The vulnerability of spinal cord neurons to excitotoxic injury: comparison with cortical neurons.

The neurotoxicity of the glutamate receptor agonists N-methyl-D-aspartate (NMDA), (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), and kainate was quantitatively assessed in murine spinal cord and cortical cultures prepared under identical conditions. Compared with cortical neurons, spinal neurons were less vulnerable to NMDA (EC50 for 24 h exposure about 30 microM versus 10 microM in cortical cultures) and more vulnerable to AMPA (EC50 5 microM versus 12 microM) and kainate (EC50 20 microM versus 50 microM). Neurons subject to kainate-activated cobalt uptake, a marker of calcium-permeable AMPA/kainate channels, were resistant to NMDA in both systems; these cells were significantly more prevalent in spinal cord cultures. Both the AMPA/kainate antagonist GYKI-52466 and the NMDA antagonist MK-801 attenuated spinal cord neuronal loss due to glucose deprivation; however, GYKI-52466 was more effective. These results support the hypothesis that AMPA/kainate receptor activation may play a significant role in excitotoxic injury to spinal cord neurons.