Biochemistry, Endogenous Opioids

Excerpt

Opiates, among the oldest drugs known to humankind, have been used medically for thousands of years for pain relief and sedation. They are natural extracts of the poppy plant, Papaver somniferum. In particular, morphine (named after Morpheus, the Greek God of dreams) binds to opioid receptors in the central and peripheral nervous systems. The search for endogenous ligands for these receptors led to the discovery of two closely related pentapeptides (enkephalins) by Hans Kosterlitz et al. in 1975: methionine-enkephalin (met-enkephalin) and leucine-enkephalin (leu-enkephalin).

Subsequently, a plethora of other endogenous opioid peptides were identified. The endogenous opioid system is vital in regulating various physiologic functions like pain relief (analgesia), euphoria induction, stress resilience, cardiovascular protection, food intake control, etc. Three genetically distinct opioid peptides families are considered classical members of the endogenous opioid system:

1. Endorphins

2. Enkephalins

3. Dynorphin