The release of [(3)H]D-aspartate ([(3)H]D-ASP) or [(3)H]GABA evoked by glycine from spinal cord synaptosomes was compared in mice expressing mutant human SOD1 with a Gly(93) Ala substitution ([SOD1-G93A(+)]), a transgenic model of amyotrophic lateral sclerosis, and in control mice. Mice expressing mutated SOD1 were killed at the advanced phase of the pathology, when they showed signs of ingestion disability, because of paralysis of the posterior limbs. In control mice glycine concentration-dependently evoked [(3)H]D-ASP and [(3)H]GABA release. Potentiation of the spontaneous release of both amino acids is likely to be mediated by activation of a glycine transporter, since the effects of glycine were counteracted by the glycine transporter blocker glycyldodecylamide but not by the glycine receptor antagonists strychnine and 5,7-dichlorokynurenate. The glycine-evoked release of [(3)H]D-ASP, but not that of [(3)H]GABA, was significantly more pronounced in SOD1-G93A(+) than in control animals.