Evidence gathered during the last years shows that the pineal hormone melatonin participates in the regulation of the heart. Melatoninergic receptors were found in the heart and vessels and also in the higher centers involved in the regulation of cardiovascular system. Melatonin protects the heart against ischaemia-reperfusion injury and also against cardiotoxic effects of adriamycin and alloxan. Lack of melatonin was repeatedly reported in patients with coronary heart disease. Intake of this hormone leads to decrease of blood pressure in normotensive and hypertensive subjects, while pinealectomy induces hypertension. In addition melatonin can probably influence the levels of intracellular calcium in cardiomyocytes. The aim of this review is to summarize available evidence about effects of melatonin on the heart. Mechanisms involved in these effects are also suggested.

• MeSH
• lidé MeSH
• melatonin fyziologie   MeSH
• srdce fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• melatonin MeSH

Melatonin is a hormone produced mainly by the pineal gland during the dark phase of the circadian cycle with typical circadian rhythm with maximal secretion at night and depression during the day. The indoleamine has wide regulatory and integrative functions. Perhaps there is no organ and system which can escape the influence of epiphysis, incl. reproductive, cardiovascular gastrointestinal, respiratory as well as renal system and water and mineral metabolism. Melatonin regulates not only neuroendocrine functions but also has immunoenhancing and antitumor effects. That is why there are trials/attempts these properties to be utilized in the treatment of malignancies and AIDS patients. The hormone plays a certain role in temperature regulation in mammals as well as in the onset of puberty and senescence. Attention has been paid to its role as a scavenger of toxic free radicals and it is believed that melatonin is the most effective lipophilic antioxidant. However, the exact mechanism of action of this high active hormone remains to be elucidated. Further studies are also necessary for discovering the next its properties and functions.

• MeSH
• cirkadiánní rytmus * MeSH
• lidé MeSH
• melatonin metabolismus   fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• melatonin MeSH

The functions of the epiphyseal hormone melatonin are: 1)it is a marker of photo periodicity, especially the length of the interval from light to darkness; 2) it directs the physiological and endocrinological processes that influence the interval from light to darkness; and 3) seasonal variations are the basis of such processes. The pineal gland in mammals is connected to the network of nerves that activates or inhibits the enzyme system of the synthesis of melatonin. Darkness stimulates it and light inhibits it. In humans the concentration of circulating melatonin during the day is less than 20 pg/ml, but at night it rises 4- or 5-fold. However, the plasma melatonin level fluctuates depending on the phase of menstruation: the peak is at the beginning of the cycle, and it decreases to the minimum at around ovulation (the maximum is about 4.5 times higher than the minimum). The association between melatonin and ovulation is the hypothalamic generator of pulsatile secretion of the gonadotropin releasing hormone (GnRH). In golden hamsters melatonin lowered the expression of estrogen receptors in the neurons of the hypothalamic area, preoptica medialis. In women with hypothalamic amenorrhea and positive progesterone test as well as in ovulating women the nighttime secretion of melatonin peaked at about 3 o'clock in the morning, but the level of plasma melatonin was significantly higher at night and during the day than in healthy women. It seems that there is a connection between the beginning of preovulatory appearance of luteinizing hormone (LH) and early morning drop in melatonin level in the sense that melatonin contributes to its initiation. There have been good results in recent research to inhibit the generator of pulsatile secretion of GnRH necessary for ovulation by using melatonin in a new type of oral contraceptive. The oral contraceptive uses melatonin rather than estrogen, either alone or in combination with norethindrone.

• Klíčová slova
• Biology, Central Nervous System, Contraception, Contraception Research *, Contraceptive Methods, Contraceptive Mode Of Action *, Endocrine System, Family Planning, Follicle Stimulating Hormone *, Gonadotropins, Gonadotropins, Pituitary *, Hormone Receptors *, Hormones, Hypothalamus *, Luteinizing Hormone *, Membrane Proteins, Oral Contraceptives, Oral Contraceptives, Combined *, Physiology, Pituitary Hormones *,
• MeSH
• cirkadiánní rytmus MeSH
• kontraceptiva orální * MeSH
• lidé MeSH
• melatonin farmakologie   fyziologie   MeSH
• ovulace účinky léků   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• Názvy látek
• kontraceptiva orální * MeSH
• melatonin MeSH

One of the major physiological roles of melatonin is its synchronizative influence on circadian rhythmicity and the induction of seasonal responses to changes in day length. In seasonally reproductive animals like the hamster, melatonin has been established as antigonadotrophic on the gonadal axis. Melatonin has been used successfully to treat jet lag and some circadian-based sleep disorders. It has the immunomodulatory role, which can be supported by the existence of specific binding sites in lymphoid cells, thymus and spleen. Not negligible is the antioxidative effect of melatonin and the ability to scavenge some reactive forms of oxygen. Melatonin has potentially important influence on the neoplastic growth and direct and indirect oncostatic effect in some forms of neoplasia. The beneficial influence of melatonin alone or its combination with immunotherapy, radiotherapy or chemotherapy in many clinical studies in patients with tumors was demonstrated.

