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Caputo R, Poirel VJ, Challet E, Meijer JH, Raison S. Bimodal serotonin synthesis in the diurnal rodent, Arvicanthis ansorgei. FASEB J 2022; 36:e22255. [PMID: 35294080 DOI: 10.1096/fj.202101726r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 02/05/2022] [Accepted: 03/04/2022] [Indexed: 11/11/2022]
Abstract
In mammals, behavioral activity is regulated both by the circadian system, orchestrated by the suprachiasmatic nucleus (SCN), and by arousal structures, including the serotonergic system. While the SCN is active at the same astronomical time in diurnal and nocturnal species, little data are available concerning the serotonergic (5HT) system in diurnal mammals. In this study, we investigated the functioning of the 5HT system, which is involved both in regulating the sleep/wake cycle and in synchronizing the SCN, in a diurnal rodent, Arvicanthis ansorgei. Using in situ hybridization, we characterized the anatomical extension of the raphe nuclei and we investigated 24 h mRNA levels of the serotonin rate-limiting enzyme, tryptophan hydroxylase 2 (tph2). Under both 12 h:12 h light/dark (LD) and constant darkness (DD) conditions, tph2 mRNA expression varies significantly over 24 h, displaying a bimodal profile with higher values around the (projected) light transitions. Furthermore, we considered several SCN outputs, namely melatonin, corticosterone, and locomotor activity. In both LD and DD, melatonin profiles display peak levels during the biological night. Corticosterone plasma levels show a bimodal rhythmic profile in both conditions, with higher levels preceding the two peaks of Arvicanthis locomotor activity, occurring at dawn and dusk. These data demonstrate that serotonin synthesis in Arvicanthis is rhythmic and reflects its bimodal behavioral phenotype, but differs from what has been previously described in nocturnal species.
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Affiliation(s)
- Rosanna Caputo
- Institute of Cellular and Integrative Neurosciences, CNRS and University of Strasbourg, Strasbourg, France.,Department of Molecular Cell Biology, Division of Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Vincent-Joseph Poirel
- Institute of Cellular and Integrative Neurosciences, CNRS and University of Strasbourg, Strasbourg, France
| | - Etienne Challet
- Institute of Cellular and Integrative Neurosciences, CNRS and University of Strasbourg, Strasbourg, France
| | - Johanna H Meijer
- Department of Molecular Cell Biology, Division of Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Sylvie Raison
- Institute of Cellular and Integrative Neurosciences, CNRS and University of Strasbourg, Strasbourg, France
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2
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Zhang J, Qiu J, Zhou Y, Wang Y, Li H, Zhang T, Jiang Y, Gou K, Cui S. LIM homeobox transcription factor Isl1 is required for melatonin synthesis in the pig pineal gland. J Pineal Res 2018; 65:e12481. [PMID: 29480946 DOI: 10.1111/jpi.12481] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/13/2018] [Indexed: 01/10/2023]
Abstract
Melatonin is a key hormone that regulates circadian rhythms, metabolism, and reproduction. However, the mechanisms of melatonin synthesis and secretion have not been fully defined. The purpose of this study was to investigate the functions of the LIM homeobox transcription factor Isl1 in regulating melatonin synthesis and secretion in porcine pineal gland. We found that Isl1 is highly expressed in the melatonin-producing cells in the porcine pineal gland. Further functional studies demonstrate that Isl1 knockdown in cultured primary porcine pinealocytes results in the decline of melatonin and arylalkylamine N-acetyltransferase (AANAT) mRNA levels by 29.2% and 72.2%, respectively, whereas Isl1 overexpression raised by 1.3-fold and 2.7-fold. In addition, the enhancing effect of norepinephrine (NE) on melatonin synthesis was abolished by Isl1 knockdown. The in vivo intracerebroventricular NE injections upregulate Isl1 mRNA and protein levels by about threefold and 4.5-fold in the porcine pineal gland. We then examined the changes in Isl1 expression in the pineal gland and global melatonin levels throughout the day. The results show that Isl1 protein level at 24:00 is 2.5-fold higher than that at 12:00, which is parallel to melatonin levels. We further found that Isl1 increases the activity of AANAT promoter, and the effect of NE on Isl1 expression was blocked by an ERK inhibitor. Collectively, the results presented here demonstrate that Isl1 positively modulates melatonin synthesis by targeting AANAT, via the ERK signaling pathway of NE. These suggest that Isl1 plays important roles in maintaining the daily circadian rhythm.
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Affiliation(s)
- Jinglin Zhang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Jingtao Qiu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Yewen Zhou
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yue Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Hongjiao Li
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Taojie Zhang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Ying Jiang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Kemian Gou
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Sheng Cui
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
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Abstract
A major factor contributing to the evolution of mammals was their ability to be active during the night, a niche previously underused by terrestrial vertebrates. Diurnality subsequently reemerged multiple times in a variety of independent lineages. This paper reviews some recent data on circadian mechanisms in diurnal mammals and considers general themes that appear to be emerging from this work. Careful examination of behavioral studies suggests that although subtle differences may exist, the fundamental functions of the circadian system are the same, as seems to be the case with respect to the molecular mechanisms of the clock. This suggests that responses to signals originating in the clock must be different, either within the SCN or at its targets or downstream from them. Some features of the SCN vary from species to species, but none of these has been clearly associated with diurnality. The region immediately dorsal to the SCN, which receives substantial input from it, exhibits dramatically different rhythms in nocturnal lab rats and diurnal grass rats. This raises the possibility that it functions as a relay that transforms the signal emitted by the SCN and transmits different patterns to downstream targets in nocturnal and diurnal animals. Other direct targets of the SCN include neurons containing orexin and those containing gonadotropin-releasing hormone, and both of these populations of cells exhibit patterns of rhythmicity that are inverted in at least one diurnal compared to one nocturnal species. The patterns that emerge from the data on diurnality are discussed in terms of the implications they have for the evolution and neural substrates of a day-active way of life.
