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Amoateng P, Tagoe TA, Karikari TK, Kukuia KKE, Osei-Safo D, Woode E, Frenguelli BG, Kombian SB. Synedrella nodiflora Extract Depresses Excitatory Synaptic Transmission and Chemically-Induced In Vitro Seizures in the Rat Hippocampus. Front Pharmacol 2021; 12:610025. [PMID: 33762938 PMCID: PMC7982396 DOI: 10.3389/fphar.2021.610025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 01/07/2021] [Indexed: 01/14/2023] Open
Abstract
Extracts of the tropical Cinderella plant Synedrella nodiflora are used traditionally to manage convulsive conditions in the West African sub-region. This study sought to determine the neuronal basis of the effectiveness of these plant extracts to suppress seizure activity. Using the hippocampal slice preparation from rats, the ability of the extract to depress excitatory synaptic transmission and in vitro seizure activity were investigated. Bath perfusion of the hydro-ethanolic extract of Synedrella nodiflora (SNE) caused a concentration-dependent depression of evoked field excitatory postsynaptic potentials (fEPSPs) recorded extracellularly in the CA1 region of the hippocampus with maximal depression of about 80% and an estimated IC50 of 0.06 mg/ml. The SNE-induced fEPSP depression was accompanied by an increase in paired pulse facilitation. The fEPSP depression only recovered partially after 20 min washing out. The effect of SNE was not stimulus dependent as it was present even in the absence of synaptic stimulation. Furthermore, it did not show desensitization as repeat application after 10 min washout produced the same level of fEPSP depression as the first application. The SNE effect on fEPSPs was not via adenosine release as it was neither blocked nor reversed by 8-CPT, an adenosine A1 receptor antagonist. In addition, SNE depressed in vitro seizures induced by zero Mg2+ and high K+ -containing artificial cerebrospinal fluid (aCSF) in a concentration-dependent manner. The results show that SNE depresses fEPSPs and spontaneous bursting activity in hippocampal neurons that may underlie its ability to abort convulsive activity in persons with epilepsy.
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Affiliation(s)
- Patrick Amoateng
- Department of Pharmacology and Toxicology, School of Pharmacy, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Thomas A Tagoe
- Department of Physiology, UG Medical School, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Thomas K Karikari
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Kennedy K E Kukuia
- Department of Medical Pharmacology, UG Medical School, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Dorcas Osei-Safo
- Department of Chemistry, School of Physical and Mathematical Sciences, College of Basic and Applied Sciences, University of Ghana, Accra, Ghana
| | - Eric Woode
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Health and Allied Sciences, Ho, Ghana
| | - Bruno G Frenguelli
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Samuel B Kombian
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Health Science Center, Kuwait University, Safat, Kuwait.,Department of Pharmacology and Toxicology, School of Medicine and Medical Sciences, University for Development Studies, Tamale, Ghana
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Sato Y, Takiguchi M, Tamano H, Takeda A. Extracellular Zn 2+-Dependent Amyloid-β 1-42 Neurotoxicity in Alzheimer's Disease Pathogenesis. Biol Trace Elem Res 2021; 199:53-61. [PMID: 32281074 DOI: 10.1007/s12011-020-02131-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 03/23/2020] [Indexed: 02/07/2023]
Abstract
The basal level of extracellular Zn2+ is in the range of low nanomolar (~ 10 nM) in the hippocampus. However, extracellular Zn2+ dynamics plays a key role for not only cognitive activity but also cognitive decline. Extracellular Zn2+ dynamics is modified by glutamatergic synapse excitation and the presence of amyloid-β1-42 (Aβ1-42), a causative peptide in Alzheimer's disease (AD). When human Aβ1-42 reaches high picomolar (> 100 pM) in the extracellular compartment of the rat dentate gyrus, Zn-Aβ1-42 complexes are readily formed and taken up into dentate granule cells, followed by Aβ1-42-induced cognitive decline that is linked with Zn2+ released from intracellular Zn-Aβ1-42 complexes. Aβ1-42-induced intracellular Zn2+ toxicity is accelerated with aging because of age-related increase in extracellular Zn2+. The recent findings suggest that Aβ1-42 secreted continuously from neuron terminals causes age-related cognitive decline and neurodegeneration via intracellular Zn2+ dysregulation. On the other hand, metallothioneins (MTs), zinc-binding proteins, quickly serve for intracellular Zn2+-buffering under acute intracellular Zn2+ dysregulation. On the basis of the idea that the defense strategy against Aβ1-42-induced pathogenesis leads to preventing the AD development, this review deals with extracellular Zn2+-dependent Aβ1-42 neurotoxicity, which is accelerated with aging.
