Fujise N, Kosaka T
Department of Anatomy and Neurobiology, Faculty of Medicine, Kyushu University, Fukuoka 812-8285, Japan.
Brain Res. 1999 Jan 23;816(2):500-11. doi: 10.1016/s0006-8993(98)01202-5.
Previously we showed that large multipolar cells immunoreactive for calretinin and subunits 2 and 3 of amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type glutamate receptors (GluR2/3) clustered in the ventral hilus of the mouse dentate gyrus and revealed that they were mossy cells. Although such large calretinin immunoreactive cells were not seen in the dorsal hilus, our Golgi study revealed the presence of mossy cells in the dorsal hilus. As we observed large intensely GluR2/3 immunoreactive cells in the dorsal hilus, we suggested that these calretinin negative but intensely GluR2/3 positive large cells in the dorsal hilus were also mossy cells. In the present study we confirmed this identification with several methods. The extracellular tracer labeling studies revealed that all of 47 mossy cells identified morphologically were intensely GluR2/3 positive but calretinin negative, whereas none of 22 non-mossy hilar neurons were intensely GluR2/3 positive. Electron microscopically most of intensely GluR2/3 positive somata and dendritic processes showed the characteristic ultrastructural features of mossy cells. Furthermore, the fimbria-fornix-hippocampal commissure transection procedures induced the calretinin expression in some of these dorsal GluR2/3 immunoreactive cells. On the basis of these observations, we concluded that the vast majority of intensely GluR2/3 immunoreactive large cells in the mouse dorsal hilus were mossy cells. Then we evaluated the presumed difference in the distribution of mossy cells along the dorsoventral axis by the disector. The numerical density of mossy cells was about 1.4 times larger at the ventral level than at the dorsal level, indicating that the dorsoventral difference in the distribution of mossy cells in the mouse hilus was far smaller than that previously speculated.
此前我们发现，对钙视网膜蛋白以及氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）型谷氨酸受体（GluR2/3）的亚基2和亚基3呈免疫反应的大型多极细胞聚集在小鼠齿状回的腹侧海马伞，并证实它们是苔藓细胞。虽然在背侧海马伞未见此类大型钙视网膜蛋白免疫反应阳性细胞，但我们的高尔基染色研究显示背侧海马伞存在苔藓细胞。由于我们在背侧海马伞观察到大型GluR2/3免疫反应阳性细胞，我们推测背侧海马伞中这些钙视网膜蛋白阴性但GluR2/3强阳性的大型细胞也是苔藓细胞。在本研究中，我们用多种方法证实了这一鉴定。细胞外示踪剂标记研究显示，47个经形态学鉴定的苔藓细胞均为GluR2/3强阳性但钙视网膜蛋白阴性，而22个非苔藓性海马伞神经元均无GluR2/3强阳性。电子显微镜下，大多数GluR2/3强阳性的胞体和树突过程呈现出苔藓细胞特有的超微结构特征。此外，切断穹窿-海马连合的操作诱导了其中一些背侧GluR2/3免疫反应阳性细胞表达钙视网膜蛋白。基于这些观察结果，我们得出结论，小鼠背侧海马伞中绝大多数GluR2/3免疫反应阳性的大型细胞是苔藓细胞。然后我们用分割法评估了苔藓细胞沿背腹轴分布的推测差异。苔藓细胞的数量密度在腹侧水平比背侧水平大约高1.4倍，这表明小鼠海马伞中苔藓细胞分布的背腹差异远小于先前推测的差异。
