Williamson S, Faulkner-Jones B E, Cram D S, Furness J B, Harrison L C
Department of Anatomy and Cell Biology, University of Melbourne, Victoria, Australia.
J Auton Nerv Syst. 1995 Oct 5;55(1-2):18-28. doi: 10.1016/0165-1838(95)00028-v.
gamma-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter, synthesised from glutamate by glutamate decarboxylase (GAD), in the central nervous system. Two forms of GAD, designated GAD 65 and GAD 67, are encoded by distinct genes and have been demonstrated in the mammalian brain. GABA has been postulated to be synthesised in neurons of the enteric nervous system (ENS), but evidence for its role as an enteric neurotransmitter is equivocal. We therefore aimed to determine whether GAD 65 and GAD 67 messenger RNAs (mRNAs) and proteins were expressed in the ileum of mice, rats and guinea pigs. Using an RNase protection assay, both GAD 65 and GAD 67 mRNAs were detected in the rodent small intestine. Antisera specific for GAD 65 or GAD 67, used in immunoblot analyses, revealed GAD 65-like and GAD 67-like immunoreactivity in rat and guinea pig ileum. Anti-GAD 65 antisera detected a major band of 65 kDa. Anti-GAD 67 antisera detected a major band of 55 kDa, which probably represented a breakdown product, and a minor band of 67 kDa. Analysis of immunoblot extracts of rat and guinea pig ileum revealed more GAD 67-like than GAD 65-like immunoreactivity. GAD enzymatic activity was high in the rat and guinea-pig brain, and low in the whole and dissected ileum. These results demonstrate that both GAD 65 and GAD 67 genes are transcribed and translated in the ileum of three rodent species and lend indirect support to the postulate that GABA is synthesised by neurons of the ENS and intestinal endocrine cells.
γ-氨基丁酸（GABA）是一种主要的抑制性神经递质，由谷氨酸脱羧酶（GAD）在中枢神经系统中催化谷氨酸合成。GAD有两种形式，分别命名为GAD 65和GAD 67，由不同基因编码，已在哺乳动物大脑中得到证实。有推测认为GABA在肠神经系统（ENS）的神经元中合成，但关于其作为肠神经递质的作用的证据并不明确。因此，我们旨在确定GAD 65和GAD 67信使核糖核酸（mRNA）及蛋白质是否在小鼠、大鼠和豚鼠的回肠中表达。使用核糖核酸酶保护分析，在啮齿动物小肠中检测到了GAD 65和GAD 67的mRNA。免疫印迹分析中使用的针对GAD 65或GAD 67的抗血清，在大鼠和豚鼠回肠中显示出GAD 65样和GAD 67样免疫反应性。抗GAD 65抗血清检测到一条65 kDa的主要条带。抗GAD 67抗血清检测到一条55 kDa的主要条带（可能代表一种降解产物）和一条67 kDa的次要条带。对大鼠和豚鼠回肠免疫印迹提取物的分析显示，GAD 67样免疫反应性比GAD 65样免疫反应性更强。GAD酶活性在大鼠和豚鼠大脑中较高，而在整个回肠和分离的回肠中较低。这些结果表明，GAD 65和GAD 67基因在三种啮齿动物的回肠中均被转录和翻译，间接支持了GABA由ENS神经元和肠内分泌细胞合成的推测。
