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Kumar D, Khan B, Okcay Y, Sis ÇÖ, Abdallah A, Murray F, Sharma A, Uemura M, Taliyan R, Heinbockel T, Rahman S, Goyal R. Dynamic endocannabinoid-mediated neuromodulation of retinal circadian circuitry. Ageing Res Rev 2024; 99:102401. [PMID: 38964508 DOI: 10.1016/j.arr.2024.102401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 06/05/2024] [Accepted: 06/28/2024] [Indexed: 07/06/2024]
Abstract
Circadian rhythms are biological rhythms that originate from the "master circadian clock," called the suprachiasmatic nucleus (SCN). SCN orchestrates the circadian rhythms using light as a chief zeitgeber, enabling humans to synchronize their daily physio-behavioral activities with the Earth's light-dark cycle. However, chronic/ irregular photic disturbances from the retina via the retinohypothalamic tract (RHT) can disrupt the amplitude and the expression of clock genes, such as the period circadian clock 2, causing circadian rhythm disruption (CRd) and associated neuropathologies. The present review discusses neuromodulation across the RHT originating from retinal photic inputs and modulation offered by endocannabinoids as a function of mitigation of the CRd and associated neuro-dysfunction. Literature indicates that cannabinoid agonists alleviate the SCN's ability to get entrained to light by modulating the activity of its chief neurotransmitter, i.e., γ-aminobutyric acid, thus preventing light-induced disruption of activity rhythms in laboratory animals. In the retina, endocannabinoid signaling modulates the overall gain of the retinal ganglion cells by regulating the membrane currents (Ca2+, K+, and Cl- channels) and glutamatergic neurotransmission of photoreceptors and bipolar cells. Additionally, endocannabinoids signalling also regulate the high-voltage-activated Ca2+ channels to mitigate the retinal ganglion cells and intrinsically photosensitive retinal ganglion cells-mediated glutamate release in the SCN, thus regulating the RHT-mediated light stimulation of SCN neurons to prevent excitotoxicity. As per the literature, cannabinoid receptors 1 and 2 are becoming newer targets in drug discovery paradigms, and the involvement of endocannabinoids in light-induced CRd through the RHT may possibly mitigate severe neuropathologies.
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Affiliation(s)
- Deepak Kumar
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University of Biotechnology and Management Sciences, Solan, HP 173229, India.
| | - Bareera Khan
- Faculty of Applied Sciences and Biotechnology, Shoolini University of Biotechnology and Management Sciences, Solan, HP 173229, India
| | - Yagmur Okcay
- University of Health Sciences Gulhane Faculty of Pharmacy Department of Pharmacology, Turkey.
| | - Çağıl Önal Sis
- University of Health Sciences Gulhane Faculty of Pharmacy Department of Pharmacology, Turkey.
| | - Aya Abdallah
- Institute of Medical Science, University of Aberdeen, Aberdeen, Scotland.
| | - Fiona Murray
- Institute of Medical Science, University of Aberdeen, Aberdeen, Scotland.
| | - Ashish Sharma
- School of Medicine, Washington University, St. Louis, USA
| | - Maiko Uemura
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
| | - Rajeev Taliyan
- Department of Pharmacy, Birla Institute of Technology Science, Pilani, Rajasthan 333301, India.
| | - Thomas Heinbockel
- Howard University College of Medicine, Department of Anatomy, Washington, DC 20059, USA
| | - Shafiqur Rahman
- Department of Pharmaceutical Sciences, College of Pharmacy South Dakota State University, Brookings, SD, USA.
| | - Rohit Goyal
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University of Biotechnology and Management Sciences, Solan, HP 173229, India.
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Lebedeva M, Kubištová A, Spišská V, Filipovská E, Pačesová D, Svobodová I, Kuchtiak V, Balík A, Bendová Z. The disruption of circadian rhythmicity of gene expression in the hippocampus and associated structures in Gria2 R/R mice; a comparison with C57BL/6J and Adar2 -/- mice strains. Brain Res 2024; 1826:148739. [PMID: 38157956 DOI: 10.1016/j.brainres.2023.148739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 11/18/2023] [Accepted: 12/18/2023] [Indexed: 01/03/2024]
Abstract
Adar2-/- mice are a widely used model for studying the physiological consequences of reduced RNA editing. These mice are viable only when the Q/R editing site of the Gria2 subunit of the AMPA receptor is constitutively mutated to the codon for arginine, and Gria2R/R mice often serve as the sole control for Adar2-/- mice. Our study aimed to investigate whether ADAR2 inactivity and the Gria2R/R phenotype affect the rhythmicity of the circadian clock gene pattern and the expression of Gria1 and Gria2 subunits in the suprachiasmatic nucleus (SCN), hippocampus, parietal cortex and liver. Our data show that Gria2R/R mice completely lost circadian rhythmicity in the hippocampus compared to Adar2-/- mice. Compared to C57BL/6J mice, the expression profiles in the hippocampus and parietal cortex of Gria2R/R mice differ to the same extent as in Adar2-/-. No alterations were detected in the circadian profiles in the livers. These data suggest that the natural gradual postnatal increase in the editing of the Q/R site of the Gria2 subunit may be important for the development of circadian clockwork in some brain structures, and the use of Gria2R/R mice as the only control to Adar2-/- mice in the experiments dependent on the hippocampus and parietal cortex should therefore be considered.
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Affiliation(s)
- Maria Lebedeva
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic; National Institute of Mental Health, Klecany, Czech Republic
| | - Aneta Kubištová
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Veronika Spišská
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Eva Filipovská
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Dominika Pačesová
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Irena Svobodová
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Viktor Kuchtiak
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Aleš Balík
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic.
| | - Zdeňka Bendová
- Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic; National Institute of Mental Health, Klecany, Czech Republic.
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Kim YS, Lee CJ, Kim JH, Kim YB, Colwell CS, Kim YI. Activation of mGluR1 negatively modulates glutamate-induced phase shifts of the circadian pacemaker in the mouse suprachiasmatic nucleus. Neurobiol Sleep Circadian Rhythms 2023; 14:100089. [PMID: 36874931 PMCID: PMC9982032 DOI: 10.1016/j.nbscr.2023.100089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 01/25/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
In mammals, photic information delivered to the suprachiasmatic nucleus (SCN) via the retinohypothalamic tract (RHT) plays a crucial role in synchronizing the master circadian clock located in the SCN to the solar cycle. It is well known that glutamate released from the RHT terminals initiates the synchronizing process by activating ionotropic glutamate receptors (iGluRs) on retinorecipient SCN neurons. The potential role of metabotropic glutamate receptors (mGluRs) in modulating this signaling pathway has received less attention. In this study, using extracellular single-unit recordings in mouse SCN slices, we investigated the possible roles of the Gq/11 protein-coupled mGluRs, mGluR1 and mGluR5, in photic resetting. We found that mGluR1 activation in the early night produced phase advances in neural activity rhythms in the SCN, while activation in the late night produced phase delays. In contrast, mGluR5 activation had no significant effect on the phase of these rhythms. Interestingly, mGluR1 activation antagonized phase shifts induced by glutamate through a mechanism that was dependent upon CaV1.3 L-type voltage-gated Ca2+ channels (VGCCs). While both mGluR1-evoked phase delays and advances were inhibited by knockout (KO) of CaV1.3 L-type VGCCs, different signaling pathways appeared to be involved in mediating these effects, with mGluR1 working via protein kinase G in the early night and via protein kinase A signaling in the late night. We conclude that, in the mouse SCN, mGluR1s function to negatively modulate glutamate-evoked phase shifts.
