A differential and time-dependent decrease in AMPA-type glutamate receptor subunits in spinal motoneurons after sciatic nerve injury.

After sciatic transection a strong decrease in immunoreactivity occurred, starting at 2 days. After 6, 10, 14, and 20 days survival only 5% of the sciatic motoneurons were strongly labeled for GluR2/3 against 80% in the control situation. From Day 20, GluR2/3 labeling started to increase again, reaching near normal levels at Day 80 after sciatic transection. In contrast, after sciatic crush, the decrease in GluR2/3 labeling in motoneurons was less pronounced and returned to normal in 30 days. In all animals, the GluR1 and GluR4 labeling of motoneurons remained unchanged after sciatic transection or crush. It is concluded that sciatic nerve injury leads to a strong, time-dependent decrease in the expression of GluR2 and 3 subunits in the corresponding motoneurons. As a consequence, AMPA receptors with a different subunit composition may be assembled, leading to a change in the functional properties of these receptors. Moreover, if they lack the GluR2 subunit, they may become calcium permeable.