Cell membrane proteins that bind opioids and trigger intracellular changes which influence the behavior of cells. The endogenous ligands for opioid receptors in mammals include three families of peptides, the enkephalins, endorphins, and dynorphins. The receptor classes include mu, delta, and kappa receptors. Sigma receptors bind several psychoactive substances, including certain opioids, but their endogenous ligands are not known.

Synonyms: Receptors, Endorphin, Receptor, Opioid, beta-Endorphin Receptor, Receptor, Opiate, Opiate Receptors, Opioid Receptor, Enkephalin Receptors, Narcotic Receptors, Receptor, beta-Endorphin, Opioid Receptors, Enkephalin Receptor, Endorphin Receptor, Receptor, Endorphin, Receptors, Opioid, Opiate Receptor, 0, Endorphin Receptors, Receptors, Normorphine, Receptor, Enkephalin, Receptors, beta-Endorphin, Receptors, Opiate, Receptors, beta Endorphin, Receptors, Narcotic, Receptors, Enkephalin, beta-Endorphin Receptors, Normorphine Receptors, beta Endorphin Receptor