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Aim: The pathogenesis of chronic diabetes complications has oxidative stress as one of the major elements, and single-nucleotide polymorphisms (SNPs) in genes belonging to antioxidant pathways modulate susceptibility to these complications. Considering that melatonin is a powerful antioxidant compound, our aim was to explore, in a longitudinal cohort study of type 1 diabetes (T1D) individuals, the association of microvascular complications and SNPs in the gene encoding melatonin receptor 1A (MTNR1A). Methods: Eight SNPs in MTNR1A were genotyped in 489 T1D individuals. Besides cross-sectional analyses of SNPs with each one of the microvascular complications (distal polyneuropathy, cardiovascular autonomic neuropathy, retinopathy, and diabetic kidney disease), a longitudinal analysis evaluated the associations of SNPs with renal function decline in 411 individuals followed up for a median of 8 years. In a subgroup of participants, the association of complications with urinary 6-sulfatoxymelatonin (aMT6s) concentration was investigated. Results: The group of individuals with a renal function decline ≥ 5 mL min-1 1.73 m-2 year-1 presented a higher frequency of the A allele of rs4862705 in comparison with nondecliners, even after adjustment for confounding variables (OR = 1.84, 95% CI = 1.20-2.82; p = 0.0046). No other significant associations were found. Conclusions: This is the first study showing an association between a variant in a gene belonging to the melatonin system and renal function decline in the diabetic setting.
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Diabetes Mellitus Tipo 1 , Melatonina , Humanos , Diabetes Mellitus Tipo 1/complicações , Diabetes Mellitus Tipo 1/genética , Antioxidantes , Receptores de Melatonina , Estudos Transversais , Estudos Longitudinais , RimRESUMO
This study investigated the seasonal variations in mRNA expression of FSH (Fshr), LH (Lhr) receptors, melatonin (Mt1 and Mt2) receptors, melatonin-synthetizing enzymes (Asmt and Aanat) and melatonin concentration in developing follicles from mares raised in natural photoperiods. For one year, ultrasonographic follicular aspiration procedures were performed monthly, and small (<20 mm), medium (20 to 35 mm) and large (>35 mm) follicles were recovered from five mares. One day before monthly sample collections, an exploratory ultrasonography conducted to record the number and the size of all follicles larger than 15 mm. The total number of large follicles were higher during the spring/summer (8.2 ± 1.9) than during autumn/winter (3.0 ± 0.5). Compared to autumn/winter seasons, there was an increase of Fshr and Aanat mRNA expressions in small, medium and large follicles, an increase of Lhr and Asmt mRNA expressions in medium and large follicles and an increase of Mt1 and Mt2 mRNA expressions in small and large follicles during spring/summer. The melatonin levels in follicular fluid were also higher during the spring/summer seasons. The present data show that melatonin locally upregulates the mRNA expression of Mt1 and Mt2 receptors and melatonin-forming enzymes in mare developing follicles during reproductive seasons.
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Preclinical and clinical evidence supports melatonin and its analogues as potential treatment for diseases involving cognitive deficit such as Alzheimer's disease. In this work, we evaluated by in silico studies a set of boron-containing melatonin analogues on MT1 and MT2 receptors. Then, we synthesized a compound (borolatonin) identified as potent agonist. After chemical characterization, its evaluation in a rat model with cognitive deficit showed that it induced ameliorative effects such as those induced by equimolar administration of melatonin in behavioral tests and in neuronal immunohistochemistry assays. Our results suggest the observed effects are by means of action on the melatonin system. Further studies are required to clarify the mechanism(s) of action, as the beneficial effects on disturbed memory by gonadectomy in male rats are attractive.
