Effectors of D-[3H]aspartate release from rat cerebellum.
The effect of aminooxyacetic acid (AOAA), NH4+, phenylsuccinate (Phs), ketone bodies (KB) and glutamine (Gln), that might interfere with the biosynthesis of neurotransmitter glutamate on the K(+)-evoked Ca(2+)-dependent release of D-[3H]aspartate from rat cerebellar slices was studied. Therefore slices were preincubated in a Krebs-Ringer-bicarbonate-glucose (KR) buffer, loaded with D-[3H]aspartate and superfused in the presence of Ca2+ or when Ca2+ was replaced by Mg2+ or in some cases by EGTA. AOAA, NH4+ and Phs increase the K(+)-evoked Ca(2+)-dependent release of radioactivity by 30%, 68% and 188% compared to the control respectively indicating that these agents are inhibitors of the K(+)-evoked Ca(2+)-dependent release of glutamate. KB and Gln had no effect on the Ca(2+)-dependent release of radioactivity. AOAA, NH4+, Phs and KB but not Gln increase the total release of radioactivity by 43%, 69%, 139%, and 37% respectively. AOAA, NH4+ and KB but not Phs or Gln increase the Ca(2+)-independent release (Mg2+ replacing Ca2+) of radioactivity by 71%, 71% and 108% respectively. The present results indicate that in the cerebellum: 1) Neurotransmitter glutamate is mostly synthesized through the phosphate activated glutaminase (PAG) reaction 2) It is further supported that glutamate released in Ca(2+)-dependent manner before entering its pool in the cytosol has to move into the mitochondrial matrix.
Svarna
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R
Laboratory of Biological Chemistry, Medical School, University of Athens, Greece.
Georgopoulos
A
A
Palaiologos
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G
D000625:Aminooxyacetic Acid / Q000494:pharmacology*; D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism*; D005973:Glutamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007657:Ketone Bodies / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013386:Succinates / Q000494:pharmacology*; D014316:Tritium
D007657:Ketone Bodies; D013386:Succinates; D005973:Glutamine; D014316:Tritium; D000625:Aminooxyacetic Acid; D001224:Aspartic Acid; C017625:2-phenylsuccinate; D000641:Ammonia; D011188:Potassium; D002118:Calcium