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Melatonin, an indoleamine, is a natural compound produced by various organisms, including bacteria and eukaryotes. [1] Its discovery in 1958 by Aaron B. Lerner and colleagues stemmed from the isolation of a substance from the pineal gland of cows that could induce skin lightening in common frogs.
The bioavailability of melatonin is between 2.5 and 50%. [6] [7] Melatonin is rapidly absorbed and distributed, reaching peak plasma concentrations after 60 minutes of administration, and is then eliminated. [6] Usual doses of exogenous melatonin of 1 to 12 mg produce melatonin concentrations 10 to 100 times higher than endogenous peak levels. [7]
Melatonin receptors are G protein-coupled receptors (GPCR) which bind melatonin. [1] Three types of melatonin receptors have been cloned.The MT 1 (or Mel 1A or MTNR1A) and MT 2 (or Mel 1B or MTNR1B) receptor subtypes are present in humans and other mammals, [2] while an additional melatonin receptor subtype MT 3 (or Mel 1C or MTNR1C) has been identified in amphibia and birds. [3]
N1-Acetyl-5-methoxykynuramine (AMK) is a metabolite of melatonin that could improve memory by acting on the melatonin receptors. AMK is produced from the metabolization of melatonin by the kynuramine pathway in the brain. [1] It significantly increased the phosphorylation of both ERK and CREB in the hippocampus. [2] It also helps scavenge free ...
For example, melatonin, a hormonal timekeeper, is considered a strongly circadian hormone, whose secretion increases at dim light and peaks during nocturnal sleep, diminishing with bright light to the eyes. [132] In some organisms melatonin secretion depends on sleep, but in humans it is independent of sleep and depends only on light level.
Additionally, the hormone melatonin, released before sleep, is triggered by darkness and can make people feel sleepy earlier, in turn affecting mood and mental health.
A chronobiotic is an agent that can cause phase adjustment of the circadian rhythm (biological body clock). That is, it is a substance capable of therapeutically entraining or re-entraining long-term desynchronized or short-term dissociated circadian rhythms in mammals, or prophylactically preventing their disruption following an environmental insult such as is caused by rapid travel across ...
This is typically a seasonal event and controlled by light exposure through the pineal gland that releases melatonin. Melatonin may repress stimulation of reproduction in long-day breeders and stimulate reproduction in short-day breeders. Melatonin is thought to act by regulating the hypothalamic pulse activity of the gonadotropin-releasing ...