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Affiliation(s)
- Yoon Sik Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon, Republic of Korea
| | - Ji-Hyeon Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
| | - Young-Beom Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
| | - Christopher S Colwell
- Department of Psychiatry & Biobehavioral Sciences, University of California-Los Angeles, 760 Westwood Plaza, Los Angeles, CA, 90024, USA
| | - Yang In Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
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A light-induced small G-protein gem limits the circadian clock phase-shift magnitude by inhibiting voltage-dependent calcium channels. Cell Rep 2022; 39:110844. [PMID: 35613591 DOI: 10.1016/j.celrep.2022.110844] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 03/09/2022] [Accepted: 04/28/2022] [Indexed: 11/23/2022] Open
Abstract
Calcium signaling is pivotal to the circadian clockwork in the suprachiasmatic nucleus (SCN), particularly in rhythm entrainment to environmental light-dark cycles. Here, we show that a small G-protein Gem, an endogenous inhibitor of high-voltage-activated voltage-dependent calcium channels (VDCCs), is rapidly induced by light in SCN neurons via the calcium (Ca2+)-mediated CREB/CRE transcriptional pathway. Gem attenuates light-induced calcium signaling through its interaction with VDCCs. The phase-shift magnitude of locomotor activity rhythms by light, at night, increases in Gem-deficient (Gem-/-) mice. Similarly, in SCN slices from Gem-/- mice, depolarizing stimuli induce larger phase shifts of clock gene transcription rhythms that are normalized by the application of an L-type VDCC blocker, nifedipine. Voltage-clamp recordings from SCN neurons reveal that Ca2+ currents through L-type channels increase in Gem-/- mice. Our findings suggest that transcriptionally activated Gem feeds back to suppress excessive light-evoked L-type VDCC activation, adjusting the light-induced phase-shift magnitude to an appropriate level in mammals.
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Haraguchi A, Du Y, Shiraishi R, Takahashi Y, Nakamura TJ, Shibata S. Oak extracts modulate circadian rhythms of clock gene expression in vitro and wheel-running activity in mice. Sleep Biol Rhythms 2022; 20:255-266. [PMID: 38469255 PMCID: PMC10899999 DOI: 10.1007/s41105-021-00365-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 12/04/2021] [Indexed: 10/19/2022]
Abstract
Introduction In mammals, the central circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which coordinates the circadian rhythm and controls locomotor activity rhythms. In addition to SCN cells, the peripheral tissues and embryonic fibroblasts also have clock genes, such as Per1/2 and Bmal1, which generate the transcriptional-translational feedback loop to produce an approximately 24-h cycle. Aging adversely affects the circadian clock system and locomotor functions. Oak extract has been reported to improve age-related physiological changes. However, no study has examined the effect of oak extract on the circadian clock system. Methods We examined the effects of oak extract and its metabolites (urolithin A [ULT] and ellagic acid [EA]) on clock gene expression rhythms in mouse embryonic fibroblasts (MEFs) and SCN. Furthermore, locomotor activity rhythm was assessed in young and aged mice. Results Chronic treatment with EA and ULT delayed the phase of PER2::LUC rhythms in SCN explants, and ULT prolonged the period of PER2::LUC rhythms in MEFs in a dose-dependent manner and increased the amplitude of PER2::LUC rhythms in MEFs, though only at low concentrations. Acute treatment with ULT affected the phase of PER2::LUC rhythms in MEFs depending on the concentration and timing of the treatment. In addition, oak extract prolonged the activity time of behavioral rhythms in old mice and tended to increase daily wheel-running revolutions in both young and old mice. Conclusions These results suggest that oak extract is a novel modulator of the circadian clock in vitro and in vivo. Supplementary Information The online version contains supplementary material available at 10.1007/s41105-021-00365-2.
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Affiliation(s)
- Atsushi Haraguchi
- Department of Electrical Engineering and Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo, 162-8480 Japan
| | - Yao Du
- Department of Electrical Engineering and Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo, 162-8480 Japan
| | - Rena Shiraishi
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, Kawasaki, Kanagawa 214-8571 Japan
| | - Yuki Takahashi
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, Kawasaki, Kanagawa 214-8571 Japan
| | - Takahiro J. Nakamura
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, Kawasaki, Kanagawa 214-8571 Japan
| | - Shigenobu Shibata
- Department of Electrical Engineering and Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo, 162-8480 Japan
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Royo M, Escolano BA, Madrigal MP, Jurado S. AMPA Receptor Function in Hypothalamic Synapses. Front Synaptic Neurosci 2022; 14:833449. [PMID: 35173598 PMCID: PMC8842481 DOI: 10.3389/fnsyn.2022.833449] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 01/03/2022] [Indexed: 12/15/2022] Open
Abstract
AMPA receptors (AMPARs) are critical for mediating glutamatergic synaptic transmission and plasticity, thus playing a major role in the molecular machinery underlying cellular substrates of memory and learning. Their expression pattern, transport and regulatory mechanisms have been extensively studied in the hippocampus, but their functional properties in other brain regions remain poorly understood. Interestingly, electrophysiological and molecular evidence has confirmed a prominent role of AMPARs in the regulation of hypothalamic function. This review summarizes the existing evidence on AMPAR-mediated transmission in the hypothalamus, where they are believed to orchestrate the role of glutamatergic transmission in autonomous, neuroendocrine function, body homeostasis, and social behavior.
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Kumar D, Sharma A, Taliyan R, Urmera MT, Herrera-Calderon O, Heinbockel T, Rahman S, Goyal R. Orchestration of the circadian clock and its association with Alzheimer's disease: Role of endocannabinoid signaling. Ageing Res Rev 2022; 73:101533. [PMID: 34844016 PMCID: PMC8729113 DOI: 10.1016/j.arr.2021.101533] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/24/2021] [Accepted: 11/22/2021] [Indexed: 01/03/2023]
Abstract
Circadian rhythms are 24-hour natural rhythms regulated by the suprachiasmatic nucleus, also known as the "master clock". The retino-hypothalamic tract entrains suprachiasmatic nucleus with photic information to synchronise endogenous circadian rhythms with the Earth's light-dark cycle. However, despite the robustness of circadian rhythms, an unhealthy lifestyle and chronic photic disturbances cause circadian rhythm disruption in the suprachiasmatic nucleus's TTFL loops via affecting glutamate and γ-aminobutyric acid-mediated neurotransmission in the suprachiasmatic nucleus. Recently, considerable evidence has been shown correlating CRd with the incidence of Alzheimer's disease. The present review aims to identify the existence and signalling of endocannabinoids in CRd induced Alzheimer's disease through retino-hypothalamic tract- suprachiasmatic nucleus-cortex. Immunohistochemistry has confirmed the expression of cannabinoid receptor 1 in the suprachiasmatic nucleus to modulate the circadian phases of the master clock. Literature also suggests that cannabinoids may alter activity of suprachiasmatic nucleus by influencing the activity of their major neurotransmitter γ-aminobutyric acid or by interacting indirectly with the suprachiasmatic nucleus's two other major inputs i.e., the geniculo-hypothalamic tract-mediated release of neuropeptide Y and serotonergic inputs from the dorsal raphe nuclei. Besides, the expression of cannabinoid receptor 2 ameliorates cognitive deficits via reduction of tauopathy and microglial activation. In conclusion, endocannabinoids may be identified as a putative target for correcting CRd and decelerating Alzheimer's disease.
