Role of desensitization and subunit expression for kainate receptor-mediated neurotoxicity in murine neocortical cultures

The neurotoxic actions of kainate and domoate were studied in cultured muri ne neocortical neurons at various days in culture and found to be developme ntally regulated involving three components of neurotoxicity: (1) toxicity via indirect activation of N-methyl-D-aspartate (NMDA) receptors, (2) toxic ity mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors, and (3) toxicity that can be mediated by kainate receptors when desensitization of the receptors is blocked. The indirect action at NMDA r eceptors was discovered because (5R,10S)-(+)-5-methyl-10,11- dihydro-5H-dib enzo[a,d] cyclohepten-5,10-imine (MK-801), an NMDA receptor antagonist, was able to block part of the toxicity. The activation of NMDA receptors is mo st likely a secondary effect resulting from glutamate release upon kainate or domoate stimulation, 1-(4-Aminophenyl) 3-methylcarbamyl-4-methyl-3,4-dih ydro-7,8-ethylenedioxy-5H-2,3-benzodiazepine (GYKI 53655), a selective AMPA receptor antagonist, abolished the remaining toxicity. These results indic ated that kainate- and domoate-mediated toxicity involves both the NMDA and the AMPA receptors, Pretreatment of the cultures with concanavalin A to pr event desensitization of kainate receptors led to an increased neurotoxicit y upon stimulation with kainate or domoate, In neurons cultured for 12 days in vitro a small but significant neurotoxic effect was observed when stimu lated with agonist in the presence of MK-801 and GYKI 53655, This indicates that the toxicity is produced by kainate receptors in mature cultures. Exa mining the submit expression of the kainate receptor subunits GluR6/7 and K A2 did, however, not reveal any major change during development of the cult ures. J. Neurosci. Res. 55:208-217, 1999. (C) 1999 Wiley-Liss, Inc.