Opioid Receptors
Opioid receptors are integral components of the endogenous opioid system, which regulates pain perception and various physiological functions. Receptors mu (MOR), delta (DOR), and kappa (KOR) mediate the effects of endorphins, enkephalins, and dynorphins, which are endogenous opioid peptides (S. S. Shenoy & Lui, 2023). While known for their role in pain modulation, opioid receptors have also been implicated in the regulation of immune responses and cancer progression (Boland & Pockley, 2018). The interaction between opioid receptors and the immune system is complex, with evidence suggesting both immunosuppressive and stimulatory effects. The immunosuppressive potential of opioids, particularly through MOR activation, has raised interests in blocking the receptor to revive anti-tumor immune responses (Gondoh et al. , 2022; Lennon, Moss, Singleton, & Riou, 2012).