NMDA RECEPTOR-DEPENDENT REFINEMENT OF SOMATOTOPIC MAPS

We have examined the role of NMDA receptor-mediated neural activity in the formation of periphery-related somatosensory patterns, using gene tically engineered mice. We demonstrate that ectopic expression of a t ransgene of an NMDAR1 splice variant rescues neonatally fatal NMDAR1 k nockout (KO) mice, although the average life span varies depending on the level of the transgene expression. In NMDAR1 KO mice with ''high'' levels of the transgene expression, sensory periphery-related pattern s were normal along both the trigeminal and dorsal column pathways. In the KO mice with ''low'' levels of the transgene expression, the patt erns were absent in the trigeminal pathway. Our results indicate that NMDA receptor-mediated neural activity plays a critical role in patter n formation; along the ascending somatosensory pathways.