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Morioka E, Miyamoto T, Tamogami S, Koketsu T, Kim J, Yoshikawa T, Mochizuki T, Ikeda M. Action potential firing rhythms in the suprachiasmatic nucleus of the diurnal grass rat, Arvicanthis niloticus. Neurosci Lett 2023; 792:136954. [PMID: 36347340 DOI: 10.1016/j.neulet.2022.136954] [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: 06/13/2022] [Revised: 10/22/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022]
Abstract
In mammals, daily physiological activities are regulated by a central circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Recently, an increasing number of studies have used diurnal grass rats to analyze neuronal mechanisms regulating diurnal behavior. However, spontaneous action potential firing rhythms in SCN neurons have not been demonstrated clearly in diurnal grass rats. Therefore, the present study examined extracellular single-unit recordings from SCN neurons in acute hypothalamic slices of Arvicanthis niloticus (Nile grass rats). The results of this study found that circadian firing rhythms with the highest frequency occurred at dusk (6.4 Hz at zeitgeber time (ZT)10-12), while the secondary peak occurred at dawn (5.6 Hz at ZT0-2), and the lowest frequency took place in the middle of the night (3.6 Hz at ZT14-16). Locomotor activity recordings from a separate group of animals demonstrated that the Nile grass rats of the laboratory colony used in this study displayed diurnal behaviors that coincided with large crepuscular peaks under 12:12 h light-dark cycles and bimodal rhythms under constant dim red light. Thus, a positive correlation between SCN firing frequencies and locomotor activity levels was observed in the Nile grass rats. Previously, behavioral coupling of action potential firings in SCN neurons has been suggested by in vivo recordings while the present study demonstrates that the sustenance of bimodal firing rhythms in grass rat SCN neurons can last at least one day in vitro.
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Affiliation(s)
- Eri Morioka
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan.
| | - Tsubasa Miyamoto
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan.
| | - Sakura Tamogami
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan; Graduate School of Innovative Life Science, University of Toyama, Gofuku, Toyama 930-8555, Japan.
| | - Takahiro Koketsu
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan
| | - Juhyon Kim
- Graduate School of Innovative Life Science, University of Toyama, Gofuku, Toyama 930-8555, Japan.
| | - Tomoko Yoshikawa
- Organization for International Education and Exchange, University of Toyama, Toyama 930-8555, Japan.
| | - Takatoshi Mochizuki
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan.
| | - Masayuki Ikeda
- Graduate School of Innovative Life Science, University of Toyama, Gofuku, Toyama 930-8555, Japan; Organization for International Education and Exchange, University of Toyama, Toyama 930-8555, Japan.
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Jha PK, Bouâouda H, Kalsbeek A, Challet E. Distinct feedback actions of behavioural arousal to the master circadian clock in nocturnal and diurnal mammals. Neurosci Biobehav Rev 2021; 123:48-60. [PMID: 33440199 DOI: 10.1016/j.neubiorev.2020.12.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 09/16/2020] [Accepted: 12/10/2020] [Indexed: 12/20/2022]
Abstract
The master clock in the suprachiasmatic nucleus (SCN) of the hypothalamus provides a temporal pattern of sleep and wake that - like many other behavioural and physiological rhythms - is oppositely phased in nocturnal and diurnal animals. The SCN primarily uses environmental light, perceived through the retina, to synchronize its endogenous circadian rhythms with the exact 24 h light/dark cycle of the outside world. The light responsiveness of the SCN is maximal during the night in both nocturnal and diurnal species. Behavioural arousal during the resting period not only perturbs sleep homeostasis, but also acts as a potent non-photic synchronizing cue. The feedback action of arousal on the SCN is mediated by processes involving several brain nuclei and neurotransmitters, which ultimately change the molecular functions of SCN pacemaker cells. Arousing stimuli during the sleeping period differentially affect the circadian system of nocturnal and diurnal species, as evidenced by the different circadian windows of sensitivity to behavioural arousal. In addition, arousing stimuli reduce and increase light resetting in nocturnal and diurnal species, respectively. It is important to address further question of circadian impairments associated with shift work and trans-meridian travel not only in the standard nocturnal laboratory animals but also in diurnal animal models.
