1
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Pissas KP, Schilling M, Korkmaz A, Tian Y, Gründer S. Melatonin alters the excitability of mouse cerebellar granule neurons by inhibiting voltage-gated sodium, potassium, and calcium channels. J Pineal Res 2024; 76:e12919. [PMID: 37794846 DOI: 10.1111/jpi.12919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 09/01/2023] [Accepted: 09/19/2023] [Indexed: 10/06/2023]
Abstract
Besides its role in the circadian rhythm, the pineal gland hormone melatonin (MLT) also possesses antiepileptogenic, antineoplastic, and cardioprotective properties, among others. The dosages necessary to elicit beneficial effects in these diseases often far surpass physiological concentrations. Although even high doses of MLT are considered to be largely harmless to humans, the possible side effects of pharmacological concentrations are so far not well investigated. In the present study, we report that pharmacological doses of MLT (3 mM) strongly altered the electrophysiological characteristics of cultured primary mouse cerebellar granule cells (CGCs). Using whole-cell patch clamp and ratiometric Ca2+ imaging, we observed that pharmacological concentrations of MLT inhibited several types of voltage-gated Na+ , K+ , and Ca2+ channels in CGCs independently of known MLT-receptors, altering the character and pattern of elicited action potentials (APs) significantly, quickly and reversibly. Specifically, MLT reduced AP frequency, afterhyperpolarization, and rheobase, whereas AP amplitude and threshold potential remained unchanged. The altered biophysical profile of the cells could constitute a possible mechanism underlying the proposed beneficial effects of MLT in brain-related disorders, such as epilepsy. On the other hand, it suggests potential adverse effects of pharmacological MLT concentrations on neurons, which should be considered when using MLT as a pharmacological compound.
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Affiliation(s)
| | - Maria Schilling
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Ahmet Korkmaz
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Yuemin Tian
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Stefan Gründer
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
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2
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Vazquez JI, Gascue V, Quintana L, Migliaro A. Understanding daily rhythms in weakly electric fish: the role of melatonin on the electric behavior of Brachyhypopomus gauderio. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024; 210:7-18. [PMID: 37002418 DOI: 10.1007/s00359-023-01626-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 03/16/2023] [Accepted: 03/20/2023] [Indexed: 04/03/2023]
Abstract
Living organisms display molecular, physiological and behavioral rhythms synchronized with natural environmental cycles. Understanding the interaction between environment, physiology and behavior requires taking into account the complexity of natural habitats and the diversity of behavioral and physiological adaptations. Brachyhypopomus gauderio is characterized by the emission of electric organ discharges (EOD), with a very stable rate modulated by social and environmental cues. The nocturnal arousal in B. gauderio coincides with a melatonin-dependent EOD rate increase. Here, we first show a daily cycle in both the EOD basal rate (EOD-BR) and EOD-BR variability of B. gauderio in nature. We approached the understanding of the role of melatonin in this natural behavior through both behavioral pharmacology and in vitro assays. We report, for the first time in gymnotiformes, a direct effect of melatonin on the pacemaker nucleus (PN) in in vitro preparation. Melatonin treatment lowered EOD-BR in freely moving fish and PN basal rate, while increasing the variability of both. These results show that melatonin plays a key role in modulating the electric behavior of B. gauderio through its effect on rate and variability, both of which must be under a tight temporal regulation to prepare the animal for the challenging nocturnal environment.
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Affiliation(s)
- Juan I Vazquez
- Dpto de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Valentina Gascue
- Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Laura Quintana
- Dpto de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Adriana Migliaro
- Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
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3
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Cruz-Sanabria F, Carmassi C, Bruno S, Bazzani A, Carli M, Scarselli M, Faraguna U. Melatonin as a Chronobiotic with Sleep-promoting Properties. Curr Neuropharmacol 2023; 21:951-987. [PMID: 35176989 PMCID: PMC10227911 DOI: 10.2174/1570159x20666220217152617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/26/2022] [Accepted: 02/10/2022] [Indexed: 11/22/2022] Open
Abstract
The use of exogenous melatonin (exo-MEL) as a sleep-promoting drug has been under extensive debate due to the lack of consistency of its described effects. In this study, we conduct a systematic and comprehensive review of the literature on the chronobiotic, sleep-inducing, and overall sleep-promoting properties of exo-MEL. To this aim, we first describe the possible pharmacological mechanisms involved in the sleep-promoting properties and then report the corresponding effects of exo-MEL administration on clinical outcomes in: a) healthy subjects, b) circadian rhythm sleep disorders, c) primary insomnia. Timing of administration and doses of exo-MEL received particular attention in this work. The exo-MEL pharmacological effects are hereby interpreted in view of changes in the physiological properties and rhythmicity of endogenous melatonin. Finally, we discuss some translational implications for the personalized use of exo-MEL in the clinical practice.
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Affiliation(s)
- Francy Cruz-Sanabria
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa - Italy
| | - Claudia Carmassi
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa - Italy
| | - Simone Bruno
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa - Italy
| | - Andrea Bazzani
- Institute of Management, Scuola Superiore Sant’Anna, Pisa – Italy
| | - Marco Carli
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa - Italy
| | - Marco Scarselli
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa - Italy
| | - Ugo Faraguna
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa - Italy
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Pisa, Italy
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4
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Somalo-Barranco G, Serra C, Lyons D, Piggins HD, Jockers R, Llebaria A. Design and Validation of the First Family of Photo-Activatable Ligands for Melatonin Receptors. J Med Chem 2022; 65:11229-11240. [PMID: 35930058 PMCID: PMC9421648 DOI: 10.1021/acs.jmedchem.2c00717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
![]()
Melatonin is a neurohormone released in a circadian manner
with
peak levels at night. Melatonin mediates its effects mainly through
G protein-coupled MT1 and MT2 receptors. Drugs
acting on melatonin receptors are indicated for circadian rhythm-
and sleep-related disorders. Tools to study the activation of these
receptors with high temporal resolution are lacking. Here, we synthesized
a family of light-activatable caged compounds by attaching o-nitrobenzyl (o-NB) or coumarin photocleavable
groups to melatonin indolic nitrogen. All caged compounds showed the
expected decrease in binding affinity for MT1 and MT2. The o-NB derivative MCS-0382 showed the
best uncaging and biological properties, with 250-fold increase in
affinity and potency upon illumination. Generation of melatonin from
MCS-0382 was further demonstrated by its ability to modulate the excitation
of SCN neurons in rat brain slices. MCS-0382 is available to study
melatonin effects in a temporally controlled manner in cellular and
physiological settings.
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Affiliation(s)
- Gloria Somalo-Barranco
- Université de Paris, Institut Cochin, INSERM, CNRS, F-75014 Paris, France.,MCS, Laboratory of Medicinal Chemistry & Synthesis, Department of Biological Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain
| | - Carme Serra
- MCS, Laboratory of Medicinal Chemistry & Synthesis, Department of Biological Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain.,SIMChem, Synthesis of High Added Value Molecules, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain
| | - David Lyons
- School of Physiology, Pharmacology and Neuroscience, Faculty of Life Sciences, University of Bristol, BS8 1TD Bristol, U.K
| | - Hugh D Piggins
- School of Physiology, Pharmacology and Neuroscience, Faculty of Life Sciences, University of Bristol, BS8 1TD Bristol, U.K
| | - Ralf Jockers
- Université de Paris, Institut Cochin, INSERM, CNRS, F-75014 Paris, France
| | - Amadeu Llebaria
- MCS, Laboratory of Medicinal Chemistry & Synthesis, Department of Biological Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), 08034 Barcelona, Spain
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5
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Cruz-Aguilar MA, Ramírez-Salado I, Hernández-González M, Guevara MA, Del Río JM. Melatonin effects on EEG activity during non-rapid eye movement sleep in mild-to-moderate Alzheimer´s disease: a pilot study. Int J Neurosci 2020; 131:580-590. [PMID: 32228330 DOI: 10.1080/00207454.2020.1750392] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
INTRODUCTION There is evidence to suggest that melatonin diminishes non-rapid eye movement sleep (NREMS) latency in patients with Alzheimer´s disease (AD). However, melatonin's effects on cortical activity during NREMS in AD have not been studied. The objective of this research was to analyze the effects of melatonin on cortical activity during the stages of NREMS in 8 mild-to-moderate AD patients that received 5-mg of fast-release melatonin. METHODS During a single-blind, placebo-controlled crossover study, polysomnographic recordings were obtained from C3-A1, C4-A2, F7-T3, F8-T4, F3-F4 and O1-O2. Also, the relative power (RP) and EEG coherences of the delta, theta, alpha1, alpha2, beta1, beta2 and gamma bands were calculated during NREMS-1, NREMS-2 and NREMS-3. These sleep latencies and all EEG data were then compared between the placebo and melatonin conditions. RESULTS During NREMS-2, a significant RP increase was observed in the theta band of the left-central hemisphere. During NREMS-3, significant RP decreases in the beta bands were recorded in the right-central hemisphere, compared to the placebo group. After melatonin administration, significant decreases of EEG coherences in the beta2, beta1 and gamma bands were observed in the right hemisphere during NREMS-3. DISCUSSION We conclude that short NREMS onset related to melatonin intake in AD patients is associated with a significant RP increase in the theta band and a decrease in RP and EEG coherences in the beta and gamma bands during NREMS-3. These results suggest that the GABAergic pathways are preserved in mild-to-moderate AD.
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Affiliation(s)
- Manuel Alejandro Cruz-Aguilar
- Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz," Dirección de Investigaciones en Neurociencias, Laboratorio de Cronobiología y Sueño, CDMX, México
| | - Ignacio Ramírez-Salado
- Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz," Dirección de Investigaciones en Neurociencias, Laboratorio de Cronobiología y Sueño, CDMX, México
| | - Marisela Hernández-González
- Instituto de Neurociencias, CUCBA, Laboratorio de Neurofisiología de la Conducta Reproductiva, Universidad de Guadalajara, Guadalajara, Jalisco, México
| | - Miguel Angel Guevara
- Instituto de Neurociencias, CUCBA, Laboratorio de Correlación Electroencefalográfica y Conducta, Universidad de Guadalajara, Guadalajara, Jalisco, México
| | - Jahaziel Molina Del Río
- Centro Universitario de los Valles, Departamento de Ciencias de la Salud, Laboratorio de Neuropsicología, División de Estudios de la Salud, Universidad de Guadalajara, Ameca, Jalisco, México
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6
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Harvey JRM, Plante AE, Meredith AL. Ion Channels Controlling Circadian Rhythms in Suprachiasmatic Nucleus Excitability. Physiol Rev 2020; 100:1415-1454. [PMID: 32163720 DOI: 10.1152/physrev.00027.2019] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Animals synchronize to the environmental day-night cycle by means of an internal circadian clock in the brain. In mammals, this timekeeping mechanism is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus and is entrained by light input from the retina. One output of the SCN is a neural code for circadian time, which arises from the collective activity of neurons within the SCN circuit and comprises two fundamental components: 1) periodic alterations in the spontaneous excitability of individual neurons that result in higher firing rates during the day and lower firing rates at night, and 2) synchronization of these cellular oscillations throughout the SCN. In this review, we summarize current evidence for the identity of ion channels in SCN neurons and the mechanisms by which they set the rhythmic parameters of the time code. During the day, voltage-dependent and independent Na+ and Ca2+ currents, as well as several K+ currents, contribute to increased membrane excitability and therefore higher firing frequency. At night, an increase in different K+ currents, including Ca2+-activated BK currents, contribute to membrane hyperpolarization and decreased firing. Layered on top of these intrinsically regulated changes in membrane excitability, more than a dozen neuromodulators influence action potential activity and rhythmicity in SCN neurons, facilitating both synchronization and plasticity of the neural code.
