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Chegodaev DA, Pavlova PA. High lactic acid levels in the brain contribute to the generation of focal slowing on the electroencephalogram. Front Neurol 2024; 15:1393274. [PMID: 38694777 PMCID: PMC11061411 DOI: 10.3389/fneur.2024.1393274] [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: 02/28/2024] [Accepted: 04/09/2024] [Indexed: 05/04/2024] Open
Abstract
Focal slowing on the EEG is often associated with structural pathology of the brain. Despite the clinical significance of focal slowing, the actual electrochemical mechanisms underlying this EEG phenomenon are still poorly understood. This paper briefly reviews the role of lactate in the pathogenesis of brain disorders that are primarily related to focal EEG slowing. An attempt is made to trace the hypothetical link between this EEG pattern and focal cerebral tissue lactacidosis.
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Affiliation(s)
- Dmitry Alexandrovich Chegodaev
- Laboratory for Brain and Neurocognitive Development, Ural Institute of Humanities, Ural Federal University named after the First President of Russia B. N. Yeltsin, Yekaterinburg, Russia
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The regulatory role of GABA A receptor in Actinia equina nervous system and the possible effect of global ocean acidification. Pflugers Arch 2021; 473:1851-1858. [PMID: 34633524 PMCID: PMC8599403 DOI: 10.1007/s00424-021-02628-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 09/24/2021] [Accepted: 09/27/2021] [Indexed: 11/25/2022]
Abstract
Global warming and connected acidification of the world ocean attract a substantial amount of research efforts, in particular in a context of their impact on behaviour and metabolism of marine organisms, such as Cnidaria. Nevertheless, mechanisms underlying Cnidarians’ neural signalling and behaviour and their (possible) alterations due to the world ocean acidification remain poorly understood. Here we researched for the first time modulation of GABAA receptors (GABAARs) in Actinia equina (Cnidaria: Anthozoa) by pH fluctuations within a range predicted by the world ocean acidification scenarios for the next 80–100 years and by selective pharmacological activation. We found that in line with earlier studies on vertebrates, both changes of pH and activation of GABAARs with a selective allosteric agonist (diazepam) modulate electrical charge transfer through GABAAR and the whole-cell excitability. On top of that, diazepam modifies the animal behavioural reaction on startle response. However, despite behavioural reactions displayed by living animals are controlled by GABAARs, changes of pH do not alter them significantly. Possible mechanisms underlying the species resistance to acidification impact are discussed.
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Amundarain MJ, Caffarena ER, Costabel MD. How does α 1Histidine102 affect the binding of modulators to α 1β 2γ 2 GABA A receptors? molecular insights from in silico experiments. Phys Chem Chem Phys 2021; 23:3993-4006. [PMID: 33554986 DOI: 10.1039/d0cp05081d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The activation of GABAA receptors by the neurotransmitter gamma-aminobutyric acid mediates the rapid inhibition response in the central nervous system of mammals. Many neurological and mental health disorders arise from alterations in the structure or function of these pentameric ion channels. GABAA receptors are targets for numerous drugs, including benzodiazepines, which bind to α1β2γ2 GABAA receptors with high affinity to a site in the extracellular domain, between subunits α1 and γ2. It has been established experimentally that the binding of these drugs depends on the presence of one particular amino acid in the α1 subunit: histidine 102. However, the specific role it plays in the intermolecular interaction has not been elucidated. In this work, we applied in silico methods to understand whether certain protonation and rotamer states of α1His102 facilitate the binding of modulators. We analysed diazepam binding, a benzodiazepine, and the antagonist flumazenil to the GABAA receptor using molecular dynamics simulations and adaptive biasing force simulations. The binding free energy follows changes in the protonation state for both ligands, and rotameric states of α1His102 were specific for the different compounds, suggesting distinct preferences for positive allosteric modulators and antagonists. Moreover, in the presence of diazepam and favoured by a neutral tautomer, we identified a water molecule that links loops A, B, and C and may be relevant to the modulation mechanism.
