Effects of Endogenous Opioids on Pain Mechanism

Abstract

Pain is defined as an unpleasant sensory and emotional experience, associated with potential tissue damage. Many studies have been conducted to reveal the effects of opioids on the pain mechanism. These studies have focused primarily on opioid peptides and opioid receptor agonists. In general, it is declared that dopaminergic, serotonergic, and glutaminergic systems as well as the opioid system are closely associated with pain. Morphine, an opioid type obtained from Papaver somniferum, has been used for pain relief for many years. Morphine and other exogenous opioids show their activity by binding to opioid receptors in living organisms. These receptors respond to opioid peptides expressed as inactive polypeptide hormones activated by proteolytic cleavage. These opioids found in living organisms are referred as endogenous opioids. Endogenous opioids and their peptides are expressed throughout the peripheral and central nervous system and regulate many different systems and functions. One of the main functions of the endogenous opioid peptide is to modulate our pain response through a descending pain modifying pathway. In light of this data, the mechanism of pain has been elucidated by studying the endogenous opioid mechanism. In this review, after the definition of pain, endogenous opioids and their receptors will be mentioned, the methodology and recent findings in pain research will be explained.