Endomorphin 1 is an endogenous opioid peptide and one of the two endomorphins. Endomorphin 1 has exceptionally high affinity and selectivity for µ opioid receptors (4000- and 15000-fold preference over delta and kappa respectively and may be the actual endogenous ligand of the µ-receptor. Endomorphin 1 is distributed throughout the human, rodent and primate central and peripheral nervous systems, and has a more potent analgesic effect in acute and neuropathic pain than other opiates such as morphine, with fewer side effects.
