Thong I G, Dreher B
Department of Anatomy, University of Sydney, N.S.W., Australia.
Neurosci Lett. 1987 Oct 5;80(3):275-82. doi: 10.1016/0304-3940(87)90467-8.
In rats ranging in age from the second postnatal day (23rd postconceptional day-23 PCD) to adulthood, we have studied the distribution of corticotectal terminals labelled anterogradely by unilateral injections of horseradish peroxidase (conjugated with wheat germ agglutinin) into the visual or motor cortices. No projection to the contralateral superior colliculus (SC) was observed. The earliest age at which the labelled axons and/or terminals from the visual cortex were observed in the ipsilateral SC was 25 PCD. At this stage the projection only involves the optic layer. From 28 to 34 PCD, the projection involves the optic layer, the intermediate layers and the deep part of superficial gray layer. Between 34 and 40 PCD the projection becomes restricted to the superficial laminae (i.e. adultlike). On the 23 PCD (the earliest age examined) we observed a projection from the motor cortex to the intermediate laminae and to a lesser extent the optic layer of the ipsilateral SC. By 34 PCD only the adult-like projection extending from the brachium to the periaqueductal gray (PAG) is apparent. The disappearance of the transient projections to the intermediate collicular laminae may be the result of withdrawal of 'misprojecting' axonal collaterals.
在出生后第二天（受孕后第23天 - 23 PCD）至成年的大鼠中，我们研究了通过将辣根过氧化物酶（与小麦胚凝集素结合）单侧注射到视觉或运动皮层中而被顺行标记的皮质顶盖终末的分布。未观察到对侧上丘（SC）有投射。在同侧上丘中最早观察到来自视觉皮层的标记轴突和/或终末的年龄是25 PCD。在此阶段，投射仅涉及视层。从28到34 PCD，投射涉及视层、中间层和浅灰质层的深部。在34到40 PCD之间，投射局限于浅层层（即类似成年的）。在23 PCD（所检查的最早年龄）时，我们观察到从运动皮层到同侧上丘中间层以及程度较轻的视层的投射。到34 PCD时，仅从臂旁核延伸到导水管周围灰质（PAG）的类似成年的投射明显可见。向中间丘层的短暂投射的消失可能是“错误投射”轴突侧支撤回的结果。
