CHANGES OF EXPLORATORY-BEHAVIOR AND ITS HABITUATION IN RATS NEONATALLY TREATED WITH MONOSODIUM GLUTAMATE

In an attempt to elucidate mechanisms involved in adaptation to a nove l environment, consequences of:neurotoxic damage induced by administra tion of monosodium glutamate (MSG) to both male (n = 42) and female (n = 45) rats in the early postnatal period were studied. Rats treated w ith MSG and appropriate controls were tested on postnatal days 21 and 65 for alterations of exploration and the rapidity of habituation chan ges in an open field test. Compared with intact animals, a high dose o f MSG (4 mg/g) increased exploratory behaviour, with a subsequent decr ease in the rapidity of habituation of male rats. Neonatal stress repr esented by hypertonic saline injection in a vehicle-control group indu ced a slight increase of exploratory behaviour as compared with intact animals. Males proved to be more vulnerable to neonatal MSG treatment and handling than females. These results suggest a negative effect of neonatal stress and treatment with MSG on habituation to a new enviro nment in male rats. (C) 1997 Elsevier Science Inc.