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Affiliation(s)
- Deepak Kumar
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University of Biotechnology and Management Sciences, Solan, H.P. 173229, India.
| | - Ashish Sharma
- School of Medicine, Washington University, St. Louis, USA.
| | - Rajeev Taliyan
- Neuropharmacology Laboratory, Department of Pharmacy, Birla Institute of Technology Science, Pilani, Rajasthan 333301, India.
| | - Maiko T Urmera
- Institute on Aging and Centre for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
| | - Oscar Herrera-Calderon
- Department of Pharmacology, Bromatology and Toxicology, Faculty of Pharmacy and Biochemistry, Universidad Nacional Mayor de San Marcos, Lima, Peru.
| | - Thomas Heinbockel
- Howard University College of Medicine, District of Columbia, WA, USA.
| | - Shafiqur Rahman
- Department of Pharmaceutical Sciences, College of Pharmacy South Dakota State University, Brookings, SD, USA.
| | - Rohit Goyal
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University of Biotechnology and Management Sciences, Solan, H.P. 173229, India.
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8
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Kumar D, Sharma A, Taliyan R, Urmera MT, Herrera-Calderon O, Heinbockel T, Rahman S, Goyal R. Orchestration of the circadian clock and its association with Alzheimer's disease: Role of endocannabinoid signaling. Ageing Res Rev 2022. [DOI: https://doi.org/10.1016/j.arr.2021.101533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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9
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Ang G, Brown LA, Tam SKE, Davies KE, Foster RG, Harrison PJ, Sprengel R, Vyazovskiy VV, Oliver PL, Bannerman DM, Peirson SN. Deletion of AMPA receptor GluA1 subunit gene (Gria1) causes circadian rhythm disruption and aberrant responses to environmental cues. Transl Psychiatry 2021; 11:588. [PMID: 34782594 PMCID: PMC8593011 DOI: 10.1038/s41398-021-01690-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 12/19/2022] Open
Abstract
Dysfunction of the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 subunit and deficits in synaptic plasticity are implicated in schizophrenia and sleep and circadian rhythm disruption. To investigate the role of GluA1 in circadian and sleep behaviour, we used wheel-running, passive-infrared, and video-based home-cage activity monitoring to assess daily rest-activity profiles of GluA1-knockout mice (Gria1-/-). We showed that these mice displayed various circadian abnormalities, including misaligned, fragmented, and more variable rest-activity patterns. In addition, they showed heightened, but transient, behavioural arousal to light→dark and dark→light transitions, as well as attenuated nocturnal-light-induced activity suppression (negative masking). In the hypothalamic suprachiasmatic nuclei (SCN), nocturnal-light-induced cFos signals (a molecular marker of neuronal activity in the preceding ~1-2 h) were attenuated, indicating reduced light sensitivity in the SCN. However, there was no change in the neuroanatomical distribution of expression levels of two neuropeptides-vasoactive intestinal peptide (VIP) and arginine vasopressin (AVP)-differentially expressed in the core (ventromedial) vs. shell (dorsolateral) SCN subregions and both are known to be important for neuronal synchronisation within the SCN and circadian rhythmicity. In the motor cortex (area M1/M2), there was increased inter-individual variability in cFos levels during the evening period, mirroring the increased inter-individual variability in locomotor activity under nocturnal light. Finally, in the spontaneous odour recognition task GluA1 knockouts' short-term memory was impaired due to enhanced attention to the recently encountered familiar odour. These abnormalities due to altered AMPA-receptor-mediated signalling resemble and may contribute to sleep and circadian rhythm disruption and attentional deficits in different modalities in schizophrenia.
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Affiliation(s)
- Gauri Ang
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
- Department of Experimental Psychology, University of Oxford, Oxford, UK
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Laurence A Brown
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- IT Services, University of Oxford, Oxford, UK
| | - Shu K E Tam
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Kay E Davies
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Russell G Foster
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Paul J Harrison
- Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK
| | - Rolf Sprengel
- Research Group of the Max Planck Institute for Medical Research at the Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Vladyslav V Vyazovskiy
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Peter L Oliver
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell, UK.
| | - David M Bannerman
- Department of Experimental Psychology, University of Oxford, Oxford, UK.
| | - Stuart N Peirson
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
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Modulation of single cell circadian response to NMDA by diacylglycerol lipase inhibition reveals a role of endocannabinoids in light entrainment of the suprachiasmatic nucleus. Neuropharmacology 2021; 185:108455. [PMID: 33444638 DOI: 10.1016/j.neuropharm.2021.108455] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/23/2020] [Accepted: 01/05/2021] [Indexed: 12/11/2022]
Abstract
Suprachiasmatic nucleus (SCN) of the hypothalamus is the master clock that drives circadian rhythms in physiology and behavior and adjusts their timing to external cues. Neurotransmitter glutamate and glutamatergic receptors sensitive to N-methyl-d-aspartate (NMDA) play a dual role in the SCN by coupling astrocytic and neuronal single cell oscillators and by resetting their phase in response to light. Recent reports suggested that signaling by endogenous cannabinoids (ECs) participates in both of these functions. We have previously shown that ECs, such as 2-arachidonoylglycerol (2-AG), act via CB1 receptors to affect the SCN response to light-mimicking NMDA stimulus in a time-dependent manner. We hypothesized that this ability is linked to the circadian regulation of EC signaling. We demonstrate that circadian clock in the rat SCN regulates expression of 2-AG transport, synthesis and degradation enzymes as well as its receptors. Inhibition of the major 2-AG synthesis enzyme, diacylglycerol lipase, enhanced the phase delay and lowered the amplitude of explanted SCN rhythm in response to NMDAR activation. Using microscopic PER2 bioluminescence imaging, we visualized how individual single cell oscillators in different parts of the SCN respond to the DAGL inhibition/NMDAR activation and shape response of the whole pacemaker. Additionally, we present strong evidence that the zero amplitude behavior of the SCN in response to single NMDA stimulus in the middle of subjective night is the result of a loss of rhythm in individual SCN cells. The paper provides new insights into the modulatory role of endocannabinoid signaling during the light entrainment of the SCN.
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11
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Míková H, Kuchtiak V, Svobodová I, Spišská V, Pačesová D, Balík A, Bendová Z. Circadian Regulation of GluA2 mRNA Processing in the Rat Suprachiasmatic Nucleus and Other Brain Structures. Mol Neurobiol 2021; 58:439-449. [PMID: 32964314 DOI: 10.1007/s12035-020-02141-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/17/2020] [Indexed: 11/30/2022]
Abstract
The mammalian circadian system consists of a major circadian pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus and peripheral clocks in the body, including brain structures. The SCN depends on glutamatergic neurotransmission for transmitting signals from the retina, and it exhibits spontaneous 24-h rhythmicity in neural activity. The aim of this work was to evaluate the degree and circadian rhythmicity of AMPA receptor GluA2 subunit R/G editing and alternative flip/flop splicing in the SCN and other brain structures in Wistar rats. Our data show that the circadian rhythmicity in the SCN's GluA2 mRNA level was highest at dawn, while the circadian rhythm in R/G editing peaked at CT10 and the rhythmic flip varied with the acrophase at the late subjective night. The circadian rhythmicity was confirmed for R/G editing and splicing in the CA3 hippocampal area, and rhythmic variation of the flip isoform was also measured in the olfactory bulbs and cerebellum. The correlations between the R/G editing and alternative flip/flop splicing revealed a structure-dependent direction. In the hippocampus, the edited (G)-form level was positively correlated with the flip variant abundance, in accord with published data; by contrast, in the SCN, the flip variant was in associated more with the unedited (R) form. The edited (G) form and flop isoform also predominated in the retina and cerebellum.