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Affiliation(s)
- Jenna R M Harvey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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Boutin JA, Legros C. The five dimensions of receptor pharmacology exemplified by melatonin receptors: An opinion. Pharmacol Res Perspect 2020; 8:e00556. [PMID: 31893125 PMCID: PMC6935684 DOI: 10.1002/prp2.556] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 12/03/2019] [Accepted: 12/03/2019] [Indexed: 12/22/2022] Open
Abstract
Receptology has been complicated with enhancements in our knowledge of G-protein-coupled-receptor (GPCR) biochemistry. This complexity is exemplified by the pharmacology of melatonin receptors. Here, we describe the complexity of GPCR biochemistry in five dimensions: (a) receptor expression, particularly in organs/tissues that are only partially understood; (b) ligands and receptor-associated proteins (interactome); (c) receptor function, which might be more complex than the known G-protein-coupled systems; (d) ligand bias, which favors a particular pathway; and (e) receptor dimerization, which might concern all receptors coexpressed in the same cell. Thus, receptor signaling might be modified or modulated, depending on the nature of the receptor complex. Fundamental studies are needed to clarify these points and find new ways to tackle receptor functionality. This opinion article emphasizes the global questions attached to new descriptions of GPCRs and aims to raise our awareness of the tremendous complexity of modern receptology.
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Affiliation(s)
- Jean A. Boutin
- Institut de Recherches Internationales ServierSuresnesFrance
| | - Céline Legros
- Institut de Recherches ServierCroissy‐sur‐SeineFrance
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8
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Legros C, Dupré C, Brasseur C, Bonnaud A, Bruno O, Valour D, Shabajee P, Giganti A, Nosjean O, Kenakin TP, Boutin JA. Characterization of the various functional pathways elicited by synthetic agonists or antagonists at the melatonin MT 1 and MT 2 receptors. Pharmacol Res Perspect 2020; 8:e00539. [PMID: 31893123 PMCID: PMC6935685 DOI: 10.1002/prp2.539] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 09/30/2019] [Accepted: 10/10/2019] [Indexed: 12/20/2022] Open
Abstract
Melatonin is a neurohormone that translates the circadian rhythm to the peripheral organs through a series of binding sites identified as G protein-coupled receptors MT1 and MT2. Due to minute amounts of receptor proteins in target organs, the main tool of studies of the melatoninergic system is recombinant expression of the receptors in cellular hosts. Although a number of studies exist on these receptors, studies of several signaling pathways using a large number of melatoninergic compounds are rather limited. We chose to fill this gap to better describe a panel of compounds that have been only partially characterized in terms of functionality. First, we characterized HEK cells expressing MT1 or MT2, and several signaling routes with melatonin itself to validate the approach: GTPγS, cAMP production, internalization, β-arrestin recruitment, and cell morphology changes (CellKey ® ). Second, we chose 21 compounds from our large melatoninergic chemical library and characterized them using this panel of signaling pathways. Notably, antagonists were infrequent, and their functionality depended largely on the pathway studied. This will permit redefining the availability of molecular tools that can be used to better understand the in situ activity and roles of these receptors.
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Affiliation(s)
- Céline Legros
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Clémence Dupré
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Chantal Brasseur
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Anne Bonnaud
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Olivier Bruno
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Damien Valour
- Pôle d’Expetise Méthodologie et Valorisation des DonnéesInstitut de Recherches Internationales ServierSuresnesFrance
| | - Preety Shabajee
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Adeline Giganti
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
| | - Olivier Nosjean
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
- Present address:
Institut de Recherches Internationales SERVIERSuresnesFrance
| | - Terrence P. Kenakin
- Department of PharmacologyUniversity of North Carolina School of MedicineChapel HillNCUSA
| | - Jean A. Boutin
- Pôle d’Expertise BiotechnologieChimie & BiologieInstitut de Recherches ServierCroissy‐sur‐SeineFrance
- Present address:
Institut de Recherches Internationales SERVIERSuresnesFrance
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9
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Mohammadi F, Shakiba S, Mehrzadi S, Afshari K, Rahimnia AH, Dehpour AR. Anticonvulsant effect of melatonin through ATP‐sensitive channels in mice. Fundam Clin Pharmacol 2019; 34:148-155. [DOI: 10.1111/fcp.12490] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Revised: 05/07/2019] [Accepted: 06/11/2019] [Indexed: 12/14/2022]
Affiliation(s)
- Fatemeh Mohammadi
- Brain and Spinal Cord Injury Research Center Neuroscience Institute Tehran University of Medical Sciences Tehran Iran
| | - Saeed Shakiba
- Brain and Spinal Cord Injury Research Center Neuroscience Institute Tehran University of Medical Sciences Tehran Iran
- Experimental Medicine Research Center Tehran University of Medical Sciences Tehran Iran
- Department of Pharmacology School of Medicine Tehran University of Medical Sciences Tehran Iran
| | - Saeed Mehrzadi
- Razi Drug Research Center Iran University of Medical Sciences Shahid Hemmat Highway Tehran 1449614535 Iran
| | - Khashayar Afshari
- Brain and Spinal Cord Injury Research Center Neuroscience Institute Tehran University of Medical Sciences Tehran Iran
- Experimental Medicine Research Center Tehran University of Medical Sciences Tehran Iran
- Department of Pharmacology School of Medicine Tehran University of Medical Sciences Tehran Iran
| | - Amir Hossein Rahimnia
- Brain and Spinal Cord Injury Research Center Neuroscience Institute Tehran University of Medical Sciences Tehran Iran
- Experimental Medicine Research Center Tehran University of Medical Sciences Tehran Iran
- Department of Pharmacology School of Medicine Tehran University of Medical Sciences Tehran Iran
| | - Ahmad Reza Dehpour
- Brain and Spinal Cord Injury Research Center Neuroscience Institute Tehran University of Medical Sciences Tehran Iran
- Experimental Medicine Research Center Tehran University of Medical Sciences Tehran Iran
- Department of Pharmacology School of Medicine Tehran University of Medical Sciences Tehran Iran
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10
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Oliveira-Abreu K, Silva-Dos-Santos NM, Coelho-de-Souza AN, Ferreira-da-Silva FW, Silva-Alves KSD, Cardoso-Teixeira AC, Cipolla-Neto J, Leal-Cardoso JH. Melatonin Reduces Excitability in Dorsal Root Ganglia Neurons with Inflection on the Repolarization Phase of the Action Potential. Int J Mol Sci 2019; 20:ijms20112611. [PMID: 31141907 PMCID: PMC6600424 DOI: 10.3390/ijms20112611] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 05/23/2019] [Indexed: 12/22/2022] Open
Abstract
Melatonin is a neurohormone produced and secreted at night by pineal gland. Many effects of melatonin have already been described, for example: Activation of potassium channels in the suprachiasmatic nucleus and inhibition of excitability of a sub-population of neurons of the dorsal root ganglia (DRG). The DRG is described as a structure with several neuronal populations. One classification, based on the repolarizing phase of the action potential (AP), divides DRG neurons into two types: Without (N0) and with (Ninf) inflection on the repolarization phase of the action potential. We have previously demonstrated that melatonin inhibits excitability in N0 neurons, and in the present work, we aimed to investigate the melatonin effects on the other neurons (Ninf) of the DRG neuronal population. This investigation was done using sharp microelectrode technique in the current clamp mode. Melatonin (0.01–1000.0 nM) showed inhibitory activity on neuronal excitability, which can be observed by the blockade of the AP and by the increase in rheobase. However, we observed that, while some neurons were sensitive to melatonin effect on excitability (excitability melatonin sensitive—EMS), other neurons were not sensitive to melatonin effect on excitability (excitability melatonin not sensitive—EMNS). Concerning the passive electrophysiological properties of the neurons, melatonin caused a hyperpolarization of the resting membrane potential in both cell types. Regarding the input resistance (Rin), melatonin did not change this parameter in the EMS cells, but increased its values in the EMNS cells. Melatonin also altered several AP parameters in EMS cells, the most conspicuously changed was the (dV/dt)max of AP depolarization, which is in coherence with melatonin effects on excitability. Otherwise, in EMNS cells, melatonin (0.1–1000.0 nM) induced no alteration of (dV/dt)max of AP depolarization. Thus, taking these data together, and the data of previous publication on melatonin effect on N0 neurons shows that this substance has a greater pharmacological potency on Ninf neurons. We suggest that melatonin has important physiological function related to Ninf neurons and this is likely to bear a potential relevant therapeutic use, since Ninf neurons are related to nociception.
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Affiliation(s)
- Klausen Oliveira-Abreu
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
| | - Nathalia Maria Silva-Dos-Santos
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
| | - Andrelina Noronha Coelho-de-Souza
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
| | - Francisco Walber Ferreira-da-Silva
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
| | - Kerly Shamyra da Silva-Alves
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
| | - Ana Carolina Cardoso-Teixeira
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
| | - José Cipolla-Neto
- Laboratório de Neurobiologia, Instituto de Ciências Biomédicas 1, Universidade de São Paulo, São Paulo 05508-000, SP, Brasil.
| | - José Henrique Leal-Cardoso
- Laboratório de Eletrofisiologia, Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza 60714-903, CE, Brazil.
