Benavides-Piccione Ruth, Arellano Jon I, DeFelipe Javier
Instituto Cajal (CSIC), Madrid, Spain.
Cereb Cortex. 2005 Oct;15(10):1584-91. doi: 10.1093/cercor/bhi036. Epub 2005 Feb 9.
In the human neocortex, catecholaminergic connections modulate the excitatory inputs of pyramidal neurons and are involved in higher cognitive functions. Catecholaminergic fibers form a dense network in which it is difficult to distinguish whether or not target specificity exists. In order to shed some light on this issue, we set out to quantify the catecholaminergic innervation of pyramidal cells in different layers of the human temporal cortex (II, IIIa, IIIb, V and VI). For this purpose, pyramidal cells were labeled in human cortical tissue by injecting them with Lucifer Yellow, and then performed immunocytochemistry for the rate limiting catecholamine synthesizing enzyme tyrosine hydroxylase (TH) to visualize catecholaminergic fibers in the same sections. Injected cells were reconstructed in three dimensions and appositions were quantified (n = 1503) in serial confocal microscopy images of each injected cell (n = 71). We found TH-immunoreactive appositions (TH-ir) in all the pyramidal cells analyzed, in both the apical and basal dendritic regions. In general, the density of TH-ir apposition was greater in layers II, V and VI than in layers IIIa and IIIb. Furthermore, TH-ir appositions showed a regular distribution in almost all dendritic compartments of the apical and basal dendritic arbors across all layers. Hence, it appears that all pyramidal neurons in the human neocortex receive catecholaminergic afferents in a rather regular pattern, independent of the layer in which they are located. Since pyramidal cells located in different layers are involved in different intrinsic and extrinsic circuits, these results suggest that catecholaminergic afferents may modify the function of a larger variety of circuits than previously thought. Thus, this aspect of human cortical organization is likely to have important implications in cortical function.
在人类新皮层中,儿茶酚胺能连接调节锥体神经元的兴奋性输入,并参与更高层次的认知功能。儿茶酚胺能纤维形成一个密集的网络,在这个网络中很难区分是否存在靶标特异性。为了阐明这个问题,我们着手量化人类颞叶皮层不同层(II、IIIa、IIIb、V和VI)中锥体细胞的儿茶酚胺能神经支配。为此,通过向人类皮质组织中的锥体细胞注射荧光黄对其进行标记,然后对限速儿茶酚胺合成酶酪氨酸羟化酶(TH)进行免疫细胞化学,以在同一切片中可视化儿茶酚胺能纤维。对注射的细胞进行三维重建,并在每个注射细胞(n = 71)的系列共聚焦显微镜图像中对突触进行量化(n = 1503)。我们在所有分析的锥体细胞的顶端和基底树突区域都发现了TH免疫反应性突触(TH-ir)。一般来说,TH-ir突触的密度在II、V和VI层比在IIIa和IIIb层更大。此外,TH-ir突触在所有层的顶端和基底树突分支的几乎所有树突区室中都呈现出规则分布。因此,似乎人类新皮层中的所有锥体神经元都以相当规则的模式接受儿茶酚胺能传入纤维,而与它们所在的层无关。由于位于不同层的锥体细胞参与不同的内在和外在回路,这些结果表明儿茶酚胺能传入纤维可能比以前认为的改变更多种类回路的功能。因此,人类皮质组织的这一方面可能对皮质功能具有重要意义。