The study employed an immunochemical quantification of brain cell marker proteins in addition to quantitative morphology in order to provide a more multifacetted and characterized model for an excitotoxic CNS lesion. The importance of the approach in the evaluation of the potential of neuroprotective agents is emphasized. The S-100 protein, the glial fibrillary acidic (GFA) protein, neuron specific enolase (NSE) and neuronal intermediary filament polypeptides (NF 68 and NF 200) were measured with a dot-immunobinding assay, 3-30 days after a unilateral injection of N-methyl-D-aspartate (NMDA) in the left dorsal hippocampus of the rat. After 3 days, the neuronal cell loss averaged 80% in the hippocampus. The S-100 content was reduced 3 days after injection, but was 150% of control at 30 days. GFA increased constantly from days 3 to 30. The neuronal marker proteins were all markedly reduced 7 days after injection. However, at 30 days, NF 68 and NF 200 were close to control (80%). Increasing content would reflect regeneration and sprouting of neurites. The content of the neuronal cytoplasmic marker, NSE, was significantly lower than control also at 10 and 30 days, although a gradual recovery could be traced.