1
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Stengl M, Schneider AC. Contribution of membrane-associated oscillators to biological timing at different timescales. Front Physiol 2024; 14:1243455. [PMID: 38264332 PMCID: PMC10803594 DOI: 10.3389/fphys.2023.1243455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 12/12/2023] [Indexed: 01/25/2024] Open
Abstract
Environmental rhythms such as the daily light-dark cycle selected for endogenous clocks. These clocks predict regular environmental changes and provide the basis for well-timed adaptive homeostasis in physiology and behavior of organisms. Endogenous clocks are oscillators that are based on positive feedforward and negative feedback loops. They generate stable rhythms even under constant conditions. Since even weak interactions between oscillators allow for autonomous synchronization, coupling/synchronization of oscillators provides the basis of self-organized physiological timing. Amongst the most thoroughly researched clocks are the endogenous circadian clock neurons in mammals and insects. They comprise nuclear clockworks of transcriptional/translational feedback loops (TTFL) that generate ∼24 h rhythms in clock gene expression entrained to the environmental day-night cycle. It is generally assumed that this TTFL clockwork drives all circadian oscillations within and between clock cells, being the basis of any circadian rhythm in physiology and behavior of organisms. Instead of the current gene-based hierarchical clock model we provide here a systems view of timing. We suggest that a coupled system of autonomous TTFL and posttranslational feedback loop (PTFL) oscillators/clocks that run at multiple timescales governs adaptive, dynamic homeostasis of physiology and behavior. We focus on mammalian and insect neurons as endogenous oscillators at multiple timescales. We suggest that neuronal plasma membrane-associated signalosomes constitute specific autonomous PTFL clocks that generate localized but interlinked oscillations of membrane potential and intracellular messengers with specific endogenous frequencies. In each clock neuron multiscale interactions of TTFL and PTFL oscillators/clocks form a temporally structured oscillatory network with a common complex frequency-band comprising superimposed multiscale oscillations. Coupling between oscillator/clock neurons provides the next level of complexity of an oscillatory network. This systemic dynamic network of molecular and cellular oscillators/clocks is suggested to form the basis of any physiological homeostasis that cycles through dynamic homeostatic setpoints with a characteristic frequency-band as hallmark. We propose that mechanisms of homeostatic plasticity maintain the stability of these dynamic setpoints, whereas Hebbian plasticity enables switching between setpoints via coupling factors, like biogenic amines and/or neuropeptides. They reprogram the network to a new common frequency, a new dynamic setpoint. Our novel hypothesis is up for experimental challenge.
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Affiliation(s)
- Monika Stengl
- Department of Biology, Animal Physiology/Neuroethology, University of Kassel, Kassel, Germany
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2
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Osuna-Lopez F, Reyes-Mendez ME, Herrera-Zamora JM, Gongora-Alfaro JL, Moreno-Galindo EG, Alamilla J. GABA Neurotransmission of the Suprachiasmatic Nucleus Is Modified During Rat Postnatal Development. J Biol Rhythms 2021; 36:567-574. [PMID: 34643150 DOI: 10.1177/07487304211048052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is the brain structure that controls circadian rhythms in mammals. The SCN is formed by two neuroanatomical regions: the ventral and dorsal. Gamma-aminobutyric acid (GABA) neurotransmission is important for the regulation of circadian rhythms. Excitatory GABA effects have been described in both SCN regions displaying a circadian variation. Moreover, the GABAergic system transfers photic information from the ventral to the dorsal SCN. However, there is almost no knowledge about GABA neurotransmission during the prenatal or postnatal development of the SCN. Here, we used whole-cell patch-clamp recordings to study spontaneous inhibitory postsynaptic currents (IPSCs) in the two SCN regions, at two zeitgeber times (day or night), and at four postnatal (P) ages: P3-5, P7-9, P12-15, and P20-25. The results herein show that the three analyzed parameters of the IPSCs, frequency, amplitude, and decay time, were significantly affected by the postnatal age: mostly, the IPSC frequency increased with age, principally in the ventral SCN in both day and night recordings; similarly, the amplitude of IPSCs augmented with age, especially at night, whereas the IPSC decay time was reduced (it was faster) with postnatal age, mainly during the day. Our findings first reveal that parameters of GABA neurotransmission are modified by postnatal development, implying that synaptic adjustments are required for an appropriate maturation of the GABAergic system in the SCN.
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Affiliation(s)
- Fernando Osuna-Lopez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
| | - Miriam E Reyes-Mendez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
| | | | - Jose Luis Gongora-Alfaro
- Departamento de Neurociencias, Centro de Investigaciones Regionales "Dr. Hideyo Noguchi," Universidad Autónoma de Yucatán, Mérida, Mexico
| | - Eloy G Moreno-Galindo
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
| | - Javier Alamilla
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico.,Consejo Nacional de Ciencia y Tecnología, Universidad de Colima, Colima, Mexico
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3
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Reyes-Mendez ME, Herrera-Zamora JM, Osuna-López F, Navarro-Polanco RA, Mendoza-Muñoz N, Góngora-Alfaro JL, Moreno-Galindo EG, Alamilla J. Light stimulation during postnatal development is not determinant for glutamatergic neurotransmission from the retinohypothalamic tract to the suprachiasmatic nucleus in rats. Eur J Neurosci 2021; 54:4497-4513. [PMID: 33998729 DOI: 10.1111/ejn.15312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 05/09/2021] [Accepted: 05/10/2021] [Indexed: 11/28/2022]
Abstract
The hypothalamic suprachiasmatic nucleus (SCN) is the leading circadian pacemaker in mammals, which synchronizes with environmental light through the retinohypothalamic tract (RHT). Although the SCN regulates circadian rhythms before birth, postnatal synaptic changes are needed for the RHT-SCN pathway to achieve total functional development. However, it is unknown whether visual experience affects developmental maturation. Here, we studied the effects of constant darkness (DD) rearing on the physiology (at pre- and postsynaptic levels) of glutamatergic neurotransmission between RHT and SCN during postnatal development in rats. Upon recording spontaneous and evoked excitatory postsynaptic currents (EPSCs) by electrical stimulation of RHT fibers, we found that DD animals at early postnatal ages (P3-19) exhibited different frequencies of spontaneous EPSCs and lower synaptic performance (short-term depression, release sites, and recruitment of RHT fibers) when compared with their normal light/dark (LD) counterparts. At the oldest age evaluated (P30-35), there was a synaptic response strengthening (probability of release, vesicular re-filling rate, and reduced synaptic depression) in DD rats, which functionally equaled (or surmounted) that of LD animals. Control experiments evaluating EPSCs in ventral SCN neurons of LD rats during day and night revealed no significant differences in spontaneous or evoked EPSCs by high-frequency trains in the RHT at any postnatal age. Our results suggest that DD conditions induce a compensatory mechanism in the glutamatergic signaling of the circadian system to increase the chances of synchronization to light at adult ages, and that the synaptic properties of RHT terminals during postnatal development are not critically influenced by environmental light.
