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Molcan L, Maier A, Zemančíková A, Gelles K, Török J, Zeman M, Ellinger I. Expression of Melatonin Receptor 1 in Rat Mesenteric Artery and Perivascular Adipose Tissue and Vasoactive Action of Melatonin. Cell Mol Neurobiol 2021; 41:1589-1598. [PMID: 32734322 PMCID: PMC8408066 DOI: 10.1007/s10571-020-00928-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 07/20/2020] [Indexed: 12/26/2022]
Abstract
Melatonin is released by the pineal gland and can modulate cardiovascular system function via the G protein-coupled melatonin receptors MT1 and MT2. Most vessels are surrounded by perivascular adipose tissue (PVAT), which affects their contractility. The aim of our study was to evaluate mRNA and protein expression of MT1 and MT2 in the mesenteric artery (MA) and associated PVAT of male rats by RT-PCR and Western blot. Receptor localization was further studied by immunofluorescence microscopy. Effects of melatonin on neurogenic contractions were explored in isolated superior MA ex vivo by measurement of isometric contractile tension. MT1, but not MT2, was present in MA, and MT1 was localized mainly in vascular smooth muscle. Moreover, we proved the presence of MT1, but not MT2 receptors, in MA-associated PVAT. In isolated superior MA with intact PVAT, neuro-adrenergic contractile responses were significantly smaller when compared to arteries with removed PVAT. Pre-treatment with melatonin of PVAT-stripped arterial rings enhanced neurogenic contractions, while the potentiating effect of melatonin was not detected in preparations with preserved PVAT. We hypothesize that melatonin can stimulate the release of PVAT-derived relaxing factor(s) via MT1, which can override the direct pro-contractile effect of melatonin on vascular smooth muscle. Our results suggest that melatonin is involved in the control of vascular tone in a complex way, which is vessel specific and can reflect a sum of action on different layers of the vessel wall and surrounding PVAT.
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Affiliation(s)
- Lubos Molcan
- Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University Bratislava, Bratislava, Slovakia
| | - Andreas Maier
- Institute for Pathophysiology and Allergy Research, Center for Pathophysiology, Infectiology and Immunology, Medical University Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Anna Zemančíková
- Institute of Normal and Pathological Physiology, Centre of Experimental Medicine, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Katharina Gelles
- Institute for Pathophysiology and Allergy Research, Center for Pathophysiology, Infectiology and Immunology, Medical University Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Jozef Török
- Institute of Normal and Pathological Physiology, Centre of Experimental Medicine, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Michal Zeman
- Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University Bratislava, Bratislava, Slovakia
| | - Isabella Ellinger
- Institute for Pathophysiology and Allergy Research, Center for Pathophysiology, Infectiology and Immunology, Medical University Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
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Gonzales-Portillo GS, Lozano D, Aguirre D, Reyes S, Borlongan CV, Tajiri N, Kaneko Y. An update on the use of melatonin as a stroke therapeutic. Minerva Med 2015; 106:169-175. [PMID: 25000217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Delivery of melatonin and targeting melatonin receptors pose as neuroprotective strategies for stroke therapy. The potential of melatonin-based therapeutics for clinical application in stroke patients requires translational research to guide the conduct of clinical trials. We review recent preclinical and clinical data that support the use of melatonin for stroke.
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Affiliation(s)
- G S Gonzales-Portillo
- Department of Neurosurgery and Brain Repair, Center of Excellence for Aging and Brain Repair, University of South Florida College of Medicine, Tampa, FL, USA -
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Zurowski D, Nowak L, Machowska A, Wordliczek J, Thor PJ. Exogenous melatonin abolishes mechanical allodynia but not thermal hyperalgesia in neuropathic pain. The role of the opioid system and benzodiazepine-gabaergic mechanism. J Physiol Pharmacol 2012; 63:641-647. [PMID: 23388480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 11/26/2012] [Indexed: 06/01/2023]
Abstract
Melatonin (MT) is a neurohormone synthesized and secreted by the pineal gland. MT plays an important role in the regulation of physiological and neuroendocrine functions. The purpose of this study was to assess the overall effect of melatonin on neuropathic pain, the type of melatonin receptor involved, and potential role of the opioid system and GABA(A) receptors. The experiments were conducted by using the animal neuropathic pain model (CCI). The rats with CCI showed the characteristic for the mechanical allodynia and thermal hyperalgesia signs that were calculated by using the von Frey's and Hargreaves' tests. The conducted studies measured the effects of intraperitoneal administration of naloxone (opioid antagonist), prazosin (MT3 antagonist), luzindole (MT1/MT2 receptor antagonist), picrotoxin (GABA(A) antagonist) and flumazenil (benzodiazepine antagonist) on the antinociceptive effects caused by melatonin. Melatonin caused the increase in the pain threshold of the mechanical allodynia and the slight increase in the threshold of the thermal hyperalgesia. The pre-treatment with naloxone completely abolished the antinociceptive effects of melatonin in von Frey's test, but not thermal sensation in the Hargreaves's test. Prazosin did not have any effects, while administration of luzindole significantly suppressed the antinociceptive effect of melatonin. The antiallodynic effect of MT was also abolished by flumazenil and picrotoxin. Melatonin influences the mechanical allodynia but not thermal hyperalgesia via activation of opioid system and benzodiazepine-GABAergic pathway. Antinociceptive effects of melatonin are mostly related to the MT1/MT2 receptors interaction.
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Affiliation(s)
- D Zurowski
- Department of Pathophysiology, Jagiellonian University Medical College, Cracow, Poland.
