Melatonin: A biogenic amine that is found in animals and plants. In mammals, melatonin is produced by the PINEAL GLAND. Its secretion increases in darkness and decreases during exposure to light. Melatonin is implicated in the regulation of SLEEP, mood, and REPRODUCTION. Melatonin is also an effective antioxidant.Receptors, Melatonin: A family of G-protein-coupled receptors that are specific for and mediate the effects of MELATONIN. Activation of melatonin receptors has been associated with decreased intracellular CYCLIC AMP and increased hydrolysis of PHOSPHOINOSITIDES.Receptor, Melatonin, MT1: A melatonin receptor subtype that is primarily found in the HYPOTHALAMUS and in the KIDNEY.Receptor, Melatonin, MT2: A melatonin receptor subtype primarily found expressed in the BRAIN and RETINA.Pineal Gland: A light-sensitive neuroendocrine organ attached to the roof of the THIRD VENTRICLE of the brain. The pineal gland secretes MELATONIN, other BIOGENIC AMINES and NEUROPEPTIDES.Circadian Rhythm: The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs and stimuli, hormone secretion, sleeping, and feeding.Arylalkylamine N-Acetyltransferase: An acetyltransferase with specificity towards the amine group of aromatic alkylamines (arylalkylamines) such as SEROTONIN. This enzyme is also referred to as serotonin acetylase despite the fact that serotonin acetylation can also occur through the action of broad specificity acetyltransferases such as ARYLAMINE N-ACETYLTRANSFERASE.Acetylserotonin O-Methyltransferase: An enzyme that catalyzes the transfer of a methyl group from S-adenosylmethionine to N-acetylserotonin to form N-acetyl-5-methoxytryptamine (MELATONIN).Tryptamines: Decarboxylated monoamine derivatives of TRYPTOPHAN.Photoperiod: The time period of daily exposure that an organism receives from daylight or artificial light. It is believed that photoperiodic responses may affect the control of energy balance and thermoregulation.Light: That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.KynuramineAntioxidants: Naturally occurring or synthetic substances that inhibit or retard the oxidation of a substance to which it is added. They counteract the harmful and damaging effects of oxidation in animal tissues.Sleep Disorders, Circadian Rhythm: Dyssomnias associated with disruption of the normal 24 hour sleep wake cycle secondary to travel (e.g., JET LAG SYNDROME), shift work, or other causes.Sleep: A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility.5-Methoxytryptamine: Serotonin derivative proposed as potentiator for hypnotics and sedatives.Drug Implants: Small containers or pellets of a solid drug implanted in the body to achieve sustained release of the drug.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Chronobiology Disorders: Disruptions of the rhythmic cycle of bodily functions or activities.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)Tryptophan Hydroxylase: An enzyme that catalyzes the hydroxylation of TRYPTOPHAN to 5-HYDROXYTRYPTOPHAN in the presence of NADPH and molecular oxygen. It is important in the biosynthesis of SEROTONIN.Biopterin: A natural product that has been considered as a growth factor for some insects.Iron: A metallic element with atomic symbol Fe, atomic number 26, and atomic weight 55.85. It is an essential constituent of HEMOGLOBINS; CYTOCHROMES; and IRON-BINDING PROTEINS. It plays a role in cellular redox reactions and in the transport of OXYGEN.GTP Cyclohydrolase: (GTP cyclohydrolase I) or GTP 7,8-8,9-dihydrolase (pyrophosphate-forming) (GTP cyclohydrolase II). An enzyme group that hydrolyzes the imidazole ring of GTP, releasing carbon-8 as formate. Two C-N bonds are hydrolyzed and the pentase unit is isomerized. This is the first step in the synthesis of folic acid from GTP. EC (GTP cyclohydrolase I) and EC (GTP cyclohydrolase II).Tryptophan: An essential amino acid that is necessary for normal growth in infants and for NITROGEN balance in adults. It is a precursor of INDOLE ALKALOIDS in plants. It is a precursor of SEROTONIN (hence its use as an antidepressant and sleep aid). It can be a precursor to NIACIN, albeit inefficiently, in mammals.Reptiles: Cold-blooded, air-breathing VERTEBRATES belonging to the class Reptilia, usually covered with external scales or bony plates.Color: The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.Vacuum: A space in which the pressure is far below atmospheric pressure so that the remaining gases do not affect processes being carried on in the space.Wakefulness: A state in which there is an enhanced potential for sensitivity and an efficient responsiveness to external stimuli.Waldenstrom Macroglobulinemia: A lymphoproliferative disorder characterized by pleomorphic B-LYMPHOCYTES including PLASMA CELLS, with increased levels of monoclonal serum IMMUNOGLOBULIN M. There is lymphoplasmacytic cells infiltration into bone marrow and often other tissues, also known as lymphoplasmacytic lymphoma. Clinical features include ANEMIA; HEMORRHAGES; and hyperviscosity.Health Food: