The role of activity blockade on glutamate receptor subunit expression in the spinal cord

Spinal cord injury (SCI) impairs descending glutamatergic neurotransmission reaching ventral motor neurons (VMN). Previously we reported Lip-regulatio n of NMDA receptor subunits NR1 and NR2A mRNAs in VMN caudal to the lesion site 24 h after SCI. The absence of effect rostral to the injury site sugge sted that injury-induced loss of descending activity might be involved. To test this hypothesis, we blocked axonal conduction by focal injection of te trodotoxin into the spinal cord. We found increased NR1 and NR2A mRNAs in V MN similar in extent to that seen after SCI. Thus, the increase in NMDA sub unit mRNAs may be 'inactivity dependent' and associated with reorganization of the spinal cord in response to loss of descending innervation. (C) 2000 Elsevier Science B.V. All rights reserved.