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Melatonina , Receptor MT1 de Melatonina , Animais , Cognição , Masculino , Melatonina/farmacologia , Melatonina/uso terapêutico , Ratos , Receptor MT1 de Melatonina/agonistas , Receptor MT2 de Melatonina , TriptofanoRESUMO
The aim of this study was to assess the effect of two types of stressors, regarding the extent of involvement of ouabain (OUA), hippocampal sodium/potassium ATPase (NKA) expression, and the hippocampal corticosterone receptors (CR)/melatonin receptors (MR) expression ratio, on the behavioral and cardiovascular responses and on the hippocampal cornu ammonis zone 3 (CA3) and dentate gyrus (DG). Thirty adult male Wistar albino rats aged 7-8 months were exposed to either chronic immobilization or a disturbed dark/light cycle and treated with either ouabain or vehicle. In the immobilized group, in the absence of hippocampal corticosterone (CORT) changes, rats were non-responsive to stress, despite experiencing increased pulse rate, downregulated hippocampal sodium/potassium pump, and enhanced hippocampal CR/MR expression ratio. Prolonged darkness precipitated a reduced upright attack posture, with elevated CORT against hippocampal MR downregulation. Both immobilization and, to a lesser extent, prolonged darkness stress resulted in histopathological and ultrastructural neurodegenerative changes in the hippocampus. OUA administration did not change the behavioral resilience in restrained rats, despite persistence of the underlying biochemical derangements, added to decreased CORT. On the contrary, with exposure to short photoperiods, OUA reverted the behavior towards a combative reduction of inactivity, with unvaried CR/MR and CORT, while ameliorating hippocampal neuro-regeneration, with co-existing NKA and MR repressions. Therefore, the extent of OUA, hippocampal NKA expression, and CR/MR expression, and subsequent behavioral and cardiac responses and hippocampal histopathology, differ according to the type of stressor, whether immobilization or prolonged darkness.
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Pulmonary arterial hypertension of newborns (PAHN) constitutes a critical condition involving both severe cardiac remodeling and right ventricle dysfunction. One main cause of this condition is perinatal hypoxia and oxidative stress. Thus, it is a public health concern for populations living above 2500 m and in cases of intrauterine chronic hypoxia in lowlands. Still, pulmonary and cardiac impairments in PAHN lack effective treatments. Previously we have shown the beneficial effects of neonatal melatonin treatment on pulmonary circulation. However, the cardiac effects of this treatment are unknown. In this study, we assessed whether melatonin improves cardiac function and modulates right ventricle (RV) oxidative stress. Ten lambs were gestated, born, and raised at 3600 m. Lambs were divided in two groups. One received daily vehicle as control, and another received daily melatonin (1 mg·kg-1·d-1) for 21 days. Daily cardiovascular measurements were recorded and, at 29 days old, cardiac tissue was collected. Melatonin decreased pulmonary arterial pressure at the end of the experimental period. In addition, melatonin enhanced manganese superoxide dismutase and catalase (CAT) expression, while increasing CAT activity in RV. This was associated with a decrease in superoxide anion generation at the mitochondria and NADPH oxidases in RV. Finally, these effects were associated with a marked decrease of oxidative stress markers in RV. These findings support the cardioprotective effects of an oral administration of melatonin in newborns that suffer from developmental chronic hypoxia.
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The purpose of this review was to search for articles on human studies investigating the relationship between melatonin and high-risk pregnancy. An electronic search was conducted in the MEDLINE and PubMed databases from September 2010 to October 2020. The initial search produced 441 articles in PubMed and 407 in MEDLINE. After sorting the titles and abstracts, and removing duplicates, we had nine articles in PubMed and three in Medline. The results of these studies mainly show that the association between melatonin receptor 1B polymorphisms and gestational diabetes mellitus is the most common physiological mechanism relating to melatonin and high-risk pregnancy in this review. In addition, the circadian rhythm, decreased melatonin production, and anti-inflammatory and antioxidant effects were explored. The findings of our review of the literature suggest that this indoleamine is essential in high-risk pregnancy for its potent anti-inflammatory and antioxidant effects, regulation of the circadian rhythm, and genic receptor expression.
