Redgrave P, Odekunle A, Dean P
Exp Brain Res. 1986;63(2):279-93. doi: 10.1007/BF00236845.
In rats, as in other mammals, one of the principal projections of the superior colliculus (SC) crosses the midline in the dorsal tegmental decussation to join the contralateral predorsal bundle (PDB). The cells of origin of this pathway were studied by injections of retrograde tracers (true blue or wheatgerm agglutinin-conjugated horseradish peroxidase) into the PDB rostral to its major fields of termination. Labelled cells were plotted with respect to fibre layers within the SC. The majority of labelled cells in the contralateral SC were located within the stratum album intermediale (SAI), between the fasciles oriented caudorostrally in that layer. They were of a wide range of sizes, and were much more numerous in lateral SC (where the SAI is broader) than in medial SC. The remaining labelled cells were found mainly in the deep layers. The effects of midline knife-cuts made prior to the injection of tracer suggested that most of the labelled SAI cells, but few of the deep-layer cells, projected across the midline in the dorsal tegmental decussation. Double-labelling procedures were used to investigate whether the cells of origin of the PDB send collaterals in the ipsilateral descending pathway of the SC. Injections of diamidino-yellow into the terminal regions of this pathway labelled very few PDB cells, although large numbers of other tectal cells were labelled. In contrast, extensive double labelling was observed after control injections of diamidino-yellow into the ipsilateral ascending pathway in the ventral diencephalon. These findings suggest that there is anatomical, and therefore perhaps functional, segregation of descending output channels from the superior colliculus in rat. This suggestion receives some support from comparison of the present results with those of tectal stimulation studies. Stimulation in the vicinity of lateral SAI gives contralaterally-directed head and body movements characteristic of orienting and approach, whereas stimulation in other tectal regions that contain predominantly the cells of origin of the ipsilateral descending pathway can give movements resembling avoidance or escape.
与其他哺乳动物一样，在大鼠中，上丘（SC）的主要投射之一在背侧被盖交叉处越过中线，加入对侧背前束（PDB）。通过将逆行示踪剂（真蓝或小麦胚芽凝集素结合辣根过氧化物酶）注射到PDB主要终末场前方的区域，研究了该通路的起源细胞。根据上丘内的纤维层绘制标记细胞。对侧上丘中的大多数标记细胞位于中间白质层（SAI）内，在该层中由尾向头排列的纤维束之间。它们大小各异，在外侧上丘（SAI较宽）中比在内侧上丘中数量多得多。其余标记细胞主要见于深层。在注射示踪剂之前进行的中线切断实验表明，大多数标记的SAI细胞，但只有少数深层细胞，在背侧被盖交叉处越过中线投射。采用双重标记程序研究PDB的起源细胞是否在同侧上丘下行通路中发出侧支。向该通路的终末区域注射双脒基黄仅标记了极少数PDB细胞，尽管大量其他顶盖细胞被标记。相反，在将双脒基黄对照注射到腹侧间脑的同侧上行通路后，观察到广泛的双重标记。这些发现表明，大鼠上丘下行输出通道在解剖学上存在分离，因此可能在功能上也存在分离。将本研究结果与顶盖刺激研究结果进行比较，为这一观点提供了一些支持。刺激外侧SAI附近会引发对侧定向和接近的头部及身体运动，而刺激主要包含同侧下行通路起源细胞的其他顶盖区域则会引发类似回避或逃避的运动。