• MeSH
• adjuvancia imunologická terapeutické užití   MeSH
• antioxidancia terapeutické užití   MeSH
• lidé MeSH
• melatonin fyziologie   terapeutické užití   MeSH
• nádory farmakoterapie   MeSH
• scavengery volných radikálů terapeutické užití   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• adjuvancia imunologická MeSH
• antioxidancia MeSH
• melatonin MeSH
• scavengery volných radikálů MeSH

Melatonin is a simple compound called N-acetyl-5-methoxy tryptamine and is known as a hormone controlling the circadian rhythm. Melatonin is produced by the human body naturally. The production of melatonin increases in the evening, causing a state of sleep at night and wakefulness during the day. Melatonin interacts with melatonin receptors MT1 and MT2, but it was revealed that melatonin is a strong antioxidant and it also has a role in the regulation of the cell cycle. Melatonin is now used as a medicine to treat some types of sleep disorders. Moreover, recent research suggests that it can also be utilized for other purposes, such as prevention from chemical exposure and treatment of various diseases, including cancer, neurodegenerative disorders, etc. This review summarizes the basic facts and direction of the current research on melatonin. The existing literature was scrutinized for this review.

• Klíčová slova
• Antioxidant, biomedicine, cancer, circadian rhythm, neurodegenerative disorder, oxidative stress, senescence, sleep,
• MeSH
• cirkadiánní rytmus fyziologie   MeSH
• lidé MeSH
• melatonin * metabolismus   farmakologie   terapeutické užití   MeSH
• melatoninové receptory MeSH
• poruchy spánku a bdění * farmakoterapie   MeSH
• spánek MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• melatonin * MeSH
• melatoninové receptory MeSH

Melatonin has been reported to cause myocardial electrophysiological changes and prevent ventricular tachycardia or fibrillation (VT/VF) in ischemia and reperfusion. We sought to identify electrophysiological targets responsible for the melatonin antiarrhythmic action and to explore whether melatonin receptor-dependent pathways or its antioxidative properties are essential for these effects. Ischemia was induced in anesthetized rats given a placebo, melatonin, and/or luzindole (MT1/MT2 melatonin receptor blocker), and epicardial mapping with reperfusion VT/VFs assessment was performed. The oxidative stress assessment and Western blotting analysis were performed in the explanted hearts. Transmembrane potentials and ionic currents were recorded in cardiomyocytes with melatonin and/or luzindole application. Melatonin reduced reperfusion VT/VF incidence associated with local activation time in logistic regression analysis. Melatonin prevented ischemia-related conduction slowing and did not change the total connexin43 (Cx43) level or oxidative stress markers, but it increased the content of a phosphorylated Cx43 variant (P-Cx43368). Luzindole abolished the melatonin antiarrhythmic effect, slowed conduction, decreased total Cx43, protein kinase Cε and P-Cx43368 levels, and the IK1 current, and caused resting membrane potential (RMP) depolarization. Neither melatonin nor luzindole modified INa current. Thus, the antiarrhythmic effect of melatonin was mediated by the receptor-dependent enhancement of impulse conduction, which was associated with Cx43 phosphorylation and maintaining the RMP level.

• Klíčová slova
• conduction velocity, connexin-43, melatonin, post-ischemic arrhythmias, potassium current, rat heart, sodium current,
• MeSH
• antiarytmika farmakologie   terapeutické užití   MeSH
• kardiomyocyty metabolismus   MeSH
• konexin 43 * metabolismus   MeSH
• krysa rodu Rattus MeSH
• melatonin * farmakologie   terapeutické užití   MeSH
• melatoninové receptory metabolismus   MeSH
• srdeční arytmie farmakoterapie   prevence a kontrola   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antiarytmika MeSH
• konexin 43 * MeSH
• luzindole MeSH Prohlížeč
• melatonin * MeSH
• melatoninové receptory MeSH

The development of melatonin receptors in the rat pituitary and median eminence was studied using [125I]melatonin as a ligand. The specific binding was detected in pituitaries of 20-day-old fetuses already. The affinity of the receptor to the ligand (Kd) was in the range 63-133 pM and it did not change significantly during development. The pituitary concentration of [125I]melatonin binding sites was highest in 20-day-old fetuses (Bmax = 31 fmol/mg protein) and then it gradually decreased in the course of postnatal development, until it reached 10% of that value in 29-day-old males. In contrast, the concentration of melatonin receptors in median eminence did not change markedly in the course of development and it was about 15 fmol/mg protein. The marked decrease in the number of the pituitary receptors may be the cause of the reported developmental loss of the melatonin inhibitory effect on LHRH-induced LH release from anterior pituitary.