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Affiliation(s)
- Miriam E Reyes-Mendez
- Centro Universitario de Investigaciones Biomédicas "CUIB", Universidad de Colima, Villas de San Sebastián, Colima, México
| | - J Manuel Herrera-Zamora
- Centro Universitario de Investigaciones Biomédicas "CUIB", Universidad de Colima, Villas de San Sebastián, Colima, México
| | - Fernando Osuna-López
- Centro Universitario de Investigaciones Biomédicas "CUIB", Universidad de Colima, Villas de San Sebastián, Colima, México
| | - Ricardo A Navarro-Polanco
- Centro Universitario de Investigaciones Biomédicas "CUIB", Universidad de Colima, Villas de San Sebastián, Colima, México
| | | | - José L Góngora-Alfaro
- Departamento de Neurociencias, Centro de Investigaciones Regionales "Dr. Hideyo Noguchi", Universidad Autónoma de Yucatán, Avenida Itzáes 490, Mérida, 97000, México
| | - Eloy G Moreno-Galindo
- Centro Universitario de Investigaciones Biomédicas "CUIB", Universidad de Colima, Villas de San Sebastián, Colima, México
| | - Javier Alamilla
- Centro Universitario de Investigaciones Biomédicas "CUIB", Universidad de Colima, Villas de San Sebastián, Colima, México.,Consejo Nacional de Ciencia y Tecnología (CONACYT), Universidad de Colima, Colima, México
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4
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Lalic T, Steponenaite A, Wei L, Vasudevan SR, Mathie A, Peirson SN, Lall GS, Cader MZ. TRESK is a key regulator of nocturnal suprachiasmatic nucleus dynamics and light adaptive responses. Nat Commun 2020; 11:4614. [PMID: 32929069 PMCID: PMC7490422 DOI: 10.1038/s41467-020-17978-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 07/24/2020] [Indexed: 11/25/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) is a complex structure dependent upon multiple mechanisms to ensure rhythmic electrical activity that varies between day and night, to determine circadian adaptation and behaviours. SCN neurons are exposed to glutamate from multiple sources including from the retino-hypothalamic tract and from astrocytes. However, the mechanism preventing inappropriate post-synaptic glutamatergic effects is unexplored and unknown. Unexpectedly we discovered that TRESK, a calcium regulated two-pore potassium channel, plays a crucial role in this system. We propose that glutamate activates TRESK through NMDA and AMPA mediated calcium influx and calcineurin activation to then oppose further membrane depolarisation and rising intracellular calcium. Hence, in the absence of TRESK, glutamatergic activity is unregulated leading to membrane depolarisation, increased nocturnal SCN firing, inverted basal calcium levels and impaired sensitivity in light induced phase delays. Our data reveals TRESK plays an essential part in SCN regulatory mechanisms and light induced adaptive behaviours. The suprachiasmatic nucleus (SCN) ensures rhythmic electrical activity that varies between day and night to determine circadian behaviours. The authors show that TRESK channels provide a feedback mechanism to maintain the SCN in the appropriate state for nocturnal light-induced behavioural changes.
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Affiliation(s)
- Tatjana Lalic
- Translational Molecular Neuroscience Group, Weatherall Institute of Molecular Medicine, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Aiste Steponenaite
- Medway School of Pharmacy, University of Kent and University of Greenwich, Anson Building, Central Avenue, Chatham, Kent, ME4 4TB, UK
| | - Liting Wei
- Translational Molecular Neuroscience Group, Weatherall Institute of Molecular Medicine, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | | | - Alistair Mathie
- Medway School of Pharmacy, University of Kent and University of Greenwich, Anson Building, Central Avenue, Chatham, Kent, ME4 4TB, UK
| | - Stuart N Peirson
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
| | - Gurprit S Lall
- Medway School of Pharmacy, University of Kent and University of Greenwich, Anson Building, Central Avenue, Chatham, Kent, ME4 4TB, UK.
| | - M Zameel Cader
- Translational Molecular Neuroscience Group, Weatherall Institute of Molecular Medicine, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
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5
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Ono D, Honma KI, Honma S. GABAergic mechanisms in the suprachiasmatic nucleus that influence circadian rhythm. J Neurochem 2020; 157:31-41. [PMID: 32198942 DOI: 10.1111/jnc.15012] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/06/2020] [Accepted: 03/09/2020] [Indexed: 01/23/2023]
Abstract
The mammalian central circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN contains multiple circadian oscillators which synchronize with each other via several neurotransmitters. Importantly, an inhibitory neurotransmitter, γ-amino butyric acid (GABA), is expressed in almost all SCN neurons. In this review, we discuss how GABA influences circadian rhythms in the SCN. Excitatory and inhibitory effects of GABA may depend on intracellular Cl- concentration, in which several factors such as day-length, time of day, development, and region in the SCN may be involved. GABA also mediates oscillatory coupling of the circadian rhythms in the SCN. Recent genetic approaches reveal that GABA refines circadian output rhythms, but not circadian oscillations in the SCN. Since several efferent projections of the SCN have been suggested, GABA might work downstream of neuronal pathways from the SCN which regulate the temporal order of physiology and behavior.
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Affiliation(s)
- Daisuke Ono
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.,Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Ken-Ichi Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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6
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Harvey JRM, Plante AE, Meredith AL. Ion Channels Controlling Circadian Rhythms in Suprachiasmatic Nucleus Excitability. Physiol Rev 2020; 100:1415-1454. [PMID: 32163720 DOI: 10.1152/physrev.00027.2019] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Animals synchronize to the environmental day-night cycle by means of an internal circadian clock in the brain. In mammals, this timekeeping mechanism is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus and is entrained by light input from the retina. One output of the SCN is a neural code for circadian time, which arises from the collective activity of neurons within the SCN circuit and comprises two fundamental components: 1) periodic alterations in the spontaneous excitability of individual neurons that result in higher firing rates during the day and lower firing rates at night, and 2) synchronization of these cellular oscillations throughout the SCN. In this review, we summarize current evidence for the identity of ion channels in SCN neurons and the mechanisms by which they set the rhythmic parameters of the time code. During the day, voltage-dependent and independent Na+ and Ca2+ currents, as well as several K+ currents, contribute to increased membrane excitability and therefore higher firing frequency. At night, an increase in different K+ currents, including Ca2+-activated BK currents, contribute to membrane hyperpolarization and decreased firing. Layered on top of these intrinsically regulated changes in membrane excitability, more than a dozen neuromodulators influence action potential activity and rhythmicity in SCN neurons, facilitating both synchronization and plasticity of the neural code.
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Affiliation(s)
- Jenna R M Harvey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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7
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Ito E, Shima R, Yoshioka T. A novel role of oxytocin: Oxytocin-induced well-being in humans. Biophys Physicobiol 2019; 16:132-139. [PMID: 31608203 PMCID: PMC6784812 DOI: 10.2142/biophysico.16.0_132] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 07/27/2019] [Indexed: 12/19/2022] Open
Abstract
We review the involvement of a small molecule, oxytocin, in various effects of physical stimulation of somatosensory organs, mindfulness meditation, emotion and fragrance on humans, and then propose a hypothesis that complex human states and behaviors, such as well-being, social bonding, and emotional behavior, are explained by oxytocin. We previously reported that oxytocin can induce pain relief and described the possibility how oxytocin in the dorsal horn and/or the dorsal root ganglion relieves joint and muscle pain. In the present article, we expand our research target from the physical analgesic effects of oxytocin to its psychologic effects to upregulate well-being and downregulate stress and anxiety. For this purpose, we propose a “hypothalamic-pituitary-adrenal (HPA) axis-oxytocin model” to explain why mindfulness meditation, placebo, and fragrance can reduce stress and anxiety, resulting in contentment. This new proposed model of HPA axis-oxytocin in the brain also provides a target to address other questions regarding emotional behaviors, learning and memory, and excess food intake leading to obesity, aimed at promoting a healthy life.
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Affiliation(s)
- Etsuro Ito
- Department of Biology, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan.,Graduate Institute of Medicine, School of Medicine, Kaohsiung Medical University, Kaohsiung 80756, Taiwan
| | - Rei Shima
- Department of Biology, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Tohru Yoshioka
- Graduate Institute of Medicine, School of Medicine, Kaohsiung Medical University, Kaohsiung 80756, Taiwan
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8
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Carmona-Alcocer V, Rohr KE, Joye DAM, Evans JA. Circuit development in the master clock network of mammals. Eur J Neurosci 2018; 51:82-108. [PMID: 30402923 DOI: 10.1111/ejn.14259] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/08/2018] [Accepted: 10/31/2018] [Indexed: 12/24/2022]
Abstract
Daily rhythms are generated by the circadian timekeeping system, which is orchestrated by the master circadian clock in the suprachiasmatic nucleus (SCN) of mammals. Circadian timekeeping is endogenous and does not require exposure to external cues during development. Nevertheless, the circadian system is not fully formed at birth in many mammalian species and it is important to understand how SCN development can affect the function of the circadian system in adulthood. The purpose of the current review is to discuss the ontogeny of cellular and circuit function in the SCN, with a focus on work performed in model rodent species (i.e., mouse, rat, and hamster). Particular emphasis is placed on the spatial and temporal patterns of SCN development that may contribute to the function of the master clock during adulthood. Additional work aimed at decoding the mechanisms that guide circadian development is expected to provide a solid foundation upon which to better understand the sources and factors contributing to aberrant maturation of clock function.
