Changes in expression of NR-1 and c-jun mRNA in rat lumbar spinal cord after neonatal common peroneal nerve crush.

We have examined the expression of the NR-1 subunit of the glutamate NMDA receptor and the immediate early gene c-jun in lumbar spinal cord following neonatal common peroneal nerve crush. The expression of these two genes was studied up to 12 days post-injury (crush occurring at neonatal day P2). The levels of both NR-1 and c-jun mRNA were increased in spinal cord ipsilateral to the site of crush, the induction of mRNA was shown to occur in a time-dependent manner, peaking at 5 days post-injury. The level of NR-1 mRNA showed the most substantial change following nerve crush, increasing 5 times from 4 h to 5 days post-crush. An increase in expression of NR-1 was also observed in spinal cord contralateral to the injury, although quantitatively this was a smaller effect. These results indicate that early postnatal injury causes a significant increase in the expression of NR-1 mRNA which is most marked at 5 days after injury. This period coincides with that of maximum cell death and indicates that the selective induction of NR-1 could underlie the mechanism of this cell death.