Opioid receptors are a group of G-protein coupled receptors with opioids as ligands. These receptors are primarily located in the central and peripheral nervous system and the gastrointestinal tract. They play a crucial role in mediating the effects of both endogenous opioids, like endorphins, and exogenous opioids, such as morphine and heroin. There are three main types of opioid receptors: mu (μ), delta (δ), and kappa (κ), each with distinct physiological functions and implications in toxicology.
