Title: Domoic acid neurotoxicity in cultured cerebellar granule neurons is mediated predominantly by NMDA receptors that are activated as a consequence of excitatory amino acid release.

Authors: Berman, F W; Murray, T F

Published In J Neurochem, (1997 Aug)

Abstract: The participation of NMDA and non-NMDA receptors in domoic acid-induced neurotoxicity was investigated in cultured rat cerebellar granule cells (CGCs). Neurons were exposed to 300 microM L-glutamate or 10 microM domoate for 2 h in physiologic buffer at 22 degrees C followed by a 22-h incubation in 37 degrees C conditioned growth media. Excitotoxic injury was monitored as a function of time by measurement of lactate dehydrogenase (LDH) activity in both the exposure buffer and the conditioned media. Glutamate and domoate evoked, respectively, 50 and 65% of the total 24-h increment in LDH efflux after 2 h. Hyperosmolar conditions prevented this early response but did not significantly alter the extent of neuronal injury observed at 24 h. The competitive NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid and the non-NMDA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline (NBQX) reduced glutamate-induced LDH efflux totals by 73 and 27%, respectively, whereas, together, these glutamate receptor antagonists completely prevented neuronal injury. Domoate toxicity was reduced 65-77% when CGCs were treated with competitive and noncompetitive NMDA receptor antagonists. Unlike the effect on glutamate toxicity, NBQX completely prevented domoate-mediated injury. HPLC analysis of the exposure buffer revealed that domoate stimulates the release of excitatory amino acids (EAAs) and adenosine from neurons. Domoate-stimulated EAA release occurred almost exclusively through mechanisms related to cell swelling and reversal of the glutamate transporter. Thus, whereas glutamate-induced injury is mediated primarily through NMDA receptors, the full extent of neurodegeneration is produced by the coactivation of both NMDA and non-NMDA receptors. Domoate-induced neuronal injury is also mediated primarily through NMDA receptors, which are activated secondarily as a consequence of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptor-mediated stimulation of EAA efflux.

PubMed ID: 9231729

MeSH Terms: Animals; Cells, Cultured; Cerebellum/drug effects*; Cerebellum/metabolism; Culture Media, Conditioned; Dizocilpine Maleate/pharmacology; Excitatory Amino Acid Antagonists/pharmacology; Excitatory Amino Acids/metabolism*; Glutamic Acid/toxicity; Kainic Acid/analogs & derivatives*; Kainic Acid/toxicity; Kinetics; L-Lactate Dehydrogenase/metabolism; Neurons/drug effects*; Neurons/metabolism; Neurotoxins*; Quinoxalines/pharmacology; Rats; Rats, Sprague-Dawley; Receptors, AMPA/physiology; Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors; Receptors, N-Methyl-D-Aspartate/physiology*; Tetrodotoxin/pharmacology