Le Bé Jean-Vincent, Silberberg Gilad, Wang Yun, Markram Henry
Laboratory of Neural Microcircuitry, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland.
Cereb Cortex. 2007 Sep;17(9):2204-13. doi: 10.1093/cercor/bhl127. Epub 2006 Nov 23.
Neocortical pyramidal cells (PCs) project to various cortical and subcortical targets. In layer V, the population of thick tufted PCs (TTCs) projects to subcortical targets such as the tectum, brainstem, and spinal cord. Another population of layer V PCs projects via the corpus callosum to the contralateral neocortical hemisphere mediating information transfer between the hemispheres. This subpopulation (corticocallosally projecting cells [CCPs]) has been previously described in terms of their morphological properties, but less is known about their electrophysiological properties, and their synaptic connectivity is unknown. We studied the morphological, electrophysiological, and synaptic properties of CCPs by retrograde labeling with fluorescent microbeads in P13-P16 Wistar rats. CCPs were characterized by shorter, untufted apical dendrites, which reached only up to layers II/III, confirming previous reports. Synaptic connections between CCPs were different from those observed between TTCs, both in probability of occurrence and dynamic properties. We found that the CCP network is about 4 times less interconnected than the TTC network and the probability of release is 24% smaller, resulting in a more linear synaptic transmission. The study shows that layer V pyramidal neurons projecting to different targets form subnetworks with specialized connectivity profiles, in addition to the specialized morphological and electrophysiological intrinsic properties.
新皮质锥体细胞（PCs）投射到各种皮质和皮质下靶点。在第V层，厚簇状PCs（TTCs）群体投射到皮质下靶点，如顶盖、脑干和脊髓。第V层PCs的另一群体通过胼胝体投射到对侧新皮质半球，介导半球间的信息传递。这个亚群（胼胝体投射细胞[CCPs]）此前已根据其形态学特性进行了描述，但对其电生理特性了解较少，且其突触连接尚不清楚。我们通过用荧光微珠逆行标记P13 - P16 Wistar大鼠中的CCPs，研究了它们的形态学、电生理学和突触特性。CCPs的特征是顶端树突较短且无簇，仅延伸至II/III层，这证实了先前的报道。CCPs之间的突触连接在发生概率和动态特性方面均与TTCs之间观察到的不同。我们发现CCP网络的相互连接程度比TTC网络低约4倍，释放概率小24%，导致突触传递更具线性。该研究表明，除了具有特殊的形态学和电生理学内在特性外，投射到不同靶点的第V层锥体神经元还形成了具有特殊连接模式的子网。
