NEURAL DEVELOPMENT FOLLOWING NMDA ADMINISTRATION IN THE RAT - AN ELECTRON-MICROSCOPIC EXAMINATION OF THE OCCIPITAL NEOCORTEX LAYER-I

Recent research has suggested that the N-methyl-D-aspartate (NMDA) rec eptor plays a role in numerous activity dependent models of synaptic p lasticity. The current research attempted to determine whether chronic activation of the NMDA receptor could induce alterations in synaptic development. An examination of acute NMDA toxicity indicated that rats become increasingly resistant to NMDA over development. Male rats age d 8 days were administered one, 1/10 LD(50), SC injection of either NM DA or saline vehicle every 8 h until 18 days of age and were sacrifice d 2 days later. Chronic administration of NMDA produced no changes in body or brain weight, the length of synaptic contacts, or the number o f synapses per unit area in the neocortical molecular layer. There was a significant 10% increase in the depth of the occipital cortex molec ular layer, yielding a 15% increase in the estimated total number of s ynapses within that area. These results suggest that activation of the NMDA receptor is capable of altering certain aspects of neural develo pment, while other components are not affected.