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Affiliation(s)
- Pawan Kumar Jha
- Circadian Clocks and Metabolism Team, Institute of Cellular and Integrative Neurosciences, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, France; Department of Endocrinology and Metabolism, Amsterdam University Medical Center (AUMC), University of Amsterdam, the Netherlands; Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, the Netherlands.
| | - Hanan Bouâouda
- Circadian Clocks and Metabolism Team, Institute of Cellular and Integrative Neurosciences, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, France
| | - Andries Kalsbeek
- Department of Endocrinology and Metabolism, Amsterdam University Medical Center (AUMC), University of Amsterdam, the Netherlands; Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, the Netherlands
| | - Etienne Challet
- Circadian Clocks and Metabolism Team, Institute of Cellular and Integrative Neurosciences, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, France
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3
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Gile J, Oyama Y, Shuff S, Eckle T. A Role for the Adenosine ADORA2B Receptor in Midazolam Induced Cognitive Dysfunction. Curr Pharm Des 2020; 26:4330-4337. [PMID: 32294028 DOI: 10.2174/1381612826666200415171622] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 04/01/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND We recently reported a role for the circadian rhythm protein Period 2 (PER2) in midazolam induced cognitive dysfunction. Based on previous studies showing a critical role for the adenosine A2B receptor (ADORA2B) in PER2 regulation, we hypothesized that hippocampal ADORA2B is crucial for cognitive function. METHODS Midazolam treated C57BL/6J mice were analyzed for Adora2b hippocampal mRNA expression levels, and spontaneous T-maze alternation was determined in Adora2b-/- mice. Using the specific ADORA2B agonist BAY-60-6583 in midazolam treated C57BL/6J mice, we analyzed hippocampal Per2 mRNA expression levels and spontaneous T-maze alternation. Finally, Adora2b-/- mice were assessed for mRNA expression of markers for inflammation or cognitive function in the hippocampus. RESULTS Midazolam treatment significantly downregulated Adora2b or Per2 mRNA in the hippocampus of C57BL/6J mice, and hippocampal PER2 protein expression or T-maze alternation was significantly reduced in Adora2b-/- mice. ADORA2B agonist BAY-60-6583 restored midazolam mediated reduction in spontaneous alternation in C57BL/6J mice. Analysis of hippocampal Tnf-α or Il-6 mRNA levels in Adora2b-/- mice did not reveal an inflammatory phenotype. However, C-fos, a critical component of hippocampus-dependent learning and memory, was significantly downregulated in the hippocampus of Adora2b-/- mice. CONCLUSION These results suggest a role of ADORA2B in midazolam induced cognitive dysfunction. Further, our data demonstrate that BAY-60-6583 treatment restores midazolam induced cognitive dysfunction, possibly via increases of Per2. Additional mechanistic studies hint towards C-FOS as another potential underlying mechanism of memory impairment in Adora2b-/- mice. These findings suggest the ADORA2B agonist as a potential therapy in patients with midazolam induced cognitive dysfunction.
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Affiliation(s)
- Jennifer Gile
- Department of Anesthesiology, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Yoshimasa Oyama
- Department of Anesthesiology, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Sydney Shuff
- Department of Anesthesiology, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Tobias Eckle
- Department of Anesthesiology, University of Colorado School of Medicine, Aurora, CO 80045, United States
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4
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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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5
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Yan L, Smale L, Nunez AA. Circadian and photic modulation of daily rhythms in diurnal mammals. Eur J Neurosci 2020; 51:551-566. [PMID: 30269362 PMCID: PMC6441382 DOI: 10.1111/ejn.14172] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/02/2018] [Accepted: 08/16/2018] [Indexed: 12/22/2022]
Abstract
The temporal niche that an animal occupies includes a coordinated suite of behavioral and physiological processes that set diurnal and nocturnal animals apart. The daily rhythms of the two chronotypes are regulated by both the circadian system and direct responses to light, a process called masking. Here we review the literature on circadian regulations and masking responses in diurnal mammals, focusing on our work using the diurnal Nile grass rat (Arvicanthis niloticus) and comparing our findings with those derived from other diurnal and nocturnal models. There are certainly similarities between the circadian systems of diurnal and nocturnal mammals, especially in the phase and functioning of the principal circadian oscillator within the hypothalamic suprachiasmatic nucleus (SCN). However, the downstream pathways, direct or indirect from the SCN, lead to drastic differences in the phase of extra-SCN oscillators, with most showing a complete reversal from the phase seen in nocturnal species. This reversal, however, is not universal and in some cases the phases of extra-SCN oscillators are only a few hours apart between diurnal and nocturnal species. The behavioral masking responses in general are opposite between diurnal and nocturnal species, and are matched by differential responses to light and dark in several retinorecipient sites in their brain. The available anatomical and functional data suggest that diurnal brains are not simply a phase-reversed version of nocturnal ones, and work with diurnal models contribute significantly to a better understanding of the circadian and photic modulation of daily rhythms in our own diurnal species.
