Neural development following NMDA administration in the rat: an electron microscopic examination of the occipital...

Recent research has suggested that the N-methyl-D-aspartate (NMDA) receptor plays a role in numerous activity dependent models of synaptic plasticity. 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 aged 8 days were administered one, 1/10 LD50, SC injection of either NMDA or saline vehicle every 8 h until 18 days of age and were sacrificed 2 days later. Chronic administration of NMDA produced no changes in body or brain weight, the length of synaptic contacts, or the number of synapses per unit area in the neocortical molecular layer. There was a significant 10% increase in the depth of the occipital cortex molecular layer, yielding a 15% increase in the estimated total number of synapses within that area. These results suggest that activation of the NMDA receptor is capable of altering certain aspects of neural development, while other components are not affected.