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Affiliation(s)
| | - Kayla E Rohr
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
| | - Deborah A M Joye
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
| | - Jennifer A Evans
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
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9
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Ono D, Honma KI, Yanagawa Y, Yamanaka A, Honma S. Role of GABA in the regulation of the central circadian clock of the suprachiasmatic nucleus. J Physiol Sci 2018; 68:333-343. [PMID: 29560549 PMCID: PMC10717195 DOI: 10.1007/s12576-018-0604-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 03/14/2018] [Indexed: 11/25/2022]
Abstract
In mammals, circadian rhythms, such as sleep/wake cycles, are regulated by the central circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN consists of thousands of individual neurons, which exhibit circadian rhythms. They synchronize with each other and produce robust and stable oscillations. Although several neurotransmitters are expressed in the SCN, almost all SCN neurons are γ-amino butyric acid (GABA)-ergic. Several studies have attempted to understand the roles of GABA in the SCN; however, precise mechanisms of the action of GABA in the SCN are still unclear. GABA exhibits excitatory and/or inhibitory characteristics depending on the circadian phase or region in the SCN. It can both synchronize and destabilize cellular circadian rhythms in individual SCN cells. Differing environmental light conditions, such as a long photoperiod, result in the decoupling of circadian oscillators of the dorsal and ventral SCN. This is due to high intracellular chloride concentrations in the dorsal SCN. Because mice with functional GABA deficiency, such as vesicular GABA transporter- and glutamate decarboxylase-deficient mice, are neonatal lethal, research has been limited to pharmacological approaches. Furthermore, different recording methods have been used to understand the roles of GABA in the SCN. The excitability of GABAergic neurons also changes during the postnatal period. Although there are technical difficulties in understanding the functions of GABA in the SCN, technical developments may help uncover new roles of GABA in circadian physiology and behavior.
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Affiliation(s)
- Daisuke Ono
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
| | - Ken-Ichi Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan
| | - Akihiro Yamanaka
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan
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10
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Belle MDC, Diekman CO. Neuronal oscillations on an ultra-slow timescale: daily rhythms in electrical activity and gene expression in the mammalian master circadian clockwork. Eur J Neurosci 2018; 48:2696-2717. [PMID: 29396876 DOI: 10.1111/ejn.13856] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 01/16/2018] [Accepted: 01/28/2018] [Indexed: 12/17/2022]
Abstract
Neuronal oscillations of the brain, such as those observed in the cortices and hippocampi of behaving animals and humans, span across wide frequency bands, from slow delta waves (0.1 Hz) to ultra-fast ripples (600 Hz). Here, we focus on ultra-slow neuronal oscillators in the hypothalamic suprachiasmatic nuclei (SCN), the master daily clock that operates on interlocking transcription-translation feedback loops to produce circadian rhythms in clock gene expression with a period of near 24 h (< 0.001 Hz). This intracellular molecular clock interacts with the cell's membrane through poorly understood mechanisms to drive the daily pattern in the electrical excitability of SCN neurons, exhibiting an up-state during the day and a down-state at night. In turn, the membrane activity feeds back to regulate the oscillatory activity of clock gene programs. In this review, we emphasise the circadian processes that drive daily electrical oscillations in SCN neurons, and highlight how mathematical modelling contributes to our increasing understanding of circadian rhythm generation, synchronisation and communication within this hypothalamic region and across other brain circuits.
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Affiliation(s)
- Mino D C Belle
- Institute of Clinical and Biomedical Sciences, University of Exeter Medical School, University of Exeter, Exeter, EX4 4PS, UK
| | - Casey O Diekman
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, USA.,Institute for Brain and Neuroscience Research, New Jersey Institute of Technology, Newark, NJ, USA
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11
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Circadian Plasticity of Mammalian Inhibitory Interneurons. Neural Plast 2017; 2017:6373412. [PMID: 28367335 PMCID: PMC5358450 DOI: 10.1155/2017/6373412] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/15/2017] [Accepted: 02/19/2017] [Indexed: 12/11/2022] Open
Abstract
Inhibitory interneurons participate in all neuronal circuits in the mammalian brain, including the circadian clock system, and are indispensable for their effective function. Although the clock neurons have different molecular and electrical properties, their main function is the generation of circadian oscillations. Here we review the circadian plasticity of GABAergic interneurons in several areas of the mammalian brain, suprachiasmatic nucleus, neocortex, hippocampus, olfactory bulb, cerebellum, striatum, and in the retina.
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12
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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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13
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Abstract
The hypothalamic suprachiasmatic nucleus (SCN) has a pivotal role in the mammalian circadian clock. SCN neurons generate circadian rhythms in action potential firing frequencies and neurotransmitter release, and the core oscillation is thought to be driven by “clock gene” transcription-translation feedback loops. Cytosolic Ca2+mobilization followed by stimulation of various receptors has been shown to reset the gene transcription cycles in SCN neurons, whereas contribution of steady-state cytosolic Ca2+levels to the rhythm generation is unclear. Recently, circadian rhythms in cytosolic Ca2+levels have been demonstrated in cultured SCN neurons. The circadian Ca2+rhythms are driven by the release of Ca2+from ryanodine-sensitive internal stores and resistant to the blockade of action potentials. These results raise the possibility that gene translation/transcription loops may interact with autonomous Ca2+oscillations in the production of circadian rhythms in SCN neurons.
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Affiliation(s)
- Masayuki Ikeda
- Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Suita, Osaka, Japan.
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14
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Rojas-Castañeda JC, Vigueras-Villaseñor RM, Chávez-Saldaña M, Rojas P, Gutiérrez-Pérez O, Rojas C, Arteaga-Silva M. Neonatal exposure to monosodium glutamate induces morphological alterations in suprachiasmatic nucleus of adult rat. Int J Exp Pathol 2016; 97:18-26. [PMID: 26799547 PMCID: PMC4840248 DOI: 10.1111/iep.12157] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 10/07/2015] [Indexed: 01/19/2023] Open
Abstract
Neonatal exposure to monosodium glutamate (MSG) induces circadian disorders in several physiological and behavioural processes regulated by the suprachiasmatic nucleus (SCN). The objective of this study was to evaluate the effects of neonatal exposure to MSG on locomotor activity, and on morphology, cellular density and expression of proteins, as evaluated by optical density (OD), of vasopressin (VP)-, vasoactive intestinal polypeptide (VIP)- and glial fibrillary acidic protein (GFAP)-immunoreactive cells in the SCN. Male Wistar rats were used: the MSG group was subcutaneously treated from 3 to 10 days of age with 3.5 mg/g/day. Locomotor activity was evaluated at 90 days of age using 'open-field' test, and the brains were processed for immunohistochemical studies. MSG exposure induced a significant decrease in locomotor activity. VP- and VIP-immunoreactive neuronal densities showed a significant decrease, while the somatic OD showed an increase. Major axes and somatic area were significantly increased in VIP neurons. The cellular and optical densities of GFAP-immunoreactive sections of SCN were significantly increased. These results demonstrated that newborn exposure to MSG induced morphological alterations in SCN cells, an alteration that could be the basis for behavioural disorders observed in the animals.