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Affiliation(s)
- Lily Yan
- Department of Psychology and Neuroscience Program, Michigan State University, East Lansing, MI 48824, United States
| | - Laura Smale
- Department of Psychology and Neuroscience Program, Michigan State University, East Lansing, MI 48824, United States
| | - Antonio A. Nunez
- Department of Psychology and Neuroscience Program, Michigan State University, East Lansing, MI 48824, United States
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6
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Ben-Hamouda N, Poirel VJ, Dispersyn G, Pévet P, Challet E, Pain L. Short-term propofol anaesthesia down-regulates clock genes expression in the master clock. Chronobiol Int 2018; 35:1735-1741. [DOI: 10.1080/07420528.2018.1499107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Nawfel Ben-Hamouda
- Institut des neurosciences cellulaires et integratives, Neurobiology of Rhythms, CNRS (UPR3212), Université de Strasbourg, Strasbourg, France
- Adult intensive Care Medicine and Burns, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Vincent-Joseph Poirel
- Institut des neurosciences cellulaires et integratives, Neurobiology of Rhythms, CNRS (UPR3212), Université de Strasbourg, Strasbourg, France
| | - Garance Dispersyn
- Institut des neurosciences cellulaires et integratives, Neurobiology of Rhythms, CNRS (UPR3212), Université de Strasbourg, Strasbourg, France
- Institut de recherche biomedicale des armees, Bretigny-sur-Orge, France
| | - Paul Pévet
- Institut des neurosciences cellulaires et integratives, Neurobiology of Rhythms, CNRS (UPR3212), Université de Strasbourg, Strasbourg, France
| | - Etienne Challet
- Institut des neurosciences cellulaires et integratives, Neurobiology of Rhythms, CNRS (UPR3212), Université de Strasbourg, Strasbourg, France
| | - Laure Pain
- Institut des neurosciences cellulaires et integratives, Neurobiology of Rhythms, CNRS (UPR3212), Université de Strasbourg, Strasbourg, France
- Anesthesiology, Hopitaux universitaires de Strasbourg, Strasbourg, France
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7
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Kim M, de la Peña JB, Cheong JH, Kim HJ. Neurobiological Functions of the Period Circadian Clock 2 Gene, Per2. Biomol Ther (Seoul) 2018; 26:358-367. [PMID: 29223143 PMCID: PMC6029676 DOI: 10.4062/biomolther.2017.131] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 08/10/2017] [Accepted: 08/22/2017] [Indexed: 12/14/2022] Open
Abstract
Most organisms have adapted to a circadian rhythm that follows a roughly 24-hour cycle, which is modulated by both internal (clock-related genes) and external (environment) factors. In such organisms, the central nervous system (CNS) is influenced by the circadian rhythm of individual cells. Furthermore, the period circadian clock 2 (Per2) gene is an important component of the circadian clock, which modulates the circadian rhythm. Per2 is mainly expressed in the suprachiasmatic nucleus (SCN) of the hypothalamus as well as other brain areas, including the midbrain and forebrain. This indicates that Per2 may affect various neurobiological activities such as sleeping, depression, and addiction. In this review, we focus on the neurobiological functions of Per2, which could help to better understand its roles in the CNS.
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Affiliation(s)
- Mikyung Kim
- Department of Pharmacy, Uimyung Research Institute for Neuroscience, Sahmyook University, Seoul 01795, Republic of Korea
| | - June Bryan de la Peña
- Department of Pharmacy, Uimyung Research Institute for Neuroscience, Sahmyook University, Seoul 01795, Republic of Korea
| | - Jae Hoon Cheong
- Department of Pharmacy, Uimyung Research Institute for Neuroscience, Sahmyook University, Seoul 01795, Republic of Korea
| | - Hee Jin Kim
- Department of Pharmacy, Uimyung Research Institute for Neuroscience, Sahmyook University, Seoul 01795, Republic of Korea
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8
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How does general anaesthesia affect the circadian clock? Sleep Med Rev 2018; 37:35-44. [DOI: 10.1016/j.smrv.2016.12.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 12/06/2016] [Accepted: 12/07/2016] [Indexed: 12/20/2022]
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9
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Van Erum J, Van Dam D, De Deyn PP. Sleep and Alzheimer's disease: A pivotal role for the suprachiasmatic nucleus. Sleep Med Rev 2017; 40:17-27. [PMID: 29102282 DOI: 10.1016/j.smrv.2017.07.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Revised: 07/10/2017] [Accepted: 07/24/2017] [Indexed: 10/19/2022]
Abstract
Alzheimer's disease (AD), which accounts for most of the dementia cases, is, aside from cognitive deterioration, often characterized by the presence of non-cognitive symptoms. Society is desperately in need for interventions that alleviate the economic and social burden related to AD. Circadian dysrhythmia, one of these symptoms in particular, immensely decreases the self-care ability of AD patients and is one of the main reasons of caregiver exhaustion. Studies suggest that these circadian disturbances form the root of sleep-wake problems, diagnosed in more than half of AD patients. Sleep abnormalities have generally been considered merely a consequence of AD pathology. Recent evidence suggests that a bidirectional relationship exists between sleep and AD, and that poor sleep might negatively impact amyloid burden, as well as cognition. The suprachiasmatic nucleus (SCN), the main circadian pacemaker, is subjected to several alterations during the course of the disease. Its functional deterioration might fulfill a crucial role in the relation between AD pathophysiology and the development of sleep abnormalities. This review aims to give a concise overview of the anatomy and physiology of the SCN, address how AD pathology precisely impacts the SCN and to what degree these alterations can contribute to the progression of the disease.