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Affiliation(s)
- Laura Smale
- Department of Psychology, Michigan State University, East Lansing Michigan, MI 48824, USA.
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Lambert CM, Machida KK, Smale L, Nunez AA, Weaver DR. Analysis of the Prokineticin 2 System in a Diurnal Rodent, the Unstriped Nile Grass Rat (Arvicanthis niloticus). J Biol Rhythms 2016; 20:206-18. [PMID: 15851527 DOI: 10.1177/0748730405275135] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Prokineticin 2 (PK2) is a putative output molecule from the SCN. PK2 RNA levels are rhythmic in the mouse SCN, with high levels during the day, and PK2 administration suppresses nocturnal locomotor activity in rats. The authors examined the PK2 system in a diurnal rodent, Arvicanthis niloticus, to determine whether PK2 or PK2 receptors differ between diurnal and nocturnal species. The major transcript variant of A. niloticus PK2 ( AnPK2) encodes a 26-residue signal peptide followed by the presumed mature peptide of 81 residues. Within the grass rat signal sequence, polymorphic sequences and amino acid substitutions were observed relative to mouse and laboratory rats, but the hydrophobic core and cleavage site of the signal sequence were preserved. The mature PK2 peptide is identical among A. niloticus, rat, and mouse. AnPK2 mRNA is rhythmically expressed in the SCN, with peak RNAlevels occurring in the morning, preceding peaks of Per1 and Per2 as in mouse SCN. Analysis of prokineticin receptor 2 (PKR2) sequences revealed polymorphisms among the grass rats studied. PKR2 mRNAwas expressed in the SCN and paraventricular nuclei of the thalamus and hypothalamus. While further analysis is necessary, there is no clear evidence indicating that a difference in the PK2 ligand/receptor system accounts for diurnality in this rodent species. These data contribute to a growing body of evidence suggesting that the key to diurnality lies downstream of the SCN in A. niloticus.
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Affiliation(s)
- Christopher M Lambert
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605-2324, USA
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Hubbard J, Ruppert E, Calvel L, Robin-Choteau L, Gropp CM, Allemann C, Reibel S, Sage-Ciocca D, Bourgin P. Arvicanthis ansorgei, a Novel Model for the Study of Sleep and Waking in Diurnal Rodents. Sleep 2015; 38:979-88. [PMID: 25409107 DOI: 10.5665/sleep.4754] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 07/18/2014] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES Sleep neurobiology studies use nocturnal species, mainly rats and mice. However, because their daily sleep/wake organization is inverted as compared to humans, a diurnal model for sleep studies is needed. To fill this gap, we phenotyped sleep and waking in Arvicanthis ansorgei, a diurnal rodent widely used for the study of circadian rhythms. DESIGN Video-electroencephalogram (EEG), electromyogram (EMG), and electrooculogram (EOG) recordings. SETTING Rodent sleep laboratory. PARTICIPANTS Fourteen male Arvicanthis ansorgei, aged 3 mo. INTERVENTIONS 12 h light (L):12 h dark (D) baseline condition, 24-h constant darkness, 6-h sleep deprivation. MEASUREMENTS AND RESULTS Wake and rapid eye movement (REM) sleep showed similar electrophysiological characteristics as nocturnal rodents. On average, animals spent 12.9 h ± 0.4 awake per 24-h cycle, of which 6.88 h ± 0.3 was during the light period. NREM sleep accounted for 9.63 h ± 0.4, which of 5.13 h ± 0.2 during dark period, and REM sleep for 89.9 min ± 6.7, which of 52.8 min ± 4.4 during dark period. The time-course of sleep and waking across the 12 h light:12 h dark was overall inverted to that observed in rats or mice, though with larger amounts of crepuscular activity at light and dark transitions. A dominant crepuscular regulation of sleep and waking persisted under constant darkness, showing the lack of a strong circadian drive in the absence of clock reinforcement by external cues, such as a running wheel. Conservation of the homeostatic regulation was confirmed with the observation of higher delta power following sustained waking periods and a 6-h sleep deprivation, with subsequent decrease during recovery sleep. CONCLUSIONS Arvicanthis ansorgei is a valid diurnal rodent model for studying the regulatory mechanisms of sleep and so represents a valuable tool for further understanding the nocturnality/diurnality switch.
