首页 | 本学科首页   官方微博 | 高级检索  
   检索      


l-Aspartate as an amino acid neurotransmitter: mechanisms of the depolarization-induced release from cerebrocortical synaptosomes
Authors:Anna Cavallero  Antonella Marte  Ernesto Fedele†
Institution:Department of Experimental Medicine, Section of Pharmacology and Toxicology, University of Genoa, Genoa, Italy;
Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
Abstract:The role of l -aspartate as a classical neurotransmitter of the CNS has been a matter of great debate. In this study, we have characterized the main mechanisms of its depolarization-induced release from rat purified cerebrocortical synaptosomes in superfusion and compared them with those of the well-known excitatory neurotransmitter l -glutamate. High KCl and 4-aminopyridine were used as depolarizing agents. At 15 mM KCl, the overflows of both transmitters were almost completely dependent on external Ca2+. At 35 and 50 mM KCl, the overflows of l -aspartate, but not those of l -glutamate, became sensitive to dl -threo-β-benzyloxyaspartic acid ( dl -TBOA), an excitatory amino acid transporter inhibitor. In the presence of dl -TBOA, the 50 mM KCl-evoked release of l -aspartate was still largely external Ca2+-dependent. The dl -TBOA insensitive, external Ca2+-independent component of the 50 mM KCl-evoked overflows of l -aspartate and l -glutamate was significantly decreased by the mitochondrial Na+/Ca2+ exchanger blocker CGP 37157. The Ca2+-dependent, KCl-evoked overflows of l -aspartate and l -glutamate were diminished by botulinum neurotoxin C, although to a significantly different extent. The 4-aminopyridine-induced l -aspartate and l -glutamate release was completely external Ca2+-dependent and never affected by dl -TBOA. Superimposable results have been obtained by pre-labeling synaptosomes with 3H] d -aspartate and 3H] l -glutamate. Therefore, our data showing that l -aspartate is released from nerve terminals by calcium-dependent, exocytotic mechanisms support the neurotransmitter role of this amino acid.
Keywords:aspartate  cerebral cortex  exocytosis  glutamate  release  synaptosomes
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号