Opioid peptides are small protein fragments that bind to opioid receptors in the body, producing effects similar to those of opioid drugs. They are naturally occurring and play a role in pain regulation, stress response, and mood enhancement. Examples of opioid peptides include endorphins, enkephalins, and dynorphins. These peptides are produced in the brain and other tissues, acting as neurotransmitters. When released, they can help alleviate pain and promote feelings of well-being. Their discovery has led to a better understanding of the body's pain management system and has implications for developing new treatments for pain and addiction.