A non-medical term defined by the lay public as a food that has little or no preservatives, which has not undergone major processing, enrichment or refinement and which may be grown without pesticides. (from Segen, The Dictionary of Modern Medicine, 1992)Kava: Dried rhizome and roots of Piper methysticum, a shrub native to Oceania and known for its anti-anxiety and sedative properties. Heavy usage results in some adverse effects. It contains ALKALOIDS; LACTONES; kawain, methysticin, mucilage, STARCH, and yangonin. Kava is also the name of the pungent beverage prepared from the plant's roots.Naturopathy: A drugless system of therapy, making use of physical forces such as air, light, water, heat, massage. Treatments are often diet- and nutrition-oriented with attention given to the patient's personal history and lifestyle. (From Cassileth, Alternative Medicine Handbook, 1998, p329)Pharmacology, Clinical: The branch of pharmacology that deals directly with the effectiveness and safety of drugs in humans.Credentialing: The recognition of professional or technical competence through registration, certification, licensure, admission to association membership, the award of a diploma or degree, etc.Barbering: The occupation concerned with the cutting and dressing of the hair of customers and, of men, the shaving and trimming of the beard and mustache. (From Random House Unabridged Dictionary, 2d ed)Niacin: A water-soluble vitamin of the B complex occurring in various animal and plant tissues. It is required by the body for the formation of coenzymes NAD and NADP. It has PELLAGRA-curative, vasodilating, and antilipemic properties.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Fertility: The capacity to conceive or to induce conception. It may refer to either the male or female.Infertility, Female: Diminished or absent ability of a female to achieve conception.Fluoxetine: The first highly specific serotonin uptake inhibitor. It is used as an antidepressant and often has a more acceptable side-effects profile than traditional antidepressants.Antidepressive Agents, Second-Generation: A structurally and mechanistically diverse group of drugs that are not tricyclics or monoamine oxidase inhibitors. The most clinically important appear to act selectively on serotonergic systems, especially by inhibiting serotonin reuptake.Blindness: The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE.Internet: A loose confederation of computer communication networks around the world. The networks that make up the Internet are connected through several backbone networks. The Internet grew out of the US Government ARPAnet project and was designed to facilitate information exchange.Pulmonary Diffusing Capacity: The amount of a gas taken up, by the pulmonary capillary blood from the alveolar gas, per minute per unit of average pressure of the gradient of the gas across the BLOOD-AIR BARRIER.Sleep Disorders: Conditions characterized by disturbances of usual sleep patterns or behaviors. Sleep disorders may be divided into three major categories: DYSSOMNIAS (i.e. disorders characterized by insomnia or hypersomnia), PARASOMNIAS (abnormal sleep behaviors), and sleep disorders secondary to medical or psychiatric disorders. (From Thorpy, Sleep Disorders Medicine, 1994, p187)Jet Lag Syndrome: A chronobiologic disorder resulting from rapid travel across a number of time zones, characterized by insomnia or hypersomnolence, fatigue, behavioral symptoms, headaches, and gastrointestinal disturbances. (From Cooper, Sleep, 1994, pp593-8)Sleep Deprivation: The state of being deprived of sleep under experimental conditions, due to life events, or from a wide variety of pathophysiologic causes such as medication effect, chronic illness, psychiatric illness, or sleep disorder.Sleep, REM: A stage of sleep characterized by rapid movements of the eye and low voltage fast pattern EEG. It is usually associated with dreaming.Serotonin: A biochemical messenger and regulator, synthesized from the essential amino acid L-TRYPTOPHAN. In humans it is found primarily in the central nervous system, gastrointestinal tract, and blood platelets. Serotonin mediates several important physiological functions including neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity. Multiple receptor families (RECEPTORS, SEROTONIN) explain the broad physiological actions and distribution of this biochemical mediator.Appetite: Natural recurring desire for food. Alterations may be induced by APPETITE DEPRESSANTS or APPETITE STIMULANTS.Serotonin Plasma Membrane Transport Proteins: Sodium chloride-dependent neurotransmitter symporters located primarily on the PLASMA MEMBRANE of serotonergic neurons. They are different than SEROTONIN RECEPTORS, which signal cellular responses to SEROTONIN. They remove SEROTONIN from the EXTRACELLULAR SPACE by high affinity reuptake into PRESYNAPTIC TERMINALS. Regulates signal amplitude and duration at serotonergic synapses and is the site of action of the SEROTONIN UPTAKE INHIBITORS.

