- For other uses, see Endorphin (disambiguation).
Endorphins are endogenous opioid biochemical compounds. They are peptides produced by the pituitary gland and the hypothalamus in vertebrates, and they resemble the opiates in their abilities to produce analgesia and a sense of well-being. In other words, they work as "natural pain killers".
The term "endorphin" is used generally to refer to all of the endogenous opioid compounds and implies a pharmacological activity (analogous to the activity of the corticosteroid category of biochemicals) as opposed to a specific chemical formulation.
History
These opioid neuropeptides were first discovered in 1975 by John Hughes and Hans Kosterlitz in the brain of a pig. They called their endorphins "enkephalins" (from the Greek εγκέφαλος, "cerebrum"). Several other types of endorphins were discovered later. The word endorphin itself is abbreviated from "endogenous morphine", which means a morphine produced naturally in the body.
Molecular biology
The best-known endorphins are α-, β- and γ-endorphin, of which β-endorphin appears to be most implicated in pain relief.
The amino acid residue sequence (primary structure) of β-endorphin is: Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr-Leu-Phe-Lys-Asn-Ala-Ile-Ile-Lys-Asn-Ala-Tyr-Lys-Lys-Gly-GluOH (Fries, 2002).
Mechanism of action
Beta-endorphin is released in peripheral, spinal and supra-spinal locations (i.e. body, spine and brain). Beta-endorphin has the highest affinity for the Mu1-opioid receptor, slightly lower affinity for the Mu2 and Delta-opioid receptors and low affinity for the Kappa1-opioid receptors receptor. Classically, Mu receptors are presynapic, and inhibit neurotransmitter release, through this mechanism, they inhibit the release of the inhibitory neurotransmitter GABA, and disinhibit the dopamine pathways, causing more dopamine to be released. By hijacking this process, exogenous opioids cause inappropriate dopamine release, and lead to abarant synaptic plasticity which causes addiction. Opioid receptors have many other and more important roles in the brain and periphery however, modulating pain, cardiac, gastric and vascular function as well as possibley panic and satiation.
Activity
Endorphins regulate feelings of pain and hunger and are connected to the production of sex hormones.
Oddly enough, they are also generated in response to certain spices such as chili peppers. Chili peppers have thus been used as a treatment for certain types of chronic pain.
According to some reports, laughter also releases endorphins in the brain. So besides widening the blood vessels, suppressing the production of stress hormones and raising antibody levels in the blood, laughing would thus also have an analgesic effect.
Another widely publicized effect of endorphin production is the so-called "runner's high", which is said to occur when strenuous exercise takes a person over a threshold that activates endorphin production. However, some research questions the mechanisms at work believing the high comes from completing a challenge rather than just through the exertion.
One theory of why some people find BDSM activities pleasurable is that these activities stimulate endorphins in a controlled way.
Ultraviolet light may also stimulate the release of endorphins.
In 1999, clinical researchers reported that inserting the acupuncture needles into specific body points triggers the production of endorphins [1].
Reference
- Goldberg, Jeff (1988). Anatomy of a Scientific Discovery. Bantam Books, 1988. ISBN 0553346318; ISBN 0553176161 (British edition); ISBN 0553052616 (hardcover).
- Fries, DS (2002). Opioid Analgesics. In Williams DA, Lemke TL. Foye's Principles of Medicinal Chemistry (5 ed.). Philadelphia: Lippincott Williams & Wilkins. ISBN 0-683-30737-1.
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