Helmstaedter Moritz, Sakmann Bert, Feldmeyer Dirk
Department of Cell Physiology, Max-Planck Institute for Medical Research, Jahnstrasse, Heidelberg, Germany.
Cereb Cortex. 2009 Apr;19(4):938-50. doi: 10.1093/cercor/bhn138. Epub 2008 Sep 11.
Interneurons in layer 2/3 (L2/3) of the somatosensory cortex show 4 types of axonal projection patterns with reference to the laminae and borders of columns in rat barrel cortex (Helmstaedter et al. 2008a). Here, we analyzed the dendritic geometry and electrical excitability of these interneurons. First, dendritic polarity, measured based on the insertion points of primary dendrites on the soma surface, yielded a continuous one-dimensional measure without a clustering of dendritic polarity types. Secondly, we analyzed polar and vertical distributions of dendritic length. A cluster analysis allowed the definition of 7 types of dendritic arborization. Thirdly, when dendritic polarity was related to the intrinsic electrical excitability we found that the ratio of frequency adaptation in trains of action potentials (APs) evoked by current injection was correlated with the number of primary dendrites. Numerical simulations of spiking patterns in L2/3 interneurons suggested that the number of primary dendrites could account for up to 50% of this correlation. Fourthly, dendritic arborization was not correlated with axonal projection, and axonal projection types could not be predicted by electrical excitability parameters. We conclude that 1) dendritic polarity is correlated to intrinsic electrical excitability, and 2) the axonal projection pattern represents an independent classifier of interneurons.
体感皮层第2/3层（L2/3）中的中间神经元，相对于大鼠桶状皮层中柱的板层和边界，呈现出4种轴突投射模式（Helmstaedter等人，2008a）。在此，我们分析了这些中间神经元的树突几何形状和电兴奋性。首先，基于初级树突在胞体表面的插入点测量的树突极性，产生了一种连续的一维测量结果，没有树突极性类型的聚集。其次，我们分析了树突长度的极性和垂直分布。聚类分析允许定义7种树突分支类型。第三，当树突极性与内在电兴奋性相关时，我们发现电流注入诱发的动作电位（AP）序列中的频率适应性比率与初级树突的数量相关。L2/3中间神经元放电模式的数值模拟表明，初级树突的数量可占这种相关性的50%。第四，树突分支与轴突投射不相关，并且轴突投射类型不能通过电兴奋性参数预测。我们得出结论：1）树突极性与内在电兴奋性相关，并且2）轴突投射模式代表中间神经元的一个独立分类器。