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Affiliation(s)
- Hana Míková
- Faculty of Science, Department of Physiology, Charles University, Viničná 7, 128 43, Prague 2, Czech Republic
| | - Viktor Kuchtiak
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Irena Svobodová
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Veronika Spišská
- Faculty of Science, Department of Physiology, Charles University, Viničná 7, 128 43, Prague 2, Czech Republic
| | - Dominika Pačesová
- Faculty of Science, Department of Physiology, Charles University, Viničná 7, 128 43, Prague 2, Czech Republic
- National Institute of Mental Health, Klecany, Czech Republic
| | - Aleš Balík
- Faculty of Science, Department of Physiology, Charles University, Viničná 7, 128 43, Prague 2, Czech Republic.
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
- Department of Cellular Neurophysiology, Institute of Physiology, Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50, Vestec, Czech Republic.
| | - Zdeňka Bendová
- Faculty of Science, Department of Physiology, Charles University, Viničná 7, 128 43, Prague 2, Czech Republic.
- National Institute of Mental Health, Klecany, Czech Republic.
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12
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Gaucher Q, Yger P, Edeline JM. Increasing excitation versus decreasing inhibition in auditory cortex: consequences on the discrimination performance between communication sounds. J Physiol 2020; 598:3765-3785. [PMID: 32538485 DOI: 10.1113/jp279902] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 06/08/2020] [Indexed: 12/18/2022] Open
Abstract
KEY POINTS Enhancing cortical excitability can be achieved by either reducing intracortical inhibition or by enhancing intracortical excitation. Here we compare the consequences of reducing intracortical inhibition and of enhancing intracortical excitation on the processing of communication sounds in the primary auditory cortex. Local application of gabazine and of AMPA enlarged the spectrotemporal receptive fields and increased the responses to communication to the same extent. The Mutual Information (an index of the cortical neurons' ability to discriminate between natural sounds) was increased in both cases, as were the noise and signal correlations. Spike-timing reliability was only increased after gabazine application and post-excitation suppression was affected in the opposite way: it was increased when reducing the intracortical inhibition but was eliminated by enhancing the excitation. A computational model suggests that these results can be explained by an additive effect vs. a multiplicative effect ABSTRACT: The level of excitability of cortical circuits is often viewed as one of the critical factors controlling perceptive performance. In theory, enhancing cortical excitability can be achieved either by reducing inhibitory currents or by increasing excitatory currents. Here, we evaluated whether reducing inhibitory currents or increasing excitatory currents in auditory cortex similarly affects the neurons' ability to discriminate between communication sounds. We attenuated the inhibitory currents by application of gabazine (GBZ), and increased the excitatory currents by applying AMPA in the auditory cortex while testing frequency receptive fields and responses to communication sounds. GBZ and AMPA enlarged the receptive fields and increased the responses to communication sounds to the same extent. The spike-timing reliability of neuronal responses was largely increased when attenuating the intracortical inhibition but not after increasing the excitation. The discriminative abilities of cortical cells increased in both cases but this increase was more pronounced after attenuating the inhibition. The shape of the response to communication sounds was modified in the opposite direction: reducing inhibition increased post-excitation suppression whereas this suppression tended to disappear when increasing the excitation. A computational model indicates that the additive effect promoted by AMPA vs. the multiplicative effect of GBZ on neuronal responses, together with the dynamics of spontaneous cortical activity, can explain these differences. Thus, although apparently equivalent for increasing cortical excitability, acting on inhibition vs. on excitation impacts differently the cortical ability to discriminate natural stimuli, and only modulating inhibition changed efficiently the cortical representation of communication sounds.
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Affiliation(s)
- Quentin Gaucher
- Paris-Saclay Institute of Neurosciences (Neuro-PSI), Department Cognition and Behaviour, CNRS UMR 9197, Orsay Cedex, 91405, France.,Université Paris-Sud, Bâtiment 446, Orsay Cedex, 91405, France
| | - Pierre Yger
- Institut de la Vision, INSERM UMRS 968, UPMC UM 80, CNRS UMR 7210, Paris, France
| | - Jean-Marc Edeline
- Paris-Saclay Institute of Neurosciences (Neuro-PSI), Department Cognition and Behaviour, CNRS UMR 9197, Orsay Cedex, 91405, France.,Université Paris-Sud, Bâtiment 446, Orsay Cedex, 91405, France
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13
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Riedel CS, Georg B, Fahrenkrug J, Hannibal J. Altered light induced EGR1 expression in the SCN of PACAP deficient mice. PLoS One 2020; 15:e0232748. [PMID: 32379800 PMCID: PMC7205239 DOI: 10.1371/journal.pone.0232748] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 04/21/2020] [Indexed: 12/16/2022] Open
Abstract
The brain’s biological clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus and generates circadian rhythms in physiology and behavior. The circadian clock needs daily adjustment by light to stay synchronized (entrained) with the astronomical 24 h light/dark cycle. Light entrainment occurs via melanopsin expressing retinal ganglion cells (mRGCs) and two neurotransmitters of the retinohypothalamic tract (RHT), PACAP and glutamate, which transmit light information to the SCN neurons. In SCN neurons, light signaling involves the immediate-early genes Fos, Egr1 and the clock genes Per1 and Per2. In this study, we used PACAP deficient mice to evaluate PACAP’s role in light induced gene expression of EGR1 in SCN neurons during early (ZT17) and late (ZT23) subjective night at high (300 lux) and low (10 lux) white light exposure. We found significantly lower levels of both EGR1 mRNA and protein in the SCN in PACAP deficient mice compared to wild type mice at early subjective night (ZT17) exposed to low but not high light intensity. No difference was found between the two genotypes at late night (ZT23) at neither light intensities. In conclusion, light mediated EGR1 induction in SCN neurons at early night at low light intensities is dependent of PACAP signaling. A role of PACAP in shaping synaptic plasticity during light stimulation at night is discussed.