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Affiliation(s)
- María Julia Amundarain
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Av. L. N. Alem 1253, B8000CPB - Bahía Blanca, Argentina.
| | - Ernesto Raúl Caffarena
- Programa de Computação Científica - PROCC, Fundação Oswaldo Cruz, Manguinhos, CEP 21040-360, Av. Brasil 4365, Rio de Janeiro, RJ, Brazil
| | - Marcelo Daniel Costabel
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Av. L. N. Alem 1253, B8000CPB - Bahía Blanca, Argentina.
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Activity- and pH-dependent adenosine shifts at the end of a focal seizure in the entorhinal cortex. Epilepsy Res 2020; 165:106401. [PMID: 32599416 DOI: 10.1016/j.eplepsyres.2020.106401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/05/2020] [Accepted: 06/14/2020] [Indexed: 11/24/2022]
Abstract
Adenosine (ADO) is an endogenous modulator of neuronal excitability, with anticonvulsant and neuroprotective effects. It has been proposed that the activity-dependent release of ADO promoted by the extracellular acidification occurring during seizures contributes to seizure termination. To verify this hypothesis, we recorded field potentials, pH and ADO changes measured with enzymatic biosensors during acute focal seizures in the medial entorhinal cortex (mEC) of the isolated guinea-pig brain maintained in vitro. The effect of ADO on seizure-like events (SLEs) induced by GABAa receptor antagonism with bicuculline methiodide (BMI; 50 μM) was assessed by arterial applications of 1 mM ADO. ADO either reduced or prevented epileptiform activity. The A1 receptor antagonist DPCPX (100-500 μM) prolonged BMI-induced seizures and was able to precipitate SLEs in the absence of proconvulsant. Simultaneous recordings of brain activity, extracellular ADO and pH shifts demonstrated that ADO decreases at the onset and progressively rises toward the end of SLEs induced by either BMI or 4-aminopyridine (4AP; 50 μM), reaching maximal values 1-5 min after SLE termination. ADO changes were preceded by a SLE-dependent extracellular acid shift. Both pH acidification and ADO changes were abolished by 22 mM HEPES in the arterial perfusate. In these conditions, SLE duration was prolonged. Our data confirm that ADO plays a role in regulating brain excitability. Its increase depends on seizure-induced acid pH shift and it is maximal after the end of the SLE. These findings strongly suggest that ADO contributes to termination of focal seizures and to the establishment of the postictal depression.
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Neuronal Glutamatergic Synaptic Clefts Alkalinize Rather Than Acidify during Neurotransmission. J Neurosci 2020; 40:1611-1624. [PMID: 31964719 DOI: 10.1523/jneurosci.1774-19.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 01/14/2020] [Accepted: 01/15/2020] [Indexed: 12/11/2022] Open
Abstract
The dogma that the synaptic cleft acidifies during neurotransmission is based on the corelease of neurotransmitters and protons from synaptic vesicles, and is supported by direct data from sensory ribbon-type synapses. However, it is unclear whether acidification occurs at non-ribbon-type synapses. Here we used genetically encoded fluorescent pH indicators to examine cleft pH at conventional neuronal synapses. At the neuromuscular junction of female Drosophila larvae, we observed alkaline spikes of over 1 log unit during fictive locomotion in vivo. Ex vivo, single action potentials evoked alkalinizing pH transients of only ∼0.01 log unit, but these transients summated rapidly during burst firing. A chemical pH indicator targeted to the cleft corroborated these findings. Cleft pH transients were dependent on Ca2+ movement across the postsynaptic membrane, rather than neurotransmitter release per se, a result consistent with cleft alkalinization being driven by the Ca2+/H+ antiporting activity of the plasma membrane Ca2+-ATPase at the postsynaptic membrane. Targeting the pH indicators to the microenvironment of the presynaptic voltage gated Ca2+ channels revealed that alkalinization also occurred within the cleft proper at the active zone and not just within extrasynaptic regions. Application of the pH indicators at the mouse calyx of Held, a mammalian central synapse, similarly revealed cleft alkalinization during burst firing in both males and females. These findings, made at two quite different non-ribbon type synapses, suggest that cleft alkalinization during neurotransmission, rather than acidification, is a generalizable phenomenon across conventional neuronal synapses.SIGNIFICANCE STATEMENT Neurotransmission is highly sensitive to the pH of the extracellular milieu. This is readily evident in the neurological symptoms that accompany systemic acid/base imbalances. Imaging data from sensory ribbon-type synapses show that neurotransmission itself can acidify the synaptic cleft, likely due to the corelease of protons and glutamate. It is not clear whether the same phenomenon occurs at conventional neuronal synapses due to the difficulties in collecting such data. If it does occur, it would provide for an additional layer of activity-dependent modulation of neurotransmission. Our findings of alkalinization, rather than acidification, within the cleft of two different neuronal synapses encourages a reassessment of the scope of activity-dependent pH influences on neurotransmission and short-term synaptic plasticity.