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Affiliation(s)
- Jan Van Erum
- Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, Department of Biomedical Sciences, University of Antwerp, Wilrijk, Antwerp, Belgium
| | - Debby Van Dam
- Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, Department of Biomedical Sciences, University of Antwerp, Wilrijk, Antwerp, Belgium; Department of Neurology and Alzheimer Research Center, University of Groningen and University Medical Center Groningen (UMCG), Groningen, The Netherlands
| | - Peter Paul De Deyn
- Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, Department of Biomedical Sciences, University of Antwerp, Wilrijk, Antwerp, Belgium; Department of Neurology and Alzheimer Research Center, University of Groningen and University Medical Center Groningen (UMCG), Groningen, The Netherlands; Department of Neurology, Memory Clinic of Hospital Network Antwerp (ZNA) Middelheim and Hoge Beuken, Antwerp, Belgium.
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10
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Albers HE, Walton JC, Gamble KL, McNeill JK, Hummer DL. The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus. Front Neuroendocrinol 2017; 44:35-82. [PMID: 27894927 PMCID: PMC5225159 DOI: 10.1016/j.yfrne.2016.11.003] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Revised: 10/16/2016] [Accepted: 11/22/2016] [Indexed: 12/31/2022]
Abstract
Virtually every neuron within the suprachiasmatic nucleus (SCN) communicates via GABAergic signaling. The extracellular levels of GABA within the SCN are determined by a complex interaction of synthesis and transport, as well as synaptic and non-synaptic release. The response to GABA is mediated by GABAA receptors that respond to both phasic and tonic GABA release and that can produce excitatory as well as inhibitory cellular responses. GABA also influences circadian control through the exclusively inhibitory effects of GABAB receptors. Both GABA and neuropeptide signaling occur within the SCN, although the functional consequences of the interactions of these signals are not well understood. This review considers the role of GABA in the circadian pacemaker, in the mechanisms responsible for the generation of circadian rhythms, in the ability of non-photic stimuli to reset the phase of the pacemaker, and in the ability of the day-night cycle to entrain the pacemaker.
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Affiliation(s)
- H Elliott Albers
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States.
| | - James C Walton
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States
| | - Karen L Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - John K McNeill
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States
| | - Daniel L Hummer
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Department of Psychology, Morehouse College, Atlanta, GA 30314, United States
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11
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Hummer DL, Ehlen JC, Larkin TE, McNeill JK, Pamplin JR, Walker CA, Walker PV, Dhanraj DR, Albers HE. Sustained activation of GABAA receptors in the suprachiasmatic nucleus mediates light-induced phase delays of the circadian clock: a novel function of ionotropic receptors. Eur J Neurosci 2015; 42:1830-8. [PMID: 25865743 DOI: 10.1111/ejn.12918] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 03/16/2015] [Accepted: 04/07/2015] [Indexed: 01/16/2023]
Abstract
The suprachiasmatic nucleus (SCN) contains a circadian clock that generates endogenous rhythmicity and entrains that rhythmicity with the day-night cycle. The neurochemical events that transduce photic input within the SCN and mediate entrainment by resetting the molecular clock have yet to be defined. Because GABA is contained in nearly all SCN neurons we tested the hypothesis that GABA serves as this signal in studies employing Syrian hamsters (Mesocricetus auratus). Activation of GABAA receptors was found to be necessary and sufficient for light to induce phase delays of the clock. Remarkably, the sustained activation of GABAA receptors for more than three consecutive hours was necessary to phase-delay the clock. The duration of GABAA receptor activation required to induce phase delays would not have been predicted by either the prevalent theory of circadian entrainment or by expectations regarding the duration of ionotropic receptor activation necessary to produce functional responses. Taken together, these data identify a novel neurochemical mechanism essential for phase-delaying the 'master' circadian clock within the SCN as well as identifying an unprecedented action of an amino acid neurotransmitter involving the sustained activation of ionotropic receptors.
