Evaluation of drugs acting at glutamate transporters in organotypic hippocampal cultures: new evidence on substrates and blockers in excitotoxicity.
Removal of L-glutamate (Glu) from the synapse is critical to maintain normal transmission and to prevent excitotoxicity, and is performed exclusively by excitatory amino acid transporters (EAATs). We investigated the effects of substrates and blockers of EAATs on extracellular Glu and cellular viability in organotypic cultures of rat hippocampus. Seven-day treatment with a range of drugs (L-trans-pyrrolidine-2,4-dicarboxylate, (2S,4R)-4-methyl-glutamate, (+/-)-threo-3-methylglutamate and DL-threo-beta-benzyloxyaspartate), in the presence of 300 microM added Glu, resulted in increased extracellular Glu and a significant correlation between Glu concentration and cellular injury (as indicated by lactate dehydrogenase release). In contrast, (2S,3s,4R)-2-(carboxycyclopropyl)glycine (L-CCG-III) exerted a novel neuroprotection against this toxicity, and elevations in extracellular Glu were not toxic in the presence of this compound. Similar results were obtained following two-week treatment of cultures without added Glu. Whilst blockade of GLT-1 alone was relatively ineffective in producing excitotoxic injury, heteroexchange of Glu by EAAT substrates may exacerbate excitotoxicity.
O'Shea
Ross D
RD
Department of Pharmacology, Monash University, Vic, Australia.
Fodera
Melissa V
MV
Apricó
Karina
K
Dehnes
Yvette
Y
Danbolt
Niels C
NC
Crawford
Duncan
D
Beart
Philip M
PM
D027322:Amino Acid Transport System X-AG / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D004341:Drug Evaluation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005110:Extracellular Space / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D027322:Amino Acid Transport System X-AG; D018691:Excitatory Amino Acid Antagonists; D018696:Neuroprotective Agents; D018698:Glutamic Acid