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Song N, Kim AJ, Kim HJ, Jee HJ, Kim M, Yoo YH, Yun J. Melatonin suppresses doxorubicin-induced premature senescence of A549 lung cancer cells by ameliorating mitochondrial dysfunction. J Pineal Res 2012; 53:335-43. [PMID: 22536785 DOI: 10.1111/j.1600-079x.2012.01003.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Melatonin is an indolamine that is synthesized in the pineal gland and shows a wide range of physiological functions. Although the anti-aging properties of melatonin have been reported in a senescence-accelerated mouse model, whether melatonin modulates cellular senescence has not been determined. In this study, we examined the effect of melatonin on anticancer drug-induced cellular premature senescence. We found that the doxorubicin (DOX)-induced senescence of A549 human lung cancer cells and IMR90 normal lung cells was substantially inhibited by cotreatment with melatonin in a dose-dependent manner. Mechanistically, the DOX-induced G2/M phase cell cycle arrest and the decrease in cyclinB and cdc2 expression were not affected by melatonin. However, the DOX-induced increase in intracellular levels of ROS, which is necessary for premature senescence, was completely abolished upon melatonin cotreatment. In addition, the reduction in mitochondrial membrane potential that occurs upon DOX treatment was inhibited by melatonin. An aberrant increase in mitochondrial respiration was also significantly suppressed by melatonin, indicating that melatonin ameliorates the mitochondrial dysfunction induced by DOX treatment. The treatment of A549 cells with luzindole, a potent inhibitor of melatonin receptors, failed to prevent the effects of melatonin treatment on mitochondrial functions and premature senescence in cells also treated with DOX; this suggests that melatonin suppresses DOX-induced senescence in a melatonin receptor-independent manner. Together, these results reveal that melatonin has an inhibitory effect of melatonin on premature senescence at the cellular level and that melatonin protects A549 cells from DOX-induced senescence. Thus, melatonin might have the therapeutic potential to prevent the side effects of anticancer drug therapy.
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Affiliation(s)
- Naree Song
- Department of Biochemistry, College of Medicine, Dong-A University, Busan, South Korea
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Sumegi A, Somoskovi C. [Lights off? Neurobiological and pharmacological aspects of the melatonergic-serotonergic synergism]. Neuropsychopharmacol Hung 2010; 12:469-475. [PMID: 21220792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
SSRI antiepressants have been widely used for treating depressive symptoms for more than two decades. Despite their frequent usage, meta-analyses proved that only 20-25% of the patients had achieved long term remission. The introduction and spreading of dual-acting agents increased remission rate, but many of the patients with depressive symptoms still suffer from the disorder due to partial pharmacotherapeutic efficacy. Chronobiological disturbances might play an important role both in the pathophysiology and in the ongoing symptoms of depression. Pathological alterations in the melatonergic system may act as the first, obscure signs of the onset of depression. Agomelatine, a new antidepressive agent may offer new possibilities in the pharmacotherapy of depression, due to its synergistic melatonergic-serotonergic activity.
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Affiliation(s)
- Andras Sumegi
- Vas Megyei Markusovszky Kórház ZRT, Pszichiátriai Centrum, Szombathely, Hungary.
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Agomelatine: new drug. Adverse effects and no proven efficacy. Prescrire Int 2009; 18:241-5. [PMID: 20020562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
(1) When an antidepressant is considered a necessary addition to psychological support in treating patients with depression, the first-line drug is a tricyclic such as clomipramine or a selective serotonin reuptake inhibitor (SSRI) such as paroxetine; (2) Agomelatine, a melatonin receptor agonist, is approved in the European Union for the treatment of depression; (3) Available evaluation does not include any clinical trials designed to compare the efficacy of agomelatine with that of a tricyclic or a selective serotonin reuptake inhibitor. Most data come from 7 placebo-controlled trials; (4) Agomelatine (25 mg/day) was statistically more effective (on a rating scale) than placebo in only 3 of these 7 trials. The clinical relevance of the score improvements is questionable. No data are available on the cure rate or on suicide prevention; (5) In one trial, increasing the daily dose from 25 mg to 50 mg provided no supplementary benefit; (6) A trial in 367 patients failed to show that agomelatine was any more effective than placebo in preventing new depressive episodes (29% after one year). In another trial including 339 patients, the relapse rate was statistically lower after 6 months on agomelatine (20.6%) than on placebo (41.4%); (7) Very high doeses of agomelatine are oncogenic in animals. The risk in humans is not known. Dizziness, gastrointestinal and cutaneous disorders have been observed. Agomelatine is probably hepatotoxic; (8) In summary, agomelatine has unproven efficacy and poorly documented adverse effects. It is better to continue to use older antidepressants such as tricyclics or serotonin reuptake inhibitors.
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Abstract
OBJECTIVE Anti-ss-adrenergic actions of several substances influence heart function significantly. The anti-ss-adrenergic effect of melatonin was investigated, with special attention to protein kinase C (PKC) and nitric oxide (NO). DESIGN Guinea pig papillary muscles were exposed to melatonin (500 pM) for 15 min and 20 min washout. Contractile force was measured during a bolus of isoproterenol (300 nM) given before melatonin, at the end of melatonin-exposure and after washout. In separate experiments blockers of PKC, NO-synthase (NOS) and melatonin receptors were added, or forskolin (10 microM) substituted for isoproterenol. RESULTS Melatonin significantly reduced the increase in contractile force in response to isoproterenol, both when present and after melatonin-washout. The reduction was unaffected by inhibition of PKC, while inhibition of melatonin receptors or NOS seemed to abolish the effect. Melatonin induced a sustained but not acute reduction of contractile force response with forskolin stimulation. This was abolished by NOS-inhibition. CONCLUSION Receptor-mediated immediate and sustained anti-ss-adrenergic effects of melatonin were demonstrated in contractile function. A role for NO in the response was indicated, while a role for PKC was not verified.