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Affiliation(s)
- Daniel L Hummer
- Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA, USA.,Department of Psychology, Morehouse College, Atlanta, GA, USA
| | - J Christopher Ehlen
- Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA, USA.,Neuroscience Institute, Georgia State University, Atlanta, GA, USA.,Neuroscience Institute, Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Tony E Larkin
- Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA, USA.,Department of Psychology, Morehouse College, Atlanta, GA, USA.,Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - John K McNeill
- Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA, USA.,Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - John R Pamplin
- Department of Psychology, Morehouse College, Atlanta, GA, USA
| | - Colton A Walker
- Department of Psychology, Morehouse College, Atlanta, GA, USA
| | | | - Daryl R Dhanraj
- Department of Psychology, Morehouse College, Atlanta, GA, USA
| | - H Elliott Albers
- Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA, USA.,Neuroscience Institute, Georgia State University, Atlanta, GA, USA
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12
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Kumar D, Singaravel M. Phase and period responses to short light pulses in a wild diurnal rodent,Funambulus pennanti. Chronobiol Int 2013; 31:320-7. [DOI: 10.3109/07420528.2013.851084] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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13
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Otalora BB, Hagenauer MH, Rol MA, Madrid JA, Lee TM. Period Gene Expression in the Brain of a Dual-Phasing Rodent, the Octodon degus. J Biol Rhythms 2013; 28:249-61. [DOI: 10.1177/0748730413495521] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Clock gene expression is not only confined to the master circadian clock in the suprachiasmatic nucleus (SCN) but is also found in many other brain regions. The phase relationship between SCN and extra-SCN oscillators may contribute to known differences in chronotypes. The Octodon degus is a diurnal rodent that can shift its activity-phase preference from diurnal to nocturnal when running wheels become available. To understand better the relationship between brain clock gene activity and chronotype, we studied the day-night expression of the Period genes, Per1 and Per2, in the SCN and extra-SCN brain areas in diurnal and nocturnal degus. Since negative masking to light and entrainment to the dark phase are involved in the nocturnalism of this species, we also compare, for the first time, Per expression between entrained (EN) and masked nocturnal (MN) degus. The brains of diurnal, MN, and EN degus housed with wheels were collected during the light (ZT4) and dark (ZT16) phases. Per1 and Per2 mRNA levels were analyzed by in situ hybridization. Within the SCN, signals for Per1 and Per2 were higher at ZT4 irrespective of chronotype. However, outside of the SCN, Per1 expression in the hippocampus of EN degus was out of phase (higher values at ZT16) with SCN values. Although a similar trend was seen in MN animals, this day-night difference in Per1 expression was not significant. Interestingly, daily differences in Per1 expression were not seen in the hippocampus of diurnal degus. For other putative brain areas analyzed (cortices, striatum, arcuate, ventromedial hypothalamus), no differences in Per1 levels were found between chronotypes. Both in diurnal and nocturnal degus, Per2 levels in the hippocampus and in the cingulate and piriform cortices were in phase with their activity rhythms. Thus, diurnal degus showed higher Per2 levels at ZT4, whereas in both types of nocturnal degus, Per2 expression was reversed, peaking at ZT16. Together, the present study supports the hypothesis that the mechanisms underlying activity-phase preference in diurnal and nocturnal mammals reside downstream from the SCN, but our data also indicate that there are fundamental differences between nocturnal masked and entrained degus.
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Affiliation(s)
- Beatriz B. Otalora
- Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Megan H. Hagenauer
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
- Molecular & Behavioral Neuroscience Institute (MBNI), University of Michigan, Ann Arbor, MI, USA
| | - Maria A. Rol
- Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Juan A. Madrid
- Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Theresa M. Lee
- College of Arts and Sciences, University of Tennessee–Knoxville, Knoxville, TN, USA
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14
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Oggier DM, Weisbrod CJ, Stoller AM, Zenker AK, Fent K. Effects of diazepam on gene expression and link to physiological effects in different life stages in zebrafish Danio rerio. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:7685-91. [PMID: 20804179 DOI: 10.1021/es100980r] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We applied zebrafish whole genome microarrays to identify molecular effects of diazepam, a neuropharmaceutical encountered in wastewater-contaminated environments, and to elucidate its neurotoxic mode of action. Behavioral studies were performed to analyze for correlations between altered gene expression with effects on the organism level. Male zebrafish and zebrafish eleuthero-embryos were exposed for 14 d or up to 3 d after hatching, respectively, to nominal levels of 273 ng/L and 273 μg/L (determined water concentrations in the adult experiment 235 ng/L and 291 μg/L). Among the 51 and 103 altered transcripts at both concentrations, respectively, the expression of genes involved in the circadian rhythm in adult zebrafish and eleuthero-embryos were of particular significance, as revealed both by microarrays and quantitative PCR. The swimming behavior of eleuthero-embryos was significantly altered at 273 μg/L. The study leads to the conclusion that diazepam-induced alterations of genes involved in circadian rhythm are paralleled by effects in neurobehavior at high, but not at low diazepam concentrations that may occur in polluted environments.
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Affiliation(s)
- Daniela M Oggier
- School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Gründenstrasse 40, CH-4132 Muttenz, Switzerland
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15
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Koch JM, Hagenauer MH, Lee TM. The response of Per1 to light in the suprachiasmatic nucleus of the diurnal degu (Octodon degus). Chronobiol Int 2009; 26:1263-71. [PMID: 19731117 DOI: 10.3109/07420520903223992] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Several studies suggest that the circadian systems of diurnal mammals respond differently to daytime light than those of nocturnal mammals. We hypothesized that the photosensitive "clock" gene Per1 would respond to light exposure during subjective day in the suprachiasmatic nucleus of the diurnal rodent, Octodon degus. Tissue was collected 1.5-2 h after a 30 min light pulse presented at five timepoints across the 24 h day and compared to controls maintained under conditions of constant darkness. Per1 mRNA was quantified using in situ hybridization. Results showed that the rhythmicity and photic responsiveness of Per1 in the degu resembles that of nocturnal animals.