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Affiliation(s)
- Yuichi Sato
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Mako Takiguchi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
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Atsushi T, Tamano H. New insight into Parkinson's disease pathogenesis from reactive oxygen species-mediated extracellular Zn 2+ influx. J Trace Elem Med Biol 2020; 61:126545. [PMID: 32438294 DOI: 10.1016/j.jtemb.2020.126545] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/07/2020] [Accepted: 04/30/2020] [Indexed: 01/21/2023]
Abstract
BACKGROUND Parkinson's disease (PD) is the common neurodegenerative disorder in the elderly characterized by motor symptoms such as tremors, which is caused by selective loss of nigral dopaminergic neurons. Oxidative stress induced by the auto-oxidation of dopamine has been implicated as a key cause of the selective loss of dopaminergic neurons. METHODS To understand the selective loss of nigral dopaminergic neurons, the PD pathogenesis is reviewed focused on paraquat (PQ) and 6-hydroxydopamine (6-OHDA)-induced PD in rats. RESULTS Reactive oxygen species (ROS), which are produced by PQ and 6-OHDA, are retrogradely transported to presynaptic glutamatergic neuron terminals. ROS activate presynaptic transient receptor potential melastatin 2 (TRPM2) cation channels and induce extracellular glutamate accumulation in the substantia nigra pars compacta (SNpc), followed by age-related intracellular Zn2+ dysregulation. Loss of nigral dopaminergic neurons is accelerated by age-related intracellular Zn2+ dysregulation in the SNpc of rat PD models. The intracellular Zn2+ dysregulation in nigral dopaminergic neurons is linked with the rapid influx of extracellular Zn2+ via postsynaptic AMPA receptor activation, suggesting that PQ- and 6-OHDA-induced pathogenesis is linked with age-related intracellular Zn2+ dysregulation in the SNpc. Postsynaptic TRPM2 channels may be also involved in intracellular Zn2+ dysregulation in the SNpc. CONCLUSION A novel mechanism of nigral dopaminergic degeneration, in which ROS induce rapid intracellular Zn2+ dysregulation, figures out the PD pathogenesis induced by PQ and 6-OHDA in rats. This review deals with new insight into PD pathogenesis from ROS-mediated extracellular Zn2+ influx and its proposed defense strategy.
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Affiliation(s)
- Takeda Atsushi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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Tamano H, Takeda A. Age-Dependent Modification of Intracellular Zn 2+ Buffering in the Hippocampus and Its Impact. Biol Pharm Bull 2019; 42:1070-1075. [PMID: 31257282 DOI: 10.1248/bpb.b18-00631] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The basal concentrations of extracellular Zn2+ and intracellular Zn2+, which are approximately 10 nM and 100 pM, respectively, in the brain, are markedly lower than those of extracellular Ca2+ (1.3 mM) and intracellular Ca2+ (100 nM), respectively, resulting in much less attention paid to Zn2+ than to Ca2+. However, intracellular Zn2+ dysregulation, which is closely linked with glutamate- and amyloid β-mediated extracellular Zn2+ influx, is more critical for cognitive decline and neurodegeneration than intracellular Ca2+ dysregulation. It is estimated that the age-dependent increase in the basal concentration of extracellular Zn2+ in the hippocampus plays a key role in cognitive decline and neurodegeneration. The characteristics of extracellular Zn2+ influx in the hippocampus may be modified age-dependently, probably followed by modification of intracellular Zn2+ buffering that is closely linked with age-related cognitive decline and neurodegeneration. Reduction of intracellular Zn2+-buffering capacity may be linked with the pathophysiology of progressive neurodegeneration such as Alzheimer's disease. This paper deals with age-dependent modification of intracellular Zn2+ buffering in the hippocampus and its impact. On the basis of the estimated impact, we propose a potential defense strategy against Zn2+-mediated neurodegeneration, i.e., metallothionein induction in the hippocampus.
