PERIPHERAL-NERVE INSULT INDUCES NMDA RECEPTOR-MEDIATED, DELAYED DEGENERATION IN SPINAL NEURONS

Injury of a peripheral nerve gives rise to adaptive functional and str uctural alterations in spinal neurons. We report that the rearrangemen t of the spinal circuitry in response to sciatic nerve transection in adult rats involves a delayed mode of degeneration of lumbar spinal co rd neurons. Nuclear fragmentation was detected by the TUNEL technique 7 days after sciatic neurectomy but not after 3 or 14 days. Dying cell s were preferentially located in the ipsilateral superficial dorsal ho rn and expressed the neuronal cytoskeletal marker SMI-31, Degeneration was prevented by continous systemic treatment with the NMDA receptor- antagonist MK-801. These data are supportive that apoptosis is induced in spinal neurons in a transsynaptic manner by an early signal from i njured afferent fibres via activation of spinal NMDA receptors.