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11
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Cipolla-Neto J, Amaral FGD. Melatonin as a Hormone: New Physiological and Clinical Insights. Endocr Rev 2018; 39:990-1028. [PMID: 30215696 DOI: 10.1210/er.2018-00084] [Citation(s) in RCA: 310] [Impact Index Per Article: 51.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 06/21/2018] [Indexed: 02/07/2023]
Abstract
Melatonin is a ubiquitous molecule present in almost every live being from bacteria to humans. In vertebrates, besides being produced in peripheral tissues and acting as an autocrine and paracrine signal, melatonin is centrally synthetized by a neuroendocrine organ, the pineal gland. Independently of the considered species, pineal hormone melatonin is always produced during the night and its production and secretory episode duration are directly dependent on the length of the night. As its production is tightly linked to the light/dark cycle, melatonin main hormonal systemic integrative action is to coordinate behavioral and physiological adaptations to the environmental geophysical day and season. The circadian signal is dependent on its daily production regularity, on the contrast between day and night concentrations, and on specially developed ways of action. During its daily secretory episode, melatonin coordinates the night adaptive physiology through immediate effects and primes the day adaptive responses through prospective effects that will only appear at daytime, when melatonin is absent. Similarly, the annual history of the daily melatonin secretory episode duration primes the central nervous/endocrine system to the seasons to come. Remarkably, maternal melatonin programs the fetuses' behavior and physiology to cope with the environmental light/dark cycle and season after birth. These unique ways of action turn melatonin into a biological time-domain-acting molecule. The present review focuses on the above considerations, proposes a putative classification of clinical melatonin dysfunctions, and discusses general guidelines to the therapeutic use of melatonin.
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Affiliation(s)
- José Cipolla-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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12
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Xu Z, Wu Y, Zhang Y, Zhang H, Shi L. Melatonin activates BK Ca channels in cerebral artery myocytes via both direct and MT receptor/PKC-mediated pathway. Eur J Pharmacol 2018; 842:177-188. [PMID: 30391348 DOI: 10.1016/j.ejphar.2018.10.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 10/17/2018] [Accepted: 10/24/2018] [Indexed: 11/28/2022]
Abstract
The pineal hormone melatonin is a neuroendocrine hormone with high membrane permeability that is involved in regulation of circadian rhythm of several biological functions. Large-conductance Ca2+-activated K+ (BKCa) channels are abundantly expressed in vascular smooth muscle cells and play an important role in vascular tone regulation. We investigated the mechanisms through which myocyte BKCa channels mediate effects of melatonin on cerebral arteries (CAs). Arterial contractility measurements showed that melatonin alone did not change vascular tone in CAs; however, it induced concentration-dependent vasodilation of phenylephrine-induced contraction in CAs. In the presence of the potent endothelial oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester, melatonin-elicited relaxation was significantly inhibited by iberiotoxin (BKCa channel blocker). Melatonin significantly increased BKCa currents but not voltage-gated K+ (KV) currents in whole-cell recordings. Melatonin decreased the amplitude of Ca2+ sparks and spontaneous transient outward currents (STOCs), however, a significant increase in open probability of BKCa channels was observed in both inside-out and cell-attached patch-clamp recordings. This melatonin-induced enhancement of BKCa channel activity was significantly suppressed by luzindole (melatonin MT1/MT2 receptor inhibitor), U73122 (phospholipase C (PLC) inhibitor), and Ro31-8220 (protein kinase C (PKC) inhibitor). Melatonin had no significant effects on sarcoplasmic reticulum release of Ca2+. These findings indicate that melatonin-induced vasorelaxation of CAs is partially attributable to direct (passing through the cell membrane) and indirect (via melatonin MT1/MT2 receptors-PLC-PKC pathway) activation of BKCa channels on CA myocytes.
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Affiliation(s)
- Zhaoxia Xu
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Ying Wu
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Yanyan Zhang
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Huirong Zhang
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Lijun Shi
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China.
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13
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Moldavan MG, Sollars PJ, Lasarev MR, Allen CN, Pickard GE. Circadian Behavioral Responses to Light and Optic Chiasm-Evoked Glutamatergic EPSCs in the Suprachiasmatic Nucleus of ipRGC Conditional vGlut2 Knock-Out Mice. eNeuro 2018; 5:ENEURO.0411-17.2018. [PMID: 29756029 PMCID: PMC5944003 DOI: 10.1523/eneuro.0411-17.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 04/06/2018] [Accepted: 04/27/2018] [Indexed: 12/26/2022] Open
Abstract
Intrinsically photosensitive retinal ganglion cells (ipRGCs) innervate the hypothalamic suprachiasmatic nucleus (SCN), a circadian oscillator that functions as a biological clock. ipRGCs use vesicular glutamate transporter 2 (vGlut2) to package glutamate into synaptic vesicles and light-evoked resetting of the SCN circadian clock is widely attributed to ipRGC glutamatergic neurotransmission. Pituitary adenylate cyclase-activating polypeptide (PACAP) is also packaged into vesicles in ipRGCs and PACAP may be coreleased with glutamate in the SCN. vGlut2 has been conditionally deleted in ipRGCs in mice [conditional knock-outs (cKOs)] and their aberrant photoentrainment and residual attenuated light responses have been ascribed to ipRGC PACAP release. However, there is no direct evidence that all ipRGC glutamatergic neurotransmission is eliminated in vGlut2 cKOs. Here, we examined two lines of ipRGC vGlut2 cKO mice for SCN-mediated behavioral responses under several lighting conditions and for ipRGC glutamatergic neurotransmission in the SCN. Circadian behavioral responses varied from a very limited response to light to near normal photoentrainment. After collecting behavioral data, hypothalamic slices were prepared and evoked EPSCs (eEPSCs) were recorded from SCN neurons by stimulating the optic chiasm. In cKOs, glutamatergic eEPSCs were recorded and all eEPSC parameters examined (stimulus threshold, amplitude, rise time or time-to-peak and stimulus strength to evoke a maximal response) were similar to controls. We conclude that a variable number but functionally significant percentage of ipRGCs in two vGlut2 cKO mouse lines continue to release glutamate. Thus, the residual SCN-mediated light responses in these cKO mouse lines cannot be attributed solely to ipRGC PACAP release.
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Affiliation(s)
- Michael G. Moldavan
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR 97239
| | - Patricia J. Sollars
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE 68583
| | - Michael R. Lasarev
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR 97239
| | - Charles N. Allen
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR 97239
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239
| | - Gary E. Pickard
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE 68583
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198
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Cruz-Aguilar MA, Ramírez-Salado I, Guevara MA, Hernández-González M, Benitez-King G. Melatonin Effects on EEG Activity During Sleep Onset in Mild-to-Moderate Alzheimer's Disease: A Pilot Study. J Alzheimers Dis Rep 2018; 2:55-65. [PMID: 30480249 PMCID: PMC6159690 DOI: 10.3233/adr-170019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/07/2018] [Indexed: 11/21/2022] Open
Abstract
There is evidence demonstrating that 5-mg of fast-release melatonin significantly reduces nocturnal sleep onset in patients with mild-to-moderate Alzheimer's disease (AD). However, the physiological mechanism that could promote sleep installation by melatonin in patients with AD is still poorly understood. The present pilot study was designed to analyze the effects of melatonin on cortical activity during the sleep onset period (SOP) in eight mild-to-moderate AD patients treated with 5-mg of fast-release melatonin. Electroencephalographic recordings were obtained from C3-A1, C4-A2, F7-T3, F8-T4, F3-F4, and O1-O2. The relative power (RP), interhemispheric, intrahemispheric, and fronto-posterior correlations of six electroencephalographic bands were calculated and compared between two conditions: placebo and melatonin. Results show that at F7-T3, F3-F4, and C3-A1, melatonin induced an increase of the RP of the delta band. Likewise, in F7-T3, melatonin induced a decrease of the RP in the alpha1 band. Similarly, results show a lower interhemispheric correlation between the F7-T3 and F8-T4 derivations in the alpha1 band compared to the placebo condition. We conclude that the short sleep onset related to melatonin intake in AD patients was associated with a lower RP of the alpha1, a higher RP of the delta band (mainly in the left hemisphere) and a decreased interhemispheric EEG coupling in the alpha1 band. The possible role of the GABAergic neurotransmission as well as of the cascade of neurochemical events that melatonin triggers on sleep onset are discussed.
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Affiliation(s)
- Manuel Alejandro Cruz-Aguilar
- Universidad de Guadalajara, Instituto de Neurociencias, CUCBA, Laboratorio de Correlación Electroencefalográfica y Conducta, Guadalajara, Jalisco, México
- Instituto Nacional de Psiquiatría “Ramón de la Fuente Muñiz”, Dirección de Investigaciones en Neurociencias, Laboratorio de Cronobiología y Sueño, CDMX, México
| | - Ignacio Ramírez-Salado
- Instituto Nacional de Psiquiatría “Ramón de la Fuente Muñiz”, Dirección de Investigaciones en Neurociencias, Laboratorio de Cronobiología y Sueño, CDMX, México
| | - Miguel Angel Guevara
- Universidad de Guadalajara, Instituto de Neurociencias, CUCBA, Laboratorio de Correlación Electroencefalográfica y Conducta, Guadalajara, Jalisco, México
| | - Marisela Hernández-González
- Universidad de Guadalajara, Instituto de Neurociencias, CUCBA, Laboratorio de Neurofisiología de la Conducta Reproductiva, Guadalajara, Jalisco, México
| | - Gloria Benitez-King
- Instituto Nacional de Psiquiatría “Ramón de la Fuente Muñiz”, Subdirección de Investigaciones Clínicas, Laboratorio de Neurofarmacología, CDMX, México
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15
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Zhao T, Zhang H, Jin C, Qiu F, Wu Y, Shi L. Melatonin mediates vasodilation through both direct and indirect activation of BK Ca channels. J Mol Endocrinol 2017; 59:219-233. [PMID: 28676563 DOI: 10.1530/jme-17-0028] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/03/2017] [Indexed: 01/14/2023]
Abstract
Melatonin, synthesized primarily by the pineal gland, is a neuroendocrine hormone with high membrane permeability. The vascular effects of melatonin, including vasoconstriction and vasodilation, have been demonstrated in numerous studies. However, the mechanisms underlying these effects are not fully understood. Large-conductance Ca2+-activated K+ (BKCa) channels are expressed broadly on smooth muscle cells and play an important role in vascular tone regulation. This study explored the mechanisms of myocyte BKCa channels and endothelial factors underlying the action of melatonin on the mesenteric arteries (MAs). Vascular contractility and patch-clamp studies were performed on myocytes of MAs from Wistar rats. Melatonin induced significant vasodilation on MAs. In the presence of Nω-nitro-l-arginine methyl ester (l-NAME), a potent endothelial oxide synthase (eNOS) inhibitor, melatonin elicited concentration-dependent relaxation, with lowered pIC50 The effect of melatonin was significantly attenuated in the presence of BKCa channel blocker iberiotoxin or MT1/MT2 receptor antagonist luzindole in both (+) l-NAME and (-) l-NAME groups. In the (+) l-NAME group, iberiotoxin caused a parallel rightward shift of the melatonin concentration-relaxation curve, with pIC50 lower than that of luzindole. Both inside-out and cell-attached patch-clamp recordings showed that melatonin significantly increased the open probability, mean open time and voltage sensitivity of BKCa channels. In a cell-attached patch-clamp configuration, the melatonin-induced enhancement of BKCa channel activity was significantly suppressed by luzindole. These findings indicate that in addition to the activation of eNOS, melatonin-induced vasorelaxation of MAs is partially attributable to its direct (passing through the cell membrane) and indirect (via MT1/MT2 receptors) activation of the BKCa channels on mesenteric arterial myocytes.
