Mu-opioid receptors are a type of protein found in the brain and other parts of the body. They play a crucial role in how we perceive pain and are involved in the body's natural response to stress. When activated by substances like endorphins or opioids, these receptors can produce feelings of pain relief and euphoria. These receptors are part of the opioid receptor family, which also includes delta and kappa receptors. Research on mu-opioid receptors is important for understanding pain management and the effects of opioid medications, as well as the potential for addiction and other side effects associated with their use.