The endomorphin system and its evolving neurophysiological role

Pharmacol Rev. 2007 Mar;59(1):88-123. doi: 10.1124/pr.59.1.3.


Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) are two endogenous opioid peptides with high affinity and remarkable selectivity for the mu-opioid receptor. The neuroanatomical distribution of endomorphins reflects their potential endogenous role in many major physiological processes, which include perception of pain, responses related to stress, and complex functions such as reward, arousal, and vigilance, as well as autonomic, cognitive, neuroendocrine, and limbic homeostasis. In this review we discuss the biological effects of endomorphin-1 and endomorphin-2 in relation to their distribution in the central and peripheral nervous systems. We describe the relationship between these two mu-opioid receptor-selective peptides and endogenous neurohormones and neurotransmitters. We also evaluate the role of endomorphins from the physiological point of view and report selectively on the most important findings in their pharmacology.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Central Nervous System / anatomy & histology
  • Central Nervous System / physiology*
  • Endorphins / chemistry
  • Endorphins / metabolism
  • Endorphins / physiology*
  • Humans
  • Models, Anatomic
  • Models, Biological
  • Pain / physiopathology
  • Peripheral Nervous System / anatomy & histology
  • Peripheral Nervous System / physiology*


  • Endorphins