Monosialoganglioside GM1 prevents excitatory amino acid (EAA)-related neuronal death in cultured central nervous system (CNS) neurons and reduces the severity of acute brain damage in different experimental models of cerebral ischemia. Using a model of brain damage induced by intracerebroventricular administration of N-methyl-D-aspartate (NMDA) in neonate rats, we evaluated whether GM1 is capable of exerting antiexcitotoxic effects following its systemic administration in vivo. Newborn rats subjected to brain damage by NMDA and contemporaneously treated subcutaneously with GM1 showed significantly reduced (i) loss in hemispheric weight, (ii) loss in tissue choline acetyltransferase activity, and (iii) morphological damage in various brain areas. These results indicate that systemic GM1 treatment is efficacious in reducing EAA-related neuronal damage in vivo and suggest that such a phenomenon may underlie its capability to ameliorate neurological outcome following cerebral ischemia.