/mel'euh toh"nin/, n. Physiol.a hormone secreted by the pineal gland in inverse proportion to the amount of light received by the retina, important in the regulation of biorhythms: in amphibians, it causes a lightening of the skin.[1955-60; < Gk méla(s) black + TONE + -IN2]
* * *It appears to be important in regulating sleeping cycles; more is produced at night, and test subjects injected with it become sleepy. Melatonin may be involved in seasonal affective disorder. In mammals other than humans, melatonin may act as a cue to breeding and mating in season.
* * *▪ hormonehormone secreted by the pineal gland, a tiny endocrine gland situated at the centre of the brain. Melatonin was discovered in 1958 by American physician Aaron B. Lerner and his colleagues at Yale University School of Medicine. Melatonin, a derivative of the amino acid tryptophan, is produced in humans, other mammals, birds, reptiles, and amphibians.In humans, melatonin plays an important role in the regulation of sleep cycles (i.e., circadian rhythm). Its production is influenced by the detection of light and dark by the retina of the eye (eye, human). For example, the production of melatonin is inhibited when the retina detects light and is stimulated in the absence of light. Special photoreceptor cells (cell) in the retina send signals about light status to the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain. These signals are then transmitted to the pineal gland. Melatonin generation by the pineal gland, which peaks during the nighttime hours, induces physiological changes that promote sleep, such as decreased body temperature and respiration rate. During the day, melatonin levels are low because large amounts of light are detected by the retina. Light inhibition of melatonin production is central to stimulating wakefulness in the morning and to maintaining alertness throughout the day.Melatonin receptors (receptor) are found in the SCN and the pituitary gland of the brain, as well as in the ovaries (ovary), blood vessels (blood vessel), and intestinal tract (intestine). There is a high concentration of receptors in the SCN because this is where melatonin mediates the majority of its affects on circadian rhythm. The binding of melatonin to its receptors on the pituitary gland and the ovaries appears to play a role in regulating the release of reproductive hormones in females. For example, the timing, length, and frequency of menstrual cycles (menstruation) in women are influenced by melatonin. In addition, in certain mammals (other than humans), such as horses and sheep, melatonin acts as a breeding and mating cue, since it is produced in greater amounts in response to the longer nights of winter and less so during summer. Animals who time their mating or breeding to coincide with favourable seasons (such as spring) may depend on melatonin production as a kind of biological clock that regulates their reproductive cycles on the basis of the length of the solar day. In amphibians, melatonin stimulates a lightening of the skin.Melatonin has anti-aging properties. For example, it acts as an antioxidant, neutralizing harmful oxidative radicals (radical), and it is capable of activating certain antioxidant enzymes (enzyme). Melatonin production gradually declines with age, and its loss is associated with several age-related diseases. Melatonin also plays a role in modulating certain functions of the immune system.
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melatonin — mel a*tonin n. (Physiology) A hormone secreted by the pineal gland. Chemically it is N acety 5 methoxytryptamine. Research has indicated that there are daily rhythms in secretion of melatonin, in particular due to the depressing effect on… … The Collaborative International Dictionary of English
Melatonin — Melatonin, 5 Methoxy N Acetyltryptamin, im Pinealorgan bzw. der Epiphyse nachgewiesenes, durch N Acetylierung und 5 Methylierung aus Serotonin entstehendes Hormon; bewirkt bei Fischen und Froschlurchen als Gegenspieler des ⇒… … Deutsch wörterbuch der biologie
melatonin — (n.) 1958, from Gk. melas black, dark (see MELANIN (Cf. melanin)) + ending from SEROTONIN (Cf. serotonin). So called because its secretion is inhibited by sunlight … Etymology dictionary
melatonin — [mel΄ə tō′nin] n. [ MELA(NO) + TON(IC) + IN1] a hormone, C13H16N2O2, produced by the pineal body, that lightens skin pigmentation, inhibits estrus, etc.: its secretion is inhibited by sunlight … English World dictionary
Melatonin — Not to be confused with Melanin or Melanotan. Melatonin Systematic (IUPAC) name … Wikipedia
Melatonin — Strukturformel Allgemeines Name Melatonin Andere Namen N … Deutsch Wikipedia
Melatonin — A hormone produced by the pineal gland, melatonin is intimately involved in regulating the sleeping and waking cycles, among other processes. Melatonin supplements are sometimes used by people who have chronic insomnia. Always see your doctor… … Medical dictionary
Melatonin — Me|la|to|nin 〈n. 15; unz.; Biol., Med.〉 Hormon der Zirbeldrüse, das bei Amphibien zu einer Aufhellung der Haut führt u. beim Menschen an der Regulation des biolog. Zeitsinnes beteiligt ist [<Melano... + grch. tonos „Spannung“] * * *… … Universal-Lexikon
melatonin — n. a hormone produced by the pineal gland in darkness but not in bright light. Melatonin receptors in the brain, in a nucleus immediately above the optic chiasm, react to this hormone and synchronize the nucleus to the 24 hour day/night rhythm,… … The new mediacal dictionary
melatonin — melatoninas statusas T sritis chemija apibrėžtis Kankorėžinės liaukos hormonas. formulė C₈H₅N(OCH₃)CH₂CH₂NHCOCH₃ atitikmenys: angl. melatonin rus. мелатонин ryšiai: sinonimas – 3 (2 etanoilaminoetil) 5 metoksiindolas … Chemijos terminų aiškinamasis žodynas