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Stimulation of γ‐[ 3 H]Aminobutyric Acid Release from Cultured Mouse Cerebral Cortex Neurons by Sulphur‐Containing Excitatory Amino Acid Transmitter Candidates: Receptor Activation Mediates Two Distinct Mechanisms of Release
Author(s) -
Dunlop John,
Grieve Angus,
Schousboe Arne,
Griffiths Roger
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08305.x
Subject(s) - nmda receptor , excitatory postsynaptic potential , depolarization , glutamate receptor , chemistry , agonist , biophysics , 2 amino 5 phosphonovalerate , glutamatergic , stimulation , calcium , biochemistry , receptor , biology , endocrinology , excitatory amino acid antagonists , organic chemistry
In primary cultures of mouse cerebral cortex neurons, sulphur‐containing excitatory amino acids (SAAs; namely, L‐cysteine sulphinate, L‐cysteate, L‐homocysteine sulphinate, L‐homocysteate, S ‐sulphocysteine) at concentrations ranging from 0.1 μ M to 1 m M evoked a saturable release of ‐γ‐[ 3 H] aminobutyric acid ([ 3 H] GABA) in the absence of any other depolarizing agent. All SAAs exhibited essentially similar potency (EC 50 ), 100–150 n M ) in releasing [ 3 H] GABA although a variable profile of maximal stimulatory effect was observed when compared with basal release. The intracellular accumulation of the lipophilic cation, [ 3 H] tetraphenylphosphonium, was significantly reduced in the presence of all SAAs, thus verifying a depolarization of the neuronal plasma membrane. SAA‐stimulated release of [ 3 H] GABA was shown to comprise two distinct components, calcium‐dependent and calcium‐independent, which occur after activation of N ‐methyl‐B‐aspartate (NMDA) and non‐NMDA receptors. Thus, all SAA‐evoked responses were antagonized by the selective, competitive NMDA‐receptor antagonist, 3‐[(±)‐2‐carboxypiperazin‐4‐yl] propyl‐1‐phosphonic acid (IC 50 range, >50 μ M ) and the non‐NMDA‐receptor antagonist, 6, 7‐dinitroquinoxalinedione (IC 50 range, 5–50 n M ). Removal of magnesium ions from the superfusion medium caused a significant potentiation of SAA‐evoked responses without having any effect on basal levels of [ 3 H] GABA efflux, a result consistent with an involvement of NMDA‐receptor activation. Calcium‐independent release (i.e., that release remaining in the presence of 1 m M cobalt ions) was a distinct component but of smaller magnitude. Using 500 pM excitatory amino acid agonist concentrations, this component of release was (1) markedly attenuated by 15 fiM SKF‐89976‐A, a non‐ transportable inhibitor of theGABA carrier, and (2) abolished when choline ions replaced sodium ions in the superfusion medium or when in the presence of excitatory amino acid receptor antagonists. These observations are dearly consistent with a receptor‐mediated, depolarization‐induced reversal of the GABA carrier.