SPECIFICATION OF RETINO-TECTAL PROJECTION IN CHICK
SPECIFICATION OF RETINO-TECTAL PROJECTION IN CHICK
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DOI：
10.1002/cne.901550202
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发表时间：
1974-01-01
影响因子：
2.5
通讯作者：
KELLY, JP
中科院分区：
文献类型：
--
作者：
CROSSLAND, WJ;COWAN, WM;KELLY, JP
已经在小鸡身上研究了视网膜和视顶盖之间连接的特异性，方法是消融 15% 到 75% 的视杯（通常在孵化的第三天），然后确定由幸存的神经节细胞的轴突形成的突触在顶盖内的分布。这是在潜伏期快结束时或孵化后不久完成的，要么在将氚化氨基酸注射到眼睛后进行放射自显影，要么在视神经切片后使用 Nauta-Gygax 方法的变体。在第 12/13 阶段之后（即孵化第二天晚些时候）放置初始视网膜病变的每种情况下，存活的神经节细胞仅在对侧视顶盖的有限区域形成突触；就通过检查峡部视神经核（视网膜的离心纤维起源于其中）的细胞损失可以确定，神经视网膜的剩余部分始终仅投射到顶盖的同伦区域（即通常预期投射到的区域）。在一些情况下，人们发现轴突已经越过了顶盖的异位区域，以便到达它们形成突触的更远的区域。在第 11 阶段之前视神经泡受损后，幸存的神经节细胞似乎支配了顶盖的所有部分；由于最早的视网膜神经节细胞是在第11/12阶段形成的，因此在小鸡中，就像非洲爪蟾一样，第一个神经节细胞从细胞周期中退出与视网膜顶盖投影的拓扑规范的建立之间存在明显的时间重合。四到五周大的小鸡，表明这些连接的组织（因此，大概是从视峡核到视网膜的离心纤维的组织）与鸽子的组织基本相同。然而，这两个物种的峡部视核的整体形态存在显着差异：从矢状切面可以清楚地看出，雏鸡的峡部视核缺乏发育良好的“前肢”，因此水平子午线的表现靠近核“体”与其“后肢”的交界处。
The specificity of the connections between the retina and the optic tectum has been studied in the chick by ablating between 15% and 75% of the optic cup (usually during the third day of incubation) and subsequently determining the distribution, within the tectum, of the synapses formed by the axons of the surviving ganglion cells. This was done towards the end of the incubation period, or shortly after hatching, either autoradiographically following the injection of a tritiated amino acid into the eye, or using a variant of the Nauta‐Gygax method after sectioning the optic nerve. In every case in which the initial retinal lesion was placed after Stage 12/13 (i.e., late on the second day of incubation) the surviving ganglion cells could be shown to have formed synapses in only a limited region of the contralateral optic tectum; and as far as could be determined from an examination of the cell loss in the isthmo‐optic nucleus (in which the centrifugal fibers to the retina have their origin) the remaining portion of the neural retina consistently projected only to the homotopic region of the tectum (i.e., the region to which it would normally have been expected to project). In several cases it was found that the axons had passed over a heterotopic region of the tectum in order to reach a more distant region in which they had formed synapses. After a lesion of the optic vesicle before Stage 11 the surviving ganglion cells appeared to innervate all parts of the tectum; since the earliest retinal ganglion cells are formed at Stage 11/12 it would seem that in the chick, as inXenopus, there is a clear temporal co‐incidence between the withdrawal of the first ganglion cells from the cell‐cycle and the establishment of the topographic specification of the retino‐tectal projection.Preliminary studies of the projection of the retina upon the optic tectum, and of the tectum upon the isthmo‐optic nucleus, in four to five week old chicks, indicates that the organization of these connections (and hence, presumably, that of the centrifugal fibers from the isthmo‐optic nucleus to the retina) is essentially the same as that in the pigeon. However, there is a significant difference in the overall morphology of the isthmo‐optic nucleus in the two species: as can best be seen in parasagittal sections, the isthmo‐optic nucleus of the chick lacks a well‐developed “anterior limb,” so that the representation of the horizontal meridian lies close to the junction of the “body” of the nucleus and its “posterior limb”.