We have performed differential screening to identify genes participating in NMDA-induced neuronal death. The gas1 (growth arrest-specific gene 1) gene, whose product is known to inhibit cell cycle progression, was induced in cultured corticohippocampal neurons committed to die after a brief exposure to NMDA. Overexpression of Gas1 in cultured hippocampal neurons and in human neuroblastoma NB69 cells produced a marked reduction in the number of viable cells. Furthermore, gas1 antisense oligodeoxynucleotide or antisense mRNA protected hippocampal neurons or NB69 cells from neuronal death. Importantly, Gas1-induced neuronal death was attenuated by coexpression of the human Bcl-2 protein or the baculoviral caspase inhibitor OpIAP2. While Gas1 does not directly interact with Bcl-2, OpIAP2 coimmunoprecipitates with Gas1. In addition, induction of gas1 also occurred in rat brain in two models of excitotoxicity: delayed neuronal death after intraperitoneal kainate injection and neuronal death in hippocampal slices after ischemia. These results indicate that Gas1 is induced by activation of glutamate receptors and is part of the gene expression program directing neuronal death after mild excitotoxic insults.