Increasing evidence supports the hypothesis that escalating levels of excitatory amino acids (EAAs) are responsible for neuronal cell death in a variety of acute neurological conditions including hypoxia/ischemia, trauma, seizures, and hypoglycemia. EAAs may also contribute to several chronic neurodegenerative diseases including Huntington's disease, parkinsonism, and acquired immunodeficiency syndrome dementia. A predominant form of neurotoxicity appears to be mediated by excessive activation of the N-methyl-D-aspartate subtype of glutamate receptor. This laboratory recently reported that memantine, an antiparkinsonian drug, is a potent N-methyl-D-aspartate antagonist capable of preventing the death of central neurons both in vitro and in vivo when given coincident to an EAA insult. In the present study, we found that 12 microM memantine prevented the death of neonatal rat retinal ganglion cells in primary culture when administered up to 4 hours after the initiation of N-methyl-D-aspartate receptor-mediated neurotoxicity.