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β-Amyloid Peptide Antagonizes the Effect of Protons on Taurine-Induced Chloride Current in Rat Hippocampal Pyramidal Neurons. Bull Exp Biol Med 2019; 167:237-241. [PMID: 31243680 DOI: 10.1007/s10517-019-04499-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Indexed: 10/26/2022]
Abstract
Taurine is an important endogenous agonist of glycine receptors (GlyR). Using the patchclamp technique, we measured chloride current induced by a short (600 msec) application of taurine (ITau) on isolated rat pyramidal neurons. pH of taurine solution in the applicator pipette was neutral (7.4) or acidic (7.0-5.0). Application of protons to a neuron causes a dosedependent decrease in the peak amplitude and acceleration of ITau desensitization. Addition of 100 nM β-amyloid peptide (Aβ) to the perfusate caused acceleration of ITau desensitization. The effects of Aβ and H+ on the rate of ITau desensitization were not additive. In addition, Aβ attenuated the effect of H+ on the peak amplitude of ITau. We also studied the effect of protons on the chloride current caused by activation of GABA receptors. In contrast to H+ effects on GlyR, Aβ did not modulate the effects of H+ on GABA receptors.
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Manfredi G, Colombo E, Barsotti J, Benfenati F, Lanzani G. Photochemistry of Organic Retinal Prostheses. Annu Rev Phys Chem 2019; 70:99-121. [DOI: 10.1146/annurev-physchem-042018-052445] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Organic devices are attracting considerable attention as prostheses for the recovery of retinal light sensitivity lost to retinal degenerative disease. The biotic/abiotic interface created when light-sensitive polymers and living tissues are placed in contact allows excitation of a response in blind laboratory rats exposed to visual stimuli. Although polymer retinal prostheses have proved to be efficient, their working mechanism is far from being fully understood. In this review article, we discuss the results of the studies conducted on these kinds of polymer devices and compare them with the data found in the literature for inorganic retinal prostheses, where the working mechanisms are better comprehended. This comparison, which tries to set some reference values and figures of merit, is intended for use as a starting point to determine the direction for further investigation.
