Disciplina de Neurologia Experimental, Universidade Federal de São Paulo/Escola Paulista de Medicina, Rua Botucatu 862, 04023-900 São Paulo, Brasil.
Neuroscience. 2010 Sep 1;169(3):965-73. doi: 10.1016/j.neuroscience.2010.05.079. Epub 2010 Jun 11.
Previous data of our laboratory have shown that the Amazonian rodents Proechimys do not present spontaneous seizures in different models of epilepsy, suggesting endogenous inhibitory mechanisms. Here, we describe a remarkably different Proechimy's cytoarchitecture organization of the hippocampal cornu Ammonis 2 (CA2) subfield. We identified a very distinctive Proechimy's CA2 sector exhibiting disorganized cell presentation of the pyramidal layer and atypical dispersion of the pyramidal-like cells to the stratum oriens, strongly contrasting to the densely packed CA2 cells in the Wistar rats. Studies showed that CA2 is the only cornu ammonis (CA) subfield resistant to the extensive pyramidal neural loss in mesial temporal lobe epilepsy (MTLE) associated to hippocampal sclerosis. Thus, in order to investigate this region, we used Nissl and Timm staining, stereological approach to count neurons and immunohistochemistry to neuronal nuclei (NeuN), parvalbumin (PV), calbindin (CB) and calretinin (CR). We did not notice statistically significant differences in the total number of neurons of the CA2 region between Proechimys and Wistar. However, Proechimys rodents presented higher CA2 volume than Wistar rats. Furthermore, no significant difference in the optical density of parvalbumin-immunoreactivity was found between subject groups. On the other hand, Proechimys presented significant higher density of calbindin and calretinin-immunoreactivity when compared to Wistar rats. In this context, this unique CA2 subfield seen in Proechimys opens up a new set of possibilities to explore the contribution of CA2 neurons in normal and pathological brain circuits.
我们实验室之前的数据表明，亚马逊啮齿动物 Proechimys 在不同的癫痫模型中不会出现自发性癫痫发作，这表明存在内源性抑制机制。在这里，我们描述了一个非常不同的 Proechimy 的海马角 2（CA2）亚区细胞结构组织。我们发现了一个非常独特的 Proechimy 的 CA2 区域，其锥体层的细胞呈现出无序排列，锥体样细胞的典型分散到腔隙，与 Wistar 大鼠中密集排列的 CA2 细胞形成强烈对比。研究表明，CA2 是唯一的角状回（CA）亚区，能够抵抗与海马硬化相关的内侧颞叶癫痫（MTLE）中广泛的锥体神经丢失。因此，为了研究这个区域，我们使用了尼氏染色和蒂姆染色、神经元计数的立体学方法以及神经元核（NeuN）、副甲状腺蛋白（PV）、钙结合蛋白（CB）和钙结合蛋白（CR）的免疫组织化学染色。我们没有注意到 Proechimys 和 Wistar 之间 CA2 区域神经元总数存在统计学上的显著差异。然而，Proechimys 啮齿动物的 CA2 体积比 Wistar 大鼠大。此外，在两个实验组之间，副甲状腺蛋白免疫反应的光密度没有显著差异。另一方面，与 Wistar 大鼠相比，Proechimys 呈现出显著更高的钙结合蛋白和钙结合蛋白免疫反应密度。在这种情况下，Proechimys 中看到的这种独特的 CA2 亚区为探索 CA2 神经元在正常和病理大脑回路中的贡献开辟了一系列新的可能性。
