Enkephalins



Enkephalins are endogenous opioid peptides. In particular they are pentapeptides, so they have shorter chain than e.g. endorphines.

Enkephalins bind to all types of opioid receptors (δ, κ i μ) as well as, for example, morphine.

Origin
Endogenous opioid peptides in general are formed in the neural tissue via clevage of larger polypeptides. The precursor proenkephalin give rise to both known types of enkephalins- met-enkephalin and leu-enkephalin.

Importance
Enkephalins are released during exercise. Their concentration will increase significantly, for example, during long-distance running. However there are only speculations that these substances increase the threshold of pain.

High concentration of enkephalins (and opioid receptors also) is among other parts of the neuronal system in the limbic system. That is the reason why there is the possibility that endogenoid opioids affect the mental state and affective behavior.

Related articles

 * Limbic System