N-methyl-D-aspartate (NMDA) receptors and nitric oxide (NO) are implicated in the induction and maintenance of long-term potentiation (LTP), an activity-induced increase in the efficacy of neurotransmission. Investigations of synaptic transmission show that the induction of LTP is blocked by NMDA receptor antagonists, whereas the maintenance of LTP is prevented by NO synthase inhibitors. LTP has been conceived to be a physiological correlate of learning and memory. This article reviews behavioral studies that utilized NMDA receptor antagonists and NO synthase inhibitors in studying of neural mechanisms of learning and memory. The review focuses mainly on the research results from our research group. It also discusses other related literature and future studies.