Nature 369, 482 - 485 (09 June 1994); doi:10.1038/369482a0

NMDA receptors and activity-dependent tuning of the receptive fields of spinal cord neurons

Gary R. Lewin^*†, Edward Mckintosh & Stephen B. McMahon^‡

Department of Physiology, United Medical and Dental Schools (St Thomas's Campus), Lambeth Palace Rd, London SE1 7EH, UK
^*Department of Neurobiology and Behavior, State University of New York at Stony Brook, New York 11794, USA
^†Present address: Department of Neurobiochemistry, Max-Planck Institute for Psychiatry, D-82152 Martinsried, Germany.
^‡To whom correspondence should be addressed.

AFTER peripheral nerve section, sensory neurons regenerate but do not regain their original topographical position in the skin¹. Here we report that in the early stages of sciatic nerve regeneration, the cutaneous receptive fields (RFs) of dorsal horn neurons are larger than normal, reflecting the disorganized topography of the regenerated afferents. When nerve regeneration is complete, small contiguous RFs emerge, indicating a central compensation for the disrupted peripheral somatotopy. If the NMDA receptor antagonist MK801 is given during regeneration, RFs do not show this reorganization, but remain large and diffuse. We suggest that the coincident activity of afferents, newly innervating adjacent or over-lapping cutaneous territory, acts through postsynaptic NMDA receptors² to strengthen the central effectiveness of these inputs at the expense of other non-adjacent and non-coincidently activated inputs. In this way, dorsal horn neurons may attain and retain restricted RFs in the face of a spatially dispersed afferent input.

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