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Affiliation(s)
- L Arvola
- Kirkenes Hospital, Kirkenes, Norway
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Ramelteon: new drug. Insomnia: no role for risky placebos. Prescrire Int 2008; 17:183-6. [PMID: 19534018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
(1) Patients complaining of insomnia should first be treated with non-drug measures (information, advice). Short-course benzodiazepine therapy can be tried if non-drug measures and established herbal remedies fail; (2) Ramelteon, a drug that antagonises receptors for melatonin, a hormone involved in circadian rhythms, is being considered for European marketing authorization in the treatment of insomnia; (3) Ramelteon has only been compared with placebo in clinical trials. Only one of three trials in which the patients were studied in their normal environment showed that ramelteon reduced the time to sleep onset, only by about 10 minutes. A similar reduction was observed in the artificial conditions of a sleep laboratory. There was no effect on sleep duration or on the number of night-time awakenings; (4) Ramelteon does not appear to have the disadvantages of benzodiazepines, such as residual daytime drowsiness, rebound insomnia on drug withdrawal, and dependence. But ramelteon provokes hyperprolactinaemia and was carcinogenic in experimental animals; (5) In practice, when a drug is needed for a patient complaining of insomnia, the best options are phytotherapy or short-course benzodiazepine treatment.
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Abstract
Aging is associated with a decline in immune function (immunosenescence), a condition known to correlate with increased incidence of cancer as well as infectious and degenerative diseases. Innate, cellular and humoral immunity all exhibit increased deterioration with age. Circulating melatonin decreases with age, and in recent years much interest has been focused on its immunomodulatory effect. Melatonin stimulates the production of progenitor cells for granulocytes and macrophages. It also stimulates the production of natural killer cells and CD4+ cells and inhibits CD8+ cells. The production and release of various cytokines from natural killer cells and T helper lymphocytes are enhanced by melatonin. Melatonin has the potential therapeutic value to enhance immune function in aged individuals.
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Affiliation(s)
- Daniel P Cardinali
- Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
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Miyamoto M. [Drugs for insomnia and improving quality of life (QOL): research and development of ramelteon, an MT1/MT2-receptor agonist]. Nihon Yakurigaku Zasshi 2008; 131:16-21. [PMID: 18187878 DOI: 10.1254/fpj.131.16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
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Doghramji K. Melatonin and its receptors: a new class of sleep-promoting agents. J Clin Sleep Med 2007; 3:S17-23. [PMID: 17824497 PMCID: PMC1978320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Affiliation(s)
- Karl Doghramji
- Department of Psychiatry and Human Behavior Jefferson Medical College, Philadelphia, PA, USA.
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Abstract
The number of patients with well-controlled hypertension is alarmingly low worldwide and new approaches to treatment of increased blood pressure (BP) are being sought. Melatonin has a role in blood pressure regulation. The nighttime production of melatonin is found to be reduced in hypertensive individuals. Administration of melatonin decreased BP in several animal models of hypertension, in healthy men and women, and in patients with arterial hypertension. Most promising results were achieved in patients with non-dipping nighttime pressure, in which the circadian rhythm of BP variation is disturbed. Several potential mechanisms of BP reduction are considered. Melatonin can, via its scavenging and antioxidant nature, improve endothelial function with increased availability of nitric oxide exerting vasodilatory and hypotensive effects. Melatonin seems to interfere with peripheral and central autonomic system, with a subsequent decrease in the tone of the adrenergic system and an increase of the cholinergic system. Melatonin may act on BP also via specific melatonin receptors localized in peripheral vessels or in parts of central nervous system participating in BP control. With a large clinical trial using melatonin in hypertension treatment, many important questions could be answered, such as the dose of melatonin and regimen of its application, the choice of patients with greatest possible benefit from melatonin treatment, the potential of anti-remodeling effect of melatonin and the interaction of melatonin with other antihypertensive drugs.
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Affiliation(s)
- Fedor Simko
- Department of Pathophysiology, School of Medicine, Komensdy University, Bratislava, Slovak Republic.
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Hirsch-Rodriguez E, Imbesi M, Manev R, Uz T, Manev H. The pattern of melatonin receptor expression in the brain may influence antidepressant treatment. Med Hypotheses 2007; 69:120-4. [PMID: 17197111 PMCID: PMC1950672 DOI: 10.1016/j.mehy.2006.11.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 11/05/2006] [Indexed: 10/23/2022]
Abstract
The pineal hormone melatonin produces most of its biological effects via G protein-coupled receptors MT1 and MT2. In mammals, these receptors are expressed in various tissues and organs including in the brain. Recent research points to a putative role of MT1/MT2 dimerization as a mechanism that could determine the receptor-mediated biological effects of melatonin. Brain content and the ratios between MT1 and MT2 receptors are affected by illness, e.g., Alzheimer's disease, and by prolonged drug treatment, e.g., antidepressants. New drugs with antidepressant properties that bind and activate melatonin receptors have been discovered. We hypothesize that endogenous, i.e., low, levels of melatonin could contribute to antidepressant effects depending on the expression pattern of melatonin receptors in the brain. Hence, we propose that a prolonged treatment with classical antidepressant drugs alters the brain ratio of MT1/MT2 receptors to enable the endogenous melatonin, which is secreted during the night, to further improve the antidepressant effects. A corollary of this hypothesis is that antidepressants would be less effective in conditions of pathologically altered brain melatonin receptors, e.g., in Alzheimer's patients or due to genetic polymorphisms. If our hypothesis is confirmed, supplementing classical antidepressant treatment with an appropriate dose of a melatonin receptor agonist might be used to improve antidepressant effects in subjects with a susceptible pattern of brain melatonin receptor expression.