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Affiliation(s)
- Jeffrey Hubbard
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.,Sleep Disorders Center, Centre Hospitalier Universitaire (CHU) and Fédération de Médecine Translationnelle de Strasbourg (FMTS), University of Strasbourg, France
| | - Elisabeth Ruppert
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.,Sleep Disorders Center, Centre Hospitalier Universitaire (CHU) and Fédération de Médecine Translationnelle de Strasbourg (FMTS), University of Strasbourg, France
| | - Laurent Calvel
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.,Sleep Disorders Center, Centre Hospitalier Universitaire (CHU) and Fédération de Médecine Translationnelle de Strasbourg (FMTS), University of Strasbourg, France
| | - Ludivine Robin-Choteau
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.,Sleep Disorders Center, Centre Hospitalier Universitaire (CHU) and Fédération de Médecine Translationnelle de Strasbourg (FMTS), University of Strasbourg, France
| | - Claire-Marie Gropp
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.,Sleep Disorders Center, Centre Hospitalier Universitaire (CHU) and Fédération de Médecine Translationnelle de Strasbourg (FMTS), University of Strasbourg, France
| | - Caroline Allemann
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France
| | - Sophie Reibel
- Chronobiotron Centre National de la Recherche Scientifique (CNRS)-UMS 3415, Strasbourg, France
| | - Dominique Sage-Ciocca
- Chronobiotron Centre National de la Recherche Scientifique (CNRS)-UMS 3415, Strasbourg, France
| | - Patrice Bourgin
- Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.,Sleep Disorders Center, Centre Hospitalier Universitaire (CHU) and Fédération de Médecine Translationnelle de Strasbourg (FMTS), University of Strasbourg, France
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Adrenergic activation of melatonin secretion in ovine pineal explants in short-term superfusion culture occurs via protein synthesis independent and dependent phenomena. BIOMED RESEARCH INTERNATIONAL 2014; 2014:715708. [PMID: 25133175 PMCID: PMC4123513 DOI: 10.1155/2014/715708] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 06/23/2014] [Accepted: 06/24/2014] [Indexed: 01/13/2023]
Abstract
The ovine pineal is generally considered as an interesting model for the study on adrenergic regulation of melatonin secretion due to some functional similarities with this gland in the human. The present investigations, performed in the superfusion culture of pineal explants, demonstrated that the norepinephrine-induced elevation of melatonin secretion in ovine pinealocytes comprised of two subsequent periods: a rapid increase phase and a slow increase phase. The first one included the quick rise in release of N-acetylserotonin and melatonin, occurring parallel to elevation of NE concentration in the medium surrounding explants. This rapid increase phase was not affected by inhibition of translation. The second, slow increase phase began after NE level had reached the maximum concentration in the culture medium and lasted about two hours. It was completely abolished by the treatment with translation inhibitors. The obtained results showed for the first time that the regulation of N-acetylserotonin synthesis in pinealocytes of some species like the sheep involves the on/off mechanism, which is completely independent of protein synthesis and works very fast. They provided strong evidence pointing to the need of revision of the current opinion that arylalkylamines N-acetyltransferase activity in pinealocytes is controlled exclusively by changes in enzyme abundance.
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7
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Ware JV, Nelson OL, Robbins CT, Carter PA, Sarver BAJ, Jansen HT. Endocrine rhythms in the brown bear (Ursus arctos): Evidence supporting selection for decreased pineal gland size. Physiol Rep 2013; 1:e00048. [PMID: 24303132 PMCID: PMC3835004 DOI: 10.1002/phy2.48] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 07/09/2013] [Accepted: 07/10/2013] [Indexed: 12/21/2022] Open
Abstract
Many temperate zone animals adapt to seasonal changes by altering their physiology. This is mediated in large part by endocrine signals that encode day length and regulate energy balance and metabolism. The objectives of this study were to determine if the daily patterns of two important hormones, melatonin and cortisol, varied with day length in captive brown bears (Ursus arctos) under anesthetized and nonanesthetized conditions during the active (March-October) and hibernation periods. Melatonin concentrations varied with time of day and season in nonanesthetized female bears despite exceedingly low nocturnal concentrations (1-4 pg/mL) in the active season. In contrast, melatonin concentrations during hibernation were 7.5-fold greater than those during the summer in anesthetized male bears. Functional assessment of the pineal gland revealed a slight but significant reduction in melatonin following nocturnal light application during hibernation, but no response to beta-adrenergic stimulation was detected in either season. Examination of pineal size in two bear species bears combined with a phylogenetically corrected analysis of pineal glands in 47 other species revealed a strong relationship to brain size. However, pineal gland size of both bear species deviated significantly from the expected pattern. Robust daily plasma cortisol rhythms were observed during the active season but not during hibernation. Cortisol was potently suppressed following injection with a synthetic glucocorticoid. The results suggest that melatonin and cortisol both retain their ability to reflect seasonal changes in day length in brown bears. The exceptionally small pineal gland in bears may be the result of direct or indirect selection.
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Affiliation(s)
- Jasmine V Ware
- Departments of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University Pullman, Washington, 99164
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8
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Smarr BL, Schwartz MD, Wotus C, de la Iglesia HO. Re-examining "temporal niche". Integr Comp Biol 2013; 53:165-74. [PMID: 23674555 DOI: 10.1093/icb/ict055] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The circadian system temporally organizes physiology and behavior throughout the 24-h day. At the core of this organization lies a network of multiple circadian oscillators located within the central nervous system as well as in virtually every peripheral organ. These oscillators define a 24-h temporal landscape of mutually interacting circadian rhythms that is known as the temporal niche of a species. This temporal niche is constituted by the collective phases of all biological rhythms emerging from this multi-oscillatory system. We review evidence showing that under different environmental conditions, this system can adopt different harmonic configurations. Thus, the classic chronobiological approach of searching for "the" circadian phase of an animal-typically by studying circadian rhythms of locomotor activity-represents a narrow look into the circadian system of an animal. We propose that the study of hormonal rhythms may lead to a more insightful assessment of a species' temporal niche.
