Kaneko T, Mizuno N
Department of Anatomy (1st Division), Faculty of Medicine, Kyoto University, Japan.
J Comp Neurol. 1988 Jan 22;267(4):590-602. doi: 10.1002/cne.902670411.
In an attempt to identify glutamatergic neurons, the cerebral cortex and thalamus of the rat were examined immunohistochemically by using a monoclonal antibody against phosphate-activated glutaminase (PAG), a major synthetic enzyme of transmitter glutamate in the central nervous system. In both the neocortex and mesocortex, pyramidal cells in layers V and VI showed intense PAG-like immunoreactivity (PAG-LI), whereas neuronal cell bodies in layers I-IV showed weak PAG-LI. At the deep border of layer VI, neurons with horizontally elongated cell bodies showed PAG-LI. In the pyriform and entorhinal cortices, neurons with intense to moderate PAG-LI were seen in layer II as well as in the deeper layers. In the hippocampal formation, pyramidal cells in CA1, CA2, and CA3 and polymorphic cells in CA4 showed PAG-LI; PAG-LI was most intense in pyramidal cells of CA3. Fine granules with weak PAG-LI were also seen on and/or within the cell bodies of granule cells in the dentate gyrus. In the thalamus, neurons with PAG-LI were distributed in all nuclei, although regional differences were observed in the distribution pattern of neurons with PAG-LI and in the intensity of PAG-LI in individual neurons. The largest neurons in each thalamic nucleus showed intense PAG-LI; these were considered to be projection neurons. In addition to perikaryal labeling, many fine, PAG-like immunoreactive granules were distributed in the neuropil of both the cerebral cortex and thalamic nuclei. Some of these fine granules with PAG-LI in the neuropil were assumed to represent fiber terminals with PAG-LI, because the distribution pattern of the deposits in the primary somatosensory and primary visual cortices resembled that of thalamocortical fiber terminals. Glutamate is rather ubiquitous in the mammalian central nervous system, and it is still debatable whether the monoclonal antibody to PAG from brain mitochondria can distinguish transmitter-related glutaminase from the other metabolism-related ones. In the present study, however, large neurons in the thalamic nuclei, as well as pyramidal neurons in the cerebral cortex, showed PAG-LI most intensely, supporting the assumption that projection neurons of the cerebral cortex and thalamus are primarily glutamatergic.
为了识别谷氨酸能神经元，利用抗磷酸激活谷氨酰胺酶（PAG）的单克隆抗体，对大鼠的大脑皮层和丘脑进行了免疫组织化学检查，PAG是中枢神经系统中递质谷氨酸的主要合成酶。在新皮层和中间皮层中，V层和VI层的锥体细胞显示出强烈的PAG样免疫反应性（PAG-LI），而I-IV层的神经元细胞体显示出较弱的PAG-LI。在VI层的深部边界，具有水平伸长细胞体的神经元显示出PAG-LI。在梨状皮层和内嗅皮层中，II层以及较深层中可见具有强烈至中度PAG-LI的神经元。在海马结构中，CA1、CA2和CA3区的锥体细胞以及CA4区的多形细胞显示出PAG-LI；CA3区的锥体细胞中PAG-LI最为强烈。在齿状回颗粒细胞的细胞体上和/或细胞体内也可见到具有弱PAG-LI的细颗粒。在丘脑中，具有PAG-LI的神经元分布于所有核团，尽管在具有PAG-LI的神经元分布模式以及单个神经元中PAG-LI的强度方面存在区域差异。每个丘脑核团中最大的神经元显示出强烈的PAG-LI；这些被认为是投射神经元。除了胞体标记外，许多细小的、PAG样免疫反应性颗粒分布于大脑皮层和丘脑核团的神经毡中。神经毡中一些具有PAG-LI的细颗粒被认为代表具有PAG-LI的纤维终末，因为初级体感皮层和初级视觉皮层中沉积物的分布模式类似于丘脑皮质纤维终末的分布模式。谷氨酸在哺乳动物中枢神经系统中相当普遍，来自脑线粒体的PAG单克隆抗体能否区分与递质相关的谷氨酰胺酶和其他与代谢相关的谷氨酰胺酶仍存在争议。然而，在本研究中，丘脑核团中的大神经元以及大脑皮层中的锥体细胞显示出最强烈的PAG-LI，支持了大脑皮层和丘脑的投射神经元主要是谷氨酸能的这一假设。
