The decrease in locomotor activity and the number of crossed sectors in open field, has been shown in the group of animals, which for four days in the neonatal period received dexamethasone treatment. Based on these data we decided in the same experimental conditions to study the animals' state of anxiety and the behavior in passive avoidance chamber. The newborn male pups were divided on four groups. The first group was left intact, the pups of the second group were injected by saline, the third group - by dexamethasone and the fourth group - with combination of dexamethasone and L-arginine. The received results show, that deficiency of nitric oxide in the early neonatal period caused by administration of dexamethasone led to statistically significant increase of anxiety level, but statisticaly significant changes in their behavior in a passive avoidance chamber was not observed.