Melatonin biosynthesis: the structure of serotonin N-acetyltransferase at 2.5 A resolution suggests a catalytic mechanism. (1/1746)

Conversion of serotonin to N-acetylserotonin, the precursor of the circadian neurohormone melatonin, is catalyzed by serotonin N-acetyltransferase (AANAT) in a reaction requiring acetyl coenzyme A (AcCoA). AANAT is a globular protein consisting of an eight-stranded beta sheet flanked by five alpha helices; a conserved motif in the center of the beta sheet forms the cofactor binding site. Three polypeptide loops converge above the AcCoA binding site, creating a hydrophobic funnel leading toward the cofactor and serotonin binding sites in the protein interior. Two conserved histidines not found in other NATs are located at the bottom of the funnel in the active site, suggesting a catalytic mechanism for acetylation involving imidazole groups acting as general acid/base catalysts.  (+info)

Prolactin replacement fails to inhibit reactivation of gonadotropin secretion in rams treated with melatonin under long days. (2/1746)

This study tested the hypothesis that prolactin (PRL) inhibits gonadotropin secretion in rams maintained under long days and that treatment with melatonin (s.c. continuous-release implant; MEL-IMP) reactivates the reproductive axis by suppressing PRL secretion. Adult Soay rams were maintained under long days (16L:8D) and received 1) no further treatment (control, C); 2) MEL-IMP for 16 wk and injections of saline/vehicle for the first 8 wk (M); 3) MEL-IMP for 16 wk and exogenous PRL (s.c. 5 mg ovine PRL 3x daily) for the first 8 wk (M+P). The treatment with melatonin induced a rapid increase in the blood concentrations of FSH and testosterone, rapid growth of the testes, an increase in the frequency of LH pulses, and a decrease in the LH response to N-methyl-D,L-aspartic acid. The concomitant treatment with exogenous PRL had no effect on these reproductive responses but caused a significant delay in the timing of the sexual skin color and growth of the winter pelage. These results do not support the hypothesis and suggest that PRL at physiological long-day concentrations, while being totally ineffective as an inhibitor of gonadotropin secretion, acts in the peripheral tissues and skin to maintain summer characteristics.  (+info)

Melatonin inhibits release of luteinizing hormone (LH) via decrease of [Ca2+]i and cyclic AMP. (3/1746)

