Mild kainate toxicity produces selective motoneuron death with marked activation of CA(2+)-permeable AMPA/kainate receptors.

Motoneuron death could be produced by higher sensitivity to excitoxicity during the development and pathological conditions. We report here that in ventral spinal cord cultures mild kainate exposure (12.5 microM, 20 min or 100 microM, 2.5 min) induced selective cobalt stain of motoneurons, indicating a specific Ca2+ entry through the Ca(2+)-permeable AMPA/kainate receptors. This result was associated with a selective motoneuron death as previously described. In these cultures, motoneuron immunoreactivity for the Ca2+ buffering protein, calretinin was negative. These findings suggest that the selective motoneuron death due to a mild excitotoxic insult could be linked to a marked Ca2+ influx associated with the lack of some Ca2+ buffering proteins.