Aitkin L M, Phillips S C
J Comp Neurol. 1984 Sep 10;228(2):210-6. doi: 10.1002/cne.902280207.
Much is known of the sources and manner of termination of ascending and descending input to the inferior colliculus (IC) but its commissural connections are less well understood. Most studies of the commissure have utilized small lesions or tracer deposits; while all agree that commissural axons terminating in the IC do so in its superficial and dorsomedial sectors, it is not clear where projecting cell bodies are located in the IC. The present study attempted total infiltration of the commissure of the cat IC with horseradish peroxidase (HRP) in an effort to label all neuronal somas whose axons cross in the commissure. The distribution of labeled cells after the brachium of the IC (BIC) was cut unilaterally and infiltrated with HRP was also examined to enable comparison of the locations and approximate proportions of cells projecting to the contralateral IC and medial geniculate body (MGB). The cells giving rise to commissural axons form an array tilted dorsally from caudal to rostral that spreads mediolaterally through the central nucleus into the external nucleus of the IC, but largely excludes the dorsomedial sector at posterior levels. A similar distribution of labeled cells, but with reduced numbers, is found when large HRP deposits are made in the contralateral BIC. These results, in conjunction with those from studies of the terminations of commissural axons made by others, suggest that the interconnections of the inferior colliculi through their commissure are complementary, rather than reciprocal.
我们对下丘（IC）的上行和下行输入的来源及终止方式了解很多，但其连合连接却知之甚少。大多数关于连合的研究都采用了小损伤或示踪剂注射；虽然所有人都认为终止于IC的连合轴突在其浅层和背内侧区域终止，但尚不清楚投射细胞体在IC中的位置。本研究试图用辣根过氧化物酶（HRP）全面浸润猫IC的连合，以标记其轴突在连合中交叉的所有神经元胞体。在单侧切断IC臂（BIC）并注射HRP后，还检查了标记细胞的分布，以便比较投射到对侧IC和内侧膝状体（MGB）的细胞的位置和大致比例。产生连合轴突的细胞形成一个从尾端向头端背侧倾斜的阵列，该阵列从中线向外侧延伸穿过中央核进入IC的外侧核，但在后部水平在很大程度上不包括背内侧区域。当在对侧BIC中进行大的HRP注射时，发现了类似的标记细胞分布，但数量减少。这些结果，结合其他关于连合轴突终末的研究结果，表明下丘通过其连合的相互连接是互补的，而不是相互的。