• MeSH
• adenohypofýza embryologie   růst a vývoj   metabolismus   MeSH
• buněčná membrána metabolismus   MeSH
• eminentia medialis embryologie   růst a vývoj   metabolismus   MeSH
• inbrední kmeny potkanů MeSH
• krysa rodu Rattus MeSH
• melatonin metabolismus   MeSH
• melatoninové receptory MeSH
• receptory neurotransmiterů metabolismus   MeSH
• stárnutí MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• melatonin MeSH
• melatoninové receptory MeSH
• receptory neurotransmiterů MeSH

Neonatal pituitary cells express MT1 and MT2 subtype of melatonin receptors that are coupled to pertussis toxin-sensitive G proteins. Their activation by melatonin leads to a decrease in cAMP production and activity of protein kinase A, and attenuation of gonadotropin-releasing hormone (GnRH)-induced gonadotropin secretion. Single cell calcium and electrophysiological recordings have revealed that a reduction in gonadotropin release results from melatonin-induced inhibition of GnRH-stimulated calcium signaling. Melatonin inhibits both calcium influx through voltage-dependent calcium channels and calcium mobilization from intracellular stores. Inhibition of calcium influx, probably in a cAMP/protein kinase C-dependent manner, and the accompanying calcium-induced calcium release from ryanodine-sensitive intracellular pools by melatonin results in a delay of GnRH-induced calcium signaling. Melatonin-induced attenuation of GnRH-induced and inositol (1,4,5)-trisphosphate-mediated calcium release from intracellular pools attenuates the amplitude of calcium signal. The potent inhibition of GnRH-induced calcium signaling and gonadotropin secretion by melatonin provides an effective mechanism to protect premature initiation of pubertal changes that are dependent on plasma gonadotropin levels. During the development, such tonic inhibitory effects of melatonin on GnRH action gradually decline due to a decrease in expression of functional melatonin receptors. In adult animals, melatonin does not have obvious direct effects on pituitary functions, whereas the connections between melatonin release and hypothalamic functions, including GnRH release, are preserved, and are critically important in synchronizing the external photoperiods and reproductive functions through still not well characterized mechanisms.

• MeSH
• gonadotropiny metabolismus   MeSH
• hypofýza metabolismus   MeSH
• kultivované buňky MeSH
• lidé MeSH
• melatonin fyziologie   MeSH
• novorozená zvířata MeSH
• receptor melatoninový MT1 metabolismus   MeSH
• receptor melatoninový MT2 metabolismus   MeSH
• receptory LHRH metabolismus   MeSH
• rozmnožování fyziologie   MeSH
• signální transdukce MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• gonadotropiny MeSH
• melatonin MeSH
• receptor melatoninový MT1 MeSH
• receptor melatoninový MT2 MeSH
• receptory LHRH MeSH

125I-Melatonin was used to localize and characterize the melatonin receptor sites in the rat hypothalamus. Autoradiography revealed that displaceable 125I-melatonin binding occurred in suprachiasmatic nuclei and median eminence only. Further studies performed on crude membrane fractions from median eminences revealed high affinity (Kd = 21 pM) melatonin binding sites (Bmax = 8.5 fmol/mg protein). The order of potency of various indole amines to inhibit 125I-melatonin binding was melatonin much greater than N-acetyl-5-hydroxytryptamine greater than 5-methoxytryptamine greater than 5-hydroxytryptamine.

• MeSH
• autoradiografie MeSH
• buněčná membrána metabolismus   MeSH
• eminentia medialis metabolismus   MeSH
• hypothalamus cytologie   metabolismus   MeSH
• inbrední kmeny potkanů MeSH
• kinetika MeSH
• krysa rodu Rattus MeSH
• melatonin metabolismus   MeSH
• melatoninové receptory MeSH
• nucleus suprachiasmaticus metabolismus   MeSH
• orgánová specificita MeSH
• radioizotopy jodu MeSH
• receptory neurotransmiterů metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• melatonin MeSH
• melatoninové receptory MeSH
• radioizotopy jodu MeSH
• receptory neurotransmiterů MeSH

The effect of castration and/or neonatal administration of testosterone propionate (TP) on 125I-melatonin binding and its daily changes was studied in rat anterior pituitary (AP) and in pars tuberalis/median eminence (PT/ME). In animals kept on a light/dark cycle of 12:12 h there was a marked increase in binding site density (Bmax) in the evening as compared to the morning, while there were no differences in the affinity (Kd). On a light/dark cycle of 8:16 h the daily rhythm in Bmax was abolished and the values were intermediate. Neonatal TP administration which increases the sensitivity of the reproductive axis to melatonin and photoperiodic regulations had no effect on the binding parameters in AP and in PT/ME. Castration, however, increased binding site density in AP by 85% while it had no effect on the affinity of the binding site (Kd).

• MeSH
• adenohypofýza účinky léků   metabolismus   MeSH
• cirkadiánní rytmus * MeSH
• down regulace MeSH
• inbrední kmeny potkanů MeSH
• kinetika MeSH
• krysa rodu Rattus MeSH
• melatonin metabolismus   MeSH
• melatoninové receptory MeSH
• orchiektomie MeSH
• receptory neurotransmiterů metabolismus   MeSH
• testis fyziologie   MeSH
• testosteron farmakologie   MeSH
• upregulace MeSH
• zpětná vazba MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• melatonin MeSH
• melatoninové receptory MeSH
• receptory neurotransmiterů MeSH
• testosteron MeSH