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MESH Headings
- Animals
- Gene Expression
- Ion Channel Gating/drug effects
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/agonists
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/genetics
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/metabolism
- Male
- Melatonin/metabolism
- Melatonin/pharmacology
- Muscle, Smooth, Vascular/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Rats
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Vasodilation/drug effects
- Vasodilation/genetics
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Affiliation(s)
- T Zhao
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - H Zhang
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - C Jin
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - F Qiu
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - Y Wu
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - L Shi
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
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16
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Rocha AKADA, de Lima E, Amaral F, Peres R, Cipolla-Neto J, Amado D. Altered MT1 and MT2 melatonin receptors expression in the hippocampus of pilocarpine-induced epileptic rats. Epilepsy Behav 2017; 71:23-34. [PMID: 28460319 DOI: 10.1016/j.yebeh.2017.01.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 01/20/2017] [Accepted: 01/20/2017] [Indexed: 12/11/2022]
Abstract
Clinical and experimental findings show that melatonin may be used as an adjuvant to the treatment of epilepsy-related complications by alleviates sleep disturbances, circadian alterations and attenuates seizures alone or in combination with AEDs. In addition, it has been observed that there is a circadian component on seizures, which cause changes in circadian system and in melatonin production. Nevertheless, the dynamic changes of the melatoninergic system, especially with regard to its membrane receptors (MT1 and MT2) in the natural course of TLE remain largely unknown. The aim of this study was to evaluate the 24-hour profile of MT1 and MT2 mRNA and protein expression in the hippocampus of rats submitted to the pilocarpine-induced epilepsy model analyzing the influence of the circadian rhythm in the expression pattern during the acute, silent, and chronic phases. Melatonin receptor MT1 and MT2 mRNA expression levels were increased in the hippocampus of rats few hours after SE, with MT1 returning to normal levels and MT2 reducing during the silent phase. During the chronic phase, mRNA expression levels of both receptors return to levels close to control, however, presenting a different daily profile, showing that there is a circadian change during the chronic phase. Also, during the acute and silent phase it was possible to verify MT1 label only in CA2 hippocampal region with an increased expression only in the dark period of the acute phase. The MT2 receptor was present in all hippocampal regions, however, it was reduced in the acute phase and it was found in astrocytes. In chronic animals, there is a reduction in the presence of both receptors especially in regions where there is a typical damage derived from epilepsy. Therefore, we conclude that SE induced by pilocarpine is able to change melatonin receptor MT1 and MT2 protein and mRNA expression levels in the hippocampus of rats few hours after SE as well as in silent and chronic phases.
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Affiliation(s)
| | - Eliangela de Lima
- Department of Neurology and Neurosurgery, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil; Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil; Department of Physiology, Universidade Federal de Mato Grosso (UFMT), Cuiabá, Brazil
| | - Fernanda Amaral
- Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil; Departament of Physiology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil
| | - Rafael Peres
- Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil
| | - José Cipolla-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Débora Amado
- Department of Neurology and Neurosurgery, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil
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17
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Yang J, Jin HJ, Mocaër E, Seguin L, Zhao H, Rusak B. Agomelatine affects rat suprachiasmatic nucleus neurons via melatonin and serotonin receptors. Life Sci 2016; 155:147-54. [DOI: 10.1016/j.lfs.2016.04.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 04/17/2016] [Accepted: 04/29/2016] [Indexed: 10/21/2022]
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18
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Abstract
UNLABELLED Melatonin supplementation has been used as a therapeutic agent for several diseases, yet little is known about the underlying mechanisms by which melatonin synchronizes circadian rhythms. G-protein signaling plays a large role in melatonin-induced phase shifts of locomotor behavior and melatonin receptors activate G-protein-coupled inwardly rectifying potassium (GIRK) channels in Xenopus oocytes. The present study tested the hypothesis that melatonin influences circadian phase and electrical activity within the central clock in the suprachiasmatic nucleus (SCN) through GIRK channel activation. Unlike wild-type littermates, GIRK2 knock-out (KO) mice failed to phase advance wheel-running behavior in response to 3 d subcutaneous injections of melatonin in the late day. Moreover, in vitro phase resetting of the SCN circadian clock by melatonin was blocked by coadministration of a GIRK channel antagonist tertiapin-q (TPQ). Loose-patch electrophysiological recordings of SCN neurons revealed a significant reduction in the average action potential rate in response to melatonin. This effect was lost in SCN slices treated with TPQ and SCN slices from GIRK2 KO mice. The melatonin-induced suppression of firing rate corresponded with an increased inward current that was blocked by TPQ. Finally, application of ramelteon, a potent melatonin receptor agonist, significantly decreased firing rate and increased inward current within SCN neurons in a GIRK-dependent manner. These results are the first to show that GIRK channels are necessary for the effects of melatonin and ramelteon within the SCN. This study suggests that GIRK channels may be an alternative therapeutic target for diseases with evidence of circadian disruption, including aberrant melatonin signaling. SIGNIFICANCE STATEMENT Despite the widespread use of melatonin supplementation for the treatment of sleep disruption and other neurological diseases such as epilepsy and depression, no studies have elucidated the molecular mechanisms linking melatonin-induced changes in neuronal activity to its therapeutic effects. Here, we used behavioral and electrophysiological techniques to address this scientific gap. Our results show that melatonin and ramelteon, a potent and clinically relevant melatonin receptor agonist, significantly affect the neurophysiological function of suprachiasmatic nucleus neurons through activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels. Given the importance of GIRK channels for neuronal excitability (with >600 publications on these channels to date), our study should generate broad interest from neuroscientists in fields such as epilepsy, addiction, and cognition.
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19
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Benleulmi-Chaachoua A, Chen L, Sokolina K, Wong V, Jurisica I, Emerit MB, Darmon M, Espin A, Stagljar I, Tafelmeyer P, Zamponi GW, Delagrange P, Maurice P, Jockers R. Protein interactome mining defines melatonin MT1 receptors as integral component of presynaptic protein complexes of neurons. J Pineal Res 2016; 60:95-108. [PMID: 26514267 DOI: 10.1111/jpi.12294] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 10/26/2015] [Indexed: 01/11/2023]
Abstract
In mammals, the hormone melatonin is mainly produced by the pineal gland with nocturnal peak levels. Its peripheral and central actions rely either on its intrinsic antioxidant properties or on binding to melatonin MT1 and MT2 receptors, belonging to the G protein-coupled receptor (GPCR) super-family. Melatonin has been reported to be involved in many functions of the central nervous system such as circadian rhythm regulation, neurotransmission, synaptic plasticity, memory, sleep, and also in Alzheimer's disease and depression. However, little is known about the subcellular localization of melatonin receptors and the molecular aspects involved in neuronal functions of melatonin. Identification of protein complexes associated with GPCRs has been shown to be a valid approach to improve our understanding of their function. By combining proteomic and genomic approaches we built an interactome of MT1 and MT2 receptors, which comprises 378 individual proteins. Among the proteins interacting with MT1 , but not with MT2 , we identified several presynaptic proteins, suggesting a potential role of MT1 in neurotransmission. Presynaptic localization of MT1 receptors in the hypothalamus, striatum, and cortex was confirmed by subcellular fractionation experiments and immunofluorescence microscopy. MT1 physically interacts with the voltage-gated calcium channel Cav 2.2 and inhibits Cav 2.2-promoted Ca(2+) entry in an agonist-independent manner. In conclusion, we show that MT1 is part of the presynaptic protein network and negatively regulates Cav 2.2 activity, providing a first hint for potential synaptic functions of MT1.
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Affiliation(s)
- Abla Benleulmi-Chaachoua
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Lina Chen
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Kate Sokolina
- Donnelly Centre, Department of Biochemistry, Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Victoria Wong
- Donnelly Centre, Department of Biochemistry, Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Igor Jurisica
- Princess Margaret Cancer Centre, University Health Network and TECHNA Institute for the Advancement of Technology for Health, Toronto, ON, Canada
| | - Michel Boris Emerit
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Centre de Psychiatrie et Neurosciences, INSERM U894, Paris, France
| | - Michèle Darmon
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Centre de Psychiatrie et Neurosciences, INSERM U894, Paris, France
| | - Almudena Espin
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Igor Stagljar
- Donnelly Centre, Department of Biochemistry, Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | | | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | | | - Pascal Maurice
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Ralf Jockers
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
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20
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Tosches MA, Bucher D, Vopalensky P, Arendt D. Melatonin signaling controls circadian swimming behavior in marine zooplankton. Cell 2015; 159:46-57. [PMID: 25259919 PMCID: PMC4182423 DOI: 10.1016/j.cell.2014.07.042] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/07/2014] [Accepted: 07/25/2014] [Indexed: 12/29/2022]
Abstract
Melatonin, the "hormone of darkness," is a key regulator of vertebrate circadian physiology and behavior. Despite its ubiquitous presence in Metazoa, the function of melatonin signaling outside vertebrates is poorly understood. Here, we investigate the effect of melatonin signaling on circadian swimming behavior in a zooplankton model, the marine annelid Platynereis dumerilii. We find that melatonin is produced in brain photoreceptors with a vertebrate-type opsin-based phototransduction cascade and a light-entrained clock. Melatonin released at night induces rhythmic burst firing of cholinergic neurons that innervate locomotor-ciliated cells. This establishes a nocturnal behavioral state by modulating the length and the frequency of ciliary arrests. Based on our findings, we propose that melatonin signaling plays a role in the circadian control of ciliary swimming to adjust the vertical position of zooplankton in response to ambient light.
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Affiliation(s)
- Maria Antonietta Tosches
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
| | - Daniel Bucher
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany; Centre for Organismal Studies (COS), University of Heidelberg, 69120 Heidelberg, Germany
| | - Pavel Vopalensky
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Detlev Arendt
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany; Centre for Organismal Studies (COS), University of Heidelberg, 69120 Heidelberg, Germany.
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21
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Hablitz LM, Molzof HE, Paul JR, Johnson RL, Gamble KL. Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein-coupled inwardly rectifying (GIRK) channels. J Physiol 2014; 592:5079-92. [PMID: 25217379 DOI: 10.1113/jphysiol.2014.282079] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
G protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time-of-day information. We sought to determine whether G protein-coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day-time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light-dark (LD) cycle than wild-type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non-photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY-induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non-photic-like phase advance of PER2::LUC rhythms on a Per2(Luc+/-) background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day-time resting membrane potential, providing a mechanism for the fine tuning responses to non-photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated.
