Decreased excitotoxic sensitivity in the olfactory cortex of adult rats after neonatal NMDA blockade.

Neonatal rats were daily treated with increasing doses of the competitive NMDA antagonist CGP 39551 from postnatal day 1 to 22. At 75-80 days of age the rats were given an excitotoxic dose of kainic acid s.c. Histological examination suggested that the olfactory cortex of the neonatally CGP 39551-treated rats was less damaged than that of controls. This was quantitatively confirmed by assaying the decrease of appropriate neurochemical markers (D-[3H]aspartate uptake and glutamate decarboxylase) as an index of the extent of neuronal degeneration. By contrast, the decrease of the same markers was not different in the hippocampus. These results suggest a selective effect on some brain circuits of adult rats consequent to the neonatal blockade of NMDA receptors and, therefore, add new evidence to a developmental role of this receptor.