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Affiliation(s)
- Benjamin L Smarr
- Department of Biology and Program of Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA
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9
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Schwimmer H, Mursu N, Haim A. Effects of light and melatonin treatment on body temperature and melatonin secretion daily rhythms in a diurnal rodent, the fat sand rat. Chronobiol Int 2010; 27:1401-19. [PMID: 20795883 DOI: 10.3109/07420528.2010.505355] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Many mammals display predictable daily rhythmicity in both neuroendocrine function and behavior. The basic rest-activity cycles are usually consistent for a given species and vary from night-active (nocturnal), those mostly active at dawn and dusk (i.e., crepuscular), and to day-active (diurnal) species. A number of daily rhythms are oppositely phased with respect to the light/dark (LD) cycle in diurnal compared with nocturnal mammals, whereas others are equally phased with respect to the LD cycle, regardless of diurnality/nocturnality. Pineal produced melatonin (MLT) perfectly matches this phase-locked feature in that its production and secretion always occurs during the night in both diurnal and nocturnal mammals. As most rodents studied to date in the field of chronobiology are nocturnal, the aim in this study was to evaluate the effect of light manipulations and different photoperiods on a diurnal rodent, the fat sand rat, Psammomys obesus. The authors studied its daily rhythms of body temperature (T(b)) and 6-sulphatoxymelatonin (6-SMT) under various photoperiodic regimes and light manipulations (acute and chronic exposures) while maintaining a constant ambient temperature of 30 degrees C +/- 1 degrees C. The following protocols were used: (A) Control (CON) conditions 12L:12D; (A1) exposure to one light interference (LI) of CON-acclimated individuals for 30 min, 5 h after lights-off; (A2) short photoperiod (SP) acclimation (8L:16D) for 3 wks; (A3) 3 wks of SP acclimation with chronic LI of 15 min, three times a night at 4-h intervals; (A4) chronic exposure to constant dim blue light (470 nm, 30 lux) for 24 h for 3 wks (LL). (B) The response to exogenous MLT administration, provided in drinking water, was measured under the following protocols: (B1) After chronic exposure to SP with LI, MLT was provided once, starting 1 h before the end of photophase; (B2) after a continuous exposure to dim blue light, MLT was provided at 15:00 h for 2 h for 2 wks; (B3) to CON animals, MLT was given intraperitoneally (i.p.) at 14:00 h. The results demonstrate that under CON acclimation, Psammomys obesus has robust T(b) and 6-SMT daily rhythms in which the acrophase (peak time) of T(b) is during the photophase, whereas that of 6-SMT is during scotophase. LI resulted in an elevation of T(b) and a reduction of 6-SMT levels. A significant difference in the response was noted between acute and chronic exposure to LI, particularly in 6-SMT levels, which were lower than CON after LI and higher after chronic LI, implying an acclimation process. Constant exposure to blue light abolished T(b) and 6-SMT rhythms in all the animals. MLT administration resumed the T(b) daily rhythm in these animals, and had a recovery effect on the chronic LI-exposed animals, resulting in a T(b) decrease. Altogether, the authors show in this study the different modifications of T(b) rhythms and MLT levels in response to environmental light manipulations. These series of experiments may serve as a basis for establishing P. obesus as an animal model for further studies in chronobiology.
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Affiliation(s)
- Hagit Schwimmer
- Department of Biology, University of Haifa, Mt. Carmel, Haifa, Israel 31905.
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10
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Møller M, Lund-Andersen C, Rovsing L, Sparre T, Bache N, Roepstorff P, Vorum H. Proteomics of the photoneuroendocrine circadian system of the brain. MASS SPECTROMETRY REVIEWS 2010; 29:313-325. [PMID: 19437489 DOI: 10.1002/mas.20237] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The photoneuroendocrine circadian system of the brain consists of (a) specialized photoreceptors in the retina, (b) a circadian generator located in the forebrain that contains "clock genes," (c) specialized nuclei in the forebrain involved in neuroendocrine secretion, and (d) the pineal gland. The circadian generator is a nucleus, called the suprachiasmatic nucleus (SCN). The neurons of this nucleus contain "clock genes," the transcription of which exhibits a circadian rhythm. Most circadian rhythms are generated by the neurons of this nucleus and, via neuronal and humoral connections, the SCN controls circadian activity of the brain and peripheral tissues. The endogenous oscillator of the SCN is each day entrained to the length of the daily photoperiod by light that reach the retina, and specialized photoreceptors transmit impulses to the SCN via the optic nerves. Mass screening for day/night variations in gene expression in the circadian system as well as in the whole brain and peripheral tissues have, during the last decade, been performed. However, studies of circadian changes in the proteome have been less investigated. In this survey, the anatomy and function of the circadian-generating system in mammals is described, and recent proteomic studies that investigate day/night changes in the retina, SCN, and pineal gland are reviewed. Further circadian changes controlled by the SCN in gene and protein expression in the liver are discussed.
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Affiliation(s)
- Morten Møller
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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11
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Abstract
Melatonin synthesis in rodents is tightly regulated at the transcriptional level by stimulatory and inhibitory transcription factors. Among them, phosphorylated cAMP-related element binding protein (pCREB) and inducible cAMP early repressor (ICER), a strong inhibitor of cAMP-related element-driven genes, have an antagonistic action in activating/inhibiting the transcription of the Aa-nat gene, which is an important enzyme in melatonin synthesis. In the Syrian hamster, a rodent displaying a seasonal control of reproduction, melatonin synthesis is strongly gated to the second part of the night. Indeed, exogenous adrenergic stimulation is unable to stimulate Aa-nat gene transcription and melatonin synthesis during daytime. In the present study, we investigated whether ICER may be the cause of this daytime repression by comparing the dynamic of ICER and the adrenergic regulation of two genes whose expression is rapidly activated by cAMP-dependant mechanisms, c-fos and Icer. Adrenergic induction of c-fos and Icer expression was not possible during daytime, except at early day. ICER immunoreactivity was elevated throughout the daily cycle but reached the highest levels at early day, when gene expression can be induced by adrenergic agonists. Additionally, CREB phosphorylation was subjected to the same daily gating with an adrenergic induction occurring in the early but not in the late day. Taken together, our results indicate that the diurnal gating of pineal activity in the Syrian hamster is not caused by the repressor ICER and that it may occur at the level of noradrenergic receptor signalling.
