Kugler P
Department of Anatomy, University of Würzburg, Germany.
Histochem J. 1993 May;25(5):329-38. doi: 10.1007/BF00159497.
The present review focuses on enzymes involved in the metabolism of amino acid neurotransmitters and the microphotometric determinations of their activities in various layers of the rat hippocampus. The enzymes are NAD-linked isocitrate dehydrogenase (NAD-ICDH), glutamate dehydrogenase (GDH), and GABA transaminase (GABAT), all of which are localized in mitochondria. GDH seems to be restricted to astrocytes, whereas NAD-ICDH and GABAT are localized in neurons as well as in astrocytes. NAD-ICDH is an important enzyme of the tricarboxylic acid cycle and may deliver alpha-ketoglutarate for the formation of glutamate and GABA, which serve as neurotransmitters in the hippocampus. GDH catalyses the interconversion of alpha-ketoglutarate and glutamate, whereas GABAT is the important GABA-degrading enzyme and requires alpha-ketoglutarate for its activity. While differing in their cellular distribution and activity levels, NAD-ICDH, GDH and GABAT are significantly correlated in their hippocampal distribution. Furthermore, developmental and pharmacohistochemical studies suggest that the distribution and activity of astrocytic GDH is correlated with amino-acidergic neurotransmission in the hippocampus. The data reported give further evidence for a metabolic relationship between neurons and astrocytes in the turnover and metabolism of glutamate and GABA.
本综述聚焦于参与氨基酸神经递质代谢的酶，以及大鼠海马体各层中这些酶活性的显微光度测定。这些酶包括NAD连接的异柠檬酸脱氢酶（NAD - ICDH）、谷氨酸脱氢酶（GDH）和GABA转氨酶（GABAT），它们均定位于线粒体中。GDH似乎仅存在于星形胶质细胞中，而NAD - ICDH和GABAT则既存在于神经元中，也存在于星形胶质细胞中。NAD - ICDH是三羧酸循环中的一种重要酶，可为谷氨酸和GABA的形成提供α - 酮戊二酸，而谷氨酸和GABA在海马体中作为神经递质发挥作用。GDH催化α - 酮戊二酸和谷氨酸的相互转化，而GABAT是重要的GABA降解酶，其活性需要α - 酮戊二酸。虽然NAD - ICDH、GDH和GABAT在细胞分布和活性水平上存在差异，但它们在海马体中的分布显著相关。此外，发育和药物组织化学研究表明，星形胶质细胞GDH的分布和活性与海马体中的氨基酸能神经传递相关。所报道的数据进一步证明了神经元与星形胶质细胞在谷氨酸和GABA的周转与代谢中存在代谢关系。
