Methionine enkephalin is primarily used in neuroscience and medical research to study the role of endogenous opioids in the brain. It acts as a natural painkiller by binding to opioid receptors, influencing pain perception and emotional responses. This peptide is also utilized in investigations related to addiction, stress, and mood disorders, as it modulates dopamine release and impacts reward pathways. Additionally, it has potential therapeutic applications in managing chronic pain and psychiatric conditions, though further clinical research is needed to fully understand its efficacy and safety.