FFiFigure 1 . The Morphine Molecule. The structure of morphine and all opium derivatives are characterized by the piperdine ring which is indicated with bold lines. Table 1 . Structures of Opioid Agonists and Antagonists Chemically Related to Morphine.
Endorphins are peptides.
A peptide is a biologically active substance composed of amino acids that are produced in neurons. The Receptor Most psychoactive drugs exert their action at a receptor. Some receptors are broken down further into subtypes as in the k1 and k2 receptors. A substance that binds to a receptor is called a ligand, thus endorphins are the natural ligand for the opiate receptor. Receptors have several properties.