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Affiliation(s)
- Jessica M Koch
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109-1043, USA
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16
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Hamada T, Shibata S. The role of GABAergic neuron on NMDA- and SP-induced phase delays in the suprachiasmatic nucleus neuronal activity rhythm in vitro. Neurosci Lett 2009; 468:344-7. [PMID: 19914338 DOI: 10.1016/j.neulet.2009.11.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 11/09/2009] [Accepted: 11/09/2009] [Indexed: 10/20/2022]
Abstract
Gamma-aminobutyric acid (GABA), and its biosynthetic enzyme, glutamic decarboxylase, are widely distributed in the suprachiasmatic nucleus (SCN). In the present study, we examined the role of the GABA(A) receptor on in vitro SCN responses to photic-like signals. We found that 100microM GABA(A) receptor antagonist bicuculline partially blocked field potentials evoked by optic nerve stimulation. NMDA- and SP-induced phase shifts of SCN neuronal activity rhythms, were blocked with 10microM bicuculline. Application of 100microM bicuculline alone induced phase advance of SCN neuronal activity rhythm. These results show that NMDA- and SP-induced phase shifts are blocked by bicuculline and suggest GABA has an important role as neurotransmitter in the neuronal network regulating phase shifts of the circadian clock.
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Affiliation(s)
- Toshiyuki Hamada
- Advanced Photonic Bioimaging Center, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido 060-8638, Japan
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17
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Mansuy V, Risold PY, Glauser M, Fraichard A, Pralong FP. Expression of the GABAA receptor associated protein Gec1 is circadian and dependent upon the cellular clock machinery in GnRH secreting GnV-3 cells. Mol Cell Endocrinol 2009; 307:68-76. [PMID: 19524128 DOI: 10.1016/j.mce.2009.02.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 02/25/2009] [Accepted: 02/25/2009] [Indexed: 11/23/2022]
Abstract
The timely regulation of gonadotropin-releasing hormone (GnRH) secretion requires a GABAergic signal. We hypothesized that GEC1, a protein promoting the transport of GABA(A) receptors, could represent a circadian effector in GnRH neurons. First, we demonstrated that gec1 is co-expressed with the GABA(A) receptor in hypothalamic rat GnRH neurons. We also confirmed that the clock genes per1, cry1 and bmal1 are expressed and oscillate in GnRH secreting GnV-3 cells. Then we could show that gec1 is expressed in GnV-3 cells, and oscillates in a manner temporally related to the oscillations of the clock transcription factors. Furthermore, we could demonstrate that these oscillations depend upon Per1 expression. Finally, we observed that GABA(A) receptor levels at the GnV-3 cell membrane are timely modulated following serum shock. Together, these data demonstrate that gec1 expression is dependent upon the circadian clock machinery in GnRH-expressing neurons, and suggest for the first time that the level of GABA(A) receptor at the cell membrane may be under timely regulation. Overall, they provide a potential mechanism for the circadian regulation of GnRH secretion by GABA, and may also be relevant to the general understanding of circadian rhythms.
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Affiliation(s)
- Virginie Mansuy
- Services of Endocrinology, Diabetology, and Metabolism of the University Hospital of Lausanne, Switzerland
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18
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Ramanathan C, Campbell A, Tomczak A, Nunez AA, Smale L, Yan L. Compartmentalized expression of light-induced clock genes in the suprachiasmatic nucleus of the diurnal grass rat (Arvicanthis niloticus). Neuroscience 2009; 161:960-9. [PMID: 19393297 DOI: 10.1016/j.neuroscience.2009.04.040] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 04/15/2009] [Accepted: 04/16/2009] [Indexed: 10/20/2022]
Abstract
Photic responses of the circadian system are mediated through light-induced clock gene expression in the suprachiasmatic nucleus (SCN). In nocturnal rodents, depending on the timing of light exposure, Per1 and Per2 gene expression shows distinct compartmentalized patterns that correspond to the behavioral responses. Whether the gene- and region-specific induction patterns are unique to nocturnal animals, or are also present in diurnal species is unknown. We explored this question by examining the light-induced Per1 and Per2 gene expression in functionally distinct SCN subregions, using diurnal grass rats Arvicanthis niloticus. Light exposure during nighttime induced Per1 and Per2 expression in the SCN, showing unique spatiotemporal profiles depending on the phase of the light exposure. After a phase delaying light pulse (LP) in the early night, strong Per1 induction was observed in the retinorecipient core region of the SCN, while strong Per2 induction was observed throughout the entire SCN. After a phase advancing LP in the late night, Per1 was first induced in the core and then extended into the whole SCN, accompanied by a weak Per2 induction. This compartmentalized expression pattern is very similar to that observed in nocturnal rodents, suggesting that the same molecular and intercellular pathways underlying acute photic responses are present in both diurnal and nocturnal species. However, after an LP in early subjective day, which induces phase advances in diurnal grass rats, but not in nocturnal rodents, we did not observe any Per1 or Per2 induction in the SCN. This result suggests that in spite of remarkable similarities in the SCN of diurnal and nocturnal rodents, unique mechanisms are involved in mediating the phase shifts of diurnal animals during the subjective day.
