Details

Autor(en) / Beteiligte

• Blitzblau, Rachel
• Gupta, Shalini
• Djali, Sina
• Robinson, Michael B.
• Rosenberg, Paul A.

Titel

The Glutamate Transport Inhibitor L-trans-pyrrolidine-2,4-dicarboxylate Indirectly Evokes NMDA Receptor Mediated Neurotoxicity in Rat Cortical Cultures

Ist Teil von

• The European journal of neuroscience, 1996-09, Vol.8 (9), p.1840-1852

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

1996

Quelle

MEDLINE

Beschreibungen/Notizen

• Because of the well‐documented importance of glutamate uptake in protecting neurons against glutamate toxicity, we were interested in testing the effects of L‐trans‐pyrrolidine‐2,4‐ dicarboxylate (PDC) on rat cortical cultures. This compound is a substrate for glutamate transporters and is a potent glutamate transport inhibitor that does not interact significantly with glutamate receptors. Using a 30 min exposure, and assessing neuronal survival after 20‐24 h, PDC was neurotoxic in conventional astrocyte‐rich cortical cultures, with an EC50 in these cultures of 320 ± 157 μM. In astrocyte‐poor cultures, an EC50 for PDC of 50 ± 5 μM was determined. The neurotoxicity of PDC in both astrocyte‐rich and astrocyte‐poor cultures was blocked by the NMDA antagonist MK‐801, but not by the non‐NMDA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX). We tested the possibility that the neurotoxicity of PDC might be due to release of excitatory amino acids using several approaches. After pre‐loading cells with the non‐metabolizable analogue of glutamate, [3H]‐D‐aspartate, first we demonstrated that PDC caused significant efflux of [3H]‐D‐aspartate. This effect of PDC was dependent upon extracellular sodium. In contrast with glutamate neurotoxicity, PDC neurotoxicity was inhibited by removal of extracellular sodium. In the presence of 1 mM PDC, sodium caused neurotoxicity with an EC50 of 18 ± 7.6 mM. Tetrodotoxin had no effect on either PDC neurotoxicity or on PDC‐evoked [3H]‐D‐aspartate release. PDC‐evoked release of [3H]‐D‐aspartate was demonstrable in astrocyte cultures with no neurons present. PDC also evoked release of endogenous glutamate. Finally, the neurotoxicity of PDC was blocked by coincubation with glutamate‐pyruvate transaminase plus pyruvate to degrade extracellular glutamate. These results demonstrate the neurotoxicity of PDC, and suggest that the mechanism of this toxicity is the glutamate transporter‐dependent accumulation of glutamate in the extracellular space.