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Affiliation(s)
- Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
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Synaptic proximity enables NMDAR signalling to promote brain metastasis. Nature 2019; 573:526-531. [PMID: 31534217 PMCID: PMC6837873 DOI: 10.1038/s41586-019-1576-6] [Citation(s) in RCA: 294] [Impact Index Per Article: 58.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 07/05/2019] [Indexed: 02/06/2023]
Abstract
Metastasis - the disseminated growth of tumours in distant organs – underlies cancer mortality. Breast-to-brain metastasis (B2BM) is disconcertingly common and disruptive, being prevalent in the aggressive basal-like subtype, albeit evident at varying frequencies in all subtypes. Previous studies revealed parameters of breast cancer metastasis to brain, but its preference for this site remains an enigma. Herein we show that B2BM cells co-opt a neuronal signaling pathway recently implicated in invasive tumour growth, involving activation by glutamate ligand of an N-methyl-D-aspartate receptor (NMDAR), whose signaling is demonstrably instrumental in model systems for metastatic colonization of the brain, and associated with poor prognosis. While NMDAR receptor activation is autocrine in some primary tumour types, human and mouse B2BM cells express receptors but secrete insufficient glutamate to activate signaling, which is instead supplied via the formation of pseudo-tripartite synapses between cancer cells and glutamatergic neurons, presenting an insidious rationale for brain metastasis.
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Takeda A, Tamano H. The Impact of Synaptic Zn 2+ Dynamics on Cognition and Its Decline. Int J Mol Sci 2017; 18:ijms18112411. [PMID: 29135924 PMCID: PMC5713379 DOI: 10.3390/ijms18112411] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 10/31/2017] [Accepted: 11/09/2017] [Indexed: 11/16/2022] Open
Abstract
The basal levels of extracellular Zn2+ are in the range of low nanomolar concentrations and less attention has been paid to Zn2+, compared to Ca2+, for synaptic activity. However, extracellular Zn2+ is necessary for synaptic activity. The basal levels of extracellular zinc are age-dependently increased in the rat hippocampus, implying that the basal levels of extracellular Zn2+ are also increased age-dependently and that extracellular Zn2+ dynamics are linked with age-related cognitive function and dysfunction. In the hippocampus, the influx of extracellular Zn2+ into postsynaptic neurons, which is often linked with Zn2+ release from neuron terminals, is critical for cognitive activity via long-term potentiation (LTP). In contrast, the excess influx of extracellular Zn2+ into postsynaptic neurons induces cognitive decline. Interestingly, the excess influx of extracellular Zn2+ more readily occurs in aged dentate granule cells and intracellular Zn2+-buffering, which is assessed with ZnAF-2DA, is weakened in the aged dentate granule cells. Characteristics (easiness) of extracellular Zn2+ influx seem to be linked with the weakened intracellular Zn2+-buffering in the aged dentate gyrus. This paper deals with the impact of synaptic Zn2+ signaling on cognition and its decline in comparison with synaptic Ca2+ signaling.
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Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
| | - Hanuna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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Tamano H, Nishio R, Shakushi Y, Sasaki M, Koike Y, Osawa M, Takeda A. In vitro and in vivo physiology of low nanomolar concentrations of Zn 2+ in artificial cerebrospinal fluid. Sci Rep 2017; 7:42897. [PMID: 28211543 PMCID: PMC5314341 DOI: 10.1038/srep42897] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/18/2017] [Indexed: 11/15/2022] Open
Abstract
Artificial cerebrospinal fluid (ACSF), i.e., brain extracellular medium, which includes Ca2+ and Mg2+, but not other divalent cations such as Zn2+, has been used for in vitro and in vivo experiments. The present study deals with the physiological significance of extracellular Zn2+ in ACSF. Spontaneous presynaptic activity is suppressed in the stratum lucidum of brain slices from young rats bathed in ACSF containing 10 nM ZnCl2, indicating that extracellular Zn2+ modifies hippocampal presynaptic activity. To examine the in vivo action of 10 nM ZnCl2 on long-term potentiation (LTP), the recording region was perfused using a recording electrode attached to a microdialysis probe. The magnitude of LTP was not modified in young rats by perfusion with ACSF containing 10 nM ZnCl2, compared to perfusion with ACSF without Zn2+, but attenuated by perfusion with ACSF containing 100 nM ZnCl2. Interestingly, the magnitude of LTP was not modified in aged rats even by perfusion with ACSF containing 100 nM ZnCl2, but enhanced by perfusion with ACSF containing 10 mM CaEDTA, an extracellular Zn2+ chelator. The present study indicates that the basal levels of extracellular Zn2+, which are in the range of low nanomolar concentrations, are critical for synaptic activity and perhaps increased age-dependently.
