Uptake and metabolism of glutamate at non-synaptic regions of crayfish central nerve fibers: implications for axon-glia signaling.
Uptake and metabolism of glutamate at non-synaptic regions of crayfish central nerve fibers: implications for axon-glia signaling.
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小龙虾中枢神经纤维非突触区域谷氨酸的摄取和代谢：对轴突神经胶质信号传导的影响。
DOI：
10.1016/s0306-4522(00)00054-3
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发表时间：
2000
期刊：
影响因子：
3.3
通讯作者：
Grossfeld,RM
中科院分区：
文献类型：
--
作者：
Kane,LS;Buttram,JG;Urazaev,AK;Lieberman,EM;Grossfeld,RM
在小龙虾和鱿鱼的巨大神经纤维中，谷氨酸似乎是轴突神经胶质细胞的信号传导剂。我们已经研究了谷氨酸的运输和代谢的小龙虾中枢神经纤维，以确定可能的机制，谷氨酸可以subserve这种非突触信号功能。脱鞘的头胸神经束的放射性标记的L-谷氨酸的积累是温度和Na+依赖性的，与时间呈线性至少8小时，饱和约0.5- 1 mM L-谷氨酸。大多数累积的放射性示踪剂与轴突周围胶质鞘相关，并保持为谷氨酸。已知在无脊椎动物外周神经或哺乳动物脑切片或细胞培养物中阻断谷氨酸转运的化合物对小龙虾中枢神经纤维也有效。当存在1 mM对氯汞苯磺酸盐时，组织放射性示踪剂水平仅为对照水平的3%，当存在l-半胱氨酸、l-半胱氨酸亚磺酸盐、l-天冬氨酸盐、d-天冬氨酸盐或dl-苏型-β-羟基天冬氨酸盐时，组织放射性示踪剂水平分别为对照水平的13%、20%、26%、38%和42%。l-谷氨酰胺、GABA、N-甲基-dl-门冬氨酸、α-氨基己二酸和d-谷氨酸对组织示踪剂积累没有抑制作用。放射性标记的d-天冬氨酸是放射性标记的l-谷氨酸的等效非代谢替代品。d-天门冬氨酸、对氯汞苯磺酸和GABA对离体内侧巨神经纤维的作用相当。这些研究表明，L-谷氨酸主要由小龙虾中枢神经纤维的轴周神经胶质细胞通过低亲和力、可饱和、Na+依赖性运输系统摄取，并主要以该形式被纤维保留。我们的研究结果表明，胶质细胞不仅是目标的谷氨酸信号释放的非突触区域的小龙虾内侧巨轴突在高频刺激，但他们也是其失活的主要网站。
In crayfish and squid giant nerve fibers, glutamate appears to be an axon–glia signaling agent. We have investigated glutamate transport and metabolism by crayfish central nerve fibers in order to identify possible mechanisms by which glutamate could subserve this non-synaptic signaling function. Accumulation of radiolabeled l-glutamate by desheathed cephalothoracic nerve bundles was temperature and Na+dependent, linear with time for at least 8h and saturable at about 0.5–1mM l-glutamate. Most accumulated radiotracer was associated with the periaxonal glial sheath and remained as glutamate. Compounds known to block glutamate transport in invertebrate peripheral nerves or mammalian brain slices or cell cultures were also effective on crayfish central nerve fibers. Tissue radiotracer levels were only 3% of control levels when 1mM p-chloromercuriphenylsulfonate was present, and 13%, 20%, 26%, 38% and 42% of control levels, respectively, when l-cysteate, l-cysteine sulfinate, l-aspartate, d-aspartate or dl-threo-β-hydroxyaspartate was present. l-Glutamine, GABA, N-methyl-dl-aspartate, α-aminoadipate and d-glutamate were without inhibitory effect on tissue tracer accumulation. Radiolabeled d-aspartate was an equivalent non-metabolized substitute for radiolabeled l-glutamate. d-Aspartate, p-chloromercuriphenylsulfonate and GABA had comparable effects on isolated medial giant nerve fibers. These studies indicate that l-glutamate is taken up primarily by the periaxonal glia of crayfish central nerve fibers by a low-affinity, saturable, Na+-dependent transport system and is retained by the fibers primarily in that form. Our results suggest that the glia are not only the target of the glutamate signal released from non-synaptic regions of the crayfish medial giant axon during high-frequency stimulation, but that they are also the primary site of its inactivation.