Garraghty P E, Sur M, Weller R E, Sherman S M
J Comp Neurol. 1986 Sep 8;251(2):198-215. doi: 10.1002/cne.902510206.
We examined the terminal arbors of single, physiologically identified retinogeniculate X and Y axons from the remaining retinas of adult cats raised from birth with monocular enucleation. These were compared with arbors of X and Y axons in normally reared cats. We used intra-axonal injections of horseradish peroxidase to label each axon after recording its response properties. While the axons in monocularly enucleated cats exhibited normal response properties, both X and Y axons in these cats had abnormally large terminal arbors. Each of the hypertrophied X arbors appeared to be completely confined to the single geniculate lamina A or A1 appropriate to its eye of origin (i.e., lamina A for the contralateral retina and lamina A1 for the ipsilateral retina). In contrast, in addition to their normal terminations, most of the Y arbors seemed to extend well into laminae normally innervated only by the retina that was removed. Thus most or all of the translaminar sprouting previously reported for monocularly enucleated cats appears to reflect extensions of Y axon arbors. These data, in addition to earlier, analogous data from young kittens and cats reared with monocular lid suture, suggest the following sequelae during postnatal development: the retinogeniculate X arbors mature first and develop exuberant arbors that are later competitively pruned as the Y axons expand their innervation of the lateral geniculate nucleus; monocular lid suture prevents the Y axons from succeeding in this competition, so they fail to establish normal arbors and cannot reduce the exuberant X arbors; monocular enucleation offers a less resistant path in the denervated laminae for the rapidly growing Y arbors from the remaining eye, and the expansion of these arbors there reduces the competitive pressure on the exuberant X arbors. Thus, in monocularly enucleated cats, sprouting is limited to Y axons, either because only they possess the capacity to sprout or because they are in the midst of a period of relatively rapid growth at the time of the neonatal enucleation. The X axon arbors are also abnormally large within their appropriate laminae. This occurs presumably because they are able to maintain their immature exuberance, although we cannot rule out the possibility that they are pruned and later regrow to the final size seen in our experiments.
我们检查了出生后即单眼摘除的成年猫剩余视网膜中经生理学鉴定的单个视网膜膝状体X和Y轴突的终末分支。将这些分支与正常饲养的猫的X和Y轴突分支进行比较。在记录每个轴突的反应特性后，我们通过轴突内注射辣根过氧化物酶来标记它。虽然单眼摘除猫的轴突表现出正常的反应特性，但这些猫的X和Y轴突都有异常大的终末分支。每个肥大的X分支似乎完全局限于与其起源眼相对应的单个膝状体板层A或A1（即，对侧视网膜对应板层A，同侧视网膜对应板层A1）。相比之下，除了正常的终末分支外，大多数Y分支似乎还延伸到通常仅由摘除的视网膜支配的板层中。因此，先前报道的单眼摘除猫的大多数或所有跨层发芽似乎反映了Y轴突分支的延伸。这些数据，以及早期来自幼猫和单眼眼睑缝合饲养的猫的类似数据，表明了出生后发育过程中的以下后遗症：视网膜膝状体X分支首先成熟并发育出旺盛的分支，随后随着Y轴突扩大其对外侧膝状体核的支配而受到竞争性修剪；单眼眼睑缝合阻止Y轴突在这场竞争中获胜，因此它们无法建立正常的分支，也无法减少旺盛的X分支；单眼摘除为来自剩余眼睛的快速生长的Y分支在去神经支配的板层中提供了一条阻力较小的路径，这些分支在那里的扩展减轻了对旺盛的X分支的竞争压力。因此，在单眼摘除的猫中，发芽仅限于Y轴突，要么是因为只有它们具有发芽的能力，要么是因为它们在新生儿摘除时正处于相对快速生长的时期。X轴突分支在其相应的板层内也异常大。这可能是因为它们能够维持其未成熟的旺盛状态，尽管我们不能排除它们被修剪并随后重新生长到我们实验中所见最终大小的可能性。