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Affiliation(s)
- Eric Hirsch-Rodriguez
- Department of Psychiatry and the Psychiatric Institute, University of Illinois at Chicago, 1601 West Taylor Street, M/C912, Chicago, IL 60612, USA
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Abstract
The activity of the novel antidepressant agomelatine was evaluated in three models of anxiety and compared with that of melatonin and two anxiolytics, diazepam and buspirone. All drugs were tested 2 h before and 2 h after the dark phase of the diurnal cycle. Morning and evening agomelatine (10-75 mg/kg) administration increased animals' responses in the elevated plus maze and Vogel tests. Melatonin (10-75 mg/kg) enhanced open arms exploration in the evening experiment and was inactive in the Vogel test. In the conditioned ultrasonic vocalization test, agomelatine, but not melatonin, was active in the morning and evening experiment. Melatonin antagonist, S22153 (20 mg/kg), enhanced the action of morning and evening agomelatine administration in the Vogel and conditioned ultrasonic vocalization tests, while in the elevated plus maze test, S22153 inhibited effects of evening but not morning melatonin and agomelatine administration. These results indicate the involvement of both the melatonin and the 5-HT2C receptors in the mechanism of anxiolytic-like action of agomelatine.
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Affiliation(s)
- Mariusz Papp
- Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland.
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Kast RE, Altschuler EL. Co-administration of ramelton and fluvoxamine to increase levels of interleukin-2. Med Hypotheses 2006; 67:1389-90. [PMID: 16893613 DOI: 10.1016/j.mehy.2006.05.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2006] [Accepted: 05/11/2006] [Indexed: 11/23/2022]
Abstract
Ramelton is a medication recently approved by the FDA for treatment of insomnia. Ramelton is an analogue of melatonin with a higher affinity even than that of the natural ligand. Clinically this potentially strong effect of the ligand is blunted by the fact that upon oral ingestion there is first pass metabolism of greater than 95%. This liver metabolism is mediated by the CYP1A2 enzyme. It turns out that the medication fluvoxamine approved by the FDA for the treatment of obsessive compulsive disorder is a potent inhibitor of the CYP1A2 enzyme, with the effect that co-administration of ramelton and fluvoxamine increases blood levels of ramelton by 100-200 fold. It turns out that lymphocytes bear the melatnonin receptors and stimulation of these receptors on lymphocytes cause the lymphocytes to elaborate the pro-inflammatory cytokine interleukin-2 (Il-2). Thus, here we point out that co-administration of ramelton and modest doses of fluvoxamine may be able to smoothly produce increased levels of Il-2, this may be useful in diseases and conditions such as metastatic cancer and maintenance of suppression of the HIV virus.
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Affiliation(s)
- Richard E Kast
- Department of Psychiatry, University of Vermont, 2 Church Street, Burlington, VT 05401, United States.
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Dubocovich ML. Agomelatine targets a range of major depressive disorder symptoms. Curr Opin Investig Drugs 2006; 7:670-80. [PMID: 16869122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Servier, and US licensee Novartis AG, are developing the oral melatonin MT1 and MT2 agonist and 5-HT2B and 5-HT2C antagonist agomelatine as a once-daily treatment for major depressive disorder (MDD) and its symptoms, particularly anxiety, and sleep and circadian disturbances. Phase III trials have been completed and a registration dossier has been submitted to the EMEA in Western Europe.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Molecular Pharmacology and Biological Chemistry, The Feinberg School of Medicine, Center for Drug Discovery and Chemical Biology, Northwestern University, Chicago, IL 60611, USA
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Abstract
This paper will review our recent data relevant to the antioxidant effects of N-acetylserotonin (NAS), the immediate precursor of melatonin, the pineal gland indole. Mechanisms of the antioxidant effects of NAS might involve interaction with melatonin type 3 receptors and nonreceptor mechanisms such as stimulation of glutathione peroxidase, an antioxidant enzyme; inhibition of lipid peroxidation; suppression of phospholipase A2 activation; attenuation of tumor necrosis factor-alpha production; prevention of pathological opening of the mitochondrial permeability transition pores; and inhibition of sepiapterin reductase, the key enzyme of biosynthesis of tetrahydrobiopterin, the essential cofactor of nitric oxide synthase. NAS actions on some of these enzymes might be receptor-mediated. Protective effects of NAS against oxidative damage are independent from the effect of melatonin and, depending on the model, are 5 to 20 times stronger than that of melatonin. Antioxidant effect of NAS might underpin its cognition-enhancing, antiaging, antidepressant, antihypertensive, and antitumor effects. NAS and its derivatives might be useful in protection against oxidative stress-related disorders (cell death, mutagenesis, aging) and diseases (sepsis, cancer, postischemic trauma, Alzheimer's disease, parkinsonism).
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Affiliation(s)
- Gregory Oxenkrug
- Melatonin Clinic and Pineal Research Laboratory, Department of Psychiatry, Tufts University School of Medicine, Boston, Massachusetts 02135, USA.