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Affiliation(s)
- L M Hablitz
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - H E Molzof
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - J R Paul
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - R L Johnson
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - K L Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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22
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Expression and putative functions of melatonin receptors in malignant cells and tissues. Wien Med Wochenschr 2014; 164:472-8. [PMID: 25023005 DOI: 10.1007/s10354-014-0289-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/10/2014] [Indexed: 01/20/2023]
Abstract
Melatonin, the popular hormone of the darkness, is primarily synthesized in the pineal gland, and acts classically through the G-protein coupled plasma membrane melatonin receptors MT1 and MT2, respectively. Although some of the receptor mediated functions of melatonin, especially those on the (central) circadian system, have been more or less clarified, the functional meaning of MT-receptors in various peripheral organs are still not sufficiently investigated yet. There is, however, accumulating evidence for oncostatic effects of melatonin with both, antioxidative and MT-receptor mediated mechanisms possibly playing a role. This review briefly summarizes the physiology of melatonin and MT-receptors, and discusses the expression and function of MT-receptors in human cancer cells and tissues.
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23
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Domínguez-López S, Howell RD, López-Canúl MG, Leyton M, Gobbi G. Electrophysiological characterization of dopamine neuronal activity in the ventral tegmental area across the light-dark cycle. Synapse 2014; 68:454-67. [PMID: 24955825 DOI: 10.1002/syn.21757] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 06/14/2014] [Accepted: 06/18/2014] [Indexed: 12/11/2022]
Abstract
Direct evidence that dopamine (DA) neurotransmission varies during the 24 h of the day is lacking. Here, we have characterized the firing activity of DA neurons located in the ventral tegmental area (VTA) using single-unit extracellular recordings in anesthetized rats kept on a standard light-dark cycle. DA neuronal firing activity was measured under basal conditions and in response to intravenous administration of increasing doses of amphetamine (AMPH: 0.5, 1, 2, 5 mg/kg), apomorphine (APO: 25, 50, 100, 200 µg/kg) and melatonin (MLT: 0.1, 1, 10 mg/kg) at different time intervals of the light-dark cycle. DA firing activity peaked between 07:00 and 11:00 h (3.5 ± 0.3 Hz) and between 19:00 and 23:00 h (4.1 ± 0.7 Hz), with lowest activity occurring between 11:00 and 15:00 h (2.4 ± 0.2 Hz) and between 23:00 and 03:00 h (2.6 ± 0.2 Hz). The highest number of spontaneously active neurons was observed between 03:00 and 06:00 h (2.5 ± 0.3 neurons/track), whereas the lowest was between 19:00 and 23:00 h (1.5 ± 0.2 neurons/track). The inhibitory effect of AMPH on DA firing rate was similar in both phases. The inhibitory effect of low dose of APO (25 μg/kg, dose selective for D2 autoreceptor) was more potent in the dark phase, whereas APO effects at higher doses were similar in both phases. Finally, MLT administration (1 mg/kg) produced a moderate inhibition of DA cell firing in both phases. These experiments demonstrate the existence of an intradiurnal rhythmic pattern of VTA DA neuronal firing activity and a higher pharmacological response of D2 autoreceptors in the dark phase.
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Affiliation(s)
- Sergio Domínguez-López
- Department of Psychiatry, Neurobiological Psychiatry Unit, McGill University, Montreal, Quebec, H3A 1A1, Canada
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Taylor AC, Horvat-Gordon M, Moore A, Bartell PA. The effects of melatonin on the physical properties of bones and egg shells in the laying hen. PLoS One 2013; 8:e55663. [PMID: 23468846 PMCID: PMC3585294 DOI: 10.1371/journal.pone.0055663] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 12/29/2012] [Indexed: 11/18/2022] Open
Abstract
Laying hens often experience unbalanced calcium utilization which can cause deficiencies in bone and egg mineralization. Because melatonin has been shown to affect bone mineralization in other animals, we examined whether treating hens with melatonin would affect eggshell thickness and improve skeletal performance, thereby reducing skeletal and egg shell defects. Birds were given a diet containing either low (30 µg/kg), medium (300 µg/kg), or high (3 mg/kg) concentrations of melatonin, or control feed through approximately one laying cycle. We examined the weight, length, and strength of egg, femur, tibia, and keel. Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls. Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin. Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin. Our data suggest that melatonin may affect the allocation of calcium to bone at the expense of egg shell mineralization.
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Affiliation(s)
- Alexander C. Taylor
- Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Intercollege Graduate Degree Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Maria Horvat-Gordon
- Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Ashli Moore
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Paul A. Bartell
- Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Intercollege Graduate Degree Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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Canonico B, Luchetti F, Ambrogini P, Arcangeletti M, Betti M, Cesarini E, Lattanzi D, Ciuffoli S, Palma F, Cuppini R, Papa S. Pharmacological doses of melatonin induce alterations in mitochondrial mass and potential, bcl-2 levels and K+currents in UVB-exposed U937 cells. Cell Biol Int 2013; 37:213-26. [DOI: 10.1002/cbin.10030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 12/06/2012] [Indexed: 12/19/2022]
Affiliation(s)
- Barbara Canonico
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Francesca Luchetti
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Patrizia Ambrogini
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Marcella Arcangeletti
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Michele Betti
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Erica Cesarini
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Davide Lattanzi
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Stefano Ciuffoli
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Fulvio Palma
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Riccardo Cuppini
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
| | - Stefano Papa
- DiSTeVA, Department of Earth, Life and Environmental Sciences; University of Urbino ‘Carlo Bo’; Urbino; Italy
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26
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Huang H, Wang Z, Weng SJ, Sun XH, Yang XL. Neuromodulatory role of melatonin in retinal information processing. Prog Retin Eye Res 2013; 32:64-87. [PMID: 22986412 DOI: 10.1016/j.preteyeres.2012.07.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/24/2012] [Accepted: 07/25/2012] [Indexed: 12/15/2022]
Affiliation(s)
- Hai Huang
- Institute of Neurobiology, Institutes of Brain Science, Fudan University, Shanghai, PR China
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27
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Abstract
Neurons in the suprachiasmatic nucleus (SCN) function as part of a central timing circuit that drives daily changes in our behaviour and underlying physiology. A hallmark feature of SCN neuronal populations is that they are mostly electrically silent during the night, start to fire action potentials near dawn and then continue to generate action potentials with a slow and steady pace all day long. Sets of currents are responsible for this daily rhythm, with the strongest evidence for persistent Na(+) currents, L-type Ca(2+) currents, hyperpolarization-activated currents (I(H)), large-conductance Ca(2+) activated K(+) (BK) currents and fast delayed rectifier (FDR) K(+) currents. These rhythms in electrical activity are crucial for the function of the circadian timing system, including the expression of clock genes, and decline with ageing and disease. This article reviews our current understanding of the ionic and molecular mechanisms that drive the rhythmic firing patterns in the SCN.
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Affiliation(s)
- Christopher S Colwell
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, California 90024, USA.
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Yang XF, Miao Y, Ping Y, Wu HJ, Yang XL, Wang Z. Melatonin inhibits tetraethylammonium-sensitive potassium channels of rod ON type bipolar cells via MT2 receptors in rat retina. Neuroscience 2010; 173:19-29. [PMID: 21094224 DOI: 10.1016/j.neuroscience.2010.11.028] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 10/29/2010] [Accepted: 11/13/2010] [Indexed: 11/16/2022]
Abstract
By challenging specific receptors, melatonin synthesized and released by photoreceptors regulates various physiological functions in the vertebrate retina. Here, we studied modulatory effects of melatonin on K+ currents of rod-dominant ON type bipolar cells (Rod-ON-BCs) in rat retinal slices by patch-clamp techniques. Double immunofluorescence experiments conducted in isolated cell and retinal section preparations showed that the melatonin MT₂ receptor was expressed in somata, dendrites and axon terminals of rat Rod-ON-BCs. Electrophysiologically, application of melatonin selectively inhibited the tetraethylammonium (TEA)-sensitive K+ current component, but did not show any effect on the 4-aminopyridine (4-AP)-sensitive component. Consistent with the immunocytochemical result, the melatonin effect was blocked by co-application of 4-phenyl-2-propionamidotetralin (4-P-PDOT), a specific MT₂ receptor antagonist. Neither protein kinase A (PKA) nor protein kinase G (PKG) seemed to be involved because both the PKA inhibitor Rp-cAMP and the PKG inhibitor KT5823 did not block the melatonin-induced suppression of the K+ currents. In contrast, application of the phospholipase C (PLC) inhibitor U73122 or the protein kinase C (PKC) inhibitor bisindolylmaleimide IV (Bis IV) eliminated the melatonin effect, and when the Ca²+ chelator BAPTA-containing pipette was used, melatonin failed to inhibit the K+ currents. These results suggest that suppression of the TEA-sensitive K+ current component via activation of MT₂ receptors expressed on rat Rod-ON-BCs may be mediated by a Ca²+-dependent PLC/inositol 1,4,5-trisphosphate (IP₃/PKC signaling pathway.
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Affiliation(s)
- X-F Yang
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, 138 Yixueyuan Road, Shanghai 200032, PR China
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29
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Scott FF, Belle MDC, Delagrange P, Piggins HD. Electrophysiological effects of melatonin on mouse Per1 and non-Per1 suprachiasmatic nuclei neurones in vitro. J Neuroendocrinol 2010; 22:1148-56. [PMID: 20819119 DOI: 10.1111/j.1365-2826.2010.02063.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The master circadian pacemaker in the suprachiasmatic nuclei (SCN) regulates the nocturnal secretion of the pineal hormone melatonin. Melatonin, in turn, has feedback effects on SCN neuronal activity rhythms via high affinity G protein-coupled receptors (MT(1) and MT(2) ). However, the precise effects of melatonin on the electrical properties of individual SCN neurones are unclear. In the present study, we investigated the acute effects of exogenous melatonin on SCN neurones using whole-cell patch-clamp recordings in brain slices prepared from Per1::d2EGFP-expressing transgenic mice. In current-clamp mode, bath applied melatonin, at near-physiological concentrations (1 nM), hyperpolarised the majority (63.7%) of SCN neurones tested at all times of the projected light/dark cycle. In addition, melatonin depolarised a small proportion of cells (11.0%). No differences were observed for the effects of melatonin between Per1::GFP or non-Per1::GFP SCN neurones. Melatonin-induced effects were blocked by the MT(1)/MT(2) antagonist, luzindole (1 μM) and the proportion of SCN neurones responsive to melatonin was greatly reduced in the presence of either tetrodotoxin (200 or 500 nM) or gabazine (20 μM). In voltage-clamp recordings, 1 nM melatonin increased the frequency of GABA-mediated currents. These findings indicate, for the first time, that exogenous melatonin can alter neuronal excitability in the majority of SCN neurones, regardless of whether or not they overtly express the core clock gene Per1. The results also suggest that melatonin acts mainly by modulating inhibitory GABAergic transmission within the SCN. This may explain why exogenous application of melatonin has heterogenous effects on individual SCN neurones.