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Melatonina , Antioxidantes , Ritmo Circadiano , Feminino , Humanos , Polimorfismo Genético , Gravidez , Gravidez de Alto RiscoRESUMO
Melatonin MT1 and MT2 receptors are expressed in the glomerular layer of the olfactory bulb (OB); however, the role of these receptors has not been evaluated until now. Considering the association of the OB with olfactory and depressive disorders in Parkinson's disease (PD), we sought to investigate the involvement of melatonin receptors in these non-motor disturbances in an intranigral 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD. We demonstrate the presence of functional melatonin receptors in dopaminergic neurons of the glomerular layer. Local administration of melatonin (MLT, 1 µg/µl), luzindole (LUZ, 5 µg/µl) or the MT2-selective receptor drug 4-P-PDOT (5 µg/µl) reversed the depressive-like behavior elicited by 6-OHDA. Sequential administration of 4-P-PDOT and MLT (5 µg/µl, 1 µg/µl) promoted additive antidepressant-like effects. In the evaluation of olfactory discrimination, LUZ induced an olfactory impairment when associated with the nigral lesion-induced impairment. Thus, our results suggest that melatonin MT2 receptors expressed in the glomerular layer are involved in depressive-like behaviors and in olfactory function associated with PD.
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Anosmia/metabolismo , Comportamento Animal , Transtorno Depressivo/metabolismo , Neurônios Dopaminérgicos/metabolismo , Bulbo Olfatório/metabolismo , Transtornos Parkinsonianos/metabolismo , Receptor MT2 de Melatonina/metabolismo , Animais , Anosmia/etiologia , Anosmia/fisiopatologia , Anosmia/psicologia , Comportamento Animal/efeitos dos fármacos , Transtorno Depressivo/etiologia , Transtorno Depressivo/fisiopatologia , Transtorno Depressivo/psicologia , Modelos Animais de Doenças , Neurônios Dopaminérgicos/efeitos dos fármacos , Locomoção/efeitos dos fármacos , Masculino , Melatonina/farmacologia , Bulbo Olfatório/efeitos dos fármacos , Bulbo Olfatório/fisiopatologia , Percepção Olfatória/efeitos dos fármacos , Oxidopamina , Transtornos Parkinsonianos/induzido quimicamente , Transtornos Parkinsonianos/fisiopatologia , Transtornos Parkinsonianos/psicologia , Ratos Wistar , Receptor MT2 de Melatonina/efeitos dos fármacos , Transdução de Sinais , Olfato/efeitos dos fármacos , Natação , Tetra-Hidronaftalenos/farmacologia , Triptaminas/farmacologiaRESUMO
In mammals, many melatonin biological functions are mediated through its interaction with the membrane receptors MT1 and MT2. We have previously reported their presence in ram spermatozoa from males located in temperate climates, but there is no information on their presence in spermatozoa from rams in areas with an equatorial photoperiod (12L:12D). Thus, we have investigated the existence and cellular distribution of melatonin receptors in spermatozoa from three sheep breeds in Colombia (Colombian Creole, Hampshire, and Romney Marsh) during dry and rainy seasons, using indirect immunofluorescence and western blot. Our results indicated the presence of melatonin receptors in spermatozoa from these rams, and that their distribution differs from that previously found in spermatozoa from rams in temperate climates. Moreover, two new immunotypes of MT2 were identified: type N, with staining only in the neck, and type E with a band of immunofluorescence in the upper part of the post-acrosome and the apical edge. Likewise, differences between breeds and climate seasons were detected for both receptors. However, densitometry analysis of western blot bands only revealed differences between seasons in the Creole rams for MT1 and the Romney Marsh rams for MT2, whereas differences between breeds were only detected for MT2. It could be inferred that melatonin receptors in rams subjected to an equatorial photoperiod might be more closely related to sperm quality than seasonal control. Therefore, the presence of these receptors suggests that melatonin could be a useful tool to increase the fertility of rams located in tropical or equatorial climates.
