In the adult CNS, ethanol prevents rather than produces NMDA antagonist-induced neurotoxicity

• Published in: Brain research 2004-11, Vol.1028 (1), p.66-74
• Main Authors: Farber, Nuri B., Heinkel, Corey, Dribben, William H., Nemmers, Brian, Jiang, Xiaoping
• Format: Article
• Language: English
• Subjects: Age Factors; Alcoholism and acute alcohol poisoning; Animals; Apoptosis - physiology; Biological and medical sciences; Cerebral Cortex - drug effects; Cerebral Cortex - pathology; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ethanol; Ethanol - pharmacology; Ethanol - toxicity; Excitatory Amino Acid Antagonists; Female; GABA A receptor; Medical sciences; Nerve Degeneration - chemically induced; Nerve Degeneration - prevention & control; Neurodegeneration; Neuroprotective Agents - pharmacology; Neurotoxicity; NMDA glutamate antagonist; Non-NMDA Glu receptor; Psychosis; Pyramidal Cells - drug effects; Pyramidal Cells - pathology; Rats; Receptors, N-Methyl-D-Aspartate - drug effects; Toxicology
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2004.08.065

Single doses of an NMDA antagonist cause an adult or a prepubertal form of neurodegeneration, depending on the age of the animal. Single doses of ethanol (EtOH) by blocking NMDA receptors produce apoptotic neurodegeneration in young animals. This capability could account, in part, for the ability of EtOH to produce the fetal alcohol syndrome. We investigated whether EtOH could produce NMDA antagonist-induced neurotoxicity (NAN), a different neurotoxicity that is seen only in adult animals. In spite of producing blood EtOH levels (30 to 600 mg/dl) known to block NMDA receptors, EtOH was unable to produce neurotoxicity in the adult central nervous system (CNS). Moreover, EtOH in a dose-dependent fashion (ED 50=138 mg/dl) prevented the selective and powerful NMDA antagonist, MK-801, from producing NAN in adult animals, suggesting that activity at another site might be negating the neurotoxic effect of EtOH's inherent NMDA antagonistic activity. Because GABA A agonism and non-NMDA glutamate antagonism, properties which EtOH possesses, can prevent NAN, we proceeded to study whether GABA A antagonists (or agents capable of reversing EtOH's GABAergic effects) and non-NMDA agonists could reverse EtOH's protective effect. Bicuculline, Ro15-4513, finasteride, kainic acid or AMPA, alone or in combination, did not significantly reverse EtOH's protective effect. Given that EtOH has effects on a wide range of ion channels and receptors, determining the precise mechanism of EtOH's protective effect will take additional effort. The inability of EtOH to acutely produce NAN in the adult CNS indicates that, in contrast to fetuses, brief exposure of the adult CNS to EtOH is non-toxic for neurons.