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Affiliation(s)
| | - Rosa María Vigueras-Villaseñor
- Subdirección de Medicina Experimental, Instituto Nacional de Pediatría, México D.F., México
- Departamento de Morfología, Facultad de Medicina Veterinaria y Zootécnia, UNAM, México D.F., México
| | | | - Patricia Rojas
- Laboratorio de Neurotoxicología, Instituto Nacional de Neurología y Neurocirugía, 'Manuel Velasco Suárez', México D.F., México
| | - Oscar Gutiérrez-Pérez
- Subdirección de Medicina Experimental, Instituto Nacional de Pediatría, México D.F., México
- Departamento de Morfología, Facultad de Medicina Veterinaria y Zootécnia, UNAM, México D.F., México
| | - Carolina Rojas
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, UNAM, México D.F., México
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15
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Toma K, Wang TC, Hanashima C. Encoding and decoding time in neural development. Dev Growth Differ 2016; 58:59-72. [PMID: 26748623 DOI: 10.1111/dgd.12257] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 11/02/2015] [Accepted: 11/03/2015] [Indexed: 02/04/2023]
Abstract
The development of a multicellular organism involves time-dependent changes in molecular and cellular states; therefore 'time' is an indispensable mathematical parameter of ontogenesis. Regardless of their inextricable relationship, there is a limited number of events for which the output of developmental phenomena primarily uses temporal cues that are generated through multilevel interactions between molecules, cells, and tissues. In this review, we focus on neural stem cells, which serve as a faithful decoder of temporal cues to transmit biological information and generate specific output in the developing nervous system. We further explore the identity of the temporal information that is encoded in neural development, and how this information is decoded into various cellular fate decisions.
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Affiliation(s)
- Kenichi Toma
- Laboratory for Neocortical Development, RIKEN Center for Developmental Biology, Kobe, 650-0047, Japan
| | - Tien-Cheng Wang
- Laboratory for Neocortical Development, RIKEN Center for Developmental Biology, Kobe, 650-0047, Japan
| | - Carina Hanashima
- Laboratory for Neocortical Development, RIKEN Center for Developmental Biology, Kobe, 650-0047, Japan.,Department of Biology, Graduate School of Science, Kobe University, Kobe, 657-8501, Japan
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16
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Belle MDC. Circadian Tick-Talking Across the Neuroendocrine System and Suprachiasmatic Nuclei Circuits: The Enigmatic Communication Between the Molecular and Electrical Membrane Clocks. J Neuroendocrinol 2015; 27:567-76. [PMID: 25845396 PMCID: PMC4973835 DOI: 10.1111/jne.12279] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 03/25/2015] [Accepted: 03/26/2015] [Indexed: 12/15/2022]
Abstract
As with many processes in nature, appropriate timing in biological systems is of paramount importance. In the neuroendocrine system, the efficacy of hormonal influence on major bodily functions, such as reproduction, metabolism and growth, relies on timely communication within and across many of the brain's homeostatic systems. The activity of these circuits is tightly orchestrated with the animal's internal physiological demands and external solar cycle by a master circadian clock. In mammals, this master clock is located in the hypothalamic suprachiasmatic nucleus (SCN), where the ensemble activity of thousands of clock neurones generates and communicates circadian time cues to the rest of the brain and body. Many regions of the brain, including areas with neuroendocrine function, also contain local daily clocks that can provide feedback signals to the SCN. Although much is known about the molecular processes underpinning endogenous circadian rhythm generation in SCN neurones and, to a lesser extent, extra-SCN cells, the electrical membrane clock that acts in partnership with the molecular clockwork to communicate circadian timing across the brain is poorly understood. The present review focuses on some circadian aspects of reproductive neuroendocrinology and processes involved in circadian rhythm communication in the SCN, aiming to identify key gaps in our knowledge of cross-talk between our daily master clock and neuroendocrine function. The intention is to highlight our surprisingly limited understanding of their interaction in the hope that this will stimulate future work in these areas.
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Affiliation(s)
- M. D. C. Belle
- Faculty of Life SciencesUniversity of ManchesterManchesterUK
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17
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Bmal1 is an essential regulator for circadian cytosolic Ca²⁺ rhythms in suprachiasmatic nucleus neurons. J Neurosci 2014; 34:12029-38. [PMID: 25186748 DOI: 10.1523/jneurosci.5158-13.2014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The hypothalamic suprachiasmatic nucleus (SCN) plays a pivotal role in the mammalian circadian clock system. Bmal1 is a clock gene that drives transcriptional-translational feedback loops (TTFLs) for itself and other genes, and is expressed in nearly all SCN neurons. Despite strong evidence that Bmal1-null mutant mice display arrhythmic behavior under constant darkness, the function of Bmal1 in neuronal activity is unknown. Recently, periodic changes in the levels of intracellular signaling messengers, such as cytosolic Ca(2+) and cAMP, were suggested to regulate TTFLs. However, the opposite aspect of how clock gene TTFLs regulate cytosolic signaling remains unclear. To investigate intracellular Ca(2+) dynamics under Bmal1 perturbations, we cotransfected some SCN neurons with yellow cameleon together with wild-type or dominant-negative Bmal1 using a gene-gun applied for mouse organotypic cultures. Immunofluorescence staining for a tag protein linked to BMAL1 showed nuclear expression of wild-type BMAL1 and its degradation within 1 week after transfection in SCN neurons. However, dominant-negative BMAL1 did not translocate into the nucleus and the cytosolic signals persisted beyond 1 week. Consistently, circadian Ca(2+) rhythms in SCN neurons were inhibited for longer periods by dominant-negative Bmal1 overexpression. Furthermore, SCN neurons transfected with a Bmal1 shRNA lengthened, whereas those overexpressing wild-type Bmal1 shortened, the periods of Ca(2+) rhythms, with a significant reduction in their amplitude. BMAL1 expression was intact in the majority of neighboring neurons in organotypic cultures. Therefore, we conclude that proper intrinsic Bmal1 expression, but not passive signaling via cell-to-cell interactions, is the determinant of circadian Ca(2+) rhythms in SCN neurons.
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18
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Circadian modulation of the Cl(-) equilibrium potential in the rat suprachiasmatic nuclei. BIOMED RESEARCH INTERNATIONAL 2014; 2014:424982. [PMID: 24949446 PMCID: PMC4052495 DOI: 10.1155/2014/424982] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/23/2014] [Accepted: 03/27/2014] [Indexed: 11/18/2022]
Abstract
The suprachiasmatic nuclei (SCN) constitute a circadian clock in mammals, where γ-amino-butyric acid (GABA) neurotransmission prevails and participates in different aspects of circadian regulation. Evidence suggests that GABA has an excitatory function in the SCN in addition to its typical inhibitory role. To examine this possibility further, we determined the equilibrium potential of GABAergic postsynaptic currents (E(GABA)) at different times of the day and in different regions of the SCN, using either perforated or whole cell patch clamp. Our results indicate that during the day most neurons in the dorsal SCN have an E(GABA) close to -30 mV while in the ventral SCN they have an E(GABA) close to -60 mV; this difference reverses during the night, in the dorsal SCN neurons have an E(GABA) of -60 mV and in the ventral SCN they have an E(GABA) of -30 mV. The depolarized equilibrium potential can be attributed to the activity of the Na(+)-K(+)-2Cl(-) (NKCC) cotransporter since the equilibrium potential becomes more negative following addition of the NKCC blocker bumetanide. Our results suggest an excitatory role for GABA in the SCN and further indicate both time (day versus night) and regional (dorsal versus ventral) modulation of E(GABA) in the SCN.