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Affiliation(s)
- Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Ryusuke Nishio
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yukina Shakushi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Miku Sasaki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yuta Koike
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Misa Osawa
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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Mendonça PR, Vargas-Caballero M, Erdélyi F, Szabó G, Paulsen O, Robinson HP. Stochastic and deterministic dynamics of intrinsically irregular firing in cortical inhibitory interneurons. eLife 2016; 5. [PMID: 27536875 PMCID: PMC5030087 DOI: 10.7554/elife.16475] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 08/17/2016] [Indexed: 11/24/2022] Open
Abstract
Most cortical neurons fire regularly when excited by a constant stimulus. In contrast, irregular-spiking (IS) interneurons are remarkable for the intrinsic variability of their spike timing, which can synchronize amongst IS cells via specific gap junctions. Here, we have studied the biophysical mechanisms of this irregular spiking in mice, and how IS cells fire in the context of synchronous network oscillations. Using patch-clamp recordings, artificial dynamic conductance injection, pharmacological analysis and computational modeling, we show that spike time irregularity is generated by a nonlinear dynamical interaction of voltage-dependent sodium and fast-inactivating potassium channels just below spike threshold, amplifying channel noise. This active irregularity may help IS cells synchronize with each other at gamma range frequencies, while resisting synchronization to lower input frequencies. DOI:http://dx.doi.org/10.7554/eLife.16475.001 Neurons send information to other neurons in the brain by generating fast electrical pulses called action potentials (or spikes). When stimulated by input signals of a constant size, neurons generally respond with regular patterns of spiking leading to rhythmical brain activity. However, neurons known as irregular spiking interneurons are unique: the relationship between the input they receive and whether or not they produce a spike appears to be random. The molecular mechanism behind this phenomenon is not clear. Mendonça et al. set out to investigate whether irregular spiking is truly random, or whether there is some degree of predictability. The experiments used genetically modified mice in which irregular spiking interneurons were specifically labeled with a fluorescent protein, which made them easier to find to record their electrical activity. Sophisticated statistical analyses showed that these neurons are not firing at random. Instead, there is a pattern to the timings of the spikes they produce. It was previously known that electrical spikes in neurons are generated by sodium ions and potassium ions moving across the membrane that surrounds each cell. Proteins called ion channels provide routes for these ions to pass through the membrane. Mendonça et al. show that compared to other neurons, irregular spiking interneurons have larger numbers of a specific type of potassium ion channel. Mimicking the effect of increasing the number of these potassium ion channels in the interneurons made the firing pattern of these neurons more irregular, while decreasing the number of these channels made the firing patterns more regular and predictable. A computer model of an irregular spiking interneuron showed that the activity of these potassium ion channels and a type of sodium ion channel plays a key role in producing irregular electrical spiking. Further analysis showed that irregular spiking interneurons can synchronize their activity with fast, but not slow, rhythms in brain activity. The findings of Mendonça et al. suggest that irregular spiking interneurons can disrupt slow regular electrical activity in the brain. Rhythms in brain activity vary depending on whether we are awake or asleep, and are altered in diseases such as epilepsy and schizophrenia. Now that we have a better understanding of how irregular spiking interneurons work, it should be possible to find out how they coordinate their activity with each other, and what effect they have on animal behavior. DOI:http://dx.doi.org/10.7554/eLife.16475.002
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Affiliation(s)
- Philipe Rf Mendonça
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Mariana Vargas-Caballero
- Institute for Life Sciences, University of Southampton, Southampton, United Kingdom.,Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom
| | - Ferenc Erdélyi
- Division of Medical Gene Technology, Institute of Experimental Medicine, Budapest, Hungary
| | - Gábor Szabó
- Division of Medical Gene Technology, Institute of Experimental Medicine, Budapest, Hungary
| | - Ole Paulsen
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Hugh Pc Robinson
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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Takeda A, Tamano H. Significance of Low Nanomolar Concentration of Zn2+ in Artificial Cerebrospinal Fluid. Mol Neurobiol 2016; 54:2477-2482. [DOI: 10.1007/s12035-016-9816-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 02/23/2016] [Indexed: 01/03/2023]