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Boussard MF, Truche S, Rousseau-Rojas A, Briss S, Descamps S, Droual M, Wierzbicki M, Ferry G, Audinot V, Delagrange P, Boutin JA. New ligands at the melatonin binding site MT3. Eur J Med Chem 2006; 41:306-20. [PMID: 16414149 DOI: 10.1016/j.ejmech.2005.12.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Revised: 12/09/2005] [Accepted: 12/12/2005] [Indexed: 12/15/2022]
Abstract
The third melatonin binding site, MT3 is a non-classical one since it is not a seven transmembrane domains receptor, but an enzyme, quinone reductase 2. A major concern for the study of the physiological role of this site is the lack of specific ligands, permitting to more accurately dissect the pathways linked to the activation of MT3. Indeed, in the course of finding new ligands, we identified a new series of compounds with affinity to the binding site in the nM range, particularly 2,3-dimethoxy 7-hydroxy 10-methyl 5H 10H indeno(1,2-b)indol-10-one (DMHMIO), with a Ki of 190 pM. Based on slightly different and novel synthons compared to most of the compounds used in melatonin pharmacology studies, these compounds offer new perspective for the description of the melatonin pathways, so much more by not having any affinity towards the MT1 and MT2 'classical' melatonin receptors.
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Abstract
The range of available antidepressants is reviewed in relation to mechanisms of action and the evidence of efficacy in general and efficacy in severe depression in particular. In studies investigating efficacy in major depressive disorder, not all antidepressants have been shown to have clear-cut efficacy in severe depression. Here, the minimum standards for the necessary methodology to investigate efficacy in severe depression are reviewed and the methods that are needed to establish efficacy as a superior antidepressant or as an antidepressant with a faster than expected response are suggested. A review of the mechanisms of action of different antidepressants is accompanied by a critical review of the properties of an antidepressant likely to achieve either efficacy in severe depression or the status of a superior antidepressant.
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Abstract
Ramelteon, approved in the US for the treatment of insomnia characterised by difficulty with sleep onset, is a highly selective agonist for the melatonin MT1/MT2 receptors, which are believed to mediate the circadian rhythm in mammals. Ramelteon has negligible affinity for the MT3 binding sites and other receptors in the brain, including the opiate, dopamine, benzodiazepine and serotonin receptors, which may explain the lack of significant adverse events and lack of abuse or dependence potential observed with ramelteon. In three clinical trials in patients with chronic insomnia, ramelteon 8mg was effective in reducing sleep latency, without being associated with any significant or clinically relevant residual effects. It also generally increased total sleep time and, where assessed, sleep efficiency. In a first-night-effect model of transient insomnia, ramelteon 8mg was significantly more effective than placebo at reducing sleep latency and increasing total sleep time. Ramelteon was generally well tolerated; the most commonly reported adverse events occurring in more ramelteon than placebo recipients were somnolence (5% vs 3%), fatigue (4% vs 2%) and dizziness (5% vs 3%). Adverse events were mostly mild or moderate in nature. Ramelteon has been shown to have no potential for abuse or dependence.
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Sharma R, McMillan CR, Tenn CC, Niles LP. Physiological neuroprotection by melatonin in a 6-hydroxydopamine model of Parkinson's disease. Brain Res 2006; 1068:230-6. [PMID: 16375867 DOI: 10.1016/j.brainres.2005.10.084] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 10/21/2005] [Accepted: 10/31/2005] [Indexed: 10/25/2022]
Abstract
There is considerable evidence that pharmacological doses of the pineal hormone, melatonin, are neuroprotective in diverse models of neurodegeneration including Parkinson's disease. However, there is limited information about the effects of physiological doses of this hormone in similar models. In this study, rats were chronically treated with melatonin via drinking water following partial 6-hydroxydopamine lesioning in the striatum. The two doses of melatonin (0.4 microg/ml and 4.0 microg/ml) were within the reported physiological concentrations present in the serum and cerebrospinal fluid respectively. At 2 weeks after surgery, the higher dose of melatonin significantly attenuated rotational behavior in hemi-parkinsonian rats compared to similarly lesioned animals receiving either vehicle (P < 0.001) or the lower dose of melatonin (P < 0.01). Animals were perfused or sacrificed 10 weeks after commencing melatonin treatment for immunohistochemical or mRNA studies. Animals treated with 4.0 microg/ml melatonin exhibited normal tyrosine hydroxylase (TH) immunoreactivity in the lesioned striatum, whereas little or no TH immunofluorescence was visible in similarly lesioned animals receiving vehicle. In contrast, semiquantitative RT-PCR analysis revealed no group differences in TH mRNA, suggesting spontaneous recovery of this transcript as observed previously in partially lesioned animals. There were no significant differences in striatal GDNF mRNA levels between sham and lesioned animals. However, there was a significant (P < 0.01) increase in GDNF mRNA expression in the intact contralateral striata of lesioned animals treated with vehicle. Interestingly, melatonin treatment attenuated this novel compensatory contralateral increase in striatal GDNF expression, presumably due to its neuroprotective effect. These findings support a physiological role for melatonin in protecting against parkinsonian neurodegeneration in the nigrostriatal system.
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Affiliation(s)
- Rohita Sharma
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5
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22
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Abstract
In diurnal species, nocturnal melatonin secretion coincides with the habitual hours of sleep, in contrast to nocturnal animals which are at the peak of their activity while producing melatonin. Studies in humans, diurnal non-human primates, birds and fish show that melatonin treatment can facilitate sleep initiation during the daytime or improve altered overnight sleep. Behaviorally, the sleep-promoting effects of melatonin are distinctly different from those of common hypnotics and are not associated with alterations in sleep architecture. The effects of melatonin on sleep are mediated via specific melatonin receptors and physiologic doses of the hormone, those inducing circulating levels under 200 pg/ml, are sufficient to promote sleep in diurnal species. Aging reduces responsiveness to melatonin treatment and this correlates with reduced functional potency of melatonin receptors. Since melatonin receptors are present in different tissues and organs and involved in multiple physiologic functions, using physiologically relevant doses (0.1-0.3 mg, orally) and time of administration (at bedtime) is recommended, in order to avoid known and unknown side effects of melatonin treatment.
