Ozaki H S, Murakami T H, Toyoshima T, Shimada M
Brain Res. 1987 Jan 6;400(2):239-46. doi: 10.1016/0006-8993(87)90623-8.
The congenital absence of the corpus callosum, a brain anomaly frequently noted in humans, has been recently found to occur in some mice of the ddN strain in our laboratory. In the brains of these mice, the Probst's longitudinal bundle is always present on both cerebral hemispheres and gives rise to some aberrant fibers toward the midline. In this research, the neuroanatomical features of these fibers were studied by iontophoretical injections of horseradish peroxidase (HRP) into the neocortex of acallosal mouse brains. The results revealed that the fibers which leave the Probst's longitudinal bundle are, at least, of 3 kinds: namely, the fibers that run out from the anterior portion of the bundle and take a U-turn ipsilaterally without crossing the midline through the septal tissue to go back again into the longitudinal bundle at the level where they have left it; the commissural fibers that leave the bundle from its middle portion and cross through a tiny bridge of tissue associated with the ventral hippocampal commissure to the opposite hemisphere; and the fibers that arise from the posterior portion of the bundle and accumulate as an anomalous fascicle below the cingulum. The observation that no labeled fibers were seen within the anterior commissure in the present HRP materials suggests that the axons from neocortex which are prevented from crossing the midline in mice with congenital absence of the corpus callosum cannot find an alternative pathway via the anterior commissure.
胼胝体先天性缺失是人类中经常发现的一种脑异常，最近在我们实验室的一些ddN品系小鼠中也被发现。在这些小鼠的大脑中，普罗布斯特氏纵束始终存在于两个大脑半球，并向中线发出一些异常纤维。在本研究中，通过将辣根过氧化物酶（HRP）离子电渗注入无胼胝体小鼠大脑的新皮层，对这些纤维的神经解剖学特征进行了研究。结果显示，离开普罗布斯特氏纵束的纤维至少有3种：即从束的前部伸出并在同侧转弯而不穿过中线，通过隔区组织再次回到其离开处水平的纵束中的纤维；从束的中部离开并穿过与腹侧海马连合相关的一小片组织桥到对侧半球的连合纤维；以及从束的后部发出并在扣带下方聚集成异常束的纤维。在目前的HRP材料中，在前连合内未见到标记纤维，这一观察结果表明，在先天性胼胝体缺失的小鼠中，被阻止穿过中线的新皮层轴突无法通过前连合找到替代途径。