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Affiliation(s)
- Casper Schwartz Riedel
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
| | - Birgitte Georg
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
| | - Jan Fahrenkrug
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
| | - Jens Hannibal
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
- * E-mail:
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14
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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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15
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Sládek M, Sumová A. Modulation of NMDA-Mediated Clock Resetting in the Suprachiasmatic Nuclei of mPer2 Luc Mouse by Endocannabinoids. Front Physiol 2019; 10:361. [PMID: 30984034 PMCID: PMC6450388 DOI: 10.3389/fphys.2019.00361] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 03/14/2019] [Indexed: 11/29/2022] Open
Abstract
Light entrains the master circadian clock in the suprachiasmatic nucleus (SCN) predominantly through glutamatergic signaling via NMDA receptors. The magnitude and the direction of resulting phase shifts depend on timing of the photic stimulus. Previous reports based on behavioral and electrophysiological data suggested that endocannabinoids (EC) might reduce the ability of the SCN clock to respond to light. However, there is little direct evidence for the involvement of EC in entrainment of the rhythmic clock gene expression in the SCN. We have used luminescence recording of cultured SCN slices from mPer2Luc mice to construct a complete phase response curve (PRC) for NMDA receptor activation. The results demonstrated that NMDA administration phase-shifts the PER2 rhythm in a time-specific manner. A stable “singularity,” in the course of which the clock seemingly stops while the overall phase is caught between delays and advances, can occur in response to NMDA at a narrow interval during the PER2 level decrease. NMDA-induced phase delays were affected neither by the agonist (WIN 55,212-2 mesylate) nor by the antagonist (rimonabant hydrochloride) of EC receptors. However, the agonist significantly reduced the NMDA-induced phase advance of the clock, while the antagonist enhanced the phase advance, causing a shift in the sensitivity window of the SCN to NMDA. The modulation of EC signaling in the SCN had no effect by itself on the phase of the PER2 rhythm. The results provide evidence for a modulatory role of EC in photic entrainment of the circadian clock in the SCN.
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Affiliation(s)
- Martin Sládek
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Alena Sumová
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czechia
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16
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Timothy JWS, Klas N, Sanghani HR, Al-Mansouri T, Hughes ATL, Kirshenbaum GS, Brienza V, Belle MDC, Ralph MR, Clapcote SJ, Piggins HD. Circadian Disruptions in the Myshkin Mouse Model of Mania Are Independent of Deficits in Suprachiasmatic Molecular Clock Function. Biol Psychiatry 2018; 84:827-837. [PMID: 28689605 PMCID: PMC6218650 DOI: 10.1016/j.biopsych.2017.04.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 04/06/2017] [Accepted: 04/27/2017] [Indexed: 11/25/2022]
Abstract
BACKGROUND Alterations in environmental light and intrinsic circadian function have strong associations with mood disorders. The neural origins underpinning these changes remain unclear, although genetic deficits in the molecular clock regularly render mice with altered mood-associated phenotypes. METHODS A detailed circadian and light-associated behavioral characterization of the Na+/K+-ATPase α3 Myshkin (Myk/+) mouse model of mania was performed. Na+/K+-ATPase α3 does not reside within the core circadian molecular clockwork, but Myk/+ mice exhibit concomitant disruption in circadian rhythms and mood. The neural basis of this phenotype was investigated through molecular and electrophysiological dissection of the master circadian pacemaker, the suprachiasmatic nuclei (SCN). Light input and glutamatergic signaling to the SCN were concomitantly assessed through behavioral assays and calcium imaging. RESULTS In vivo assays revealed several circadian abnormalities including lengthened period and instability of behavioral rhythms, and elevated metabolic rate. Grossly aberrant responses to light included accentuated resetting, accelerated re-entrainment, and an absence of locomotor suppression. Bioluminescent recording of circadian clock protein (PERIOD2) output from ex vivo SCN revealed no deficits in Myk/+ molecular clock function. Optic nerve crush rescued the circadian period of Myk/+ behavior, highlighting that afferent inputs are critical upstream mediators. Electrophysiological and calcium imaging SCN recordings demonstrated changes in the response to glutamatergic stimulation as well as the electrical output indicative of altered retinal input processing. CONCLUSIONS The Myshkin model demonstrates profound circadian and light-responsive behavioral alterations independent of molecular clock disruption. Afferent light signaling drives behavioral changes and raises new mechanistic implications for circadian disruption in affective disorders.
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Affiliation(s)
- Joseph W S Timothy
- Faculty of Biology, Medicine, and Health, University of Manchester, Manchester
| | - Natasza Klas
- Faculty of Biology, Medicine, and Health, University of Manchester, Manchester
| | | | | | - Alun T L Hughes
- Faculty of Biology, Medicine, and Health, University of Manchester, Manchester
| | - Greer S Kirshenbaum
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Vincent Brienza
- Department of Psychology, University of Toronto, Toronto, Canada
| | - Mino D C Belle
- Faculty of Biology, Medicine, and Health, University of Manchester, Manchester
| | - Martin R Ralph
- Department of Psychology, University of Toronto, Toronto, Canada
| | - Steven J Clapcote
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Hugh D Piggins
- Faculty of Biology, Medicine, and Health, University of Manchester, Manchester.
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17
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Davies B, Brown LA, Cais O, Watson J, Clayton AJ, Chang VT, Biggs D, Preece C, Hernandez-Pliego P, Krohn J, Bhomra A, Twigg SRF, Rimmer A, Kanapin A, Sen A, Zaiwalla Z, McVean G, Foster R, Donnelly P, Taylor JC, Blair E, Nutt D, Aricescu AR, Greger IH, Peirson SN, Flint J, Martin HC. A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability. Hum Mol Genet 2018; 26:3869-3882. [PMID: 29016847 PMCID: PMC5639461 DOI: 10.1093/hmg/ddx270] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 07/06/2017] [Indexed: 01/19/2023] Open
Abstract
The discovery of genetic variants influencing sleep patterns can shed light on the physiological processes underlying sleep. As part of a large clinical sequencing project, WGS500, we sequenced a family in which the two male children had severe developmental delay and a dramatically disturbed sleep-wake cycle, with very long wake and sleep durations, reaching up to 106-h awake and 48-h asleep. The most likely causal variant identified was a novel missense variant in the X-linked GRIA3 gene, which has been implicated in intellectual disability. GRIA3 encodes GluA3, a subunit of AMPA-type ionotropic glutamate receptors (AMPARs). The mutation (A653T) falls within the highly conserved transmembrane domain of the ion channel gate, immediately adjacent to the analogous residue in the Grid2 (glutamate receptor) gene, which is mutated in the mouse neurobehavioral mutant, Lurcher. In vitro, the GRIA3(A653T) mutation stabilizes the channel in a closed conformation, in contrast to Lurcher. We introduced the orthologous mutation into a mouse strain by CRISPR-Cas9 mutagenesis and found that hemizygous mutants displayed significant differences in the structure of their activity and sleep compared to wild-type littermates. Typically, mice are polyphasic, exhibiting multiple sleep bouts of sleep several minutes long within a 24-h period. The Gria3A653T mouse showed significantly fewer brief bouts of activity and sleep than the wild-types. Furthermore, Gria3A653T mice showed enhanced period lengthening under constant light compared to wild-type mice, suggesting an increased sensitivity to light. Our results suggest a role for GluA3 channel activity in the regulation of sleep behavior in both mice and humans.
