Pharmacology of Endogenous Opioids, Opiates and Their Receptors

Abstract

The search for analgesia is the main drive for the discovery of opioid receptors and their endogenous ligand peptides. Although opioid peptides are very similar in their N-terminal sequence, they are classified into different types according to their precursor proteins. The peptides activate opioid receptors by binding to orthosteric-binding sites to mediate intracellular second messengers. Biased signaling and allosteric modulation is a new approach to obtain receptor subtype selectivity and separates the desirable from a myriad of unwanted pharmacological effects. This chapter describes endogenous opioids and opiates with an emphasis on structure, origin and processing, receptors, physiological roles, and potential involvement in therapeutic interventions. Further, it also provides a brief discussion on the effect of opioids on various ion channels and recent developments of established and investigational opioid molecules.