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Serotonin-2C receptor involved serotonin-induced Ca²⁺ mobilisations in neuronal progenitors and neurons in rat suprachiasmatic nucleus. Sci Rep 2014; 4:4106. [PMID: 24531181 PMCID: PMC3925950 DOI: 10.1038/srep04106] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 01/30/2014] [Indexed: 02/03/2023] Open
Abstract
The hypothalamic suprachiasmatic nucleus (SCN), the central circadian pacemaker in mammals, undergoes serotonergic regulation, but the underlying mechanisms remain obscure. Here, we generated a subclone of an SCN progenitor cell line expressing Ca(2+) sensors (SCN2.2YC) and compared its 5-HT receptor signalling with that of rat SCN neurons in brain slices. SCN2.2YC cells expressed 5-HT1A/2A/2B/2C, but not 5A/7, while all six subtypes were expressed in SCN tissues. High K(+) or 5-HT increased cytosolic Ca(2+) in SCN2.2YC cells. The 5-HT responses were inhibited by ritanserin and SB-221284, but resistant to WAY-100635 and RS-127445, suggesting predominant involvement of 5-HT2C for Ca(2+) mobilisations. Consistently, Ca(2+) imaging and voltage-clamp electrophysiology using rat SCN slices demonstrated post-synaptic 5-HT2C expression. Because 5-HT2C expression was postnatally increased in the SCN and 5-HT-induced Ca(2+) mobilisations were amplified in differentiated SCN2.2YC cells and developed SCN neurons, we suggest that this signalling development occurs in accordance with central clock maturations.
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20
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Irwin RP, Allen CN. Simultaneous electrophysiological recording and calcium imaging of suprachiasmatic nucleus neurons. J Vis Exp 2013:50794. [PMID: 24335611 DOI: 10.3791/50794] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Simultaneous electrophysiological and fluorescent imaging recording methods were used to study the role of changes of membrane potential or current in regulating the intracellular calcium concentration. Changing environmental conditions, such as the light-dark cycle, can modify neuronal and neural network activity and the expression of a family of circadian clock genes within the suprachiasmatic nucleus (SCN), the location of the master circadian clock in the mammalian brain. Excitatory synaptic transmission leads to an increase in the postsynaptic Ca(2+) concentration that is believed to activate the signaling pathways that shifts the rhythmic expression of circadian clock genes. Hypothalamic slices containing the SCN were patch clamped using microelectrodes filled with an internal solution containing the calcium indicator bis-fura-2. After a seal was formed between the microelectrode and the SCN neuronal membrane, the membrane was ruptured using gentle suction and the calcium probe diffused into the neuron filling both the soma and dendrites. Quantitative ratiometric measurements of the intracellular calcium concentration were recorded simultaneously with membrane potential or current. Using these methods it is possible to study the role of changes of the intracellular calcium concentration produced by synaptic activity and action potential firing of individual neurons. In this presentation we demonstrate the methods to simultaneously record electrophysiological activity along with intracellular calcium from individual SCN neurons maintained in brain slices.
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Affiliation(s)
- Robert P Irwin
- Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University
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21
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Ozaki T, Mohammad S, Morioka E, Takiguchi S, Ikeda M. Infant satiety depends on transient expression of cholecystokinin-1 receptors on ependymal cells lining the third ventricle in mice. J Physiol 2012; 591:1295-312. [PMID: 23266937 DOI: 10.1113/jphysiol.2012.247676] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cholecystokinin (CCK) is a hypothetical controller for suckling and infancy body weight, although the underlying mechanisms remain unclear. Therefore, the present study analysed the mechanisms using mice lacking the CCK-1 receptor (CCK1R-/-). Although CCK1R-/- mice displayed normal weights at birth and adulthood, CCK1R-/- pups had enlarged adipocytes and were overweight from the first to second week after birth, regardless of maternal genotype. The lacZ reporter gene assay and/or calcium imaging analysis demonstrated that CCK-1 receptors were abundant in satiety-controlling regions such as the hypothalamus, brainstem, nodose ganglion and pylorus in adults, whereas these signals were few to lacking at pre-weanling stages. At postnatal day (PD) 6, the increase in cFos expression in the medullary nucleus tractus solitarius was similarly triggered by gastrointestinal milk- or saline filling in both genotypes, further indicating immature CCK-1 receptor function in an ascending satiety-controlling system during infancy. Conversely, third ventricle ependymal tanycyte-like cells expressed CCK-1 receptors with expression peaking at PD6. At PD6, wild-type but not CCK1R-/- mice had increased cFos immunoreactivity in ependymal cells following gastrointestinal milk filling whereas the response became negligible at PD12. In addition, ependymal cFos was not increased by saline filling, indicating that these responses are dependent on CCK-1 receptors, developmental stage and nutrients. Furthermore, body weights of wild-type pups were transiently increased by blocking ependymal CCK receptor function with microinjection of a CCK-1 antagonist, but not a CCK-2 antagonist. Hence, we demonstrate de novo functions of ependymal CCK-1 receptors and reveal a new aspect of infant satiety-controlling mechanisms.
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Affiliation(s)
- Tomoya Ozaki
- 1Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
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22
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Mohammad S, Ozaki T, Takeuchi K, Unno K, Yamoto K, Morioka E, Takiguchi S, Ikeda M. Functional compensation between cholecystokinin-1 and -2 receptors in murine paraventricular nucleus neurons. J Biol Chem 2012; 287:39391-401. [PMID: 23038256 PMCID: PMC3501058 DOI: 10.1074/jbc.m112.416214] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/02/2012] [Indexed: 01/11/2023] Open
Abstract
Cholecystokinin (CCK) and its receptor subtypes CCK-1 and -2 have diverse homeostatic functions. CCK-1 and -2 receptors share a common phosphatidylinositol signaling pathway, yet little is known regarding their possible functional coupling. We focused on CCK-mediated Ca(2+) signaling in parvocellular paraventricular nucleus (PVN) cells, which control satiety and other autonomic functions. Analysis of mouse hypothalamic slices demonstrated that the general CCK receptor agonist CCK-8s (10 nM) triggered Ca(2+) transients most significantly in the posterior subregion of the PVN (PaPo). This 10 nM CCK-8s-induced response was absent in CCK-1 receptor knock-out (CCK1R(-/-)) slices, showing that the response is mediated by CCK-1 receptors. CCK-8s concentrations higher than 30 nM triggered a Ca(2+) rise similarly in wild-type and CCK1R(-/-) slices. The large CCK-8s (100 nM)-induced Ca(2+) responses in CCK1R(-/-) slices were blocked by a CCK-2 receptor antagonist (CI-988), whereas those in wild-type slices required a mixture of CI-988 and lorglumide (a CCK-1 receptor antagonist) for complete antagonism. Therefore, CCK-1 and -2 receptors may function synergistically in single PaPo neurons and deletion of CCK-1 receptors may facilitate CCK-2 receptor signaling. This hypothesis was supported by results of real-time RT-PCR, immunofluorescence double labeling and Western blotting assays, which indicated CCK-2 receptor overexpression in PaPo neurons of CCK1R(-/-) mice. Furthermore, behavioral studies showed that intraperitoneal injections of lorglumide up-regulated food accesses in wild-type but not in CCK1R(-/-) mice, whereas CI-988 injections up-regulated food accesses in CCK1R(-/-) but not in wild-type mice. Compensatory CCK signaling via CCK-2 receptors in CCK1R(-/-) mice shed light on currently controversial satiety-controlling mechanisms.