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Affiliation(s)
- Benjamin Davies
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK
| | - Laurence A Brown
- Nuffield Department of Clinical Neurosciences, Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, Oxfordshire OX3 9DU, UK
| | - Ondrej Cais
- Medical Research Council (MRC) Laboratory of Molecular Biology, Neurobiology Division, Cambridge, Cambridgeshire CB2 0QH, UK
| | - Jake Watson
- Medical Research Council (MRC) Laboratory of Molecular Biology, Neurobiology Division, Cambridge, Cambridgeshire CB2 0QH, UK
| | - Amber J Clayton
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK
| | - Veronica T Chang
- Medical Research Council (MRC) Laboratory of Molecular Biology, Neurobiology Division, Cambridge, Cambridgeshire CB2 0QH, UK
| | - Daniel Biggs
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK
| | - Christopher Preece
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK
| | | | - Jon Krohn
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK
| | - Amarjit Bhomra
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK
| | - Stephen R F Twigg
- Clinical Genetics Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, Oxfordshire OX3 9DS, UK
| | | | - Alexander Kanapin
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK.,Department of Oncology, University of Oxford, Oxford, Oxfordshire OX3 7DQ, UK
| | | | - Arjune Sen
- Oxford Epilepsy Research Group, NIHR Biomedical Research Centre, Nuffield Department of Clinical Neuroscience, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Zenobia Zaiwalla
- Department of Neuroscience, John Radcliffe Hospital, Oxford, Oxfordshire OX3 9DU, UK
| | - Gil McVean
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK.,Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, Oxfordshire OX3 7FZ, UK
| | - Russell Foster
- Nuffield Department of Clinical Neurosciences, Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, Oxfordshire OX3 9DU, UK
| | - Peter Donnelly
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK.,Department of Statistics, University of Oxford, Oxford, Oxfordshire OX1 3LB, UK
| | - Jenny C Taylor
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire OX3 7BN, UK.,National Institute for Health Research Oxford Biomedical Research Centre (NIHR Oxford BRC), Oxford, Oxfordshire OX3 7LE, UK
| | - Edward Blair
- Department of Clinical Genetics, Oxford University Hospitals NHS Trust, Oxford, Oxfordshire OX3 7HE, UK
| | - David Nutt
- Division of Brain Sciences, Department of Medicine, Centre for Neuropsychopharmacology, Imperial College London, London W12 0NN, UK
| | - A Radu Aricescu
- Medical Research Council (MRC) Laboratory of Molecular Biology, Neurobiology Division, Cambridge, Cambridgeshire CB2 0QH, UK
| | - Ingo H Greger
- Medical Research Council (MRC) Laboratory of Molecular Biology, Neurobiology Division, Cambridge, Cambridgeshire CB2 0QH, UK
| | - Stuart N Peirson
- Nuffield Department of Clinical Neurosciences, Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, Oxfordshire OX3 9DU, UK
| | - Jonathan Flint
- Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, University of California-Los Angeles, CA 90095, USA
| | - Hilary C Martin
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, UK
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18
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Kiessling S, O'Callaghan EK, Freyburger M, Cermakian N, Mongrain V. The cell adhesion molecule EphA4 is involved in circadian clock functions. GENES BRAIN AND BEHAVIOR 2017; 17:82-92. [PMID: 28425198 DOI: 10.1111/gbb.12387] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/11/2017] [Accepted: 04/11/2017] [Indexed: 12/29/2022]
Abstract
Circadian (∼24 h) rhythms of cellular network plasticity in the central circadian clock, the suprachiasmatic nucleus (SCN), have been described. The neuronal network in the SCN regulates photic resetting of the circadian clock as well as stability of the circadian system during both entrained and constant conditions. EphA4, a cell adhesion molecule regulating synaptic plasticity by controlling connections of neurons and astrocytes, is expressed in the SCN. To address whether EphA4 plays a role in circadian photoreception and influences the neuronal network of the SCN, we have analyzed circadian wheel-running behavior of EphA4 knockout (EphA4-/- ) mice under different light conditions and upon photic resetting, as well as their light-induced protein response in the SCN. EphA4-/- mice exhibited reduced wheel-running activity, longer endogenous periods under constant darkness and shorter periods under constant light conditions, suggesting an effect of EphA4 on SCN function. Moreover, EphA4-/- mice exhibited suppressed phase delays of their wheel-running activity following a light pulse during the beginning of the subjective night (CT15). Accordingly, light-induced c-FOS (FBJ murine osteosarcoma viral oncogene homolog) expression was diminished. Our results suggest a circadian role for EphA4 in the SCN neuronal network, affecting the circadian system and contributing to the circadian response to light.
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Affiliation(s)
- S Kiessling
- Douglas Mental Health University Institute, McGill University, Montreal, QC, Canada.,Present address: Nutrition and Immunology, Technical University of Munich, Freising, Germany
| | - E K O'Callaghan
- Center for Advanced Research in Sleep Medicine and Research Center, Hôpital du Sacré-Coeur de Montréal, Montreal, QC, Canada.,Department of Neuroscience, Université de Montréal, Montreal, QC, Canada
| | - M Freyburger
- Center for Advanced Research in Sleep Medicine and Research Center, Hôpital du Sacré-Coeur de Montréal, Montreal, QC, Canada.,Department of Neuroscience, Université de Montréal, Montreal, QC, Canada
| | - N Cermakian
- Douglas Mental Health University Institute, McGill University, Montreal, QC, Canada
| | - V Mongrain
- Center for Advanced Research in Sleep Medicine and Research Center, Hôpital du Sacré-Coeur de Montréal, Montreal, QC, Canada.,Department of Neuroscience, Université de Montréal, Montreal, QC, Canada
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19
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Dojo K, Yamaguchi Y, Fustin JM, Doi M, Kobayashi M, Okamura H. Carbachol Induces Phase-dependent Phase Shifts of Per1 Transcription Rhythms in Cultured Suprachiasmatic Nucleus Slices. J Biol Rhythms 2017; 32:101-108. [PMID: 28470123 DOI: 10.1177/0748730417691205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Among nonphotic stimulants, a classic cholinergic agonist, carbachol, is known to have a strong and unique phase-resetting effect on the circadian clock: Intracerebroventricular carbachol treatment causes phase delays during the subjective early night and phase advances in the subjective late night, but the effects of this drug on the suprachiasmatic nucleus (SCN) in vivo and in vitro are still controversial. In the present study, we succeeded in reproducing the biphasic phase-shifting effect of carbachol on clock gene expression in organotypic SCN slices prepared from mice carrying a Per1-promoter fused luciferase gene ( Per1-luc). Since this biphasic effect of carbachol in Per1-luc SCN was prevented by atropine but not by mecamylamine, we concluded that these phase shifts were muscarinic receptor-dependent. Next, we analyzed the expression of muscarinic receptors in the SCN by in situ hybridization and found that M3 and M4 subtypes were expressed in SCN cells. These signals appeared neonatally and reached adult levels at postnatal day 10. Together, these findings suggest that carbachol has a phase-dependent phase-shifting effect on the SCN clock through muscarinic receptor subtypes expressed in the SCN.
