Divac I, Regidor J, Milosevic S, Mogensen J, Zilles K
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
Anat Embryol (Berl). 1995 Jul;192(1):63-75. doi: 10.1007/BF00186992.
Fluorescent somatopetal tracers were used to infiltrate, by diffusion rather than injections, the dorsolateral cortex of one hemisphere in rats. In different animals the tracers penetrated into the cortex to different depths. We found several interesting features of the commissural system: first, there were no areas without commissural neurons. At least a few labelled cell bodies were present in a single-cell layer also in "acallosal" cortical areas. Secondly, there is a considerable variety of laminar distribution patterns of labelled perikarya in different areas. Thirdly, some cortical fields, which cytoarchitecturally appear uniform, can be subdivided according to different distributions of cell bodies with commissural projections. Fourthly, when only supragranular layers were infiltrated, labelled cell bodies were present mainly in the supragranular layers of the contralateral cortex. Infiltration of the first layer alone did not label any neurons in the contralateral cortex but did label neurons in layer VIb ipsilaterally. In the subcortex, the labelled perikarya were found in the structures already known to project directly to the cortex. In rats with the tracer restricted mainly to the supragranular layers, a conspicuously reduced labelling was found in the basal forebrain and the thalamus. In the thalami of those animals, labelled neurons were found only in paralamellar nuclei. The high sensitivity of the tracer used, together with infiltration of the entire dorsolateral cortex, allows us to conclude that probably all sources of innervation of the isocortex in rats have been seen.
荧光体向性示踪剂通过扩散而非注射的方式渗透到大鼠一侧半球的背外侧皮质。在不同的动物中，示踪剂渗透到皮质的深度不同。我们发现了连合系统的几个有趣特征：首先，不存在没有连合神经元的区域。在“无胼胝体”皮质区域的单细胞层中也至少存在一些标记的细胞体。其次，不同区域中标记核周体的层状分布模式有相当大的差异。第三，一些在细胞结构上看似均匀的皮质区域，可以根据具有连合投射的细胞体的不同分布进行细分。第四，当仅浸润颗粒上层时，标记的细胞体主要存在于对侧皮质的颗粒上层。仅浸润第一层并没有标记对侧皮质中的任何神经元，但确实标记了同侧VIb层中的神经元。在皮质下，标记的核周体存在于已知直接投射到皮质的结构中。在示踪剂主要局限于颗粒上层的大鼠中，在基底前脑和丘脑中发现标记明显减少。在这些动物的丘脑中，仅在板旁核中发现了标记的神经元。所用示踪剂的高灵敏度，以及整个背外侧皮质的浸润，使我们能够得出结论，大鼠新皮质的所有可能的神经支配来源可能都已被观察到。
