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 melatonin production by light received by the retina. Conversely it appears that melatonin may influence the circadian rhythms of animals. There is some experimental evidence that administration of melatonin may increase the amount of sleep in people with sleep disorders. However, the evidence is not convincing and the effect is not profound. Nevertheless, the deregulation of melatonin and its availability over-the-counter has led to many people taking melatonin to help sleep, without consulting a physician. [WordNet 1.5 +PJC]

A role for melatonin in sleep facilitation has been inferred from its effect on electroencephalogram patterns, but it has not been possible to demonstrate that wakefulness sleep cycles are driven by periodic accumulation, depletion, or regeneration of melatonin. --Uwe Ackermann, Essentials of Human Physiology, 1992

The Collaborative International Dictionary of English. 2000.

Look at other dictionaries:

  • 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 — /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; <… …   Universalium

  • 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

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