Our laboratory and others have demonstrated that animals can make morphine, meaning its biosynthetic pathway has been conserved during evolution. Among the many enzymes involved in this process, CYP2D6 is of particular importance because of its role in multiple steps of morphine precursor metabolism, as well as its distribution in a variety of tissues, such as neuronal and immune. Additionally, its genetic variations support its role in this process. Elucidating its role in the critical metabolic processes involved with many drugs, not just opiate alkaloids may provide a critical understanding of induced addiction, analgesia, immune- and vascular regulation. Its presence in invertebrate tissues underscores its singular significance in these processes as well, allowing one to hypothesize its role in actions of many substances of abuse.

Keywords: Morphine - biosynthesis, Cytochrome P-450 CYP2D6 - metabolism, Brain - metabolism