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Affiliation(s)
- Kumiko Dojo
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Yoshiaki Yamaguchi
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Jean-Michel Fustin
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Masao Doi
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Masaki Kobayashi
- Department of Electronics and Intelligent Systems, Tohoku Institute of Technology, Sendai, Japan
| | - Hitoshi Okamura
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
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20
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Millan MJ, Rivet JM, Gobert A. The frontal cortex as a network hub controlling mood and cognition: Probing its neurochemical substrates for improved therapy of psychiatric and neurological disorders. J Psychopharmacol 2016; 30:1099-1128. [PMID: 27756833 DOI: 10.1177/0269881116672342] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The highly-interconnected and neurochemically-rich frontal cortex plays a crucial role in the regulation of mood and cognition, domains disrupted in depression and other central nervous system disorders, and it is an important site of action for their therapeutic control. For improving our understanding of the function and dysfunction of the frontal cortex, and for identifying improved treatments, quantification of extracellular pools of neuromodulators by microdialysis in freely-moving rodents has proven indispensable. This approach has revealed a complex mesh of autoreceptor and heteroceptor interactions amongst monoaminergic pathways, and led from selective 5-HT reuptake inhibitors to novel classes of multi-target drugs for treating depression like the mixed α2-adrenoceptor/5-HT reuptake inhibitor, S35966, and the clinically-launched vortioxetine and vilazodone. Moreover, integration of non-monoaminergic actions resulted in the discovery and development of the innovative melatonin receptor agonist/5-HT2C receptor antagonist, Agomelatine. Melatonin levels, like those of corticosterone and the "social hormone", oxytocin, can now be quantified by microdialysis over the full 24 h daily cycle. Further, the introduction of procedures for measuring extracellular histamine and acetylcholine has provided insights into strategies for improving cognition by, for example, blockade of 5-HT6 and/or dopamine D3 receptors. The challenge of concurrently determining extracellular levels of GABA, glutamate, d-serine, glycine, kynurenate and other amino acids, and of clarifying their interactions with monoamines, has also been resolved. This has proven important for characterizing the actions of glycine reuptake inhibitors that indirectly augment transmission at N-methyl-d-aspartate receptors, and of "glutamatergic antidepressants" like ketamine, mGluR5 antagonists and positive modulators of AMPA receptors (including S47445). Most recently, quantification of the neurotoxic proteins Aβ42 and Tau has extended microdialysis studies to the pathogenesis of neurodegenerative disorders, and another frontier currently being broached is microRNAs. The present article discusses the above themes, focusses on recent advances, highlights opportunities for clinical "translation", and suggests avenues for further progress.
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Affiliation(s)
- Mark J Millan
- Pole for Therapeutic Innovation in CNS disorders, IDR Servier, Croissy-sur-Seine, France
| | - Jean-Michel Rivet
- Pole for Therapeutic Innovation in CNS disorders, IDR Servier, Croissy-sur-Seine, France
| | - Alain Gobert
- Pole for Therapeutic Innovation in CNS disorders, IDR Servier, Croissy-sur-Seine, France
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21
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Abstract
The suprachiasmatic nucleus (SCN) receives direct retinal input from the intrinsically photosensitive retinal ganglion cells (ipRGCs) for circadian photoentrainment. Interestingly, the SCN is the only brain region that receives equal inputs from the left and right eyes. Despite morphological assessments showing that axonal fibers originating from ipRGCs cover the entire SCN, physiological evidence suggests that only vasoactive intestinal polypeptide (VIP)/gastrin-releasing peptide (GRP) cells located ventrally in the SCN receive retinal input. It is still unclear, therefore, which subpopulation of SCN neurons receives synaptic input from the retina and how the SCN receives equal inputs from both eyes. Here, using single ipRGC axonal tracing and a confocal microscopic analysis in mice, we show that ipRGCs have elaborate innervation patterns throughout the entire SCN. Unlike conventional retinal ganglion cells (RGCs) that innervate visual targets either ipsilaterally or contralaterally, a single ipRGC can bilaterally innervate the SCN. ipRGCs form synaptic contacts with major peptidergic cells of the SCN, including VIP, GRP, and arginine vasopressin (AVP) neurons, with each ipRGC innervating specific subdomains of the SCN. Furthermore, a single SCN-projecting ipRGC can send collateral inputs to many other brain regions. However, the size and complexity of the axonal arborizations in non-SCN regions are less elaborate than those in the SCN. Our results provide a better understanding of how retinal neurons connect to the central circadian pacemaker to synchronize endogenous circadian clocks with the solar day.
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22
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Koo J, Choe HK, Kim HD, Chun SK, Son GH, Kim K. Effect of Mefloquine, a Gap Junction Blocker, on Circadian Period2 Gene Oscillation in the Mouse Suprachiasmatic Nucleus Ex Vivo. Endocrinol Metab (Seoul) 2015; 30:361-70. [PMID: 25491783 PMCID: PMC4595362 DOI: 10.3803/enm.2015.30.3.361] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 07/31/2014] [Accepted: 10/17/2014] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND In mammals, the master circadian pacemaker is localized in an area of the ventral hypothalamus known as the suprachiasmatic nucleus (SCN). Previous studies have shown that pacemaker neurons in the SCN are highly coupled to one another, and this coupling is crucial for intrinsic self-sustainability of the SCN central clock, which is distinguished from peripheral oscillators. One plausible mechanism underlying the intercellular communication may involve direct electrical connections mediated by gap junctions. METHODS We examined the effect of mefloquine, a neuronal gap junction blocker, on circadian Period 2 (Per2) gene oscillation in SCN slice cultures prepared from Per2::luciferase (PER2::LUC) knock-in mice using a real-time bioluminescence measurement system. RESULTS Administration of mefloquine causes instability in the pulse period and a slight reduction of amplitude in cyclic PER2::LUC expression. Blockade of gap junctions uncouples PER2::LUC-expressing cells, in terms of phase transition, which weakens synchrony among individual cellular rhythms. CONCLUSION These findings suggest that neuronal gap junctions play an important role in synchronizing the central pacemaker neurons and contribute to the distinct self-sustainability of the SCN master clock.
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Affiliation(s)
- Jinmi Koo
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Han Kyoung Choe
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Hee Dae Kim
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Sung Kook Chun
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Gi Hoon Son
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Legal Medicine, Korea University College of Medicine, Seoul, Korea
| | - Kyungjin Kim
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea.
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Bunney BG, Li JZ, Walsh DM, Stein R, Vawter MP, Cartagena P, Barchas JD, Schatzberg AF, Myers RM, Watson SJ, Akil H, Bunney WE. Circadian dysregulation of clock genes: clues to rapid treatments in major depressive disorder. Mol Psychiatry 2015; 20:48-55. [PMID: 25349171 PMCID: PMC4765913 DOI: 10.1038/mp.2014.138] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 09/06/2014] [Accepted: 09/10/2014] [Indexed: 12/19/2022]
Abstract
Conventional antidepressants require 2-8 weeks for a full clinical response. In contrast, two rapidly acting antidepressant interventions, low-dose ketamine and sleep deprivation (SD) therapy, act within hours to robustly decrease depressive symptoms in a subgroup of major depressive disorder (MDD) patients. Evidence that MDD may be a circadian-related illness is based, in part, on a large set of clinical data showing that diurnal rhythmicity (sleep, temperature, mood and hormone secretion) is altered during depressive episodes. In a microarray study, we observed widespread changes in cyclic gene expression in six regions of postmortem brain tissue of depressed patients matched with controls for time-of-death (TOD). We screened 12 000 transcripts and observed that the core clock genes, essential for controlling virtually all rhythms in the body, showed robust 24-h sinusoidal expression patterns in six brain regions in control subjects. In MDD patients matched for TOD with controls, the expression patterns of the clock genes in brain were significantly dysregulated. Some of the most robust changes were seen in anterior cingulate (ACC). These findings suggest that in addition to structural abnormalities, lesion studies, and the large body of functional brain imaging studies reporting increased activation in the ACC of depressed patients who respond to a wide range of therapies, there may be a circadian dysregulation in clock gene expression in a subgroup of MDDs. Here, we review human, animal and neuronal cell culture data suggesting that both low-dose ketamine and SD can modulate circadian rhythms. We hypothesize that the rapid antidepressant actions of ketamine and SD may act, in part, to reset abnormal clock genes in MDD to restore and stabilize circadian rhythmicity. Conversely, clinical relapse may reflect a desynchronization of the clock, indicative of a reactivation of abnormal clock gene function. Future work could involve identifying specific small molecules capable of resetting and stabilizing clock genes to evaluate if they can rapidly relieve symptoms and sustain improvement.