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Receptor MT1 de Melatonina/metabolismo , Receptor MT2 de Melatonina/metabolismo , Ovinos/fisiologia , Animais , Regulação da Expressão Gênica/fisiologia , Masculino , Melatonina/fisiologia , Fotoperíodo , Receptor MT1 de Melatonina/genética , Receptor MT2 de Melatonina/genética , Estações do Ano , EspermatozoidesRESUMO
Pharmacological concentrations of melatonin reduce reperfusion arrhythmias, but less is known about the antiarrhythmic protection of the physiological circadian rhythm of melatonin. Bilateral surgical removal of the superior cervical ganglia irreversibly suppresses melatonin rhythmicity. This study aimed to analyze the cardiac electrophysiological effects of the loss of melatonin circadian oscillation and the role played by myocardial melatonin membrane receptors, SERCA2A, TNFα, nitrotyrosine, TGFß, KATP channels, and connexin 43. Three weeks after bilateral removal of the superior cervical ganglia or sham surgery, the hearts were isolated and submitted to ten minutes of regional ischemia followed by ten minutes of reperfusion. Arrhythmias, mainly ventricular tachycardia, increased during reperfusion in the ganglionectomy group. These hearts also suffered an epicardial electrical activation delay that increased during ischemia, action potential alternants, triggered activity, and dispersion of action potential duration. Hearts from ganglionectomized rats showed a reduction of the cardioprotective MT2 receptors, the MT1 receptors, and SERCA2A. Markers of nitroxidative stress (nitrotyrosine), inflammation (TNFα), and fibrosis (TGFß and vimentin) did not change between groups. Connexin 43 lateralization and the pore-forming subunit (Kir6.1) of KATP channels increased in the experimental group. We conclude that the loss of the circadian rhythm of melatonin predisposes the heart to suffer cardiac arrhythmias, mainly ventricular tachycardia, due to conduction disorders and changes in repolarization.
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Arritmias Cardíacas/patologia , Ganglionectomia/efeitos adversos , Coração/fisiopatologia , Traumatismo por Reperfusão Miocárdica/cirurgia , Animais , Arritmias Cardíacas/etiologia , Arritmias Cardíacas/metabolismo , Ritmo Circadiano , Conexina 43/genética , Conexina 43/metabolismo , Masculino , Melatonina/metabolismo , Ratos , Ratos Wistar , Receptores de Melatonina/genética , Receptores de Melatonina/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/genética , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismoRESUMO
This study examined the effects of pinealectomy in Wistar rats and melatonin replacement therapy on the daily mRNA expression of melatonin (Tph1, Aanat, Asmt, Mt1, Mt2, and Rorα), and steroidogenic (Star, 17ßhsd3, and Lhr) related genes as well as clock genes (Rev-erbα, Bmal1, Per1, Per2, Cry1, and Cry2) in testes. The testes of control animals express the Tph1, Aanat, and Asmt and Per2 genes with 24-h rhythms in mRNA, reaching the maximal values during the dark phase. Pinealectomy abolished and melatonin treatment restored the 24-h rhythmicity. Daytime differences in mRNA expression were significant for Star, Lhr, Mt1, Mt2, Rorα, Rev-erbα, Bmal1, Cry1, and Cry2 genes in testes of control rats. Conversely, 17ßhsd3 and Per1 mRNA expression did not show a daytime difference in testes of control animals. Pinealectomy abolished the peak time of Mt1 and Mt2 mRNA expression, phase shifted the peak time of Star, Rorα, Rev-erbα, Bmal1, and Cry2 mRNA expression, downregulated the 24-h Lhr mRNA expression, and inverted the peak time of Per1, Per2, and Cry1 mRNA expression to the light phase. The melatonin replacement therapy completely restored the control levels of Lhr, Rev-erbα, and Per1 mRNA expression patterns, partially restored the daily control of Star, Mt2, Rorα, Bmal1, Cry1, and Cry2 mRNA expression but did not re-establish the daily control of Mt1 mRNA expression. This suggests that the daily mRNA expression of these genes is probably driven by pineal melatonin and melatonin treatment restores (partially or completely) the daily control of gene expression patterns.
