Rabbit antibodies against GluR1 subunit of AMPA glutamate receptors in a concentration of 1 mug/ml significantly increased intracellular Ca(2+)concentration and decreased mitochondrial potential in hippocampal neurons, i.e. produced changes typical of the influence of glutamate in toxic concentrations. In cerebellar neurons rabbit antibodies potentiated glutamate-induced increase in intracellular Ca(2+)concentration and significantly decreased the mitochondrial potential (compared to the level observed after application of glutamate alone). The exposure of cultured cerebellar neurons to antibodies in a concentration of 0.1 mug/ml for 24 h was followed by a 50% decrease in ATP concentration and development of neuronal necrosis. Our results attest to an important role of autoimmune damage to neurons during hyperstimulation of glutamate receptors.