Ingestion of 3-nitropropionic acid (3-NPA) in moldy sugar cane causes brain damage in children. The mechanism of 3-NPA toxicity is thought to be inhibition of energy production, leading to ATP depletion and excitotoxicity. We exposed cultured mouse striatal or cortical neurons to 1-2 mM 3-NPA for 48 h. This exposure produced gradual neuronal degeneration characterized by cell body shrinkage and DNA fragmentation. Addition of glutamate antagonists during 3-NPA exposure did not reduce neuronal death. However, addition of the macromolecular synthesis inhibitors cycloheximide, emetine or actinomycin D markedly reduced neuronal death. Our results do not exclude that 3-NPA can induce excitotoxicity in more intact systems, but raise the additional possibility that 3-NPA may also act to induce neuronal apoptosis.