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Acetilserotonina O-Metiltransferasa/metabolismo , Arilalquilamina N-Acetiltransferase/metabolismo , Ritmo Circadiano , Melatonina/deficiência , Glândula Pineal/metabolismo , Triptofano Hidroxilase/metabolismo , Acetilserotonina O-Metiltransferasa/genética , Análise de Variância , Animais , Arilalquilamina N-Acetiltransferase/genética , Ritmo Circadiano/genética , Masculino , Melatonina/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos Wistar , TestículoRESUMO
Calmodulin is vital for chick embryos morphogenesis in the incubation time 48-66â h when the rudimentary C-shaped heart attains an S-shaped pattern and the optic vesicles develop into optic cups. Melatonin is in the extraembryonic yolk sac of the avian egg; melatonin binds calmodulin. The aim of this study was to investigate the function of melatonin in the formation of the chick embryo optic cups and S-shaped heart, by pharmacological methods and immunoassays. Mel1a melatonin receptor immunofluorescence was distributed in the optic cups and rudimentary hearts. We separated embryonated chicken eggs at 48â h of incubation into basal, control and drug-treated groups, with treatment applied in the egg air sac. At 66 h of incubation, embryos were excised from the eggs and analyzed. Embryos from the basal, control (distilled water), melatonin and 6-chloromelatonin (melatonin receptor agonist) groups had regular optic cups and an S-shaped heart, while those from the calmidazolium (calmodulin inhibitor) group did not. Embryos from the luzindole (melatonin receptor antagonist) and prazosin (Mel1c melatonin receptor antagonist) groups did not have regular optic cups. Embryos from the 4-P-PDOT (Mel1b melatonin receptor antagonist) group did not have an S-shaped heart. Previous application of the melatonin, 6-chloromelatonin or forskolin (adenylate cyclase enhancer) prevented the abnormal appearance of chick embryos from the calmidazolium, luzindole, prazosin and 4-P-PDOT groups. However, 6-chloromelatonin and forskolin only partially prevented the development of defective eye cups in embryos from the calmidazolium group. The results suggested that melatonin modulates chick embryo morphogenesis via calmodulin and membrane receptors.
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Embrião de Galinha/crescimento & desenvolvimento , Olho/crescimento & desenvolvimento , Coração/crescimento & desenvolvimento , Melatonina/fisiologia , Morfogênese , Transdução de Sinais , Animais , Embrião de Galinha/fisiologia , Coração/fisiologiaRESUMO
This study investigated the maturational stage (immature and mature ovaries) differences of mRNA expression of melatonin-forming enzymes (Aanat and Asmt), melatonin membrane receptors (Mt1 and Mt2) and putative nuclear (Rorα) receptors, and clock genes (Clock, Bmal1, Per1, Per2, Cry1, Cry2) in cumulus-oocyte complexes (COC) from weaning Wistar rats. We also examined the effects of pinealectomy and of melatonin pharmacological replacement on the daily expression of these genes in COC. qRT-PCR analysis revealed that in oocytes, the mRNA expression of Asmt, Mt2, Clock, Bmal1, Per2, and Cry1 were higher (P < 0.05) in immature ovaries than in the mature ones. In cumulus cells, the same pattern of mRNA expression for Asmt, Aanat, Rorα, Clock, Per1, Cry1, and Cry2 genes was observed. In oocytes, pinealectomy altered the daily mRNA expression profiles of Asmt, Mt1, Mt2, Clock, Per1, Cry1, and Cry2 genes. In cumulus cells, removal of the pineal altered the mRNA expression profiles of Mt1, Mt2, Rorα, Aanat, Asmt, Clock, Bmal1, Per2, Cry1, and Cry2 genes. Melatonin treatment partially or completely re-established the daily mRNA expression profiles of most genes studied. The mRNA expression of melatonin-related genes and clock genes in rat COC varies with the maturational stage of the meiotic cellular cycle in addition to the hour of the day. This suggests that melatonin might act differentially in accordance with the maturational stage of cumulus/oocyte complex. In addition, it seems that circulating pineal melatonin is very important in the design of the daily profile of mRNA expression of COC clock genes and genes related to melatonin synthesis and action.