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Affiliation(s)
- F F Scott
- Faculty of Life Sciences, University of Manchester, Manchester, UK
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Molecular organization and dynamics of the melatonin MT₁ receptor/RGS20/G(i) protein complex reveal asymmetry of receptor dimers for RGS and G(i) coupling. EMBO J 2010; 29:3646-59. [PMID: 20859254 DOI: 10.1038/emboj.2010.236] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 08/27/2010] [Indexed: 12/27/2022] Open
Abstract
Functional asymmetry of G-protein-coupled receptor (GPCR) dimers has been reported for an increasing number of cases, but the molecular architecture of signalling units associated to these dimers remains unclear. Here, we characterized the molecular complex of the melatonin MT₁ receptor, which directly and constitutively couples to G(i) proteins and the regulator of G-protein signalling (RGS) 20. The molecular organization of the ternary MT₁/G(i)/RGS20 complex was monitored in its basal and activated state by bioluminescence resonance energy transfer between probes inserted at multiple sites of the complex. On the basis of the reported crystal structures of G(i) and the RGS domain, we propose a model wherein one G(i) and one RGS20 protein bind to separate protomers of MT₁ dimers in a pre-associated complex that rearranges upon agonist activation. This model was further validated with MT₁/MT₂ heterodimers. Collectively, our data extend the concept of asymmetry within GPCR dimers, reinforce the notion of receptor specificity for RGS proteins and highlight the advantage of GPCRs organized as dimers in which each protomer fulfils its specific task by binding to different GPCR-interacting proteins.
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31
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Dubocovich ML, Delagrange P, Krause DN, Sugden D, Cardinali DP, Olcese J. International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, classification, and pharmacology of G protein-coupled melatonin receptors. Pharmacol Rev 2010; 62:343-80. [PMID: 20605968 PMCID: PMC2964901 DOI: 10.1124/pr.110.002832] [Citation(s) in RCA: 392] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The hormone melatonin (5-methoxy-N-acetyltryptamine) is synthesized primarily in the pineal gland and retina, and in several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Melatonin receptors receive and translate melatonin's message to influence daily and seasonal rhythms of physiology and behavior. The melatonin message is translated through activation of two G protein-coupled receptors, MT(1) and MT(2), that are potential therapeutic targets in disorders ranging from insomnia and circadian sleep disorders to depression, cardiovascular diseases, and cancer. This review summarizes the steps taken since melatonin's discovery by Aaron Lerner in 1958 to functionally characterize, clone, and localize receptors in mammalian tissues. The pharmacological and molecular properties of the receptors are described as well as current efforts to discover and develop ligands for treatment of a number of illnesses, including sleep disorders, depression, and cancer.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo State University of New York, 3435 Main Street, Buffalo, NY 14214, USA.
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Abstract
The mammalian circadian pacemaker, the suprachiasmatic nucleus (SCN), contains receptors to the adipose tissue hormone leptin. In the present study, the effects of leptin on the electrophysiological activity of the SCN cells were characterised in vitro in rat brain slices. During extracellular recording, application of 20 nm leptin (n = 36) decreased mean spike frequency (Wilcoxon signed rank test, z = -3.390, P < 0.001) and increased the irregularity of firing measured by the entropy of the log interspike interval distribution (Student's paired t-test, t = 2.377, P = 0.023), but had no consistent effect on spike patterning as measured by the mutual information between adjacent log interspike intervals (z = 0.745, P = 0.456). Intracellular current-clamp recordings (n = 25) revealed a hyperpolarising effect of 20 nm leptin on SCN neurones (z = -2.290, P = 0.022). The hyperpolarisation largely resulted from the effect of leptin on the subgroup of cells (n = 13) that generated 'rebound' spikes upon termination of a hyperpolarising current pulse (z = -2.697, P = 0.007). Leptin application also increased the group mean duration of the afterhyperpolarisation (n = 25, t = 2.512, P = 0.023). The effects of leptin on extracellularly recorded spike activity were consistent with the changes in membrane potential and spike shape. They suggest that leptin can directly modulate the electrical properties of SCN neurones and, in this way, contribute to the mechanism by which metabolic processes influence the circadian clock.
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Affiliation(s)
- A N Inyushkin
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK
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33
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Tremere LA, Pinaud R, Irwin RP, Allen CN. Postinhibitory rebound spikes are modulated by the history of membrane hyperpolarization in the SCN. Eur J Neurosci 2008; 28:1127-35. [PMID: 18783377 DOI: 10.1111/j.1460-9568.2008.06410.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus regulates biological circadian time thereby directly impacting numerous physiological processes. The SCN is composed almost exclusively of gamma-aminobutyric acid (GABA)ergic neurons, many of which synapse with other GABAergic cells in the SCN to exert an inhibitory influence on their postsynaptic targets for most, if not all, phases of the circadian cycle. The overwhelmingly GABAergic nature of the SCN, along with its internal connectivity properties, provide a strong model to examine how inhibitory neurotransmission generates output signals. In the present work we show that hyperpolarizations that range from 5 to 1000 ms elicit rebound spikes in 63% of all SCN neurons tested in voltage-clamp in the SCN of adult rats and hamsters. In current-clamp recordings, hyperpolarizations led to rebound spike formation in all cells; however, low-amplitude or short-duration current injections failed to consistently activate rebound spikes. Increasing the duration of hyperpolarization from 5 to 1000 ms is strongly and positively correlated with enhanced spike probability. Additionally, the magnitude of hyperpolarization exerts a strong influence on both the amplitude of the spike, as revealed by voltage-clamp recordings, and the latency to peak current obtained in either voltage- or current-clamp mode. Our results suggest that SCN neurons may use rebound spikes as one means of producing output signals from a largely interconnected network of GABAergic neurons.
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Melatonin receptors, heterodimerization, signal transduction and binding sites: what's new? Br J Pharmacol 2008; 154:1182-95. [PMID: 18493248 DOI: 10.1038/bjp.2008.184] [Citation(s) in RCA: 219] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Melatonin is a neurohormone that has been claimed to be involved in a wide range of physiological functions. Nevertheless, for most of its effects, the mechanism of action is not really known. In mammals, two melatonin receptors, MT1 and MT2, have been cloned. They belong to the G-protein-coupled receptor (GPCR) superfamily. They share some specific short amino-acid sequences, which suggest that they represent a specific subfamily. Another receptor from the same subfamily, the melatonin-related receptor has been cloned in different species including humans. This orphan receptor also named GPR50 does not bind melatonin and its endogenous ligand is still unknown. Nevertheless, this receptor has been shown to behave as an antagonist of the MT1 receptor, which opens new pharmacological perspectives for GPR50 despite the lack of endogenous or synthetic ligands. Moreover, MT1 and MT2 interact together through the formation of heterodimers at least in cells transfected with the cDNA of these two receptors. Lastly, signalling complexes associated with MT1 and MT2 receptors are starting to be deciphered. A third melatonin-binding site has been purified and characterized as the enzyme quinone reductase 2 (QR2). Inhibition of QR2 by melatonin may explain melatonin's protective effect that has been reported in different animal models and that is generally associated with its well-documented antioxidant properties.
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Abstract
Descartes intuitively anticipated the so-called 'binding problem' of consciousness and thought that the pineal gland enables spatio-temporal integration in cognitive processing. Recent findings indicate that a major role in the process of temporal integration and binding involve neurons in suprachiasmatic nuclei, specifically targeting the pineal gland and other structures, and control the neuroendocrine rhythms. Melatonin is an endocrine output signal of the clock and provides circadian information as an endogenous synchronizer which stabilizes and reinforces circadian rhythms. This integrative process occurs at the different levels of the circadian network via gene expression in some brain regions and peripheral structures that enables integration of circadian, hormonal, and metabolic information and creating temporal order of bodily and mental experience. This specific temporal order is reflected in associative sequentiality that is necessary for cognition, behavior and all processes of memory consolidation that must preserve all information in the temporal causal order and synchrony. In this context, recent findings suggest that melatonin could be a potential regulator in the processes that contribute to memory formation, long-term potentiation, and synaptic plasticity in the hippocampus and other brain regions. There is evidence that stress disrupts normal activity and memory consolidation in the hippocampus and prefrontal cortex, and this process leads to memories that are stored without a contextual or spatiotemporal frame. These findings emphasize a specific role of melatonin in mechanisms of consciousness, memory and stress and are also consistent with reported studies that indicate melatonin alterations under stressful conditions and in mental disorders.
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Affiliation(s)
- Petr Bob
- Center for Neuropsychiatric Research of Traumatic Stress & Department of Psychiatry, First Faculty of Medicine, Charles University, Prague, Czech Republic.
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36
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Ping Y, Huang H, Zhang XJ, Yang XL. Melatonin potentiates rod signals to ON type bipolar cells in fish retina. J Physiol 2008; 586:2683-94. [PMID: 18388138 DOI: 10.1113/jphysiol.2008.152959] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Melatonin is involved in regulation of a variety of physiological functions through activation of specific G-protein coupled receptors. However, the neuromodulatory role of melatonin, released from photoreceptors in the retina, is poorly understood. Here we show that melatonin enhances the sensitivity of the rod signal pathway by potentiating signal transfer from rod photoreceptors to ON bipolar cells (Rod-ON-BCs). Whole-cell patch-clamp recordings showed that melatonin induced a sustained inward current from Rod-ON-BCs, through activation of the melatonin MT2 receptor, which was identified as one mediated by a cGMP-dependent cation channel. Consistent with this, melatonin was found, using immunocytochemistry, to increase intracellular cGMP levels, which was identified due to an inhibition of phosphodiesterase. Physiologically, melatonin potentiated responses of Rod-ON-BCs to simulated light flashes (brief puffs of CPPG, an mGluR6 antagonist, in the presence of l-AP4, an mGluR6 agonist), which was mediated by cGMP-dependent kinase, and increased the amplitude of the scotopic electroretinographic b-wave, a reflection of Rod-ON-BC activity. These results suggest that melatonin, being at a higher level at night, may improve the signal/noise ratio for rod signals in the outer retina by enhancing signal transfer from rods to BCs.
