Chronic neonatal blockade of NMDA receptor does not affect developmental polyamine metabolism but results in altered response to the excitotoxic induction of ornithine decarboxylase.

Neonatal rats were subjected to chronic blockade of the N-methyl-D-aspartate (NMDA) receptor through daily systemic administration of increasing doses of the competitive antagonist CGP 39551 from postnatal days 1-22. Treatment did not result in any significant alteration of the levels of putrescine, spermidine and spermine or in the constitutively expressed activity of the key enzyme for polyamine biosynthesis, ornithine decarboxylase (ODC), as evaluated at 10 and 20 days of age. However, in 30-day-old rats significant differences were observed in the process of excitotoxic ODC induction in the olfactory cortex and the hippocampus of chronically-treated rats: the increase of ODC activity caused by systemic administration of kainic acid took place more rapidly but it was shorter and apparently reached a smaller peak in treated animals as compared to controls. This result, in conjunction with previous data on neurochemistry and locomotor activity of similarly treated rats, strengthens the suggestion that functional alterations of some brain circuits may be the consequence of the blockade of NMDA receptor during the critical neonatal period of brain maturation.