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Affiliation(s)
- C Ramanathan
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
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19
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Ehlen JC, Paul KN. Regulation of light's action in the mammalian circadian clock: role of the extrasynaptic GABAA receptor. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1606-12. [PMID: 19244580 DOI: 10.1152/ajpregu.90878.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
GABA(A) receptor agonists act in the suprachiasmatic nucleus (SCN) to reset circadian rhythms during the day but inhibit the ability of light to reset rhythms during the night. In the present study, we examined whether these paradoxical differences in the effect of GABA(A) receptor stimulation on the circadian system are mediated by separate GABA(A) receptor subtypes. 4,5,6,7-Tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), a GABA(A) receptor agonist, preferentially activates GABA(A) receptors in extrasynaptic locations. THIP, muscimol (a GABA(A) agonist), or vehicle were microinjected into the SCN region of Syrian hamsters free-running in constant darkness during the mid-subjective day, early subjective night, or late subjective night. The subjective night injections were followed by a light pulse or sham control. Behavioral phase shifts of wheel running rhythms and both Period1 (Per1) and Per2 mRNA levels in the SCN were assessed. Animals that received THIP during the subjective day did not exhibit significant phase alterations. During the early and late subjective night, however, THIP abolished the phase-shifting effects of light and the ability of light to increase Per1 and Per2 mRNA levels. The ability of N-methyl-d-aspartic acid to phase-shift wheel running rhythms was also attenuated by THIP. Together these data demonstrate that THIP does not produce phase shifts during the subjective day, but does inhibit the ability of light to produce phase shifts. Thus, extrasynaptic GABA(A) receptors appear to play a role in regulating light input to the SCN, while a different population of GABA(A) receptors appears to be responsible for daytime effects of GABA.
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Affiliation(s)
- J Christopher Ehlen
- Circadian Rhythms and Sleep Disorders Program, Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA
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20
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Vosko AM, Hagenauer MH, Hummer DL, Lee TM. Period gene expression in the diurnal degu (Octodon degus) differs from the nocturnal laboratory rat (Rattus norvegicus). Am J Physiol Regul Integr Comp Physiol 2008; 296:R353-61. [PMID: 19036829 DOI: 10.1152/ajpregu.90392.2008] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent data suggest that both nocturnal and diurnal mammals generate circadian rhythms using similarly phased feedback loops involving Period genes in the suprachiasmatic nuclei (SCN) of the hypothalamus. These molecular oscillations also exist in the brain outside of the SCN, but the relationship between SCN and extra-SCN oscillations is unclear. We hypothesized that a comparison of "diurnal" and "nocturnal" central nervous system Per rhythms would uncover differences in the underlying circadian mechanisms between these two chronotypes. Therefore, this study compared the 24-h oscillatory patterns of Per1 and Per2 mRNA in the SCN and putative striatum and cortex of Octodon degus (degu), a diurnal hystricognath rodent, with those of the nocturnal laboratory rat, Rattus norvegicus. The brains of adult male degus and rats were collected at 2-h intervals across 24 h in entrained light-dark and constant darkness conditions, and sections were analyzed via in situ hybridization. In the SCN, degu Per1 and Per2 hybridization signal exhibited 24-h oscillatory patterns similar in phasing to those seen in other rodents, with peaks occurring during the light period and troughs during the dark period. However, Per1 remained elevated for five fewer hours in the degu than in the rat, and Per2 remained elevated for two fewer hours in the degu. In brain areas outside of the SCN, the phase of Per2 hybridization signal rhythms in the degu were 180 degrees out of phase with those found in the rat, and Per1 hybridization signal lacked significant rhythmicity. These results suggest that, while certain basic components of the transcriptional-translational feedback loop generating circadian rhythms are similar in diurnal and nocturnal mammals, there are variations that may reflect adaptations to circadian niche.
