Enkephalins are small peptides that function as neurotransmitters in the brain. They are part of the body's natural pain relief system and are involved in regulating pain, mood, and stress responses. Enkephalins bind to opioid receptors, which are also targeted by drugs like morphine, to produce feelings of euphoria and reduce the perception of pain. These peptides are produced in various parts of the body, including the central nervous system and the adrenal glands. There are two main types of enkephalins: met-enkephalin and leu-enkephalin. Their role in pain modulation makes them important for understanding both natural pain relief and the effects of opioid medications.