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Affiliation(s)
- Irina V Zhdanova
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
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23
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Abstract
Melatonin attenuates carotid chemoreceptor response to hypercapnic acidosis and may contribute to the effect of circadian rhythms on the chemoreflex. The purpose of this study was to test the hypothesis that melatonin modulates rat carotid chemoreceptor response to hypoxia. To examine the effect of melatonin on the hypoxic response of the chemosensitive cells, cytosolic calcium ([Ca2+]i) was measured by spectrofluorometry in fura-2-loaded type-I (glomus) cells dissociated from rat carotid bodies. Melatonin (0.01-10 nm) did not change the resting Ca2+]i level of the glomus cells but it concentration-dependently increased peak Ca2+]i response to cyanide or deoxygenated buffer. An agonist of melatonin receptors, iodomelatonin also enhanced the Ca2+]i response to hypoxia. The melatonin-induced enhancement of the Ca2+]i response was abolished by pretreatment with nonselective mt1/MT2 antagonist, luzindole, and by MT2 antagonists, 4-phenyl-2-propionamidotetraline or DH97. These findings suggest that melatonin receptors in the glomus cells mediate the effect of melatonin on the chemoreceptor response to hypoxia. In addition, melatonin increased the carotid afferent response to hypoxia in unitary activities recorded from the sinus nerve in isolated carotid bodies superfused with bicarbonate-buffer saline. Furthermore, plethysmographic measurement of ventilatory activities in unanesthetized rats revealed that melatonin (1 mg/kg, i.p.) increased the ventilatory response to hypoxia. Hence, the circadian rhythm of melatonin in arterial blood can modulate the carotid chemoreceptor response to hypoxia. This modulation may be a physiological mechanism involved in the day-light differences in ventilatory activities.
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Affiliation(s)
- Yueping Chen
- Department of Physiology, University of Hong Kong, Hong Kong, China
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24
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Turek FW, Gillette MU. Melatonin, sleep, and circadian rhythms: rationale for development of specific melatonin agonists. Sleep Med 2005; 5:523-32. [PMID: 15511698 DOI: 10.1016/j.sleep.2004.07.009] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Revised: 07/20/2004] [Accepted: 07/23/2004] [Indexed: 10/26/2022]
Abstract
Circadian rhythm sleep disorders (CRSDs), whether chronic or transient, affect a broad range of individuals, including many elderly, those with severe visual impairments, shift workers, and jet travelers moving rapidly across many time zones. In addition, various forms of insomnia affect another large sector of the population. A feature common among CRSDs and some forms of insomnia is sensitivity to the hormone melatonin, which is secreted by the pineal gland. Accumulating evidence suggests that melatonin may regulate the circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Although the light-dark cycle is the primary signal that entrains the circadian clock to environmental cycles, exogenous melatonin has been shown to entrain the clock in individuals with no light perception and free-running circadian rhythms. Furthermore, studies have reported beneficial effects of melatonin for treatment of certain insomnias. Together, these studies suggest that melatonin may be useful for treating some insomnias and CRSDs. In these contexts, use of melatonin as a supplement has been popular in the United States. Unfortunately, the therapeutic potential of melatonin has been difficult to realize in clinical trials, possibly owing to non-specific actions of the agent and its unfavorable pharmacokinetic properties when administered orally. In an attempt to take advantage of the therapeutic opportunities available through the brain's melatonin system, researchers have developed several melatonin agonists with improved properties in comparison to melatonin. Some of these agents are now in clinical trials for treatment of insomnia or CRSDs.
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Affiliation(s)
- Fred W Turek
- Department of Neurobiology and Physiology, Center for Sleep and Circadian Biology, Northwestern University, 2205 Tech Drive, Hogan Hall 2-160, Evanston, IL 60208, USA.
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25
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Abstract
The pineal hormone melatonin exhibits immunomodulatory activity well documented in mammals and birds. The mechanism of melatonin action within the immune system is, however, poorly understood. In mammalian immune cells in vitro, melatonin acts mainly as an antiapoptotic, oncostatic and antiproliferative agent, and these effects are exerted via specific receptors or are related to its free radical scavenging activity. In previous studies we have found that in short-term chicken splenocyte cultures in vitro melatonin stimulated basil proliferation and inhibited that stimulated with phytohemagglutinin, a T-cell mitogen. This paper is devoted to the involvement of membrane receptors, previously characterised by us as MT2 (Mel(1b)) and Mel(1c) subtypes, in the above mentioned melatonin effects in chicken splenocyte cultures. For this purpose, in present study a nonselective melatonin receptor antagonist, luzindole, and the selective MT2 blocker, 4P-PDOT, were used. The effect of melatonin on second messengers, cyclic adenosine-3',5'-monophosphate (cAMP) and inositol-1,4,5-trisphosphate (IP(3)), involved in the regulation of proliferation, was examined. We have found that the stimulation of proliferation occurs via Mel(1c) receptor and is associated with the changes in intracellular second messengers concentration: a decrease in cAMP and an increase in IP(3). In contrast, in mitogen-activated splenocytes, melatonin-induced inhibition of proliferation is mediated by MT2 receptors and is related to cAMP accumulation, as well as a decrease in IP(3). In conclusion, we have demonstrated that the stimulatory and inhibitory effect of melatonin on chicken splenocytes in vitro, dependent on the magnitude of cell stimulation, resulted from two different subtypes of membrane receptors.