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Affiliation(s)
- BG Bunney
- Department of Psychiatry and Human Behavior, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - JZ Li
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - DM Walsh
- Department of Psychiatry and Human Behavior, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - R Stein
- Department of Psychiatry and Human Behavior, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - MP Vawter
- Department of Psychiatry and Human Behavior, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - P Cartagena
- Department of Psychiatry and Human Behavior, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - JD Barchas
- Department of Psychiatry, Weill Cornell Medical College, New York, NY, USA
| | - AF Schatzberg
- Department of Psychiatry, Stanford University, Palo Alto, CA, USA
| | - RM Myers
- HudsonAlpha, Institute for Biotechnology, Huntsville, AL, USA
| | - SJ Watson
- Department of Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
| | - H Akil
- Department of Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
| | - WE Bunney
- Department of Psychiatry and Human Behavior, School of Medicine, University of California, Irvine, Irvine, CA, USA
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Yamada Y, Prosser RA. Copper chelation and exogenous copper affect circadian clock phase resetting in the suprachiasmatic nucleus in vitro. Neuroscience 2013; 256:252-61. [PMID: 24161278 DOI: 10.1016/j.neuroscience.2013.10.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 10/14/2013] [Accepted: 10/14/2013] [Indexed: 10/26/2022]
Abstract
Light stimulates specialized retinal ganglion cells to release glutamate (Glu) onto circadian clock neurons of the suprachiasmatic nucleus (SCN). Glu resets the phase of the SCN circadian clock by activating N-methyl-d-aspartate receptors (NMDAR) causing either delays or advances in the clock phase, depending on early- or late-night stimulation, respectively. In addition, these Glu-induced phase shifts require tropomyosin receptor kinase B (TrkB) receptor activity. Previous studies show that copper (Cu) released at hippocampal synapses can inhibit NMDAR activity, and application of exogenous Cu likewise inhibits NMDAR activity. We investigated the effects of Cu in acute SCN brain slices prepared from C57BL/6Nhsd adult, male mice using treatments that decrease or increase available Cu levels in vitro and recorded neuronal activity on the following day. When bath-applied for 10 min at zeitgeber time (ZT) 16 (where ZT0=lights-on in the donor animal colony), the Cu-specific chelators tetrathiomolybdate (TTM) and bathocuproine disulfonate each induce ∼2.5-3-h phase delays in circadian neuronal activity rhythms, similarly to Glu-induced phase delays. Co-application of 10 μM CuCl2, but not 10 μM CoCl₂ blocks TTM-induced phase delays. Furthermore, TTM causes phase advances when applied at ZT23. At both application times, TTM-induced phase shifts are blocked by NMDA or TrkB receptor antagonists. Surprisingly, bath-application of 10 μM Cu alone also induces phase shifts in analogous experiments at ZT16 and ZT23. Inhibiting NMDAR does not block Cu-induced phase shifts. TrkB inhibition blocks Cu-induced phase delays but not phase advances. Thus, increasing and decreasing Cu availability appear to shift the SCN clock phase through different mechanisms, at least at the receptor level. We propose that Cu plays a role in the SCN circadian clock by modulating Glu signaling.
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Affiliation(s)
- Y Yamada
- University of Tennessee, Knoxville, Department of Biochemistry, Cellular and Molecular Biology, Knoxville, TN 37996, USA
| | - R A Prosser
- University of Tennessee, Knoxville, Department of Biochemistry, Cellular and Molecular Biology, Knoxville, TN 37996, USA.
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Lall GS, Atkinson LA, Corlett SA, Broadbridge PJ, Bonsall DR. Circadian entrainment and its role in depression: a mechanistic review. J Neural Transm (Vienna) 2012; 119:1085-96. [PMID: 22798027 DOI: 10.1007/s00702-012-0858-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 06/27/2012] [Indexed: 12/24/2022]
Abstract
The natural rotation of the earth generates an environmental day-night cycle that repeats every 24 h. This daily transition from dawn to dusk provides one of the most important time cues to which the majority of organisms synchronise their activity. Under these conditions, natural light, a photic stimulus, provides the principal entraining cue. In mammals, an endogenous circadian pacemaker located within the suprachiasmatic nucleus (SCN) of the hypothalamus acts as a coordinating centre to align physiological activity with the environmental light-dark cycle. However, the SCN also receives regulatory input from a number of behavioural, non-photic, cues such as physical activity, social interactions and feeding routines. The unique ability of the SCN to integrate both photic and non-photic cues allows it to generate a rhythm that is tailored to the individual and entrained to the environment. Here, we review the key neurotransmitter systems involved in both photic and non-photic transmission to the SCN and their interactions that assist in generating an entrained output rhythm. We also consider the impact on health of a desynchronised circadian system with a focus on depressive affective disorders and current therapies aimed at manipulating the relationship between photic and non-photic SCN regulators.
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Affiliation(s)
- G S Lall
- Medway School of Pharmacy, University of Kent, Chatham ME4 4TB, UK.
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Positive and negative modulation of circadian activity rhythms by mGluR5 and mGluR2/3 metabotropic glutamate receptors. Neuropharmacology 2010; 60:209-15. [PMID: 20831878 DOI: 10.1016/j.neuropharm.2010.08.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/25/2010] [Accepted: 08/27/2010] [Indexed: 11/23/2022]
Abstract
Glutamate released from retinal ganglion cells conveys information about the daily light:dark cycle to master circadian pacemaker neurons within the suprachiasmatic nucleus that then synchronize internal circadian rhythms with the external day-length. Glutamate activation of ionotropic glutamate receptors in the suprachiasmatic nucleus is well established, but the function of the metabotropic glutamate receptors that are also located in this nucleus is not known. Therefore, in this study we evaluated agonists and antagonists acting at orthosteric or allosteric sites for mGluR5 and mGluR2/3 metabotropic glutamate receptors for their ability to modulate light-induced phase advances and delays of hamster circadian activity rhythms. mGluR5 allosteric antagonists fenobam, MPEP and MTEP, each 10 mg/kg, potentiated light-induced phase advances of hamster circadian activity rhythms, while the mGluR5 agonists CHPG, (S)-3,5-DHPG or positive allosteric modulator CDPPB had no effect. Neither mGluR5 agonists nor antagonists had any effect on light-induced phase delays of activity rhythms. The competitive mGluR2/3 antagonist LY341495, 10 mg/kg, also potentiated light-induced phase advances, but inhibited light-induced phase delays. The mGluR2/3 agonists LY354740 and LY404039 were without effect on phase advances while a third agonist LY379268, 10 mg/kg, inhibited both light-induced advances and delays. Finally, mGluR2/3 agonists LY379268 and LY404039 also inhibited light-induced phase delays of activity rhythms. These results suggest that during light-induced phase advances, mGluR2/3 and mGluR5 receptors act to negatively modulate the effects of light on the circadian pacemaker or its output(s). mGluR5 receptors do not appear to be involved during light-induced phase delays. In contrast, the role for mGluR2/3 receptors during phase delays is more complicated as both agonists and antagonists inhibit light-induced phase delays. Dysfunctions in human circadian rhythms have been implicated in some forms of depression, and metabotropic glutamate receptor ligands, which are also being evaluated for antidepressant activity, are shown here to be capable of modifying light-induced phase shifts of circadian activity rhythms.
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