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Affiliation(s)
- Yong Ping
- Institute of Neurobiology, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
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37
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Inyushkin AN, Bhumbra GS, Gonzalez JA, Dyball REJ. Melatonin modulates spike coding in the rat suprachiasmatic nucleus. J Neuroendocrinol 2007; 19:671-81. [PMID: 17680882 DOI: 10.1111/j.1365-2826.2007.01574.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The effects of the application of melatonin in vitro on the electrophysiological activity of suprachiasmatic neurones were characterised using novel measures of coding based on the analysis of interspike intervals. Perfusion of 1 nM melatonin in vitro (n = 53) had no consistent effect on mean spike frequency (Wilcoxon's sign rank, z = -0.01, P = 0.989), but increased the irregularity of firing (Student's paired t-test, t = -3.02, P = 0.004), as measured by the log interval entropy, and spike patterning (z = -3.43, P < 0.001), as measured by the mutual information between adjacent log intervals. Intracellular recordings in vitro in current clamp mode showed that 1 nM melatonin significantly hyperpolarised (n = 11, z = -2.35, P = 0.019) those cells that showed 'rebound' spikes upon termination of a hyperpolarising current pulse. Grouping all cells together (n = 27), melatonin application decreased the duration of the afterhyperpolarisation (z = -2.49, P = 0.013) and increased the amplitude of the depolarising afterpotential (z = -2.71, P = 0.007). The effects of melatonin seen in vitro from extracellular recordings on interspike interval coding were consistent with the changes in spike shape seen from intracellular recordings. A melatonin-induced increase in the size of the depolarising afterpotential of suprachiasmatic cells might underlie the increased irregularity of spike firing seen during the subjective night time. The method of analysis demonstrated a difference in spike firing that is not revealed by frequency alone and is consistent with the presence of a melatonin-induced depolarising current.
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Affiliation(s)
- A N Inyushkin
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge, UK
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Abstract
The hypnotic, antinociceptive, and anticonvulsant properties of melatonin endow this neurohormone with the profile of a novel hypnotic-anesthetic agent. Sublingually or orally administered melatonin is an effective premedicant in adults and children. Melatonin premedication like midazolam is associated with sedation and preoperative anxiolysis, however, unlike midazolam these effects are not associated with impaired psychomotor skills or the quality of recovery. Melatonin administration also is associated with a tendency toward faster recovery and a lower incidence of postoperative excitement than midazolam. Oral premedication with 0.2 mg/kg melatonin significantly reduces the propofol and thiopental doses required for loss of responses to verbal commands and eyelash stimulation. In rats, melatonin and the more potent melatonin analogs 2-bromomelatonin and phenylmelatonin have been found to have anesthetic properties similar to those of thiopental and propofol, with the added advantage of providing potent antinociceptive effects. The exact mechanism(s) by which structurally diverse intravenous and volatile anesthetics produce general anesthesia is still largely unknown, but positive modulation of gamma-aminobutyric acid type A (GABAA) receptor function has been recognized as an important and common pathway underlying the depressant effects of many of these agents. Accumulating evidence indicates that there is interplay between the melatonergic and GABAergic systems, and it has been demonstrated that melatonin administration produces significant, dose-dependent increases in GABA concentrations in the central nervous system. Additional in vitro data suggest that melatonin alters GABAergic transmission by modulating GABAA receptor function. Of greater importance, data from in vivo studies suggest that the central anesthetic effects of melatonin are mediated, at least in part, via GABAergic system activation, as they can be blocked or reversed by GABAA receptor antagonists. Further work is needed to better understand the general anesthetic properties of melatonin at the molecular, cellular, and systems levels.
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Affiliation(s)
- Mohamed Naguib
- Department of Anesthesiology and Pain Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
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39
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Abstract
In addition to its antioxidative effects melatonin acts through specific nuclear and plasma membrane receptors. To date, two G-protein coupled melatonin membrane receptors, MT(1) and MT(2), have been cloned in mammals, while the newly purified MT(3) protein belongs to the family of quinone reductases. Screening studies have shown that various tissues of rodents express MT(1) and/or MT(2) melatonin receptors. In humans, melatonin receptors were also detected in several organs, including brain and retina, cardiovascular system, liver and gallbladder, intestine, kidney, immune cells, adipocytes, prostate and breast epithelial cells, ovary/granulosa cells, myometrium, and skin. This review summarizes the data published so far about MT(1) and MT(2) receptors in human tissues and human cells. Established and putative functions of melatonin after receptor activation as well as the clinical relevance of these findings will be discussed.
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MESH Headings
- Adipocytes/metabolism
- Animals
- Biliary Tract/metabolism
- Breast/metabolism
- Cardiovascular System/metabolism
- Central Nervous System/metabolism
- Female
- Gastrointestinal Tract/metabolism
- Genitalia, Female/metabolism
- Humans
- Immune System/metabolism
- Male
- Melatonin/metabolism
- Polymorphism, Genetic
- Prostate/metabolism
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Signal Transduction
- Skin/cytology
- Skin/metabolism
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Affiliation(s)
- C Ekmekcioglu
- Department of Physiology, Center for Physiology and Pathophysiology, Medical University Vienna, Schwarzpanierstrasse 17, A-1090 Vienna, Austria.
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40
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Wang LM, Suthana NA, Chaudhury D, Weaver DR, Colwell CS. Melatonin inhibits hippocampal long-term potentiation. Eur J Neurosci 2006; 22:2231-7. [PMID: 16262661 PMCID: PMC2581482 DOI: 10.1111/j.1460-9568.2005.04408.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The goal of this study is to investigate the effect of the hormone melatonin on long-term potentiation and excitability measured by stimulating the Schaffer collaterals and recording the field excitatory postsynaptic potential from the CA1 dendritic layer in hippocampal brain slices from mice. Application of melatonin produced a concentration-dependent inhibition of the induction of long-term potentiation, with a concentration of 100 nm producing an approximately 50% inhibition of long-term potentiation magnitude. Long-duration melatonin treatments of 6 h were also effective at reducing the magnitude of long-term potentiation. Melatonin (100 nm) did not alter baseline evoked responses or paired-pulse facilitation recorded at this synapse. The inhibitory actions of melatonin were prevented by application of the melatonin (MT) receptor antagonist luzindole as well as the MT2 receptor subtype antagonist 4-phenyl-2-propionamidotetraline. These inhibitory actions of melatonin were lost in mice deficient in MT2 receptors but not those deficient in MT1 receptors. In addition, application of the protein kinase A inhibitor H-89 both mimicked the effects of melatonin and precluded further inhibition by melatonin. Finally, the application an activator of adenylyl cyclase, forskolin, overcame the inhibitory effects of melatonin on LTP without affecting the induction of long-term potentiation on its own. These results suggest that hippocampal synaptic plasticity may be constrained by melatonin through a mechanism involving MT2-receptor-mediated regulation of the adenylyl cyclase-protein kinase A pathway.
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Affiliation(s)
- Louisa M Wang
- Department of Psychiatry and Biobehavioural Sciences, University of California--Los Angeles, 760 Westwood Plaza, Los Angeles, California 90024-1759, USA
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41
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Teshima K, Minoguchi M, Tounai S, Ashimori A, Eguchi J, Allen CN, Shibata S. Nonphotic entrainment of the circadian body temperature rhythm by the selective ORL1 receptor agonist W-212393 in rats. Br J Pharmacol 2005; 146:33-40. [PMID: 15980870 PMCID: PMC1576254 DOI: 10.1038/sj.bjp.0706311] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
We synthesized a small-molecule opioid receptor-like 1 (ORL1) receptor agonist, 2-{3-[1-((1R)-acenaphthen-1-yl)piperidin-4-yl]-2,3-dihydro-2-oxo-benzimidazol-1-yl}-N-methylacetamide (W-212393), and investigated its effect on the circadian body temperature rhythm of rats. W-212393 has high affinity for ORL1 receptors in the rat cerebral cortex and human ORL1 receptors expressed in HEK293 cells with K(i) values of 0.76 and 0.50 nM, respectively. W-212393 concentration-dependently stimulated GTPgamma(35)S binding and its efficacy was similar to nociceptin/orphanin FQ (N/OFQ), suggesting that W-212393 is a full agonist at ORL1 receptors. W-212393 dose-dependently occupied ORL1 receptors following intraventricular or intraperitoneal administration, suggesting that W-212393 is a brain-penetrating compound. W-212393 (100 nM) and N/OFQ (100 nM) significantly suppressed the activity of spontaneously firing rat suprachiasmatic nucleus neurons. These suppressive effects were blocked by an ORL1 receptor antagonist, J-113397 (1 microM). W-212393 (3 mg kg(-1), i.p.) induced a significant phase advance at circadian time 6 (CT6) and CT9, but not at other CTs. The magnitude of the W-212393 (0.3-3 mg kg(-1), i.p.)-induced phase advance was dose-dependent and greater than those produced by 8-hydroxy-2-(di-n-propylamino)tetralin (0.3-3 mg kg(-1), i.p.) or melatonin (0.3-3 mg kg(-1), i.p.). The W-212393 (3 mg kg(-1), i.p.)-induced phase advance was antagonized by J-113397 (10 mg kg(-1), i.p.).W-212393 (3 mg kg(-1), i.p.) significantly accelerated the re-entrainment of the body temperature rhythm to a 6 h advanced light-dark cycle. These results indicate that activation of ORL1 receptors contributes to the circadian entrainment and W-212393 may represent an interesting agent for the study of circadian rhythms.
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Affiliation(s)
- Koji Teshima
- Research Laboratory I (CNS), Pharmaceutical Research Unit, R&D Division, Mitsubishi Pharma Corporation, Koyata, Iruma, Saitama, Japan.
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42
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Abstract
Melatonin, dubbed the hormone of darkness, is known to regulate a wide variety of physiological processes in mammals. This review describes well-defined functional responses mediated through activation of high-affinity MT1 and MT2 G protein-coupled receptors viewed as potential targets for drug discovery. MT1 melatonin receptors modulate neuronal firing, arterial vasocon-striction, cell proliferation in cancer cells, and reproductive and metabolic functions. Activation of MT2 melatonin receptors phase shift circadian rhythms of neuronal firing in the suprachiasmatic nucleus, inhibit dopamine release in retina, induce vasodilation and inhibition of leukocyte rolling in arterial beds, and enhance immune responses. The melatonin-mediated responses elicited by activation of MT1 and MT2 native melatonin receptors are dependent on circadian time, duration and mode of exposure to endogenous or exogenous melatonin, and functional receptor sensitivity. Together, these studies underscore the importance of carefully linking each melatonin receptor type to specific functional responses in target tissues to facilitate the design and development of novel therapeutic agent.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Molecular Pharmacology & Biological Chemistry, Northwestern University Feinberg School of Medicine Center for Drug Discovery and Chemical Biology, Chicago, IL 60611, USA.
