Gayer N S, Horsburgh G M, Dreher B
Department of Anatomy, University of Sydney, NSW, Australia.
Brain Res Dev Brain Res. 1989 Nov 1;50(1):33-54. doi: 10.1016/0165-3806(89)90125-9.
The distribution of retinal axons and/or terminals in the retino-recipient nuclei of pigmented and albino rabbits varying in age from the 24th postconceptional day (24PCD) to adulthood was examined following unilateral intraocular injections of the enzyme horseradish peroxidase. Both in pigmented and albino rabbits contralateral retinal axons and/or terminals in the dorsal and ventral lateral geniculate nuclei (DLG and VLG), superior colliculi (SC), pretecta (PT) and accessory optic tract nuclei (AON) were already present on 24PCD. In the period 26-30PCD the contralateral projection occupied the entire volume of the DLG, VLG and SC. Although 32PCD (the day of birth) the proportions of the volumes of DLG and VLG occupied by the contralateral projections were slightly reduced, their volume continued to increase in absolute terms up to adulthood. In pigmented rabbits the ipsilateral projections to all retino-recipient nuclei were most dense and extensive on 26PCD. From 26PCD, the relative extent of the ipsilateral projections was gradually reduced, but a reduction in their absolute extent did not become evident until 32PCD. By 32PCD the ipsilateral projection to the AON had disappeared completely. The distribution of ipsilateral axons and/or terminals and the relative proportion of the nuclei occupied by the ipsilateral projection in all other retino-recipient nuclei had become adult-like by 34PCD. In albino rabbits only a sparse ipsilateral projection to the presumptive superficial collicular layers was present on 24PCD. In the remaining retino-recipient nuclei an ipsilateral projection was present on 26PCD. From 26PCD the relative extent and from 30PCD the absolute extent of ipsilateral retinal axons and/or terminals was gradually reduced. The relative extent of the ipsilateral projection had become almost adult-like by 34PCD. Throughout development ipsilateral projections in albinos were consistently less dense and less extensive than those in pigmented rabbits, and unlike in pigmented rabbits, the ipsilateral projections to the VLG and PT were only transient. The differences between the two strains in the pattern of retinofugal projections were further enhanced during the period of segregation of the ipsilateral and contralateral projections. Considering the fact that in both strains there is a partial correspondence between the period in which the spatial extent of the ipsilateral projections is reduced and the period of retinal ganglion cell (RGC) death, it is likely that RGC death plays a role in the process of segregation of the retinal afferents into ocular domains. However, our data suggest that other mechanism(s) also play an important role in the process.
在单侧眼内注射辣根过氧化物酶后，研究了从受孕后第24天（24PCD）到成年期不同年龄的有色和白化兔视网膜轴突和/或终末在视网膜接受核中的分布。在24PCD时，有色和白化兔背侧和腹侧外侧膝状核（DLG和VLG）、上丘（SC）、顶盖前区（PT）和副视束核（AON）中的对侧视网膜轴突和/或终末就已经存在。在26 - 30PCD期间，对侧投射占据了DLG、VLG和SC的整个体积。尽管在出生日（32PCD）时，对侧投射占据的DLG和VLG体积比例略有降低，但其体积绝对值一直增加到成年。在有色兔中，到所有视网膜接受核的同侧投射在26PCD时最为密集和广泛。从26PCD开始，同侧投射的相对范围逐渐减小，但直到32PCD其绝对范围的减小才变得明显。到32PCD时，到AON的同侧投射完全消失。到34PCD时，同侧轴突和/或终末的分布以及同侧投射在所有其他视网膜接受核中占据的核的相对比例已变得与成年时相似。在白化兔中，在24PCD时仅存在稀疏的同侧投射到假定的上丘浅层。在其余视网膜接受核中，26PCD时存在同侧投射。从26PCD开始同侧投射的相对范围以及从30PCD开始其绝对范围逐渐减小。到34PCD时，同侧投射的相对范围已变得几乎与成年时相似。在整个发育过程中，白化兔的同侧投射始终比有色兔的密度低且范围小，并且与有色兔不同，到VLG和PT的同侧投射只是短暂的。在同侧和对侧投射分离期间，两种品系在视网膜传出投射模式上的差异进一步增大。考虑到在两个品系中，同侧投射空间范围减小的时期与视网膜神经节细胞（RGC）死亡的时期部分对应，RGC死亡很可能在视网膜传入纤维分离到眼区的过程中起作用。然而，我们的数据表明其他机制在这个过程中也起重要作用。
