Melatonin functions

Naturally Occurring Compounds. Many derivatives of iadole are found ia plants and animals where they are derived from the amino acid tryptophan. Several of these have important biological function or activity. Serotonin [50-67-9] (12) functions as a neurotransmitter and vasoconstrictor (35). Melatonin [73-31-4] (13) production is controlled daily by the circadian cycle and its physiological level iafluences, and seasonal rhythms ia humans and other species (36). Indole-3-acetic acid [87-51-4] (14) is a plant growth stimulant used ia several horticultural appHcations (37). 

Melatonin. Melatonin (A/-acetyl-5-metlioxytryptaniine) [73-31-4] C 2H gN2O2(250) is secreted from the pineal gland and retina during dark periods of the vertebrate circadian rhythm (65). Melatonin regulates biological rhythms and neuroendocrine function and is formed from serotonin (5-HT). 

Pharmacomodulated melatonin analogs were prepared by Berteina-Raboin et al. using SPOS [33]. C-2 carbon functionalized 5-carboxamido-... 

Figure 22.9 Summary of the influence of varying factors on sleep and waking. The EEG is shown diagramatically in the typical arousal (awake) state and in both non-REM (slow wave) and REM sleep. Appropriate activity levels, high or low, are shown for the different factors such as light input, melatonin secretion or ACh, NA, and 5-HT function in the different phases...

Melatonin and its receptors biological function in circadian sleep-wake regulation... 

Melatonin secretion is synchronized to the light/dark (LD) cycle, with a nocturnal maximum (in young humans, about 200 pg/ml plasma) and low diurnal baseline levels (about 10 pg/ml plasma). Studies have supported the value of the exogenous administration of melatonin in circadian rhythm sleep disorders, insomnia, cancer, neurodegenerative diseases, disorders of the immune function, and oxidative damage (Karasek et al. 2002 Pandi-Perumal et al. 2005, 2006 Srinivasan et al. 2005a,b, 2006 Hardeland et al. 2006). 

Figure 10.3 Possible cellular pathways involved in the physiological modulation of GABAergic function by melatonin via the MTi receptor. See text for explanation. (See also Plate 2.)...

Brydon, L., Petit, L., Delagrange, P., Strosberg, A. D. Jockers, R. (2001). Functional expression of mt2 (mellb) melatonin receptors in human paz6 adipocytes. Endocrinology 142, 4264-71. 

Macchi, M. M. Bruce, J. N. (2004). Human pineal physiology and functional significance of melatonin. Front. Neuroendocrinol. 25, 177-95. 

Masana, M. I., Soares, J. M. Jr Dubocovich, M. L. (2005). 17beta-Estradiol modulates hMT(l) melatonin receptor function. Neuroendocrinology 81, 87-95. 

Tricoire, H., Moller, M., Chemineau, P. 8r Malpaux, B. (2003). Origin of cerebrospinal fluid melatonin and possible function in the integration of photoperiod. Reprod. Suppl. 61, 311-21. 

HT modulates neuroendocrine function 239 5-HT modulates circadian rhythmicity 239 5-HT modulates feeding behavior and food intake 239 Not only does 5-HT have important physiological effects of its own but it is also the precursor of the hormone melatonin 240... 

Dubocovich, M. L., Rivera-Bermudez, M. A., Gerdin, M. J. and Masana, M. I. Molecular pharmacology, regulation and function of mammalian melatonin receptors. Front. Biol. 8 dl093—1108, 2003. 

Lucas RJ, Foster RG 1999 Neither functional rod photoreceptors nor rod or cone outer segments are required for the photic inhibition of pineal melatonin. Endocrinology 140 1520-1524... 

Plasma melatonin levels and urinary levels of its primary metabolite, 6-hydroxy melatonin, have been used in research as indices of noradrenergic functioning before and after treatment with antidepressants. 

Barrenetxe J, Delagrange P, Martinez JA Physiologic and metabolic functions of melatonin. J Physiol Biochem 2004 60 61. [PMID 15352385]... 

The monoamine hypothesis, like the neurotrophic hypothesis, is at best incomplete. Many studies have not found an alteration in function or levels of monoamines in depressed patients. In addition, some candidate antidepressant agents under study do not act directly on the monoamine system. These include glutamate antagonists, melatonin agonists, and glucocorticoid-specific agents. Thus, monoamine function appears to be an important but not exclusive factor in the pathophysiology of depression. 

Protected and unprotected indole derivatives dissolved in hydrogen fluoride are also fluorinated by 18F-F. The relatively stable melatonin (10), a neurohormone responsible for the biological clock and other brain functions, gave only the 6-[l8F]fluoro derivative 11, but even the more fragile 5-hydroxytryptophan (12) could be fluorinated under these conditions resulting in a mixture of 4- and 6-[l8F]fluorohydroxytryptophan 13.54... 

Serotonin and melatonin are evidently involved in maintenance of the 24-h circadian rhythm of the body (see Section 13).792/792a Melatonin regulates the sexual cycle in photoperiodic animals and influences the onset of puberty.792-794 The serotonin content of the brain is influenced by the diet, being higher after a meal rich in carbohydrates. Serotonin may serve as a chemical message sent from one set of neurons to the rest of the brain, reporting on the nature of dietary intake.784 Melatonin, which can readily form free radicals, may function as part of the body s antioxidant system.795 796... 

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