The role of [Ca2+]i and cAMP in transduction of the melatonin inhibitory effect on GnRH-induced LH release from neonatal rat gonadotrophs has been studied, because melatonin inhibits the increase of both intracellular messengers. Treatments increasing Ca2+ influx (S(-) Bay K8644 or KCI) or cAMP concentration (8-bromo-cAMP or 3-isobutyl-1-methylxanthine) potentiated the GnRH-induced LH release and partially diminished the inhibitory effect of melatonin. Combination of the treatments increasing cAMP and calcium concentrations blocked completely the melatonin inhibition of LH release. The combined treatment with 8-bromo-cAMP and S(-) Bay K8644 also blocked the melatonin inhibition of GnRH-induced [Ca2+]i increase in 89 % of the gonadotrophs, while any of the treatments alone blocked the melatonin effect in about 25 % of these cells. These observations suggest that a cAMP-dependent pathway is involved in regulation of Ca2+ influx by melatonin and melatonin inhibition of LH release may be mediated by the decrease of both messengers.  (+info)

Two arylalkylamine N-acetyltransferase genes mediate melatonin synthesis in fish. (4/1746)

Serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT, EC is the first enzyme in the conversion of serotonin to melatonin. Large changes in AANAT activity play an important role in the daily rhythms in melatonin production. Although a single AANAT gene has been found in mammals and the chicken, we have now identified two AANAT genes in fish. These genes are designated AANAT-1 and AANAT-2; all known AANATs belong to the AANAT-1 subfamily. Pike AANAT-1 is nearly exclusively expressed in the retina and AANAT-2 in the pineal gland. The abundance of each mRNA changes on a circadian basis, with retinal AANAT-1 mRNA peaking in late afternoon and pineal AANAT-2 mRNA peaking 6 h later. The pike AANAT-1 and AANAT-2 enzymes (66% identical amino acids) exhibit marked differences in their affinity for serotonin, relative affinity for indoleethylamines versus phenylethylamines and temperature-activity relationships. Two AANAT genes also exist in another fish, the trout. The evolution of two AANATs may represent a strategy to optimally meet tissue-related requirements for synthesis of melatonin: pineal melatonin serves an endocrine role and retinal melatonin plays a paracrine role.  (+info)

Ageing and the circadian and homeostatic regulation of human sleep during forced desynchrony of rest, melatonin and temperature rhythms. (5/1746)

1. The circadian timing system has been implicated in age-related changes in sleep structure, timing and consolidation in humans. 2. We investigated the circadian regulation of sleep in 13 older men and women and 11 young men by forced desynchrony of polysomnographically recorded sleep episodes (total, 482; 9 h 20 min each) and the circadian rhythms of plasma melatonin and core body temperature. 3. Stage 4 sleep was reduced in older people. Overall levels of rapid eye movement (REM) sleep were not significantly affected by age. The latencies to REM sleep were shorter in older people when sleep coincided with the melatonin rhythm. REM sleep was increased in the first quarter of the sleep episode and the increase of REM sleep in the course of sleep was diminished in older people. 4. Sleep propensity co-varied with the circadian rhythms of body temperature and plasma melatonin in both age groups. Sleep latencies were longest just before the onset of melatonin secretion and short sleep latencies were observed close to the temperature nadir. In older people sleep latencies were longer close to the crest of the melatonin rhythm. 5. In older people sleep duration was reduced at all circadian phases and sleep consolidation deteriorated more rapidly during the course of sleep, especially when the second half of the sleep episode occurred after the crest of the melatonin rhythm. 6. The data demonstrate age-related decrements in sleep consolidation and increased susceptibility to circadian phase misalignment in older people. These changes, and the associated internal phase advance of the propensity to awaken from sleep, appear to be related to the interaction between a reduction in the homeostatic drive for sleep and a reduced strength of the circadian signal promoting sleep in the early morning.  (+info)

Potentiation of isoniazid activity against Mycobacterium tuberculosis by melatonin. (6/1746)

