Ethanol inhibits NMDA receptor-mediated excitotoxicity in rat primary neuronal cultures.
Excessive or prolonged stimulation of N-methyl-D-aspartate (NMDA) receptors appears to play an important role in many neurodegenerative processes in brain through a process known as excitotoxicity. This study examined the effects of ethanol on NMDA receptor-mediated excitotoxicity in primary neuronal cultures obtained from embryonic rat whole brain. Neurotoxicity was quantitated by measuring the amount of lactate dehydrogenase released into the media during a 20-hr time period following NMDA washout. Exposure of 12- to 14-day-old cultures to NMDA in Mg(2+)-free HEPES buffer (pH 7.4) for a 25-min period resulted in a concentration-dependent toxicity (EC50 = 54 microM). Time-course experiments showed that exposure to NMDA for as little as 5 min was excitotoxic and reached a plateau after a 20-min exposure period. Preincubation of the cultures with ethanol (25 to 200 mM) resulted in a concentration-dependent inhibition of NMDA-mediated toxicity with approximately 38% inhibition produced by 25 mM ethanol and essentially complete inhibition at 200 mM ethanol (IC50 = 60 mM). Increasing the glycine concentration to 100 microM did not potentiate NMDA neurotoxicity or antagonize the neuroprotective effect of ethanol. NMDA-Mediated excitotoxicity was reduced by approximately 50% by the glycine antagonist 7-chlorokynurenate (50 microM). Ethanol (50 mM) reduced NMDA neurotoxicity similar to 7-chlorokynurenate, and the two together produced greater inhibition than either alone. These results show that intoxicating concentrations of ethanol can potently inhibit NMDA receptor-mediated excitotoxicity and may have important implications in terms of ethanols interactions with brain trauma, ischemia, and other neuropathologies associated with NMDA receptor-mediated neurotoxicity.
Department of Pharmacology, J. H. Miller Health Center, University of Florida College of Medicine, Gainesville 32610-0267.
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Chandler
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Sumners
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D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D005998:Glycine / Q000502:physiology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology; D009410:Nerve Degeneration / Q000187:drug effects* / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate; D000431:Ethanol; D016202:N-Methylaspartate; D007770:L-Lactate Dehydrogenase; D005998:Glycine