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Affiliation(s)
| | - Tomoya Ozaki
- From the Graduate School of Innovative Life Science and
| | - Kouhei Takeuchi
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
| | - Katsuya Unno
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
| | - Kurumi Yamoto
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
| | - Eri Morioka
- From the Graduate School of Innovative Life Science and
| | - Soichi Takiguchi
- the Institute for Clinical Research, National Kyushu Cancer Center, 3-1-1 Notame, Minami-ku, Fukuoka 811-1395, Japan
| | - Masayuki Ikeda
- From the Graduate School of Innovative Life Science and
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
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23
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Clark JP, Kofuji P. Stoichiometry of N-methyl-D-aspartate receptors within the suprachiasmatic nucleus. J Neurophysiol 2010; 103:3448-64. [PMID: 20410362 DOI: 10.1152/jn.01069.2009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The circadian pacemaker within the suprachiasmatic nucleus (SCN) confers daily rhythms to bodily functions. In nature, the circadian clock will adopt a 24-h period by synchronizing to the solar light/dark cycle. This light entrainment process is mediated, in part, at glutamatergic synapses formed between retinal ganglion afferents and SCN neurons. N-methyl-D-aspartate receptors (NMDARs) located on SCN neurons gate light-induced phase resetting. Despite their importance in circadian physiology, little is known about their functional stoichiometry. We investigated the NR2-subunit composition with whole cell recordings of SCN neurons within the murine hypothalamic brain slice using a combination of subtype-selective NMDAR antagonists and voltage-clamp protocols. We found that extracellular magnesium ([Mg](o)) strongly blocks SCN NMDARs exhibiting affinities and voltage sensitivities associated with NR2A and NR2B subunits. These NMDAR currents were inhibited strongly by NR2B-selective antagonists, Ro 25-6981 (3.5 microM, 55.0 +/- 9.0% block; mean +/- SE) and ifenprodil (10 microM, 55.8 +/- 3.0% block). The current remaining showed decreased [Mg](o) affinities reminiscent of NR2C and NR2D subunits but was highly sensitive to [Zn](o), a potent NR2A blocker, showing a approximately 44.2 +/- 1.1% maximal inhibition at saturating concentrations with an IC(50) of 7.8 +/- 1.1 nM. Considering the selectivity, efficacy, and potency of the drugs used in combination with [Mg](o)-block characteristics of the NMDAR, our data show that both diheteromeric NR2B NMDARs and triheteromeric NR2A NMDARs (paired with an NR2C or NR2D subunits) account for the vast majority of the NMDAR current within the SCN.
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Affiliation(s)
- J P Clark
- Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455, USA
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24
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Hong JH, Min CH, Jeong B, Kojiya T, Morioka E, Nagai T, Ikeda M, Lee KJ. Intracellular calcium spikes in rat suprachiasmatic nucleus neurons induced by BAPTA-based calcium dyes. PLoS One 2010; 5:e9634. [PMID: 20224788 PMCID: PMC2835761 DOI: 10.1371/journal.pone.0009634] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 02/17/2010] [Indexed: 12/05/2022] Open
Abstract
Background Circadian rhythms in spontaneous action potential (AP) firing frequencies and in cytosolic free calcium concentrations have been reported for mammalian circadian pacemaker neurons located within the hypothalamic suprachiasmatic nucleus (SCN). Also reported is the existence of “Ca2+ spikes” (i.e., [Ca2+]c transients having a bandwidth of 10∼100 seconds) in SCN neurons, but it is unclear if these SCN Ca2+ spikes are related to the slow circadian rhythms. Methodology/Principal Findings We addressed this issue based on a Ca2+ indicator dye (fluo-4) and a protein Ca2+ sensor (yellow cameleon). Using fluo-4 AM dye, we found spontaneous Ca2+ spikes in 18% of rat SCN cells in acute brain slices, but the Ca2+ spiking frequencies showed no day/night variation. We repeated the same experiments with rat (and mouse) SCN slice cultures that expressed yellow cameleon genes for a number of different circadian phases and, surprisingly, spontaneous Ca2+ spike was barely observed (<3%). When fluo-4 AM or BAPTA-AM was loaded in addition to the cameleon-expressing SCN cultures, however, the number of cells exhibiting Ca2+ spikes was increased to 13∼14%. Conclusions/Significance Despite our extensive set of experiments, no evidence of a circadian rhythm was found in the spontaneous Ca2+ spiking activity of SCN. Furthermore, our study strongly suggests that the spontaneous Ca2+ spiking activity is caused by the Ca2+ chelating effect of the BAPTA-based fluo-4 dye. Therefore, this induced activity seems irrelevant to the intrinsic circadian rhythm of [Ca2+]c in SCN neurons. The problems with BAPTA based dyes are widely known and our study provides a clear case for concern, in particular, for SCN Ca2+ spikes. On the other hand, our study neither invalidates the use of these dyes as a whole, nor undermines the potential role of SCN Ca2+ spikes in the function of SCN.
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Affiliation(s)
- Jin Hee Hong
- Center for Cell-dynamics and Department of Physics, Korea University, Seoul, Republic of Korea
| | - Cheol Hong Min
- Center for Cell-dynamics and Department of Physics, Korea University, Seoul, Republic of Korea
| | - Byeongha Jeong
- Center for Cell-dynamics and Department of Physics, Korea University, Seoul, Republic of Korea
| | - Tomoyoshi Kojiya
- Graduate School of Innovative Life Science, Toyama University, Toyama, Japan
| | - Eri Morioka
- Graduate School of Innovative Life Science, Toyama University, Toyama, Japan
| | - Takeharu Nagai
- Laboratory for Nanosystems Physiology, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Masayuki Ikeda
- Graduate School of Innovative Life Science, Toyama University, Toyama, Japan
| | - Kyoung J. Lee
- Center for Cell-dynamics and Department of Physics, Korea University, Seoul, Republic of Korea
- * E-mail:
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25
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Irwin RP, Allen CN. GABAergic signaling induces divergent neuronal Ca2+ responses in the suprachiasmatic nucleus network. Eur J Neurosci 2009; 30:1462-75. [PMID: 19821838 DOI: 10.1111/j.1460-9568.2009.06944.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intercellular communication between gamma-aminobutyric acid (GABA)ergic suprachiasmatic nucleus (SCN) neurons facilitates light-induced phase changes and synchronization of individual neural oscillators within the SCN network. We used ratiometric Ca(2+) imaging techniques to record changes in the intracellular calcium concentration ([Ca(2+)](i)) to study the role of GABA in interneuronal communication and the response of the SCN neuronal network to optic nerve stimulations that mimic entraining light signals. Stimulation of the retinohypothalamic tract (RHT) evoked divergent Ca(2+) responses in neurons that varied regionally within the SCN with a pattern that correlated with those evoked by pharmacological GABA applications. GABA(A) and GABA(B) receptor agonists and antagonists were used to evaluate components of the GABA-induced changes in [Ca(2+)](i). Application of the GABA(A) receptor antagonist gabazine induced changes in baseline [Ca(2+)](i) in a direction opposite to that evoked by GABA, and similarly altered the RHT stimulation-induced Ca(2+) response. GABA application induced Ca(2+) responses varied in time and region within the SCN network. The NKCC1 cotransporter blocker, bumetanide, and L-type calcium channel blocker, nimodipine, attenuated the GABA-induced rise of [Ca(2+)](i). These results suggest that physiological GABA induces opposing effects on [Ca(2+)](i) based on the chloride equilibrium potential, and may play an important role in neuronal Ca(2+) balance, synchronization and modulation of light input signaling in the SCN network.
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Affiliation(s)
- Robert P Irwin
- Center for Research on Occupational and Environmental Toxicology (CROET), Oregon Health & Science University, Portland, OR 97239, USA.
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26
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Wagner S, Yarom Y. Excitation by GABA in the SCN reaches its time and place (Commentary on Irwin & Allen). Eur J Neurosci 2009; 30:1461. [DOI: 10.1111/j.1460-9568.2009.07011.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Benca R, Duncan MJ, Frank E, McClung C, Nelson RJ, Vicentic A. Biological rhythms, higher brain function, and behavior: Gaps, opportunities, and challenges. ACTA ACUST UNITED AC 2009; 62:57-70. [PMID: 19766673 DOI: 10.1016/j.brainresrev.2009.09.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 09/14/2009] [Accepted: 09/15/2009] [Indexed: 10/20/2022]
Abstract
Increasing evidence suggests that disrupted temporal organization impairs behavior, cognition, and affect; further, disruption of circadian clock genes impairs sleep-wake cycle and social rhythms which may be implicated in mental disorders. Despite this strong evidence, a gap in understanding the neural mechanisms of this interaction obscures whether biological rhythms disturbances are the underlying causes or merely symptoms of mental disorder. Here, we review current understanding, emerging concepts, gaps, and opportunities pertinent to (1) the neurobiology of the interactions between circadian oscillators and the neural circuits subserving higher brain function and behaviors of relevance to mental health, (2) the most promising approaches to determine how biological rhythms regulate brain function and behavior under normal and pathological conditions, (3) the gaps and challenges to advancing knowledge on the link between disrupted circadian rhythms/sleep and psychiatric disorders, and (4) the novel strategies for translation of basic science discoveries in circadian biology to clinical settings to define risk, prevent or delay onset of mental illnesses, design diagnostic tools, and propose new therapeutic strategies. The review is organized around five themes pertinent to (1) the impact of molecular clocks on physiology and behavior, (2) the interactions between circadian signals and cognitive functions, (3) the interface of circadian rhythms with sleep, (4) a clinical perspective on the relationship between circadian rhythm abnormalities and affective disorders, and (5) the pre-clinical models of circadian rhythm abnormalities and mood disorders.
