Mitochondrial apoptotic cell death and moderate superoxide generation upon selective activation of non‐desensitizing AMPA receptors in hippocampal cultures

In the present work we investigated the effect of selective stimulation of non‐desensitizing α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) receptors in the intracellular processes leading to hippocampal neuronal death and production of reactive oxygen species (ROS). Activation of AMPA receptors in the presence of cyclothiazide (CYZ), a blocker of AMPA receptor desensitization, resulted in the death of approximately 25% of neurones, which was prevented by 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoyl‐benzo(f)quinoxaline (NBQX), an AMPA‐preferring receptor antagonist. (+)‐5‐Methyl‐10,11‐dihydro‐5H‐dibenzo[a,d]cyclohepten‐5,10‐imine hydrogen maleate (MK‐801) protected the neurones from necrotic death induced by AMPA or NMDA receptor activation. Neurodegeneration caused by selective activation of non‐desensitizing AMPA receptors, in the presence of AMPA, CYZ and MK‐801, significantly decreased the number of Co 2+ ‐positive neurones, used as a cytochemical marker of Ca 2+ ‐permeable AMPA receptors, but maintained intracellular ATP/ADP. The AMPA‐mediated apoptotic cell death involved mitochondrial cytochrome c release and the activation of caspases‐1 and ‐3, which was prevented by NBQX. Interestingly, although selective activation of AMPA receptors was not associated with production of intracellular peroxides, a moderate increase in superoxide production was observed upon exposure to antimycin A (AA). Furthermore, increased activity of Mn‐ superoxide dismutase (SOD) was observed on selective activation of non‐desensitizing AMPA receptors. Taken together, these data make important contributions to the elucidation of the downstream pathways activated in AMPA receptor‐mediated excitotoxicity in cultured rat hippocampal neurones.