Development of anomalous retinal projections to nonvisual thalamic nuclei in Syrian hamsters: a quantitative study.
Development of anomalous retinal projections to nonvisual thalamic nuclei in Syrian hamsters: a quantitative study.
复制标题
叙利亚仓鼠非视觉丘脑核的异常视网膜投射的发展：一项定量研究。
DOI：
10.1002/cne.902520106
复制
发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Frost,DO
中科院分区：
文献类型：
--
作者：
Frost,DO
当新生仓鼠视网膜轴突的两个主要目标——外侧膝状体的上丘和背核被切除，体感核（腹基底核）或听觉核（内侧膝状核）部分失传入时，视轴突在后者核中形成永久性的异常连接。手术仓鼠的外侧后核也有异常大的视网膜投影。在这里，我们报告了一项定量研究的结果，该研究是为了阐明这些异常连接是如何形成的。在正常的新生仓鼠中，有一个短暂的视网膜投射到腹基底核，在出生后3 - 4天消失。我们的定量数据显示，手术后，视网膜-腹底投影的体积比腹底核的体积成比例地增加，因此，成年仓鼠手术后的视网膜-腹底投影是由于正常瞬态投影的稳定和反应性发芽增加了投影的大小。视网膜内侧膝状突起是由通常穿过核的视束纤维的反应性萌发引起的；在未手术的仓鼠中，任何年龄的仓鼠都看不到终止的突起。定量数据还表明，异常大的视网膜外侧后突几乎完全是由于出生当天已经存在的正常突起和/或正常通道纤维的反应性发芽，尽管可能有一小部分成分可归因于一小群正常瞬时的视网膜外侧后轴突的稳定。目前的研究结果表明，正常新生仓鼠的瞬态视网膜-腹底轴突能够与腹底神经元建立永久连接。这一发现提出了一个重要的问题，即决定未成熟神经元连接是稳定还是消除的细胞机制。结果还表明，在正常和异常发育过程中，生长轴突对靶标的选择可能取决于轴突在能够接收传入信号的潜在末端位置附近。
When two of the principal targets of retinofugal axons, the superior colliculus and dorsal nucleus of the lateral geniculate body, are ablated in newborn hamsters and the somatosensory (ventrobasal) or auditory (medial geniculate) thalamic nuclei are partially deafferented, the optic axons form permanent, abnormal connections in the latter nuclei. The lateral posterior nucleus of the operated hamsters also receives an anomalously large retinal projection. Here, we report on the results of a quantitative study that was undertaken in order to elucidate how these abnormal connections are formed.In normal, newborn hamsters, there is a transient retinal projection to the ventrobasal nucleus that disappears 3‐‐4 days postnatally. Our quantitative data show that postoperatively, the volume of the retino‐ventrobasal projection increases proportionately more than the volume of the ventrobasal nucleus so that the retino‐ventrobasal projection in operated adult hamsters is due both to the stabilization of the normally transient projection and to a reactive sprouting that increases the size of the projection. The retino‐medial geniculate projection arisesde novoby reactive sprouting of optic tract fibers that normally pass over and through the nucleus; in unoperated hamsters, terminating projections are never seen at any age. The quantitative data also show that the anomalously large retino‐lateral posterior projection is due almost entirely to the reactive sprouting of the normal projection and/or normal fibers of passage that are already present on the day of birth, although it is possible that a minor component can be attributed to the stabilization of a small population of normally transient retino‐lateral posterior axons.The present results demonstrate that the transient retino‐ventrobasal axons in normal, newborn hamsters are capable of making permanent connections with ventrobasal neurons. This finding raises the important question of the cellular mechanisms that determine whether immature neuronal connections are stabilized or eliminated. The results also suggest that during both normal and abnormal development, the choice of a target by growing axons may depend upon the axons being in proximity to a potential terminal site just at the time when that site is capable of receiving afferents.