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.
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.
Berman
F W
FW
College of Pharmacy and Toxicology Program, Oregon State University, Corvallis 97331, USA.
Murray
T F
TF
D000818:Animals; D002478:Cells, Cultured; D002531:Cerebellum / Q000187:drug effects* / Q000378:metabolism; D017077:Culture Media, Conditioned; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018846:Excitatory Amino Acids / Q000378:metabolism*; D018698:Glutamic Acid / Q000633:toxicity; D007608:Kainic Acid / Q000031:analogs & derivatives* / Q000633:toxicity; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D017077:Culture Media, Conditioned; D018691:Excitatory Amino Acid Antagonists; D018846:Excitatory Amino Acids; D009498:Neurotoxins; D011810:Quinoxalines; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D018698:Glutamic Acid; D013779:Tetrodotoxin; D016291:Dizocilpine Maleate; D007770:L-Lactate Dehydrogenase; C012301:domoic acid; D007608:Kainic Acid