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Affiliation(s)
- Andrew M Vosko
- Department of Psychology, University of Michigan, 530 Church St., Ann Arbor, MI 48109-1043, USA
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21
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Ramanathan C, Nunez AA, Smale L. Daily rhythms in PER1 within and beyond the suprachiasmatic nucleus of female grass rats (Arvicanthis niloticus). Neuroscience 2008; 156:48-58. [PMID: 18692118 PMCID: PMC2758417 DOI: 10.1016/j.neuroscience.2008.07.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 06/02/2008] [Accepted: 07/03/2008] [Indexed: 11/30/2022]
Abstract
Although circadian rhythms of males and females are different in a variety of ways in many species, their mechanisms have been primarily studied in males. Furthermore, rhythms are dramatically different in diurnal and nocturnal animals but have been studied predominantly in nocturnal ones. In the present study, we examined rhythms in one element of the circadian oscillator, the PER1 protein, in a variety of cell populations in brains of diurnal female grass rats. Every 4 h five adult female grass rats kept on a 12-h light/dark (LD) cycle were perfused and their brains were processed for immunohistochemical detection of PER1. Numbers of PER1-labeled cells were rhythmic not only within the suprachiasmatic nucleus (SCN), the locus of the primary circadian clock in mammals, but also in the peri-suprachiasmatic region, the oval nucleus of the bed nucleus of the stria terminalis, the central amygdala, and the nucleus accumbens. In addition, rhythms were detected within populations of neuroendocrine cells that contain tyrosine hydroxylase. The phase of the rhythm within the SCN was advanced compared with that seen previously in male grass rats. Rhythms beyond the SCN were varied and different from those seen in most nocturnal species, suggesting that signals originating in the SCN are modified by its direct and/or indirect targets in different ways in nocturnal and diurnal species.
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Affiliation(s)
- C. Ramanathan
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - A. A. Nunez
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - L. Smale
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
- Department of Zoology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
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22
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Hagenauer MH, Lee TM. Circadian organization of the diurnal Caviomorph rodent,Octodon degus. BIOL RHYTHM RES 2008. [DOI: 10.1080/09291010701683425] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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23
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Novak CM, Ehlen JC, Albers HE. Photic and nonphotic inputs to the diurnal circadian clock. BIOL RHYTHM RES 2008. [DOI: 10.1080/09291010701683482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Ehlen JC, Novak CM, Karom MC, Gamble KL, Albers HE. Interactions of GABA A receptor activation and light on period mRNA expression in the suprachiasmatic nucleus. J Biol Rhythms 2008; 23:16-25. [PMID: 18258754 DOI: 10.1177/0748730407310785] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Activation of gamma-aminobutyric acid (GABA) A receptors in the suprachiasmatic nucleus (SCN) resets the circadian clock during the day and inhibits the ability of light to reset the clock at night. Light in turn acts during the day to inhibit the phase-resetting effects of GABA. Some evidence suggests that Period mRNA changes in the SCN are responsible for these interactions between light and GABA. Here, the hypothesis that light and the GABA A receptor interact by altering the expression of Period 1 and/or Period 2 mRNA in the SCN is tested. The GABA A agonist muscimol was injected near the SCN just prior to a light pulse, during the mid-subjective day and the early and late subjective night. Changes in Period 1 and Period 2 mRNA were measured in the SCN by in situ hybridization. Light-induced Period 1 mRNA was inhibited by GABA A receptor activation in the early and late subjective night, while Period 2 mRNA was only inhibited during the late night. During the subjective day, light had no effect on the ability of muscimol to suppress Period 1 mRNA hybridization signal. Thus, light and GABA A receptor activation inhibit each other's ability to induce behavioral phase shifts throughout the subjective day and night. However, only in the late night are these behavioral effects correlated with changes in Period gene expression. Together, our data support the hypothesis that the interacting effects of light and GABA are the result of the opposing actions of these stimuli on Period mRNA, but only during the subjective night.
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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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26
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Brown TM, Piggins HD. Electrophysiology of the suprachiasmatic circadian clock. Prog Neurobiol 2007; 82:229-55. [PMID: 17646042 DOI: 10.1016/j.pneurobio.2007.05.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Revised: 03/29/2007] [Accepted: 05/30/2007] [Indexed: 01/28/2023]
Abstract
In mammals, an internal timekeeping mechanism located in the suprachiasmatic nuclei (SCN) orchestrates a diverse array of neuroendocrine and physiological parameters to anticipate the cyclical environmental fluctuations that occur every solar day. Electrophysiological recording techniques have proved invaluable in shaping our understanding of how this endogenous clock becomes synchronized to salient environmental cues and appropriately coordinates the timing of a multitude of physiological rhythms in other areas of the brain and body. In this review we discuss the pioneering studies that have shaped our understanding of how this biological pacemaker functions, from input to output. Further, we highlight insights from new studies indicating that, more than just reflecting its oscillatory output, electrical activity within individual clock cells is a vital part of SCN clockwork itself.
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Affiliation(s)
- Timothy M Brown
- Faculty of Life Sciences, Stopford Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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