The limited number of effective antituberculosis drugs available necessitates optimizing current treatments. We show that melatonin, which is synthesized in the pineal gland, can cause at least a threefold increase in the efficacy of isoniazid. This suggests that tuberculosis chemotherapy can be improved by innate molecules such as melatonin.  (+info)

The relationship between 6-sulphatoxymelatonin and polysomnographic sleep in good sleeping controls and wake maintenance insomniacs, aged 55-80 years. (7/1746)

The pineal hormone, melatonin, is reported to possess hypnotic properties. This has led to an investigation of the relationship between the endogenous melatonin rhythm and sleep. However, this relationship has yet to be fully examined in aged insomniacs and controls. From media advertisements, 16 good sleeping controls (11F, 5M) and 16 sleep maintenance insomniacs (11F, 5M), aged over 55 years, were recruited to participate in a study involving four nights of polysomnographically (PSG) measured sleep followed by a 26 h constant routine. During the constant routine, 2 h urine samples were collected and analysed for the melatonin metabolite, 6-sulphatoxymelatonin (aMT.6S). This was used to determine total melatonin excretion. As well, the following circadian melatonin parameters were calculated from fifth order polynomial curve fitting analyses, the goodness of the polynomial curve fit, peak melatonin concentration, the phase of the melatonin rhythm, and melatonin and sleep rhythm synchrony. Apart for one control, all subjects showed significant circadian melatonin rhythms. Although insomniacs showed a greater amount of wakefulness, less sleep in total, and lower sleep efficiency, no significant group differences were observed in any of the melatonin parameters. In addition, while subjects with more reliable melatonin curve fits showed shorter sleep latencies and higher sleep efficiencies, correlational analyses revealed no other significant relationships between any melatonin and PSG sleep parameters. Overall, the present results suggest that neither melatonin amplitude nor phase are related to sleep quality in the aged.  (+info)

A 50-Hz electromagnetic field impairs sleep. (8/1746)

In view of reports of health problems induced by low frequency (50-60 Hz) electromagnetic fields (EMF), we carried out a study in 18 healthy subjects, comparing sleep with and without exposure to a 50 Hz/1 mu Tesla electrical field. We found that the EMF condition was associated with reduced: total sleep time (TST), sleep efficiency, stages 3 + 4 slow wave sleep (SWS), and slow wave activity (SWA). Circulating melatonin, growth hormone, prolactin, testosterone or cortisol were not affected. The results suggest that commonly occurring low frequency electromagnetic fields may interfere with sleep.  (+info)

