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Amino acid neurotransmitters in the CNS
Author(s) -
Erecińska Maria,
Troeger Melody B.
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)81231-5
Subject(s) - amino acid , chemistry , biochemistry , neuroscience , biology
D‐Aspartate exchange, defined as amino acid‐stimulated D‐[ 3 H]aspartate efflux, was investigated in a preparation of rat brain synaptosomes. The efflux of radiolabelled D‐aspartate was found to be enhanced by micromolar concentrations of externally added D‐ and L‐aspartate, L‐glutamate, L‐cysteate.and L‐cysteinesulphinate. The stimulation of release by external amino acids followed Michaelis‐Menten kinetics; the apparent K m values (in μM) were: 14.65 ± 0.98 for D‐aspartate; 8.00±1.5 for L‐aspartate; 22.31 ± 1.62 for L‐glutamate; 6.76 ± 0.3 for L‐cysteate and 7.89± 1.23 for L‐cysteinesulphinate. The ν max values for efflux were 2.16–4.06 per mg protein. The exchange process was found to require external NaCl but was very little affected by increase in the external [K + ]. The demonstration of exchange as a part of the transport process provides support for the suggestion that in synaptosomal preparations a substantial portion of influx and efflux of amino acid neurotransmitters occurs via a reversible membrane carrier.