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Takeda A, Shakushi Y, Tamano H. Modification of hippocampal excitability in brain slices pretreated with a low nanomolar concentration of Zn2+. J Neurosci Res 2015; 93:1641-7. [DOI: 10.1002/jnr.23629] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 07/24/2015] [Accepted: 07/24/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology; School of Pharmaceutical Sciences, University of Shizuoka; Shizuoka Japan
| | - Yukina Shakushi
- Department of Neurophysiology; School of Pharmaceutical Sciences, University of Shizuoka; Shizuoka Japan
| | - Haruna Tamano
- Department of Neurophysiology; School of Pharmaceutical Sciences, University of Shizuoka; Shizuoka Japan
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Carmeli C, Bonifazi P, Robinson HPC, Small M. Quantifying network properties in multi-electrode recordings: spatiotemporal characterization and inter-trial variation of evoked gamma oscillations in mouse somatosensory cortex in vitro. Front Comput Neurosci 2013; 7:134. [PMID: 24137127 PMCID: PMC3797413 DOI: 10.3389/fncom.2013.00134] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 09/18/2013] [Indexed: 11/25/2022] Open
Abstract
Linking the structural connectivity of brain circuits to their cooperative dynamics and emergent functions is a central aim of neuroscience research. Graph theory has recently been applied to study the structure-function relationship of networks, where dynamical similarity of different nodes has been turned into a “static” functional connection. However, the capability of the brain to adapt, learn and process external stimuli requires a constant dynamical functional rewiring between circuitries and cell assemblies. Hence, we must capture the changes of network functional connectivity over time. Multi-electrode array data present a unique challenge within this framework. We study the dynamics of gamma oscillations in acute slices of the somatosensory cortex from juvenile mice recorded by planar multi-electrode arrays. Bursts of gamma oscillatory activity lasting a few hundred milliseconds could be initiated only by brief trains of electrical stimulations applied at the deepest cortical layers and simultaneously delivered at multiple locations. Local field potentials were used to study the spatio-temporal properties and the instantaneous synchronization profile of the gamma oscillatory activity, combined with current source density (CSD) analysis. Pair-wise differences in the oscillation phase were used to determine the presence of instantaneous synchronization between the different sites of the circuitry during the oscillatory period. Despite variation in the duration of the oscillatory response over successive trials, they showed a constant average power, suggesting that the rate of expenditure of energy during the gamma bursts is consistent across repeated stimulations. Within each gamma burst, the functional connectivity map reflected the columnar organization of the neocortex. Over successive trials, an apparently random rearrangement of the functional connectivity was observed, with a more stable columnar than horizontal organization. This work reveals new features of evoked gamma oscillations in developing cortex.
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Affiliation(s)
- Cristian Carmeli
- Laboratoire de Recherche en Neuroimagerie, Department of Clinical Neurosciences, Centre Hospitalier Universitaire Vaudois and University of Lausanne Lausanne, Switzerland
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Moradi K, Moradi K, Ganjkhani M, Hajihasani M, Gharibzadeh S, Kaka G. A fast model of voltage-dependent NMDA receptors. J Comput Neurosci 2012; 34:521-31. [PMID: 23224774 DOI: 10.1007/s10827-012-0434-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 10/29/2012] [Accepted: 10/31/2012] [Indexed: 11/25/2022]
Abstract
NMDA receptors are among the crucial elements of central nervous system models. Recent studies show that both conductance and kinetics of these receptors are changing voltage-dependently in some parts of the brain. Therefore, several models have been introduced to simulate their current. However, on the one hand, kinetic models-which are able to simulate these voltage-dependent phenomena-are computationally expensive for modeling of large neural networks. On the other hand, classic exponential models, which are computationally less expensive, are not able to simulate the voltage-dependency of these receptors, accurately. In this study, we have modified these classic models to endow them with the voltage-dependent conductance and time constants. Temperature sensitivity and desensitization of these receptors are also taken into account. We show that, it is possible to simulate the most important physiological aspects of NMDA receptor's behavior using only three to four differential equations, which is significantly smaller than the previous kinetic models. Consequently, it seems that our model is both fast and physiologically plausible and therefore is a suitable candidate for the modeling of large neural networks.
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Affiliation(s)
- Keivan Moradi
- Neuroscience Research Center, Baqyatallah (a.s.) Medical Sciences University, Tehran, Iran
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