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Affiliation(s)
- Magdalena Markowska
- Department of Vertebrate Physiology, Faculty of Biology, Warsaw University, Warsaw, Poland.
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26
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Mailliet F, Audinot V, Malpaux B, Bonnaud A, Delagrange P, Migaud M, Barrett P, Viaud-Massuard MC, Lesieur D, Lefoulon F, Renard P, Boutin JA. Molecular pharmacology of the ovine melatonin receptor: comparison with recombinant human MT1 and MT2 receptors. Biochem Pharmacol 2004; 67:667-77. [PMID: 14757166 DOI: 10.1016/j.bcp.2003.09.037] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The variations of the pharmacological properties of melatonin receptors between different mammalian species in transfected cell lines have been poorly investigated. In the present study, melatonin analogues have been used to characterize the pharmacology of the recombinant ovine melatonin receptor (oMT1) expressed in CHO cell lines and the native oMT1 from the pars tuberalis (PT). Studies with selective ligands on native and transfected oMT1 showed similar properties for binding affinities [r2(PT/CHO) = 0.85]. The affinities and the functional activities of these ligands were compared with the human receptors (hMT1 or hMT2) expressed in CHO cells as well. The oMT1 and hMT1 receptors had similar pharmacological profiles (r2=0.82). Nevertheless, some of the selective compounds at the human receptor presented a reduced affinity at the ovine receptor. Furthermore, some compounds showed marked different functional activities at oMT1 vs. hMT1 receptors. Our findings demonstrated differences in the pharmacological properties of melatonin receptors in ovine and human species.
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MESH Headings
- Animals
- Binding, Competitive
- CHO Cells
- Cricetinae
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Humans
- Iodine Radioisotopes
- Radioligand Assay
- Receptor, Melatonin, MT1/drug effects
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/drug effects
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Receptors, Melatonin/drug effects
- Receptors, Melatonin/genetics
- Receptors, Melatonin/metabolism
- Recombinant Proteins/metabolism
- Sheep, Domestic
- Species Specificity
- Sulfur Radioisotopes
- Transfection
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Affiliation(s)
- François Mailliet
- UMR INRA-CNRS-Université de Tours 6073, Physiologie de la Reproduction et des Comportements, Nouzilly 37380, France
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27
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Bourin M, Mocaër E, Porsolt R. Antidepressant-like activity of S 20098 (agomelatine) in the forced swimming test in rodents: involvement of melatonin and serotonin receptors. J Psychiatry Neurosci 2004; 29:126-33. [PMID: 15069466 PMCID: PMC383344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
OBJECTIVE To study agomelatine (S 20098), a potent agonist at melatonin receptors and antagonist at serotonin-2C (5-HT(2C)) receptors, in an animal model of depression, namely, the rodent forced swimming test (FST). METHODS The effects of acute and repeated administration of S 20098 were compared with those of melatonin (4, 8, 16, 32, 64 mg/kg intraperitoneally [IP] for mice), imipramine (64 mg/kg orally for rats, 8 mg/kg IP for mice) and fluoxetine (16 mg/kg IP for mice). The influence of the pretreatments with 5-HT(1A) or 5-HT(1B) receptor agonists (8-OH-DPAT, anpirtoline) and 5-HT(1A/1B), 5-HT(2A/2C) or 5-HT(3) antagonists (pindolol, ritanserin, ondansetron) on the effects of S 20098 or melatonin were compared with imipramine and fluoxetine in mice. RESULTS Acute or repeated (13 days) administration of S 20098 or imipramine in rats significantly decreased the duration of immobility during the FST at all doses. A dose-dependent effect was observed after the repeated treatment with S 20098. When given for 10 days to mice in the evening, S 20098 was active on the FST at doses of 4, 16 and 32 mg/kg, whereas the acute administration of S 20098 (in the morning and evening) was without any significant effect. Acute or repeated administration of S 20098 did not modify the locomotor activity of mice. The combination of S 20098 with the above-mentioned pretreatments enhanced the effects of S 20098, given alone, on the duration of immobility. By comparison, acute melatonin was inactive in the FST and only pretreatment with 8-OH-DPAT or pindolol revealed an anti-immobility effect. A pretreatment with 8-OH-DPAT also induced anti-immobility effects with imipramine, but not fluoxetine, whereas pindolol exerted additive effects with fluoxetine but not imipramine. CONCLUSION These results demonstrate the antidepressant-like activity of repeated administration of S 20098 in the FST. Moreover, the combination of 5-HT agonists and antagonists leads to more powerful effects with S 20098 than with melatonin, thereby emphasizing the contribution of 5-HT receptors to the antidepressant activity of S 20098. Compared with imipramine and fluoxetine, the 5-HT receptor subtypes that may be involved in the antidepressant-like activity of S 20098 are not similar. Indeed, when considering the binding properties of S 20098, the 5-HT(2C) receptor subtype appears to be the most attractive candidate. It is concluded that the antidepressant-like activity of S 20098 in this model most probably involves a combination of both its melatonin agonist and 5-HT(2C )receptor antagonist properties.
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Affiliation(s)
- Michel Bourin
- EA 3256, Neurobiologie de l'anxiété et de la dépression, Faculté de Médecine, Nantes, France.
