Microglia, but not astrocytes, react to sciatic nerve injury in aging rats.

Peripheral nerve axotomy activates microglia and astrocytes within regions of brainstem or spinal cord from which the nerve arises. The present study demonstrates that unilateral sciatic axotomy in rats 2 to 18 months of age results in differing responses with age between these two glial populations. By 4 days postaxotomy, both astrocytes and microglia become activated in 2-month-old rats, whereas only the microglial population shows evidence of activation in rats 8 to 18 months of age.