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Affiliation(s)
- Ruth Benca
- Department of Psychology and Psychiatry, University of Wisconsin-Madison, 53792, USA
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Wong KY, Graham DM, Berson DM. The retina-attached SCN slice preparation: an in vitro mammalian circadian visual system. J Biol Rhythms 2008; 22:400-10. [PMID: 17876061 DOI: 10.1177/0748730407305376] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The suprachiasmatic nucleus (SCN), the mammalian circadian pacemaker, receives information about ambient light levels through the retinohypothalamic tract. This information resets the molecular clock of SCN neurons, thereby entraining overt animal behavior and physiology to the solar cycle. Progress toward functional characterization of retinal influences on the SCN has been hampered by limitations of established experimental paradigms. To overcome this hurdle, the authors have developed a novel in vitro preparation of the rat retinohypothalamic circuit that maintains functional connectivity between the retinas and the SCN. This method permits whole-cell patch-clamp recordings from visually identified, light-responsive SCN neurons. Using this preparation, the authors have found that in the SCN, light-evoked responses are partly driven by the melanopsin photosensory system of the intrinsically photosensitive retinal ganglion cells and that SCN neurons exhibit light adaptation. The authors have also been able to generate this preparation from mice, demonstrating the feasibility of applying this method to transgenic mice.
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Affiliation(s)
- Kwoon Y Wong
- Department of Neuroscience, Brown University, Providence, RI 02912, USA.
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Calcium response to retinohypothalamic tract synaptic transmission in suprachiasmatic nucleus neurons. J Neurosci 2007; 27:11748-57. [PMID: 17959816 DOI: 10.1523/jneurosci.1840-07.2007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Glutamate released from retinohypothalamic tract (RHT) synapses with suprachiasmatic nucleus (SCN) neurons induces phase changes in the circadian clock presumably by using Ca2+ as a second messenger. We used electrophysiological and Ca2+ imaging techniques to simultaneously record changes in the membrane potential and intracellular calcium concentration ([Ca2+]i) in SCN neurons after stimulation of the RHT at physiologically relevant frequencies. Stimulation of the RHT sufficient to generate an EPSP did not produce detectable changes in [Ca2+]i, whereas EPSP-induced action potentials evoked an increase in [Ca2+]i, suggesting that the change in postsynaptic somatic [Ca2+]i produced by synaptically activated glutamate receptors was the result of membrane depolarization activating voltage-dependent Ca2+ channels. The magnitude of the Ca2+ response was dependent on the RHT stimulation frequency and duration, and on the SCN neuron action potential frequency. Membrane depolarization-induced changes in [Ca2+]i were larger and decayed more quickly in the dendrites than in the soma and were attenuated by nimodipine, suggesting a compartmentalization of Ca2+ signaling and a contribution of L-type Ca2+ channels. RHT stimulation at frequencies that mimicked the output of light-sensitive retinal ganglion cells (RGCs) evoked [Ca2+]i transients in SCN neurons via membrane depolarization and activation of voltage-dependent Ca2+ channels. These data suggest that for Ca2+ to induce phase advances or delays, light-induced signaling from RGCs must augment the underlying oscillatory somatic [Ca2+]i by evoking postsynaptic action potentials in SCN neurons during a period of slow spontaneous firing such as occurs during nighttime.
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Roychowdhury S, Noack J, Engelmann M, Wolf G, Horn TFW. AMPA receptor-induced intracellular calcium response in the paraventricular nucleus is modulated by nitric oxide: calcium imaging in a hypothalamic organotypic cell culture model. Nitric Oxide 2006; 14:290-9. [PMID: 16442320 DOI: 10.1016/j.niox.2005.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 11/25/2005] [Accepted: 12/02/2005] [Indexed: 10/25/2022]
Abstract
An organotypic cell culture (OCC) model of the rat hypothalamic paraventricular nucleus (PVN) was established to monitor intracellular calcium levels ([Ca(2+)](i)) of magnocellular neurons in response to glutamate and nitric oxide (NO). The histoarchitectural organization of these cultures was characterized either by immunohistochemical labeling of vasopressin, neuronal nitric oxide synthase (nNOS) and the neuronal marker NeuN or by the enzyme histochemical NADPH-diaphorase staining. A distinct NeuN positive cell population in 14-days old OCC's was confirmed as being the PVN by its vasopressin- and nNOS-immunostained neurons as well as by its NADPH-diaphorase labeling. Life cell imaging was performed using the [Ca(2+)](i) sensor Fluo-4 to measure [Ca(2+)](i) transients in response to bath applications of glutamate, high potassium (60 mM), and ATP. The glutamate-induced [Ca(2+)](i) response was mimicked by AMPA but not NMDA in the PVN. NMDA, however, elicited a [Ca(2+)](i) transient in a different area of the OCC that corresponds to the suprachiasmatic nucleus indicating the potential effectiveness of the stimulus. The AMPA-receptor blocker NBQX abolished the glutamate-induced response in the PVN. An inhibition of endogenous NO production by the NOS inhibitor L-NAME decreased the amplitude of AMPA- and glutamate-induced [Ca(2+)](i) rises. Taken together, these data suggest that AMPA mediates the glutamate-induced [Ca(2+)](i) rises within the PVN, where endogenous NO is able to modulate such glutamate signaling in OCC.
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Affiliation(s)
- Sanjoy Roychowdhury
- Institute of Medical Neurobiology, Otto von Guericke University, Leipziger Strasse 44, D-39120 Magdeburg, Germany
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31
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Zhang LL, Pathak HR, Coulter DA, Freed MA, Vardi N. Shift of intracellular chloride concentration in ganglion and amacrine cells of developing mouse retina. J Neurophysiol 2005; 95:2404-16. [PMID: 16371454 DOI: 10.1152/jn.00578.2005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
GABA and glycine provide excitatory action during early development: they depolarize neurons and increase intracellular calcium concentration. As neurons mature, GABA and glycine become inhibitory. This switch from excitation to inhibition is thought to result from a shift of intracellular chloride concentration ([Cl-]i) from high to low, but in retina, measurements of [Cl-]i or chloride equilibrium potential (ECl) during development have not been made. Using the developing mouse retina, we systematically measured [Cl-]i in parallel with GABA's actions on calcium and chloride. In ganglion and amacrine cells, fura-2 imaging showed that before postnatal day (P) 6, exogenous GABA, acting via ionotropic GABA receptors, evoked calcium rise, which persisted in HCO3- -free buffer but was blocked with 0 extracellular calcium. After P6, GABA switched to inhibiting spontaneous calcium transients. Concomitant with this switch we observed the following: 6-methoxy-N-ethylquinolinium iodide (MEQ) chloride imaging showed that GABA caused an efflux of chloride before P6 and an influx afterward; gramicidin-perforated-patch recordings showed that the reversal potential for GABA decreased from -45 mV, near threshold for voltage-activated calcium channel, to -60 mV, near resting potential; MEQ imaging showed that [Cl-]i shifted steeply around P6 from 29 to 14 mM, corresponding to a decline of ECl from -39 to -58 mV. We also show that GABAergic amacrine cells became stratified by P4, potentially allowing GABA's excitatory action to shape circuit connectivity. Our results support the hypothesis that a shift from high [Cl-]i to low causes GABA to switch from excitatory to inhibitory.