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Affiliation(s)
- A Salingre
- Institut des Neurosciences Cellulaires et Intégratives, Département de Neurobiologie des Rythmes, UMR CNRS, Université de Strasbourg, France
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12
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Lee SJ, Liu T, Chattoraj A, Zhang SL, Wang L, Lee TM, Wang MM, Borjigin J. Posttranscriptional regulation of pineal melatonin synthesis in Octodon degus. J Pineal Res 2009; 47:75-81. [PMID: 19538336 PMCID: PMC2837936 DOI: 10.1111/j.1600-079x.2009.00690.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Small laboratory animals have provided significant information about melatonin regulation, yet most of these organisms are nocturnal and regulate melatonin synthesis by mechanisms that diverge from those of humans. For example, in all rodents examined, melatonin secretion occurs with a time lag of several hours after the onset of darkness; in addition, arylalkylamine N-acetyltransferase (AANAT), the key enzyme in melatonin synthesis, displays dynamic transcriptional activation specifically at night in all rodents studied to date. In ungulates and primates including humans, on the other hand, melatonin secretion occurs immediately during the early night and is controlled by circadian posttranscriptional regulation of AANAT. We hypothesize that the diurnal Octodon degus (an Hystricognath rodent) could serve as an improved experimental model for studies of human melatonin regulation. To test this, we monitored melatonin production in degus using pineal microdialysis and characterized the regulation of melatonin synthesis by analyzing degu Aanat. Degu pineal melatonin rises with little latency at night, as in ungulates and primates. In addition, degu Aanat mRNA expression displays no detectable diurnal variation, suggesting that, like ungulates and primates, melatonin in this species is regulated by a posttranscriptional mechanism. Compared with AANAT from all rodents examined to date, the predicted amino acid sequence of degu AANAT is phylogenetically more closely related to ungulate and primate AANAT. These data suggest that Octodon degus may provide an ideal model system for laboratory investigation of mechanisms of melatonin synthesis and secretion in diurnal mammals.
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Affiliation(s)
- Soo Jung Lee
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Tiecheng Liu
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Asamanja Chattoraj
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Samantha L. Zhang
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Department of Neuroscience Program, University of Michigan, Ann Arbor, MI, USA
| | - Lijun Wang
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Theresa M. Lee
- Department of Neuroscience Program, University of Michigan, Ann Arbor, MI, USA
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
| | - Michael M. Wang
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Department of Neuroscience Program, University of Michigan, Ann Arbor, MI, USA
| | - Jimo Borjigin
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Department of Neuroscience Program, University of Michigan, Ann Arbor, MI, USA
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Simonneaux V, Sinitskaya N, Salingre A, Garidou ML, Pévet P. Rat And Syrian Hamster: Two Models for The Regulation ofAANATGene Expression. Chronobiol Int 2009; 23:351-9. [PMID: 16687308 DOI: 10.1080/07420520500521962] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The Syrian hamster is a rodent species in which the photoperiodic change in the melatonin peak duration is pivotal for the synchronization of annual functions, like reproduction. In this species, the activity of arylalkylamine N-acetyltransferase (AANAT), the key enzyme for the rhythmic synthesis of melatonin, is precisely controlled and time-gated, suggesting regulatory mechanisms different from those in the rat or mouse. At the beginning of the night, norepinephrine (NE) elicits a rapid and sustained phosphorylation of CREB into pCREB and a transient synthesis of the immediate early gene products c-FOS and c-JUN that peak 3 h after dark onset. c-FOS synthesis requires both pCREB and the pERK1/2 pathways. Interestingly, injection of the protein synthesis inhibitor cycloheximide before, but not after, the c-FOS/c-JUN peak markedly reduces Aanat mRNA levels. This finding suggests that the c-FOS/c-JUN dimer is required for transcriptional activation of the Aanat gene. During daylight, exogenous noradrenergic stimulation cannot stimulate Aanat expression and, therefore, melatonin synthesis. The inhibitory transcription factor ICER is present in the pineal gland but with highest values when AANAT may be activated, suggesting the blockade takes place upstream of Aanat expression. Preliminary experiments indicate that the diurnal inhibition of AANAT occurs at the level of the adrenergic receptor signalling pathway, but it is not known whether this is sufficient to explain the pineal resistance to NE during the daytime. Together, these findings demonstrate that AANAT regulation in the Syrian hamster requires a complex intracellular signalling cascade, different from that described in laboratory rodents like mice and rats.
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Affiliation(s)
- Valérie Simonneaux
- Institut des Neurosciences Cellulaires et Intégratives, Département de Neurobiologie des Rythmes, CNRS-Université Louis Pasteur, IFR des Neurosciences de Strasbourg, Strasbourg, France.
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14
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El Allali K, Sinitskaya N, Bothorel B, Achaaban R, Pévet P, Simonneaux V. Daily Aa-nat gene expression in the camel (Camelus dromedarius) pineal gland. Chronobiol Int 2009; 25:800-7. [PMID: 18780205 DOI: 10.1080/07420520802384085] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Arylalkylamine N-acetyltransferase (AA-NAT) is the rhythm-generating enzyme for the synthesis of pineal melatonin. Molecular investigations have revealed two biological models for the activation of AA-NAT. In rodent species, Aa-nat gene transcription is turned off during the daytime and markedly activated at night. In primates, sheep, and cows, the Aa-nat gene is constitutively transcripted with no visible daily variations. This inter-species difference in Aa-nat gene regulation leads to different daily profiles in melatonin synthesis and release. Thus, the nighttime onset of the rise in circulating melatonin is delayed and slow in rodents, whereas it is fast and sharp in sheep. In the camel (Camelus dromedarius), we have observed that circulating melatonin rises immediately after sunset, suggesting AA-NAT activity is regulated at the post-transcriptional level. In agreement with this hypothesis, we report herein the amount of Aa-nat mRNA in the camel pineal gland is high, during both the day and night with no daily variations, while melatonin concentration in the same pineal tissue is five times higher during the night than daytime.
