Kyotorphin is a neuroactive dipeptide

Dipeptide

A dipeptide is a molecule consisting of two amino acids joined by a single peptide bond.Dipeptides are produced from polypeptides by the action of the hydrolase enzyme dipeptidyl peptidase. Dietary proteins are digested to dipeptides and amino acids, and the dipeptides are absorbed more rapidly...

 which plays a role in pain regulation in the brain. It was first isolated from bovine brain, by Japanese scientists in 1979. Kyotorphin was named for the site of its discovery, Kyoto

Kyoto

is a city in the central part of the island of Honshū, Japan. It has a population close to 1.5 million. Formerly the imperial capital of Japan, it is now the capital of Kyoto Prefecture, as well as a major part of the Osaka-Kobe-Kyoto metropolitan area.-History:...

, Japan and because of its morphine

Morphine

Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...

- (or endorphin

Endorphin

Endorphins are endogenous opioid peptides that function as neurotransmitters. They are produced by the pituitary gland and the hypothalamus in vertebrates during exercise, excitement, pain, consumption of spicy food, love and orgasm, and they resemble the opiates in their abilities to produce...

-) like analgesic activity. Kyotorphin has an analgesic

Analgesic

An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

 effect, but it does not interact with the opioid receptors. Instead, it acts by releasing met-enkephalin

Met-enkephalin

[Met]enkephalin, sometimes referred to as opioid growth factor , is a naturally-occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being [leu]enkephalin...

 and stabilizing it from degradation. It may also possess properties of neuromediator

Neurotransmitter

Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

/neuromodulator. It has been shown that kyotorphin is present in the human cerebrospinal fluid

Cerebrospinal fluid

Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...

and that its concentration is lower in patients with persistent pain.