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Affiliation(s)
- Ling-Li Zhang
- Deaprtment of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA
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Marty A, Llano I. Excitatory effects of GABA in established brain networks. Trends Neurosci 2005; 28:284-9. [PMID: 15927683 DOI: 10.1016/j.tins.2005.04.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Revised: 03/21/2005] [Accepted: 04/14/2005] [Indexed: 10/25/2022]
Abstract
Although GABA remains the predominant inhibitory neurotransmitter of the brain, there are numerous recent examples of excitatory actions of GABA. These actions can be classified in two broad categories: phasic excitatory effects, as follow single activation of GABAergic afferents, and sustained excitatory effects, as follow prolonged activation of GABA(A) receptors. Evidence reviewed here indicates that, contrary to common belief, these effects are not restricted to embryonic or neonatal preparations.
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Affiliation(s)
- Alain Marty
- Laboratoire de Physiologie Cérébrale, Université Paris 5/CNRS, 45 Rue des Saints Pères, 75006 Paris, France.
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Schuster C, Williams LM, Morris A, Morgan PJ, Barrett P. The human MT1 melatonin receptor stimulates cAMP production in the human neuroblastoma cell line SH-SY5Y cells via a calcium-calmodulin signal transduction pathway. J Neuroendocrinol 2005; 17:170-8. [PMID: 15796769 DOI: 10.1111/j.1365-2826.2005.01288.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin regulates circadian and seasonal physiology via melatonin receptors expressed in the brain. However, little is known about the signal transduction mechanisms that mediate the action of melatonin in neuronal cells. To begin to address this issue, we expressed the human MT(1) receptor in the human neuroblastoma SH-SY5Y cell line. In this cell line, melatonin acutely stimulated cAMP synthesis through a calcium-calmodulin dependent pathway. This stimulatory effect was independent of an interaction with G(i) or G(s) G proteins and dependent upon internal calcium stores. Melatonin also potentiated forskolin-activated cAMP synthesis. Differentiation of the neuroblastoma cells with retinoic acid to the neuronal phenotype did not alter the ability of melatonin to acutely stimulate cAMP. These data may be relevant to the neuronal action of melatonin and highlight the importance of the cellular context of expression of melatonin and other G protein-coupled receptors.
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Affiliation(s)
- C Schuster
- Rowett Research Institute, Bucksburn, Aberdeen, UK
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Abstract
The circadian clock in mammals is located in the hypothalamic suprachiasmatic nucleus. At the core of the clock are molecular autofeedback loops associated with clock gene transcription. However, the mechanisms of circadian signal transduction are basically unknown. A recent report by Ikeda et al. provides new insights into the intracellular signaling pathways involved in conveying circadian clock information from the core loop to cellular functions. Cytosolic Ca(2+) is proposed to be a key substance linking the 'pendulum' to the 'hands' of the clock.
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Affiliation(s)
- Sato Honma
- Department of Physiology, Hokkaido University Graduate School of Medicine, 060-8638, Sapporo, Japan.
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Kononenko NI, Dudek FE. Mechanism of Irregular Firing of Suprachiasmatic Nucleus Neurons in Rat Hypothalamic Slices. J Neurophysiol 2004; 91:267-73. [PMID: 14715720 DOI: 10.1152/jn.00314.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanisms of irregular firing of spontaneous action potentials in neurons from the rat suprachiasmatic nucleus (SCN) were studied in hypothalamic slices using cell-attached and whole cell recording. The firing pattern of spontaneous action potentials could be divided into regular and irregular, based on the interspike interval (ISI) histogram and the membrane potential trajectory between action potentials. Similar to previous studies, regular neurons had a firing rate about >3.5 Hz and irregular neurons typically fired about <3.5 Hz. The ISI of irregular-firing neurons was a linear function of the sum of inhibitory postsynaptic potentials (IPSPs) between action potentials. Bicuculline (10–30 μM) suppressed IPSPs and converted an irregular pattern to a more regular firing. Bicuculline also depolarized SCN neurons and induced bursting-like activity in some SCN neurons. Gabazine (20 μM), however, suppressed IPSPs without depolarization, and also converted irregular activity to regular firing. Thus GABAA receptor–mediated IPSPs appear responsible for irregular firing of SCN neurons in hypothalamic slices.
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Affiliation(s)
- Nikolai I Kononenko
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA
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Ikeda M, Sugiyama T, Wallace CS, Gompf HS, Yoshioka T, Miyawaki A, Allen CN. Circadian Dynamics of Cytosolic and Nuclear Ca2+ in Single Suprachiasmatic Nucleus Neurons. Neuron 2003; 38:253-63. [PMID: 12718859 DOI: 10.1016/s0896-6273(03)00164-8] [Citation(s) in RCA: 219] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Intracellular free Ca(2+) regulates diverse cellular processes, including membrane potential, neurotransmitter release, and gene expression. To examine the cellular mechanisms underlying the generation of circadian rhythms, nucleus-targeted and untargeted cDNAs encoding a Ca(2+)-sensitive fluorescent protein (cameleon) were transfected into organotypic cultures of mouse suprachiasmatic nucleus (SCN), the primary circadian pacemaker. Circadian rhythms in cytosolic but not nuclear Ca(2+) concentration were observed in SCN neurons. The cytosolic Ca(2+) rhythm period matched the circadian multiple-unit-activity (MUA)-rhythm period monitored using a multiple-electrode array, with a mean advance in phase of 4 hr. Tetrodotoxin blocked MUA, but not Ca(2+) rhythms, while ryanodine damped both Ca(2+) and MUA rhythms. These results demonstrate cytosolic Ca(2+) rhythms regulated by the release of Ca(2+) from ryanodine-sensitive stores in SCN neurons.
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Affiliation(s)
- Masayuki Ikeda
- Department of Molecular Behavioral Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, 565-0874, Osaka, Japan.
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Ikeda M, Allen CN. Developmental changes in calbindin-D28k and calretinin expression in the mouse suprachiasmatic nucleus. Eur J Neurosci 2003; 17:1111-8. [PMID: 12653988 DOI: 10.1046/j.1460-9568.2003.02515.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The hypothalamic suprachiasmatic nucleus, the primary circadian pacemaker in mammals, and the retinohypothalamic tract, the retinal afferent fibres to the suprachiasmatic nucleus, both mature during early postnatal life. The establishment of circadian rhythms is thought to depend on input from the retina, but the mechanism remains unknown. Here we examined developmental changes in the expression of the Ca2+-binding proteins calbindin-D28k and calretinin in the mouse hypothalamus. Robust calbindin-D28k immunoreactivity was observed in the dorsomedial suprachiasmatic nucleus and the supraoptic nucleus in neonatal mice (postnatal day 3). The calbindin-D28k immunoreactivity decreased significantly in the suprachiasmatic nucleus but not in the supraoptic nucleus during postnatal days 9-15, when retinohypothalamic tract projections to the suprachiasmatic nucleus are completed. Calretinin immunoreactivity was low in the neonatal suprachiasmatic nucleus and increased with development in the ventrolateral suprachiasmatic nucleus, in parallel with the developmental reduction of calbindin-D28k immunoreactivity observed in the dorsomedial suprachiasmatic nucleus. Developmentally stable calretinin immunoreactivity was also observed in retinohypothalamic tract fibres. Organotypic slice cultures of the suprachiasmatic nucleus were prepared from postnatal day 3 mice to examine the effect of the absence of retinohypothalamic tract inputs on developmental changes in calbindin-D28k and calretinin expression. After 12 days in vitro, the cultured suprachiasmatic nucleus slices exhibited dense calbindin-D28k immunoreactivity similar to neonatal mice, and calretinin immunoreactivity in the ventrolateral suprachiasmatic nucleus similar to young adult mice. These results demonstrate a developmental reduction in calbindin-D28k expression that paralleled retinohypothalamic tract formation and a developmental increase in calretinin expression that is independent of retinohypothalamic tract connections to suprachiasmatic nucleus neurons.
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Affiliation(s)
- Masayuki Ikeda
- Department of Molecular Behavioural Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, 565-0874 Osaka, Japan.
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