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Células do Cúmulo/metabolismo , Melatonina/metabolismo , Oócitos/metabolismo , Glândula Pineal/cirurgia , Animais , Arilalquilamina N-Acetiltransferase/metabolismo , Ritmo Circadiano/fisiologia , Feminino , Proteínas Circadianas Period/metabolismo , Ratos , Ratos Wistar , Receptores de Melatonina/metabolismoRESUMO
Melatonin can contribute to glucose homeostasis either by decreasing gluconeogenesis or by counteracting insulin resistance in distinct models of obesity. However, the precise mechanism through which melatonin controls glucose homeostasis is not completely understood. Male Wistar rats were administered an intracerebroventricular (icv) injection of melatonin and one of following: an icv injection of a phosphatidylinositol 3-kinase (PI3K) inhibitor, an icv injection of a melatonin receptor (MT) antagonist, or an intraperitoneal (ip) injection of a muscarinic receptor antagonist. Anesthetized rats were subjected to pyruvate tolerance test to estimate in vivo glucose clearance after pyruvate load and in situ liver perfusion to assess hepatic gluconeogenesis. The hypothalamus was removed to determine Akt phosphorylation. Melatonin injections in the central nervous system suppressed hepatic gluconeogenesis and increased hypothalamic Akt phosphorylation. These effects of melatonin were suppressed either by icv injections of PI3K inhibitors and MT antagonists and by ip injection of a muscarinic receptor antagonist. We conclude that melatonin activates hypothalamus-liver communication that may contribute to circadian adjustments of gluconeogenesis. These data further suggest a physiopathological relationship between the circadian disruptions in metabolism and reduced levels of melatonin found in type 2 diabetes patients.
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Antioxidantes/farmacologia , Gluconeogênese/efeitos dos fármacos , Hipotálamo/metabolismo , Fígado/metabolismo , Melatonina/farmacologia , Proteína Oncogênica v-akt/metabolismo , Receptor MT1 de Melatonina/efeitos dos fármacos , Receptor MT2 de Melatonina/efeitos dos fármacos , Animais , Western Blotting , Imunofluorescência , Teste de Tolerância a Glucose , Hipotálamo/efeitos dos fármacos , Injeções Intraventriculares , Fígado/efeitos dos fármacos , Masculino , Fosfatidilinositol 3-Quinases/metabolismo , Ácido Pirúvico/metabolismo , Ratos , Ratos Wistar , Receptores Muscarínicos/efeitos dos fármacosRESUMO
Chagas' disease is a severe health problem in Latin America, causing approximately 50 000 deaths a year, with approximately 18 million infected people. About 25-30% of the patients infected with Trypanosoma cruzi develop the chronic form of the disease. The protective response against T. cruzi depends on both innate and acquired immunity involving macrophages, natural killer cells, T and B lymphocytes, and the production of proinflammatory Th-1 cytokines. In addition, an increased nitric oxide (NO) production in macrophages leading to effective microbicidal action is needed to control parasitemia. Melatonin is detectable in T. cruzi and may play a role in promoting infection whereas, when administered in high doses during the acute phase of T. cruzi infection, it can decrease parasitemia while reducing NO production. During chronic disease progression, the sustained oxidative stress concomitant to myocardial damage could be reduced by administering melatonin. It is hypothesized that the coordinated administration of a melatonin agonist like the MT1/MT2 agonist ramelteon, that lacks antioxidant activity and may not affect NO production during the acute phase, and of melatonin in doses high enough to decrease oxidative damage, to preserve mitochondrial and to prevent cardiomyopathy during the chronic phase, could be a novel add-on treatment of Chagas´ disease.