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43
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Abstract
Circadian clock systems are composed of an input or "entrainment" pathway by which synchronization to the external environment occurs, a pacemaker responsible for generating rhythmicity, and an output or "expression" pathway through which rhythmic signals act to modulate physiology and behavior. The circadian pacemaker contains molecular feedback loops of rhythmically expressed genes and their protein products, which, through interactions, generate a circa 24-h cycle of transcription and translation of clock and clock-controlled genes. Neuronal membrane events appear to play major roles in entrainment of circadian rhythms in mollusks and mammals. In mammals, the suprachiasmatic nuclei of the hypothalamus receive photic information via the retinohypothalamic tract. Retinal signals, mediated by glutamate, induce calcium release and activate a number of intracellular cascades involved in photic gating and phase shifting. Membrane events are also involved in rhythm expression. Calcium and potassium currents influence the electrical output of pacemaker neurons by altering shape and intervals of impulse prepotentials, afterhyperpolarization periods, and interspike intervals, as well as altering membrane potentials and thereby shaping the spontaneous rhythmic spiking patterns. Unlike the involvement of membrane events in circadian entrainment and expression, it is less clear whether electrical activity, postsynaptic events, and transmembrane ion fluxes also are essential elements in rhythm generation. Studies, however, suggest that neuronal membrane activity may indeed play a crucial role in circadian rhythm generation.
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Affiliation(s)
- Gabriella B Lundkvist
- Department of Biology, Center for Biological Timing, University of Virginia, Charlottesville, Virginia 22903, USA
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44
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Musshoff U, Speckmann EJ. Diurnal actions of melatonin on epileptic activity in hippocampal slices of rats. Life Sci 2003; 73:2603-10. [PMID: 12967684 DOI: 10.1016/s0024-3205(03)00614-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Since melatonin receptors have been found in the hippocampus of mammals it has been suggested that melatonin can modulate neuronal functions of hippocampal cells. The effect of melatonin (10 nM/l and 1 microM/l) on frequency and amplitude of epileptiform field potentials (EFP) elicited by low Mg(2+) or by bicuculline was tested in the CA1 region of hippocampal slices of rats. In the low Mg(2+) model, melatonin, applied in a near physiological concentration of 10 nM/l, exerts no effect on EFP in slices prepared at night or during the day. In a concentration of 1 microM/l, however, melatonin enhances the frequency of EFP to approximately 140% in slices prepared during the day. This effect was suppressed through simultaneous administration of the melatonin receptor antagonist luzindole (10 microM/l). In contrast, melatonin did not affect epileptic activity in slices prepared at night. Epileptiform discharges elicited by blocking the GABAergic inhibition (bicuculline model) were not affected by melatonin, either during the day or at night. The results indicate that melatonin affects epileptic activity in a diurnal manner and that the action of melatonin is different in relation to the epilepsy model.
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Affiliation(s)
- Ulrich Musshoff
- Institute of Physiology, University of Muenster, Robert-Koch-Str. 27a, 48149 Muenster, Germany.
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Witt-Enderby PA, Bennett J, Jarzynka MJ, Firestine S, Melan MA. Melatonin receptors and their regulation: biochemical and structural mechanisms. Life Sci 2003; 72:2183-98. [PMID: 12628439 DOI: 10.1016/s0024-3205(03)00098-5] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is growing evidence demonstrating the complexity of melatonin's role in modulating a diverse number of physiological processes. This complexity could be attributed to the fact that melatonin receptors belong to two distinct classes of proteins, that is, the G-protein coupled receptor superfamily (MT(1), MT(2)) and the quinone reductase enzyme family (MT(3)) which makes them unique at the molecular level. Also, within the G-protein coupled receptor family of proteins, the MT(1) and MT(2) receptors can couple to multiple and distinct signal transduction cascades whose activation can lead to unique cellular responses. Also, throughout the 24-hour cycle, the receptors' sensitivity to specific cues fluctuates and this sensitivity can be modulated in a homologous fashion, that is, by melatonin itself, and in a heterologous manner, that is, by other cues including the photoperiod or estrogen. This sensitivity of response may reflect changes in melatonin receptor density that also occurs throughout the 24-hour light/dark cycle but out of phase with circulating melatonin levels. The mechanisms that underlie the changes in melatonin receptor density and function are still not well-understood, but data is beginning to show that transcriptional events and G-protein uncoupling may be involved. Even though this area of research is still in its infancy, great strides are being made everyday in elucidating the mechanisms that underlie melatonin receptor function and regulation. The focus of this review is to highlight some of these discoveries in an attempt to reveal the uniqueness of the melatonin receptor family while at the same time provide thought-provoking ideas to further advance this area of research. Thus, a brief overview of each of the mammalian melatonin receptor subtypes and the signal transduction cascades to which they couple will be discussed with a greater emphasis placed on the mechanisms underlying their regulation and the domains within the receptors essential for proper signaling.
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Affiliation(s)
- Paula A Witt-Enderby
- Division of Pharmaceutical Sciences, Duquesne University School of Pharmacy, 421 Mellon Hall, Pittsburgh, PA 15282, USA.
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46
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Abstract
Cluster I neurons of the suprachiasmatic nucleus (SCN), which are thought to be pacemakers supporting circadian activity, fire spontaneous action potentials that are followed by a monophasic afterhyperpolarization (AHP). Using a brain slice preparation, we have found that the AHP has a shorter duration in cells firing at higher frequency, consistent with circadian modulation of the AHP. The AHP is supported by at least three subtypes of K(Ca) channels, including apamin-sensitive channels, iberiotoxin-sensitive channels, and channels that are insensitive to both of these antagonists. The latter K(Ca) channel subtype is involved in rate-dependent regulation of the AHP. Voltage-clamped, whole-cell Ca(2+) channel currents recorded from SCN neurons were dissected pharmacologically, revealing all of the major high-voltage activated subtypes: L-, N-, P/Q-, and R-type Ca(2+) channel currents. Application of Ca(2+) channel antagonists to spontaneously firing neurons indicated that predominantly L- and R-type currents trigger the AHP. Our findings suggest that apamin- and iberiotoxin-insensitive K(Ca) channels are subject to diurnal modulation by the circadian clock and that this modulation either directly or indirectly leads to the expression of a circadian rhythm in spiking frequency.
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Abstract
The neurons of the mammalian suprachiasmatic nuclei (SCN) control circadian rhythms in molecular, physiological, endocrine, and behavioral functions. In the SCN, circadian rhythms are generated at the level of individual neurons. The last decade has provided a wealth of information on the genetic basis for circadian rhythm generation. In comparison, a modest but growing number of studies have investigated how the molecular rhythm is translated into neuronal function. Neuronal attributes have been measured at the cellular and tissue level with a variety of electrophysiological techniques. We have summarized electrophysiological research on neurons that constitute the SCN in an attempt to provide a comprehensive view on the current state of the art.
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Affiliation(s)
- Jeroen Schaap
- Department of Neurophysiology, Leiden University Medical School, RC Leiden, The Netherlands
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49
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Musshoff U, Riewenherm D, Berger E, Fauteck JD, Speckmann EJ. Melatonin receptors in rat hippocampus: molecular and functional investigations. Hippocampus 2002; 12:165-73. [PMID: 12000116 DOI: 10.1002/hipo.1105] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Since binding sites for melatonin have been found in the hippocampus of several mammals, it has been suggested that the pineal hormone melatonin is able to modulate neuronal functions of hippocampal cells. In order to get more insight into the role of melatonin for the functions of hippocampal cells, the following experiments were performed: male rats, maintained under a 12/12-h light-dark cycle, were sacrificed by decapitation at zeitgeber times (h) ZT2, ZT8, and ZT15 (ZT0 = lights on); for experiment 1, gene expression for melatonin receptors was detected in the hippocampus and in hippocampal subfields by means of the RT-PCR technique; for experiment 2, electrophysiological and pharmacological properties of melatonin receptors heterologously expressed in Xenopus oocytes after injection of mRNA from the hippocampus were analyzed by means of voltage clamp technique; and for experiment 3, effects of melatonin on the spontaneous firing rate of action potentials in the CA1 regions of hippocampal slices were analyzed by means of extracellular recordings. The RT-PCR data revealed that transcripts for both the MT1 and MT2 melatonin receptors are present in the dentate gyrus, CA3, and CA1 regions, and the subiculum of the hippocampus. Injection of mRNA from rat hippocampus into the Xenopus oocytes led to the functional reconstitution of melatonin-sensitive receptors, which activates calcium-dependent chloride inward currents. The melatonin responses were abolished by simultaneous administration of the antagonists 2-phenylmelatonin and luzindole, and were unaffected by the MT2 antagonist 4-phenyl-2-propionamidotetralin. Bath-applied melatonin (1 micromol/l) enhances the firing rate of neurons in the CA1 region. The effect was small in experiments performed at ZT8 (<2 times the initial level) and large in experiments performed at ZT15 (>6 times). The changes of neuronal firing rate induced by melatonin were completely suppressed with simultaneous administration of the melatonin receptor antagonist luzindole (10 micromol/l). The results indicate that melatonin may play an important role in modulating neuronal excitability in the hippocampus.
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50
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El-Sherif Y, Hogan MV, Tesoriero J, Wieraszko A. Factors regulating the influence of melatonin on hippocampal evoked potentials: comparative studies on different strains of mice. Brain Res 2002; 945:191-201. [PMID: 12126881 DOI: 10.1016/s0006-8993(02)02752-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Factors regulating the influence of melatonin on the hippocampal glutamergic system in mouse hippocampal slices were evaluated. The sensitivity of hippocampal pyramidal neurons to melatonin (Sigma) was highest at 2 h following slice preparation and then declined with time. This pattern of sensitivity to melatonin correlated well with a reduced binding of melatonin to its receptors. The slices obtained from older animals remained sensitive to melatonin through the entire incubation period. Most of the experiments evaluating the influence of melatonin on hippocampal evoked potentials were performed within 2 h following slice preparation. The effect of melatonin was biphasic: an initial depression of the potential was followed by a recovery/amplification phase. The recovery phase was not a result of melatonin decomposition. The effect of melatonin was similar in three different strains of mice tested: CD-1, C57J/B6, and Swiss Webster. While the melatonin from another vendor (Regis) gave similar results, it was effective at much lower concentrations. In slices obtained from CD-1 light-deprived mice, the sensitivity to melatonin was significantly reduced. Thus, it appears that melatonin may control the hippocampal glutamergic system in a complex manner, which may be regulated by the circadian rhythm. This may influence memory formation in the hippocampus.
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Affiliation(s)
- Yasir El-Sherif
- Department of Biology/CSI/IBR Center for Developmental Neuroscience, College of Staten Island/CUNY, 2800 Victory Boulevard, Staten Island, NY 10314, USA
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