文章基本信息

标题：High K+-induced Increase in Extracellular Glutamate in Zinc Deficiency and Endogenous Zinc Action
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作者：Atsushi Takeda ; Hiromasa Itoh ; Haruna Tamano 等
期刊名称：Journal of Health Science
印刷版ISSN：1344-9702
电子版ISSN：1347-5207
出版年度：2009
卷号：55
期号：3
页码：405-412
DOI：10.1248/jhs.55.405
出版社：The Pharmaceutical Society of Japan
摘要：To understand the physiological significance of endogenous zinc release under excess excitation in the hippocampus, in the present study, high K⁺-induced increase in extracellular glutamate and endogenous zinc action against its increase were examined in young rats fed a zinc-deficient diet for 2 weeks. When the ventral hippocampus was perfused by 100mM KCl, the extracellular concentration of glutamate was more increased in zinc-deficient rats than the control rats. Calcium orange signal in mossy fiber boutons was more increased in slices from zinc-deficient rats after delivery of tetanic stimuli (100 Hz, 5 sec) to the dentate granule cell layer. The decrease in FM4-64 signal, which is a measurement of exocytosis, in mossy fiber boutons was also enhanced in slices from zinc-deficient rats. These results suggest that the abnormal increase in extracellular glutamate in the hippocampus induced with high K⁺ in zinc deficiency is due to the enhancement of exocytosis associated with affected Ca²⁺ mobilization. The expression of GLT-1, a glial glutamate transporter, in the hippocampus was higher in zinc-deficient rats, suggesting that GLT-1 protein increased serves to maintain the basal concentration of extracellular glutamate, which was not different between the control and zinc-deficient rats. On the other hand, the increase in extracellular glutamate concentration induced with high K⁺ was enhanced in the presence of 1 mM CaEDTA, a membrane-impermeable zinc chelator, in both the control and zinc-deficient rats. It is likely that zinc released from glutamatergic neurons serves to suppress glutamate release under excess excitation in the hippocampus.
关键词：zinc;neuromodulator;hippocampus;glutamate;exocytosis;in vivo microdialysis