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Affiliation(s)
- Giovanni Manfredi
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, 20133 Milan, Italy;,
| | - Elisabetta Colombo
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, 16132 Genoa, Italy;,
| | - Jonathan Barsotti
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, 20133 Milan, Italy;,
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, 16132 Genoa, Italy;,
- Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
| | - Guglielmo Lanzani
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, 20133 Milan, Italy;,
- Department of Physics, Politecnico di Milano, 20133 Milan, Italy
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Kisiel M, Jatczak-Śliwa M, Mozrzymas JW. Protons modulate gating of recombinant α 1β 2γ 2 GABA A receptor by affecting desensitization and opening transitions. Neuropharmacology 2018; 146:300-315. [PMID: 30326242 DOI: 10.1016/j.neuropharm.2018.10.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 09/28/2018] [Accepted: 10/12/2018] [Indexed: 01/27/2023]
Abstract
Protons are potent modulators of GABAA receptors (GABAARs) and α1Phe64 residue was implicated in their pH sensitivity. Recently, we have demonstrated that this residue is involved in flipping transitions which precede channel opening. We thus re-addressed the mechanism of GABAAR modulation by protons by considering the gating scheme extended by flipping. The impact of pH changes was examined on currents mediated by wild-type α1β2γ2 receptors or by their α1Phe64Leu or α1Phe64Cys mutants and elicited by saturating concentrations of full (GABA) or partial (piperidine-4-sulfonic acid) agonists. To describe the impact of extracellular pH on receptor gating, we combined macroscopic analysis of currents elicited by rapid agonist applications with single-channel studies. Acidification (pH 6.0) increased current amplitudes (in the case of leucine mutants effect was stronger when P4S was used) and decreased the rate and the extent of desensitization whereas alkalization (pH 8.0) had the opposite but weaker effect. Deactivation kinetics for wild-type receptors was slowed down by acidification while in the case of mutants this effect was observed upon alkalization. Moreover, α1Phe64 mutations enhanced GABAAR sensitivity to alkaline pH. Single-channel analysis revealed that acidification prolonged burst durations and affected shut but not open time distributions. Model simulations for macroscopic and single-channel activity indicated a novel mechanism in which protons primarily affected opening and desensitization rates but not flipping/unflipping. This evidence for the impact of protons on the receptor gating together with previously demonstrated effect on the agonist binding, point to a complex effect of extracellular pH on GABAAR macromolecule.
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Affiliation(s)
- Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
| | - Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Molecular Physiology and Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
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Soto E, Ortega-Ramírez A, Vega R. Protons as Messengers of Intercellular Communication in the Nervous System. Front Cell Neurosci 2018; 12:342. [PMID: 30364044 PMCID: PMC6191491 DOI: 10.3389/fncel.2018.00342] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/14/2018] [Indexed: 12/18/2022] Open
Abstract
In this review, evidence demonstrating that protons (H+) constitute a complex, regulated intercellular signaling mechanisms are presented. Given that pH is a strictly regulated variable in multicellular organisms, localized extracellular pH changes may constitute significant signals of cellular processes that occur in a cell or a group of cells. Several studies have demonstrated that the low pH of synaptic vesicles implies that neurotransmitter release is always accompanied by the co-release of H+ into the synaptic cleft, leading to transient extracellular pH shifts. Also, evidence has accumulated indicating that extracellular H+ concentration regulation is complex and implies a source of protons in a network of transporters, ion exchangers, and buffer capacity of the media that may finally establish the extracellular proton concentration. The activation of membrane transporters, increased production of CO2 and of metabolites, such as lactate, produce significant extracellular pH shifts in nano- and micro-domains in the central nervous system (CNS), constituting a reliable signal for intercellular communication. The acid sensing ion channels (ASIC) function as specific signal sensors of proton signaling mechanism, detecting subtle variations of extracellular H+ in a range varying from pH 5 to 8. The main question in relation to this signaling system is whether it is only synaptically restricted, or a volume modulator of neuron excitability. This signaling system may have evolved from a metabolic activity detection mechanism to a highly localized extracellular proton dependent communication mechanism. In this study, evidence showing the mechanisms of regulation of extracellular pH shifts and of the ASICs and its function in modulating the excitability in various systems is reviewed, including data and its role in synaptic neurotransmission, volume transmission and even segregated neurotransmission, leading to a reliable extracellular signaling mechanism.