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28
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Abstract
Respiratory activity is under circadian modulation and the physiological mechanisms may involve the pineal secretory product, melatonin, and the carotid chemoreceptor. We hypothesized that melatonin modulates the carotid chemoreceptor response to hypercapnic acidosis. To determine whether the effect of melatonin on the chemoreceptor response to hypercapnic acidosis is mediated by melatonin receptors in the chemosensitive cells, cytosolic calcium ([Ca2+]i) was measured by spectrofluorometry in fura-2-loaded glomus cells dissociated from rat carotid bodies. Melatonin (0.01-10 nm) per se did not change the [Ca2+]i levels of the glomus cells but it concentration-dependently attenuated the peak [Ca2+]i response to hypercapnic acidosis in the glomus cells. In addition, the [Ca2+]i response was attenuated by 2-iodomelatonin, an agonist of melatonin receptors. The melatonin-induced attenuation of the [Ca2+]i response to hypercapnic acidosis was abolished by pretreatment with an non-selective mt1/MT2 antagonist, luzindole, and by MT2 antagonists, 4-phenyl-2-propionamidotetraline or DH97. In situ hybridization study with antisense mt1 and MT2 receptor mRNA oligonucleotide probes showed an expression of mt1 and MT2 receptors in the rat carotid body. Also, melatonin attenuated the carotid afferent response to hypercapnic acidosis in single- or pauci-fibers recorded from the sinus nerve in isolated carotid bodies superfused with bicarbonate-buffer saline. Results suggest that an activation of the melatonin receptors expressed in the glomus cells of the rat carotid body reduces the chemoreceptor response to hypercapnic acidosis. This modulation may play a physiological role in the influence of the circadian rhythms on the chemoreflex.
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MESH Headings
- Acidosis, Respiratory/drug therapy
- Acidosis, Respiratory/metabolism
- Animals
- Calcium/metabolism
- Carotid Body/cytology
- Carotid Body/drug effects
- Carotid Body/metabolism
- Chemoreceptor Cells/drug effects
- Electrophysiology/methods
- Fura-2/metabolism
- Hypercapnia/drug therapy
- Hypercapnia/metabolism
- Melatonin/analogs & derivatives
- Melatonin/antagonists & inhibitors
- Melatonin/pharmacology
- Melatonin/physiology
- Rats
- Rats, Sprague-Dawley
- Receptor, Melatonin, MT1/antagonists & inhibitors
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/antagonists & inhibitors
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Receptors, Melatonin/antagonists & inhibitors
- Receptors, Melatonin/drug effects
- Tetrahydronaphthalenes/pharmacology
- Tryptamines/pharmacology
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Affiliation(s)
- Yung Wui Tjong
- Department of Physiology, University of Hong Kong, Hong Kong, China
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29
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O'Rourke ST, Hammad H, Delagrange P, Scalbert E, Vanhoutte PM. Melatonin inhibits nitrate tolerance in isolated coronary arteries. Br J Pharmacol 2003; 139:1326-32. [PMID: 12890712 PMCID: PMC1573966 DOI: 10.1038/sj.bjp.0705383] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2003] [Revised: 03/28/2003] [Accepted: 05/13/2003] [Indexed: 11/09/2022] Open
Abstract
(1) The present study was designed to test the hypothesis that melatonin inhibits nitrate tolerance in coronary arteries. (2) Rings of porcine coronary arteries were suspended in organ chambers for isometric tension recording. Nitrate tolerance was induced by incubating the tissues with nitroglycerin (10(-4) M) for 90 min, followed by repeated rinsing for 1 h. Control rings that had not been exposed previously to nitroglycerin, but were otherwise treated identically, were studied simultaneously. The rings were contracted with U46619 (1-3 x 10(-9) M) and concentration-response curves to nitroglycerin (10(-9)-10(-4) M) were obtained. (3) Nitrate tolerance was evident by a 15- to 20-fold rightward shift in the concentration-response curve to nitroglycerin in rings with and without endothelium exposed previously to the drug for 90 min. Addition of melatonin (10(-9)-10(-7) M) to the organ chamber during the 90-min incubation period with nitroglycerin partially inhibited nitrate tolerance in coronary arteries with intact endothelium; however, melatonin had no effect on nitrate tolerance in coronary arteries without endothelium. (4) The effect of melatonin on nitrate tolerance in coronary arteries with endothelium was abolished by the melatonin receptor antagonist, S20928 (10(-6) M). In contrast to melatonin, the selective MT(3)-melatonin receptor agonist, 5-MCA-NAT (10(-8)-10(-7) M), had no effect on nitrate tolerance in coronary arteries. (5) The results demonstrate that melatonin, acting via specific melatonin receptors, inhibits nitrate tolerance in coronary arteries and that this effect is dependent on the presence of the vascular endothelium.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/antagonists & inhibitors
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Arteries
- Coronary Vessels/drug effects
- Coronary Vessels/physiology
- Cromakalim/pharmacology
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/surgery
- In Vitro Techniques
- Isometric Contraction/drug effects
- Isometric Contraction/physiology
- Isoproterenol/pharmacology
- Melatonin/pharmacology
- Melatonin/physiology
- Muscle, Smooth, Vascular/drug effects
- Naphthalenes/pharmacology
- Nitrates/administration & dosage
- Nitrates/adverse effects
- Nitrates/pharmacokinetics
- Nitroglycerin/adverse effects
- Nitroglycerin/pharmacology
- Receptors, Melatonin/antagonists & inhibitors
- Receptors, Melatonin/drug effects
- Swine
- Tachyphylaxis/physiology
- Time Factors
- Tryptamines/pharmacology
- Vasoconstriction/drug effects
- Vasodilation/drug effects
- Vasodilator Agents/pharmacology
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Affiliation(s)
- Stephen T O'Rourke
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND 58105, USA.
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