  • BACKGROUND: Experimental data from animals suggest a protective role for the pineal hormone melatonin in the etiology of breast cancer, but results from the few retrospective case-control studies that examined the association in humans have been inconsistent. (
  • To determine whether low levels of endogenous melatonin are associated with an increased risk for developing breast cancer, we conducted a prospective nested case-control study among British women. (
  • However] till there is more research study in addition to clinical trials to determine how precisely the melatonin is working, we can't advise that people with osteoporosis go on and just take melatonin supplements. (
  • If you feel the need to take melatonin then it is sensible to start with a low dosage of 1 mg, after some time you can work that up to 3 mg. (
  • METHODS: Concentrations of 6-sulfatoxymelatonin, the main metabolite of melatonin in urine and a validated marker of circulating melatonin levels, were measured by radioimmunoassay in 24-hour urine samples collected from women shortly after enrollment in the prospective Guernsey III Study. (
  • The aim of the study was to examine concentrations and relationships between melatonin levels assessed at 0:200 hrs and 0:700 hrs, lipid hydroperoxide (LPO) assessed at 0:200 hrs and 0:700 hrs, and apolipoprotein (apo)AI, apoAII, apoB, high sensitivity C-reactive protein (hsCRP) and NT-proBNP, in 27 patients with chronic heart failure (CHF) (17 patients - with NYHA class II and 10 - with NYHA class III). (
  • Furthermore, evening chronotypes' melatonin rhythms had later peak onset compared with morning types (4.90 hours, 95% CI, 3.94-6.09 vs. 3.64 hours, 95% CI, 2.99-4.43). (
  • Not an ideal frame for environments where light can reach the eye from the side, but may work to help preserve and entrain melatonin onset where light is ONLY coming from the front, say in a darkened movie theater for example. (
  • Melatonin has a unique ability to pass through all the blood barriers in the body and serves as a focal point for physiological function. (
  • At the American Academy of Neurology 65th Annual Meeting, sleep researchers from the S o Paulo Headache Center presented results from a multicenter, randomized, double-blind, placebo-controlled trial assessing the ability of melatonin to prevent migraine headaches. (
  • Melatonin also works great for jet lag from eastward travel, says Breus, who recommends taking 0.5 mg of melatonin 90 minutes before bedtime in the place you're traveling to. (
  • Most of the research on melatonin has focused on its role in maintaining normal sleep/wake rhythms. (
  • Liposomal technology helps to maintain the benefits of melatonin by protecting it from the degradative environment of the stomach. (
  • Participants were randomly assigned to 3 mg of melatonin, 25 mg of amitriptyline, or placebo for 3 months. (
  • The mean reduction in headache frequency was 2.7 in the melatonin group, 2.18 in the amitriptyline group, and 1.18 in the placebo group. (
  • The proportion of responders was greatest in the melatonin group at 54% vs 39% for amitriptyline and 20% for placebo. (
  • Patients gained weight in both the amitriptyline and placebo groups, but melatonin was associated with weight loss. (
  • 3) This study evaluates the effects of cow's milk intake (Group 1: G1) for 20 days at breakfast on saliva melatonin concentration at 22:00 and 23:00 on 0, 10, and 21 days of the intervention period in Japanese university male athletes attending a university soccer club. (
  • The effects of a single 3-mg dose of melatonin on the postural control and cognitive performance of community-dwelling older adults were documented. (
  • Immediately before and 1 hr after taking a dose of melatonin, they completed a single-leg standing task after stepping down with and without a simultaneous Stroop test, and a double-leg standing task. (
  • After a weekend of staying up late and sleeping in, a low (0.3 mg) dose of melatonin late Sunday afternoon can also help you get to sleep at a regular hour and avoid the "Monday morning blues" that often happen when your days off disrupt your body clock, says Lewy. (
  • Intriguingly, melatonin rhythms were dependent on both chronotype and rotating-shift work type, and better alignment of rotating-shift work and chronotype appeared to produce less disrupted melatonin rhythms. (
  • His research also suggests that for some patients, as little as 0.3 mg of melatonin daily in the late afternoon may ease symptoms of winter depression brought on by shorter days and shifting circadian rhythms. (
  • Because its internal regulation depends on light, melatonin is part of chronobiology, the study of biological mechanisms and their adaptations to lunar and solar related rhythms (Klein et al. (
  • Previous studies associated night-shift work with melatonin disruption, with mixed evidence regarding the modulating effects of chronotype (i.e., diurnal preference). (
  • The volunteers received either 10 mg oral melatonin or 10 mg intravenous melatonin on two separate study days. (
  • k a , t 1/2 absorption , t max , C max , t 1/2 elimination, AUC 0-∞ , and bioavailability were determined for oral melatonin. (
  • Mean (SD) t 1/2 absorption of oral melatonin was 6.0 (3.1) min. (
  • Oral melatonin consisted of one gelatine capsule containing 10 mg melatonin. (
  • In addition, supplemental melatonin may also assist in helping improve blood sugar, blood pressure, and weight loss. (
  • In the intervention group (G1), salivary melatonin concentration increased at 22:00 in comparison with that before intervention, but there was no significant change in the control group (Group 2: G2). (
  • As melatonin diminishes with age, our biological functions are impaired. (
  • Photoresponsiveness of the reproductive system is mediated by the internal biological clock, transcriptional factors, period genes, photic input, GnRH (gonadotropin-releasing hormone) neurons, and melatonin secretions. (