EARLY NMDA RECEPTOR BLOCKADE IMPAIRS DEFENSIVE BEHAVIOR AND INCREASESCELL-PROLIFERATION IN THE DENTATE GYRUS OF DEVELOPING RATS

These studies were conducted to determine whether (a) early N-methyl-D -aspartate (NMDA) receptor blockade impairs defensive behavior and (b) a relationship exists between defensive behavior and the production o f granule cells in the dentate gyrus. Rat pups were treated with diffe rent doses of the NMDA receptor antagonist CGP 43487 on postnatal day (P) 5, and their behavior was observed following exposure to an unfami liar adult male rat, a potential predator, on P13, P20, and P30. A dos e-dependent impairment in freezing behavior was observed in rat pups t reated with NMDA receptor antagonist on P13, P20, but not P30. Moreove r, a dose-dependent increase in the number of H-3-thymidine-labeled ce lls in the dentate gyrus was detected following CGP 43487 treatment, s uggesting that an inverse relationship exists between cell proliferati on and freezing behavior in rat pups following NMDA receptor blockade.