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Affiliation(s)
- Khalid El Allali
- Unite d'Anatomie Comparee, Institut Agronomique et Veterinaire Hassan II, Rabat, Morocco
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15
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Abstract
Daily rhythmicity, including timing of wakefulness and hormone secretion, is mainly controlled by a master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN clockwork involves various clock genes, with specific temporal patterns of expression that are similar in nocturnal and diurnal species (e.g. the clock gene Per1 in the SCN peaks at midday in both categories). Timing of sensitivity to light is roughly similar, during nighttime, in diurnal and nocturnal species. Molecular mechanisms of photic resetting are also comparable in both species categories. By contrast, in animals housed in constant light, exposure to darkness can reset the SCN clock, mostly during the resting period, i.e. at opposite circadian times between diurnal and nocturnal species. Nonphotic stimuli, such as scheduled voluntary exercise, food shortage, exogenous melatonin, or serotonergic receptor activation, are also capable of shifting the master clock and/or modulating photic synchronization. Comparison between day- and night-active species allows classifications of nonphotic cues in two, arousal-independent and arousal-dependent, families of factors. Arousal-independent factors, such as melatonin (always secreted during nighttime, independently of daily activity pattern) or gamma-aminobutyric acid (GABA), have shifting effects at the same circadian times in both nocturnal and diurnal rodents. By contrast, arousal-dependent factors, such as serotonin (its cerebral levels follow activity pattern), induce phase shifts only during resting and have opposite modulating effects on photic resetting between diurnal and nocturnal species. Contrary to light and arousal-independent nonphotic cues, arousal-dependent nonphotic stimuli provide synchronizing feedback signals to the SCN clock in circadian antiphase between nocturnal and diurnal animals.
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Affiliation(s)
- Etienne Challet
- Department of Neurobiology of Rhythms, Institute of Cellular and Integrative Neurosciences, Centre National de la Recherche Scientifique (UMR 7168/LC2), University Louis Pasteur, 5 rue Blaise Pascal, Strasbourg, France.
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16
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Ramanathan C, Nunez AA, Martinez GS, Schwartz MD, Smale L. Temporal and spatial distribution of immunoreactive PER1 and PER2 proteins in the suprachiasmatic nucleus and peri-suprachiasmatic region of the diurnal grass rat (Arvicanthis niloticus). Brain Res 2006; 1073-1074:348-58. [PMID: 16430875 DOI: 10.1016/j.brainres.2005.11.082] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Revised: 11/15/2005] [Accepted: 11/16/2005] [Indexed: 11/20/2022]
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus contains the primary circadian pacemaker in both diurnal and nocturnal mammals. The lower subparaventricular zone (LSPV) immediately dorsal to the SCN may also play an important role in the regulation of circadian rhythms. The SCN contains a multitude of oscillator cells that generate circadian rhythms through transcriptional/translational feedback loops involving a set of clock genes including per1 and per2. Little is known about the temporal and spatial features of the proteins encoded by these genes in day-active mammals. The first objective of this study was to characterize the expression of PER1 and PER2 in the SCN of a diurnal rodent, the unstriped Nile grass rat (Arvicanthis niloticus). The second objective was to evaluate the hypothesis that a molecular clock could exist in the LSPV, where endogenous rhythms in Fos expression are seen in grass rats but not in laboratory rats. Animals were kept on a 12:12 light/dark cycle and perfused at 4-h intervals, and their brains were processed for immunohistochemical detection of PER1 and PER2. Both proteins were seen in the SCN where they peaked early in the dark phase, providing further evidence that the differences between diurnal and nocturnal patterns of behavior emerge from mechanisms lying downstream from the pacemaker within the SCN. Rhythmic expression of PER1 and PER2 was also seen in the LSPV providing support for the hypothesis that this region might participate in circadian time keeping in the diurnal grass rat. In addition, rhythms were seen lateral to the LSPV and the SCN. Results of this study are discussed in light of similarities and differences in the circadian time-keeping systems of day- and night-active animals.
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Affiliation(s)
- Chidambaram Ramanathan
- Neuroscience Program, 108 Giltner Hall, Michigan State University, East Lansing, MI 48824, USA
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17
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Neuman A, Gothilf Y, Haim A, Ben-Aharon G, Zisapel N. Nocturnal patterns and up-regulated excretion of the melatonin metabolite 6-sulfatoxymelatonin in the diurnal rodent Psammomys obesus post-weaning under a short photoperiod. Comp Biochem Physiol A Mol Integr Physiol 2005; 142:297-307. [PMID: 16172010 DOI: 10.1016/j.cbpa.2005.07.005] [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] [Received: 04/28/2005] [Revised: 07/18/2005] [Accepted: 07/19/2005] [Indexed: 10/25/2022]
Abstract
The ontogeny of daily rhythms in body temperature (T(b)) oxygen intake (VO(2)) and urinary excretion of the major melatonin metabolite, 6-sulfatoxymelatonin (6SMT) was studied in the day-active rodent, Psammomys obesus. Generally, T(b) and VO2 were high during the light phase in this diurnal species. However, after weaning, and only under the short photoperiod, P. obesus individuals display elevated T(b) and VO2 levels during the dark phase, as in nocturnally active species. In parallel, 6SMT and nocturnal activity of pineal arylalkylamine N-acetyltransferase (AANAT) were greatly enhanced. The cDNA encoding P. obesus pineal AANAT was cloned and found to share 90.2% homology with rat and 83.8% with human AANAT, and based on homology modeling, to structurally resemble the ovine enzyme. A robust diurnal rhythm in P. obesus pineal AANAT-mRNA was found, with maximal levels at night. AANAT-mRNA levels were not enhanced in the post-weaning phase, suggesting post-transcriptional up-regulation of pineal AANAT activity. The photoperiod-dependent post-weaning change into nocturnal behavior and up-regulation melatonin production (as evidenced from the increase in both 6SMT and AANAT activity) represent a hitherto unobserved pattern of transition of a diurnal mammal into independent life. Possibly, this pattern may be physiologically important to facilitate T(b) maintenance in the cold nights of winter in the desert.
