Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Hippocampus. 2010 Jul;20(7):829-40. doi: 10.1002/hipo.20685.
Recent studies have emphasized functional dissociations between dorsal and ventral hippocampus in learning, emotion, and affect. A rigorous quantitative analysis concerning lamellar cytoarchitecture would be important for promoting further research on the regional differentiation of the hippocampus. Here, we stereologically estimated the numerical densities (NDs) of glutamatergic principal neurons in the mouse hippocampus and encountered the significant differences along the dorsoventral axis. In the CA1 region, the NDs of CA1 pyramidal neurons were almost three times higher at the dorsal level (447.5 x 10(3)/mm(3)) than at the ventral level (180.5 x 10(3)/mm(3)); meanwhile, along the transverse axis, the NDs were significantly higher in the proximal portion than in the distal portion both at the dorsal and ventral levels. An EF-hand calcium-binding protein, calbindin D28K, was expressed in approximately 45% of CA1 pyramidal neurons both at the dorsal and ventral level. In the CA3 region, there were no significant differences in the NDs along the dorsoventral and transverse axes (dorsal, 165.2 x 10(3)/mm(3); ventral, 172.4 x 10(3)/mm(3)). In the dentate gyrus (DG), the NDs of granule cells were significantly higher at the dorsal level (916.7 x 10(3)/mm(3)) than at the ventral level (788.9 x 10(3)/mm(3)). The significant differences were observed only in the suprapyramidal blade, but not in the infrapyramidal blade. Then, we calculated the total neuron numbers contained in a 300-microm-thick hypothetical transverse slice of the hippocampus and found that the ratios of GABAergic to glutamatergic neuron numbers were two to three times higher in the ventral slice than in the dorsal slice. The ratios of numbers of eight GABAergic neuron subtypes to principal cells indicate structural dissociations in the neural network between dorsal and ventral slices. These findings provide an essential quantitative basis for elucidating mechanisms of distinct neural circuits underlying various hippocampal functions.
最近的研究强调了背侧和腹侧海马在学习、情绪和情感中的功能分离。对于促进海马区域性分化的进一步研究，关于层状细胞结构的严格定量分析将是重要的。在这里，我们通过体视学方法估计了小鼠海马中的谷氨酸能主神经元的数量密度（NDs），并在背腹轴上发现了显著差异。在 CA1 区，背侧水平（447.5×10^3/mm^3）的 CA1 锥体神经元 ND 几乎是腹侧水平（180.5×10^3/mm^3）的三倍；同时，在背腹水平，沿横向轴，近侧部的 ND 明显高于远侧部。EF 手钙结合蛋白钙结合蛋白 D28K 在背侧和腹侧水平的大约 45%的 CA1 锥体神经元中表达。在 CA3 区，背腹轴和横向轴上的 ND 没有差异（背侧，165.2×10^3/mm^3；腹侧，172.4×10^3/mm^3）。在齿状回（DG）中，背侧水平的颗粒细胞 ND（916.7×10^3/mm^3）明显高于腹侧水平（788.9×10^3/mm^3）。这种差异仅在锥体细胞层中观察到，而在锥体细胞下层中则没有观察到。然后，我们计算了海马体 300μm 厚的假设横切片中包含的总神经元数量，并发现腹侧切片中 GABA 能神经元与谷氨酸能神经元数量的比例是背侧切片的两到三倍。八种 GABA 能神经元亚型与主细胞数量的比值表明了背侧和腹侧切片之间神经网络的结构分离。这些发现为阐明不同海马功能背后的不同神经回路机制提供了必要的定量基础。
