GLUTAMATE-TREATED RAT CORTICAL NEURONAL CULTURES DIE IN A WAY DIFFERENT FROM THE CLASSICAL APOPTOSIS INDUCED BY STAUROSPORINE

The alkaloid protein kinase inhibitor staurosporine induced neuronal c ell death with both the morphological and the biochemical characterist ics of apoptosis. The punctate chromatin associated with apoptosis wit h retention of plasma membrane integrity was observed in neurons ident ified by colocalization of NeuN staining. Such cells had DNA fragmenta tion visualized by in situ end-labeling which was seen as a laddered p attern upon gel electrophoresis. In contrast cells treated with glutam ate did not exhibit either of these morphological or biochemical hallm arks of apoptosis. Instead a much smaller and more compact pyknotic st ructure was observed associated with smeared DNA fragmentation pattern s. A confocal time-lapse study of the appearance of the morphological changes in individual nuclei after staurosporine treatment showed coll apse into punctate chromatin over a period of 10 min. In contrast, the collapse into small pyknotic nuclei after glutamate treatment was at least 10 times slower. It is concluded that excitotoxicity produced by glutamate did not induce cell death by an apoptotic mechanism in cult ured cortical neurons. (C) 1997 Academic Press.