比，在核中占据相对更多的空间。所有分支成熟迅速，在出生后第4周或第5周时看起来像成年分支。
