Peterson D A, Lucidi-Phillipi C A, Murphy D P, Ray J, Gage F H
Laboratory of Genetics, Salk Institute, La Jolla, California 92037, USA.
J Neurosci. 1996 Feb 1;16(3):886-98. doi: 10.1523/JNEUROSCI.16-03-00886.1996.
The entorhinal cortex is a major relay between the hippocampus and other cortical and subcortical regions. Glutamatergic axons from layer II neurons form the entorhinal cortical projection to the hippocampus via the perforant pathway. We have demonstrated previously that lesion of the perforant pathway causes the death of approximately 30% of entorhinal layer II (ECL2) neurons. To elucidate mechanisms contributing to neuronal death and to investigate strategies preventing it, we identified the phenotype of the vulnerable neuronal population. Sections were immunolabeled with antibodies to the neuronal markers NeuN, glutamate, and calbindin-D28k, and to receptors for fibroblast growth factor-2 (FGFR1) and NMDA (NMDAR1) and were examined using confocal microscopy. Calbindin immunoreactivity was strikingly lamina-specific to ECL2, where one-third of all ECL2 neurons were calbindin-positive. Localization of glutamate revealed that half of the glutamatergic ECL2 neurons coexpressed calbindin. Quantification using unbiased stereology at 9 weeks after lesion of the perforant pathway revealed that the only ECL2 neuronal population that experienced a significant (70%) loss (20% of the total) was the population of glutamatergic ECL2 neurons that did not coexpress calbindin. All ECL2 neurons expressed FGFR1; therefore, we tested the role of FGF-2 in the survival of glutamatergic ECL2 neurons. We grafted fibroblasts genetically engineered to express nerve growth factor or FGF-2 and found that only FGF-2 grafts prevented loss of the vulnerable glutamatergic/calbindin-negative neurons. We present a hypothesis for the selective vulnerability of these glutamatergic/calbindin-negative ECL2 neurons and address the role of FGF-2 in neuronal rescue.
内嗅皮层是海马体与其他皮层及皮层下区域之间的主要中继站。来自II层神经元的谷氨酸能轴突通过穿通通路形成内嗅皮层至海马体的投射。我们之前已经证明，穿通通路损伤会导致约30%的内嗅II层（ECL2）神经元死亡。为了阐明导致神经元死亡的机制并研究预防神经元死亡的策略，我们确定了易损神经元群体的表型。切片用针对神经元标志物NeuN、谷氨酸和钙结合蛋白-D28k的抗体，以及针对成纤维细胞生长因子-2（FGFR1）和NMDA（NMDAR1）受体的抗体进行免疫标记，并使用共聚焦显微镜进行检查。钙结合蛋白免疫反应性在内嗅II层具有显著的层特异性，所有ECL2神经元中有三分之一是钙结合蛋白阳性。谷氨酸的定位显示，一半的谷氨酸能ECL2神经元共表达钙结合蛋白。在穿通通路损伤9周后使用无偏立体学方法进行定量分析，结果显示唯一经历显著（70%）损失（占总数的20%）的ECL2神经元群体是不共表达钙结合蛋白的谷氨酸能ECL2神经元群体。所有ECL2神经元均表达FGFR1；因此，我们测试了FGF-2在谷氨酸能ECL2神经元存活中的作用。我们移植了经过基因工程改造以表达神经生长因子或FGF-2的成纤维细胞，发现只有FGF-2移植能够防止易损的谷氨酸能/钙结合蛋白阴性神经元的损失。我们提出了关于这些谷氨酸能/钙结合蛋白阴性ECL2神经元选择性易损性的假说，并探讨了FGF-2在神经元拯救中的作用。