La enfermedad de Chagas es un problema grave de salud en América Latina, causando cerca de 50 000 muertes al año y unos 18 millones de infectados. Alrededor del 25-30% de los pacientes infectados con Trypanosoma cruzi desarrollan la forma crónica de la enfermedad. La respuesta de defensa ante el T. cruzi depende de la inmunidad innata y adquirida con la participación de macrófagos, células natural killer, linfocitos T y B, y la producción de citoquinas proinflamatorias de tipo Th-1. Además, el aumento en la producción de óxido nítrico (NO) en los macrófagos lleva a una acción microbicida eficaz necesaria para controlar la parasitemia. La melatonina es detectable en T. cruzi y podría desempeñar un papel en la promoción de la infección como lo hace en el paludismo, mientras que, cuando se administra en dosis farmacológicas altas durante la fase aguda de la infección por T. cruzi, disminuye la parasitemia, aun en presencia de una reducción de la producción de NO. Durante la progresión de la enfermedad de Chagas a la cronicidad, el estrés oxidativo aumentado con el concomitante daño miocárdico podría reducirse por la administración de melatonina, de reconocida acción antioxidante. Se propone como un nuevo enfoque complementario en el tratamiento de la enfermedad de Chagas la administración durante la fase aguda de un agonista MT1/MT2 de la melatonina como el ramelteon, que carece de actividad antioxidante y podría no afectar a la producción de NO, y de melatonina durante la fase crónica de en dosis suficientemente altas como para disminuir el daño oxidativo y prevenir la miocardiopatía.
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Animais , Humanos , Antioxidantes/administração & dosagem , Doença de Chagas/tratamento farmacológico , Melatonina/administração & dosagem , Óxido Nítrico/biossíntese , Estresse Oxidativo/efeitos dos fármacos , Trypanosoma cruzi/efeitos dos fármacos , Doença Crônica , Depressores do Sistema Nervoso Central/administração & dosagem , Cardiomiopatia Chagásica/prevenção & controle , Relação Dose-Resposta a Droga , Mediadores da Inflamação/fisiologia , Parasitemia/prevenção & controle , Receptores de Melatonina/fisiologiaRESUMO
Melatonin, a hormone secreted by the pineal gland, has been successfully employed to improve sleep in both normal patients and insomniacs, and for the treatment of circadian rhythm sleep disorders. Melatonergic MT1 and MT2 receptors exist in high concentrations in the suprachiasmatic nucleus of the hypothalamus and have been shown to be instrumental for the sleep-promoting and circadian rhythm-regulating effects of melatonin. A lack of consistency among reports on the therapeutic efficacy of melatonin has been attributed to differences in melatonin's bioavailability and the short half-life of the hormone. In view of the need for longer acting melatonergic agonists that improve sleep efficiency without causing drug abuse or dependency, ramelteon (Rozerem™, Takeda) was developed. Ramelteon, which acts via MT1/MT2 melatonergic agonism, has been found clinically effective for improving total sleep time and sleep efficiency in insomniacs. Agomelatine (Valdoxan™, Servier) is another MT1/MT2 melatonergic agonist that also displays antagonist activity at 5-HT2C serotonin receptors. Agomelatine has been found effective in treating depression and sleep disorders in patients with major depressive disorder. A slow-release preparation of melatonin (Circadin™, Neurim) has been shown to be effective in treating sleep disorders in the elderly population.