Effective drugs are not available to protect against beta-amyloid peptide (A beta)-induced neurotoxicity. Cortical neurons from rat embryos were treated with the toxic fragment A beta25-35 at 1 microM in the presence or absence of flupirtine, a triaminopyridine, successfully applied clinically as a nonopiate analgesic drug. Five days later 1 microM A beta25-35 caused reduction of cell viability to 31.1%. Preincubation of cells with flupirtine (1 or 5 microg/ml) resulted in a significant increase of the percentage of viable cells (74.6 and 65.4%, respectively). During incubation with A beta25-35 the neurons undergo apoptosis as determined by appearance of the characteristic stepladder-like DNA fragmentation pattern and by the TUNEL technique. A beta25-35-induced DNA fragmentation could be abolished by preincubation of the cells with 1 microg/ml flupirtine. Incubation with A beta25-35 reduces the intraneuronal level of GSH from 21.4 to 7.4 nmol/10(6) cells. This depletion could be partially prevented by preincubation of the cells with flupirtine. Thus, flupirtine may be adequate for the treatment of the neuronal loss in Alzheimer's disease (where A beta accumulates in senile plaques) and probably other neurological diseases such as amyotrophic lateral sclerosis.