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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
Author(s) -
Berman Frederick W.,
Murray Thomas F.
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.69020693.x
Subject(s) - nbqx , nmda receptor , glutamate receptor , neurotoxicity , pharmacology , chemistry , biology , receptor , biochemistry , ampa receptor , toxicity , organic chemistry
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 µ M l ‐glutamate or 10 µ M domoate for 2 h in physiologic buffer at 22°C followed by a 22‐h incubation in 37°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 α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA)/kainate receptor‐mediated stimulation of EAA efflux.