Changes in glutamate/aspartate transporter (GLAST/GluT-1) mRNA expression following facial nerve transection

Expression of glutamate/aspartate transporter (GLAST/GluT-1) was investigated in the axotomized facial nucleus by in-situ hybridization. Hybridization signals for GLAST mRNA were almost undetectable in the facial nucleus of sham-operated animals. However, the hybridization signals were seen from 3 days after facial nerve transection onward in the nucleus of the affected side. These signals lasted at least 5 weeks. Microautoradiograms showed that small non-neuronal cells in the ipsilateral facial nucleus expressed signals of GLAST mRNA after axotomy. These findings suggest that non-neuronal cells, presumably astrocytes, may protect axotomized motor neurons against glutamate toxicity via up-regulation of GLAST in the facial nucleus.