Pow D V, Robinson S R
Department of Physiology and Pharmacology, University of Queensland, Brisbane, Australia.
Neuroscience. 1994 May;60(2):355-66. doi: 10.1016/0306-4522(94)90249-6.
Glutamate is the most abundant excitatory neurotransmitter in the vertebrate central nervous system. It is widely assumed that neurons using this transmitter derive it from several sources: (i) synthesizing it themselves from alpha-ketoglutarate or aspartate, (ii) synthesize it from glial-derived glutamine, or (iii) take up glutamate from the extracellular space. By use of immunocytochemistry we show that glutamate is abundant in the retinal ganglion and bipolar cells of the rabbit, but that immunoreactivity for glutamate in these neurons is reduced below immunocytochemical detection limits after the specific inhibition of glutamine synthesis in glial cells by D,L-methionine D,L-sulphoximine. GABA immunoreactivity in retinal amacrine cells was also reduced after inhibition of glutamine synthetase but the patterns and densities of immunoreactivity for taurine and glycine were unaffected. Therefore, this experimental paradigm does not induce generalized metabolic changes in neurons or glia. This study demonstrates that some glutamatergic neurons are dependent on the synthetic processes in glia for their neurotransmitter content.
谷氨酸是脊椎动物中枢神经系统中含量最为丰富的兴奋性神经递质。人们普遍认为，使用这种递质的神经元可从多种来源获取谷氨酸：（i）由α-酮戊二酸或天冬氨酸自身合成；（ii）从神经胶质细胞衍生的谷氨酰胺合成；或（iii）从细胞外空间摄取谷氨酸。通过免疫细胞化学方法，我们发现谷氨酸在兔视网膜神经节细胞和双极细胞中含量丰富，但在用D，L-蛋氨酸D，L-亚砜胺特异性抑制神经胶质细胞中的谷氨酰胺合成后，这些神经元中谷氨酸的免疫反应性降低至免疫细胞化学检测限以下。抑制谷氨酰胺合成酶后，视网膜无长突细胞中的GABA免疫反应性也降低，但牛磺酸和甘氨酸的免疫反应性模式和密度未受影响。因此，该实验范式不会在神经元或神经胶质细胞中诱导普遍的代谢变化。本研究表明，一些谷氨酸能神经元的神经递质含量依赖于神经胶质细胞中的合成过程。