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Affiliation(s)
- Alina Neuman
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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18
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Abstract
Circadian melatonin production in the pineal gland and retina is under the control of serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase. Because NAT activity varies diurnally, it has been considered both the melatonin rhythm-generating enzyme and the rate-limiting enzyme of melatonin synthesis. In rats with dramatically reduced NAT activity due to a H28Y mutation in NAT, melatonin levels remained the same as in wildtype controls, suggesting that NAT does not determine the rate of melatonin production at night. Using a combination of molecular approaches with a sensitive in vivo measurement of pineal diurnal melatonin production, we demonstrate that (i) N-acetylserotonin (NAS), the enzymatic product of NAT, is present in vast excess in the night pineals compared with melatonin; (ii) the continuous increase in NAT protein levels at late night does not produce a proportional increase in melatonin; and (iii) an increase in NAS in the same animal over several circadian cycles do not result in corresponding increase in melatonin output. These results strongly suggest that NAT is not the rate-limiting enzyme of melatonin formation at night.
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Affiliation(s)
- Tiecheng Liu
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109-0622, USA
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19
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Garidou-Boof ML, Sicard B, Bothorel B, Pitrosky B, Ribelayga C, Simonneaux V, Pévet P, Vivien-Roels B. Environmental control and adrenergic regulation of pineal activity in the diurnal tropical rodent, Arvicanthis ansorgei. J Pineal Res 2005; 38:189-97. [PMID: 15725341 DOI: 10.1111/j.1600-079x.2004.00192.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Like nocturnal rodents, the diurnal tropical rodent Arvicanthis ansorgei shows a daily rhythm in pineal melatonin content. Seasonal and photoperiodic variations in the biosynthetic activity of the pineal gland: arylalkylamine-N-acetyltransferase (AA-NAT), hydroxyindole-O-methyltransferase (HIOMT) activities and melatonin content were measured in male and female A. ansorgei captured near Samaya, Mali, and kept either under artificial laboratory photoperiods [light-dark (LD) cycles: LD 14:10, LD 12:12 or LD 10:14 or caught in the field in Mali and killed at four different times of the year (January, April, June and November). Under artificial photoperiod, the duration of the nocturnal peak of AA-NAT activity and melatonin content increased with the duration of the dark period while the amplitude did not significantly change. In the field, annual variations in the amplitude of the nocturnal melatonin peak were observed with a maximum in April (highest temperature, low humidity and no grass availability, only seeds) and a minimum in November (high humidity, maximum green grass availability). The variations in the amplitude of the melatonin peak were not correlated with changes in AA-NAT HIOMT activities, suggesting that seasonal variations in the amplitude of the melatonin peak are not driven by these enzymes. Daytime injections of the beta-adrenergic agonist, isoproterenol, stimulated melatonin synthesis in January, April and June, but not in November. The annual differences in the amplitude of the melatonin peak as well as the seasonal differences in the response to an adrenergic stimulation suggest that environmental factors other than photoperiod, such as temperature, humidity and consequent food availability, could be important in the regulation of the annual variations in the pineal biosynthetic activity in this species.
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Affiliation(s)
- Marie-Laure Garidou-Boof
- Laboratoire de Neurobiologie des Rythmes, UMR 7518 CNRS-Université Louis Pasteur, Strasbourg, France
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20
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Perreau-Lenz S, Kalsbeek A, Van Der Vliet J, Pévet P, Buijs RM. In vivo evidence for a controlled offset of melatonin synthesis at dawn by the suprachiasmatic nucleus in the rat. Neuroscience 2005; 130:797-803. [PMID: 15590161 DOI: 10.1016/j.neuroscience.2004.10.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2004] [Indexed: 11/23/2022]
Abstract
The daily rhythm of melatonin synthesis in the rat pineal gland is controlled by the central biological clock, located in the suprachiasmatic nucleus (SCN), via a multi-synaptic pathway involving, successively, neurones of the paraventricular nucleus of the hypothalamus (PVN), sympathetic preganglionic neurones of the intermediolateral cell column of the spinal cord, and norepinephrine containing sympathetic neurones of the superior cervical ganglion. Recently, we showed that, in the rat, the SCN uses a combination of daytime inhibitory and nighttime stimulatory signals toward the PVN-pineal pathway in order to control the daily rhythm of melatonin synthesis, GABA being responsible for the daytime inhibitory message and glutamate for the nighttime stimulation. The present study was initiated to further check this concept, and to investigate the involvement of the inhibitory SCN output in the early morning circadian decline of melatonin release, with the hypothesis that, at dawn, the increased release of GABA onto pre-autonomic PVN neurones results in a diminished norepinephrine stimulation of the pineal, and ultimately an arrest of melatonin release. First, we established that prolonged norepinephrine stimulation of the pineal gland was indeed sufficient to prevent the early morning decline of melatonin release. Blockade of GABA-ergic signaling in the PVN at dawn could not prevent the early morning decline of melatonin completely. Therefore, these results show that an increased GABAergic inhibition of the PVN neurones that control the sympathetic innervation of the pineal gland, at dawn, is not sufficient to explain the early morning decline of melatonin release.
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Affiliation(s)
- S Perreau-Lenz
- Netherlands Institute for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, The Netherlands.
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21
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Simonneaux V, Poirel VJ, Garidou ML, Nguyen D, Diaz-Rodriguez E, Pévet P. Daily rhythm and regulation of clock gene expression in the rat pineal gland. ACTA ACUST UNITED AC 2004; 120:164-72. [PMID: 14741406 DOI: 10.1016/j.molbrainres.2003.10.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Rhythms in pineal melatonin synthesis are controlled by the biological clock located in the suprachiasmatic nuclei. The endogenous clock oscillations rely upon genetic mechanisms involving clock genes coding for transcription factors working in negative and positive feedback loops. Most of these clock genes are expressed rhythmically in other tissues. Because of the peculiar role of the pineal gland in the photoneuroendocrine axis regulating biological rhythms, we studied whether clock genes are expressed in the rat pineal gland and how their expression is regulated.Per1, Per3, Cry2 and Cry1 clock genes are expressed in the pineal gland and their transcription is increased during the night. Analysis of the regulation of these pineal clock genes indicates that they may be categorized into two groups. Expression of Per1 and Cry2 genes shows the following features: (1) the 24 h rhythm persists, although damped, in constant darkness; (2) the nocturnal increase is abolished following light exposure or injection with a beta-adrenergic antagonist; and (3) the expression during daytime is stimulated by an injection with a beta-adrenergic agonist. In contrast, Per3 and Cry1 day and night mRNA levels are not responsive to adrenergic ligands (as previously reported for Per2) and daily expression of Per3 and Cry1 appears strongly damped or abolished in constant darkness. These data show that the expression of Per1 and Cry2 in the rat pineal gland is regulated by the clock-driven changes in norepinephrine, in a similar manner to the melatonin rhythm-generating enzyme arylalkylamine N-acetyltransferase. The expression of Per3 and Cry1 displays a daily rhythm not regulated by norepinephrine, suggesting the involvement of another day/night regulated transmitter(s).
