Alzheimer’s disease (AD) is a long-lasting progressive neurodegenerative disease that degrades memory and cognitive function and is often complicated by disorientation and other psychiatric syndromes. At present, to improve the condition of patients with AD, for their treatment, use the drug memantine. The drug is a noncompetitive antagonist of NMDA glutamate receptors in the brain. The present experiments aimed to test the influence of memantine on the memory processes in rats. We used the passive avoidance test “Stepdown”. The latter is used to assess memory function based on the association formed between a particular environment that an animal is learning to avoid and a negative stimulus in the form of a weak electric shock to the feet. We found that memantine significantly, twice, decreased the latency time step-down from the platform in rats during their familiarization with the chamber. The rats became more determined and less afraid of the unknown environment under memantine. Memantine significantly affected the emotionality of young rats, which leads to errors in the passive avoidance test. However, it did not impair memory. It can be concluded that memantine induces a shift toward greater excitability in rats.