Chemistry, Structure and Possible Analgesia Mechanism of Morphine: A Review

Abstract

The opium or poppy (Papaver somniferum) is annual herbaceous plant belongs to Papaveraceae family that can grow almost everywhere. The species Papaver somniferum is most widely used species due to its lovely blossoms as well as its edible seeds. Morphine is an amphoteric pentacyclic alkaloid that occurs naturally as columnar white prisms in its levorotatory form. Only natural diastereomer of morphine is bioactive. The alkaloid contains one phenolic and one alcoholic group in its pentacyclic skeleton. Central and peripheral neurons, as well as neuroendocrine, immunological, and ectodermal cells, express opioid receptors. Three major types of opioid receptors mu µ, delta δ and kappa κ were established through receptor binding studies and cloning experiments. The endogenous opioid analgesic system can be activated by morphine to cause analgesia. The production of analgesia can be explained by basic two mechanisms. First mechanism is presynaptic inhibition of sP or possible transmitters involved in pain transfer while in second mechanism, postsynaptic hyperpolarization of neurons involved in transmission of pain to higher centers