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Affiliation(s)
- V Simonneaux
- Neurobiologie des Rythmes, UMR-CNRS 7518, Lab Zoology, Université Louis Pasteur, 12 rue de l'Université, 67000, Strasbourg, France.
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22
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Simonneaux V, Ribelayga C. Generation of the melatonin endocrine message in mammals: a review of the complex regulation of melatonin synthesis by norepinephrine, peptides, and other pineal transmitters. Pharmacol Rev 2003; 55:325-95. [PMID: 12773631 DOI: 10.1124/pr.55.2.2] [Citation(s) in RCA: 443] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Melatonin, the major hormone produced by the pineal gland, displays characteristic daily and seasonal patterns of secretion. These robust and predictable rhythms in circulating melatonin are strong synchronizers for the expression of numerous physiological processes in photoperiodic species. In mammals, the nighttime production of melatonin is mainly driven by the circadian clock, situated in the suprachiasmatic nucleus of the hypothalamus, which controls the release of norepinephrine from the dense pineal sympathetic afferents. The pivotal role of norepinephrine in the nocturnal stimulation of melatonin synthesis has been extensively dissected at the cellular and molecular levels. Besides the noradrenergic input, the presence of numerous other transmitters originating from various sources has been reported in the pineal gland. Many of these are neuropeptides and appear to contribute to the regulation of melatonin synthesis by modulating the effects of norepinephrine on pineal biochemistry. The aim of this review is firstly to update our knowledge of the cellular and molecular events underlying the noradrenergic control of melatonin synthesis; and secondly to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis. This information reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism. This also clarifies the role of these various inputs in the seasonal variation of melatonin synthesis and their subsequent physiological function.
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Affiliation(s)
- Valerie Simonneaux
- Laboratoire de Neurobiologie Rythmes, UMR 7518 CNRS/ULP, 12, rue de l'Université, 67000 Strasbourg, France.
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Diaz E, Garidou ML, Dardente H, Salingre A, Pévet P, Simonneaux V. Expression and regulation of Icer mRNA in the Syrian hamster pineal gland. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 112:163-9. [PMID: 12670714 DOI: 10.1016/s0169-328x(03)00087-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Inducible-cAMP early repressor (ICER) is a potent inhibitor of CRE (cAMP-related element)-driven gene transcription. In the rat pineal gland, it has been proposed to be part of the mechanisms involved in the shutting down of the transcription of the gene coding for arylalkylamine N-acetyltransferase (AA-NAT, the melatonin rhythm-generating enzyme). In this study, we report that ICER is expressed in the pineal gland of the photoperiodic rodent Syrian hamster although with some difference compared to the rat. In the Syrian hamster pineal, Icer mRNA levels, low at daytime, displayed a 20-fold increase during the night. Nighttime administration of a beta-adrenergic antagonist, propranolol, significantly reduced Icer mRNA levels although daytime administration of a beta-adrenergic agonist, isoproterenol, was unable to raise the low amount of Icer mRNA. These observations indicate that Icer mRNA expression is induced by the clock-driven norepinephrine release and further suggest that this stimulation is restricted to nighttime, as already observed for Aa-nat gene transcription. Furthermore, we found that the daily profile of Icer mRNA displayed photoperiodic variation with a lengthening of the nocturnal peak in short versus long photoperiod. These data indicate that ICER may be involved in both daily and seasonal regulation of melatonin synthesis in the Syrian hamster.
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Affiliation(s)
- Elena Diaz
- Departamento de Biologi;a Funcional, Area Fisiologi;a, Facultad de Medicina, Universidad de Oviedo, 33006, Oviedo, Spain
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Garidou ML, Vivien-Roels B, Pevet P, Miguez J, Simonneaux V. Mechanisms regulating the marked seasonal variation in melatonin synthesis in the European hamster pineal gland. Am J Physiol Regul Integr Comp Physiol 2003; 284:R1043-52. [PMID: 12626365 DOI: 10.1152/ajpregu.00457.2002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Like many wild species, the European hamster (Cricetus cricetus) adapts to the marked seasonal changes in its environment, namely by hibernation and inhibition of sexual activity in winter. These annual functions are driven by the variation in the environmental factors (light, temperature) that are transmitted to the body through large variations in the duration and amplitude of the nocturnal melatonin rhythm. Here we report that the seasonal variation in melatonin synthesis is mainly driven by arylalkylamine N-acetyltransferase gene transcription and enzyme activation. This, however, does not exclude participation of hydroxyindole-O-methyltransferase, which may relay environmental temperature information. The in vivo experiments show that norepinephrine stimulates melatonin synthesis, this effect being gated at night. The possibility that the variation in pineal metabolism depends on a seasonal change in the suprachiasmatic nuclei clock circadian activity that is transmitted by norepinephrine is discussed.
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Affiliation(s)
- Marie-Laure Garidou
- Neurobiologie des Rythmes, Unité Mixte de Recherche-Centre National de la Recherche Scientifique 7518, Université Louis Pasteur, 67000 Strasbourg, France
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