Shatz C J, Luskin M B
J Neurosci. 1986 Dec;6(12):3655-68. doi: 10.1523/JNEUROSCI.06-12-03655.1986.
To study the prenatal development of connections between the lateral geniculate nucleus (LGN) and the primary visual cortex in the cat, we have examined the relationship between the position of ingrowing afferents from the LGN and their target cells in cortical layers 4 and 6 at various times during the cat's 65 d gestation period and during the first 3 weeks of postnatal life. In 1 series of experiments, the method of transneuronal transport of intraocularly injected tritiated proline (3H-proline), followed by autoradiography, was used to label the developing geniculocortical pathway. In another series, the tritiated thymidine (3H-thymidine) method was employed to keep track of the cells destined for layers 4 and 6 by labeling them on their birthdates (layer 4: embryonic day (E) 37-43; layer 6: E31-36) (Luskin and Shatz, 1985b) and then charting their locations at subsequent times during development. The results of the 2 sets of experiments were compared at corresponding ages. By E39, many of the cells of cortical layer 6 have completed their migrations and are situated within the cortical plate immediately above the subplate. However, the transneuronal labeling pattern indicates that the geniculocotical afferents have not yet arrived within the vicinity of the future visual cortex, but rather are still en route and confined within the optic radiations of the telencephalon. By E42, a week after the first afferents can be detected in the radiations, substantial transneuronal label is found in the subplate immediately below future visual cortex. However, the overlying cortical plate is free of label. Over the next 2 weeks, geniculocortical axons continue to accumulate in the subplate zone, and, in addition, transneuronal label can be found in the marginal zone. By E55 a faint geniculocortical projection can be detected within the cortical plate, but only within its deeper half (future layers 5 and 6), and even then the major portion of the projection is still confined to the subplate. The absence of a projection to cortical layer 4 at these ages is remarkable in view of the results from our 3H-thymidine experiments, which indicate that by E57 the majority of cells destined to belong to layer 4 have already completed their migrations and assumed positions superficial to the cells of layers 5 and 6. By birth, a substantial geniculocortical projection to cortical layer 4 can be detected in the transneuronal autoradiographs.(ABSTRACT TRUNCATED AT 400 WORDS)
为了研究猫的外侧膝状体核（LGN）与初级视皮层之间连接的产前发育情况，我们在猫65天的妊娠期以及出生后的前3周内，在不同时间点检查了来自LGN的生长中传入纤维的位置与其在皮层第4层和第6层靶细胞之间的关系。在一系列实验中，采用眼内注射氚标记脯氨酸（³H - 脯氨酸）后进行跨神经元运输，随后进行放射自显影的方法来标记发育中的膝状体 - 皮层通路。在另一系列实验中，运用氚标记胸腺嘧啶核苷（³H - 胸腺嘧啶核苷）方法，通过在细胞出生日期（第4层：胚胎第37 - 43天；第6层：胚胎第31 - 36天）标记注定要进入第4层和第6层的细胞（Luskin和Shatz，1985b），然后在发育过程中的后续时间绘制它们的位置。将两组实验在相应年龄的结果进行比较。到胚胎第39天，皮层第6层的许多细胞已完成迁移，位于紧挨着下层板的皮层板内。然而，跨神经元标记模式表明，膝状体 - 皮层传入纤维尚未到达未来视皮层附近，而是仍在途中，局限于端脑的视辐射内。到胚胎第42天，在辐射中首次检测到传入纤维一周后，在未来视皮层正下方的下层板中发现大量跨神经元标记。然而，上方的皮层板没有标记。在接下来的2周内，膝状体 - 皮层轴突继续在下层板区域积累，此外，在边缘区也能发现跨神经元标记。到胚胎第55天，在皮层板内可以检测到微弱的膝状体 - 皮层投射，但仅在其较深的一半（未来的第5层和第6层），即便如此，大部分投射仍局限于下层板。鉴于我们³H - 胸腺嘧啶核苷实验的结果，这些年龄时向皮层第4层缺乏投射是值得注意的，该实验结果表明到胚胎第57天，大多数注定要属于第4层的细胞已经完成迁移，并位于第5层和第6层细胞的浅层位置。到出生时，在跨神经元放射自显影片中可以检测到向皮层第4层的大量膝状体 - 皮层投射。（摘要截取自400字）