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Affiliation(s)
- Enrique Soto
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | | | - Rosario Vega
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
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Ren J, Shang T, Sherry AD, Malloy CR. Unveiling a hidden 31 P signal coresonating with extracellular inorganic phosphate by outer-volume-suppression and localized 31 P MRS in the human brain at 7T. Magn Reson Med 2018; 80:1289-1297. [PMID: 29427295 DOI: 10.1002/mrm.27121] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 12/22/2017] [Accepted: 01/15/2018] [Indexed: 01/19/2023]
Abstract
PURPOSE The study was undertaken to demonstrate that there is more than 1 component in the extracellular Pi31 P signal ( Piex) acquired from human head using nonlocalized 31 P MRS. METHODS Outer-volume-suppression (OVS) saturation and 1D/2D 31 P CSI were utilized to reveal the presence of an additional component in the Piex signal. RESULTS 67% of the head extracellular Pi signal was attenuated upon OVS saturation of the peripheral meningeal tissues, likely reflecting elimination of the Pi signal in the meningeal fluids (the blood and CSF). Localized 1D/2D CSI data provided further support for this assignment. Upon correction for the meningeal contribution, the extracellular Pi concentration was 0.51 ± 0.07 mM, whereas the intracellular Pi was 0.85 ± 0.10 mM. The extracellular pH was measured as 7.32 ± 0.04 when using OVS, as compared to 7.39 ± 0.03 when measured without OVS (N = 7 subjects). CONCLUSION The extracellular Pi signal acquired from the human head using nonlocalized 31 P MRS contains a significant component likely contributed by peripheral blood and CSF in meninges that must be removed in order to use this signal as an endogenous probe for measuring extracellular pH and other properties in the brain.
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Affiliation(s)
- Jimin Ren
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Ty Shang
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - A Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Chemistry, University of Texas at Dallas, Richardson, Texas, USA
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,VA North Texas Health Care System, Dallas, Texas, USA
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Bukanova JV, Solntseva EI, Kondratenko RV, Skrebitsky VG. The influence of acidic media on the effect of beta-amyloid peptide on the function of glycine receptor in hippocampal neurons. Neurochem Int 2017; 110:69-74. [PMID: 28919253 DOI: 10.1016/j.neuint.2017.09.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 09/05/2017] [Accepted: 09/13/2017] [Indexed: 11/25/2022]
Abstract
We have previously shown that application of beta-amyloid peptide 1-42 (Aβ) at picomolar/nanomolar concentrations caused a decrease in the peak amplitude and acceleration of desensitization of the glycine-activated chloride current (IGly) in hippocampal pyramidal neurons (Bukanova et al., 2016). The aim of this work was to study the effect of Aβ on IGly in an acidified medium. The relevance of this work is determined by the fact that the pathogenic effects of Aβ in Alzheimer's disease are usually accompanied by inflammatory processes and acidosis. The IGly was induced by 600 ms application of 100 μM (nearly EC50) or 500 μM (nearly saturating) glycine on isolated rat hippocampal neurons. The solution of glycine was neutral (pH 7.4) or acidic over a pH range of 5.0-7.0. It was found that 600 ms application of protons rapidly, reversibly and in dose-dependent manner decreased the peak amplitude and accelerated the desensitization of IGly. The effect of H+ on IGly desensitization did not depend on glycine concentration and may be considered noncompetitive, while the effect on IGly peak disappeared at saturating glycine concentration and can be regarded as a competitive. These characteristics of the proton effects on IGly coincide with the characteristics of the Aβ effects on IGly. Experiments with joint application of Aβ and H+ showed interdependence of their effects. Addition of Aβ to perfusing solution reduced H+ effects on IGly while long pretreatment of Aβ with acid solution prevented the effects of the peptide on IGly. Our results suggest the existence of common sites for Aβ and H+ on the GlyR and indicate a mutual weakening of the inhibitory action of these molecules on IGly.
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12
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Chen Z, Liu R, Yang SH, Dillon GH, Huang R. Methylene blue inhibits GABA A receptors by interaction with GABA binding site. Neuropharmacology 2017; 119:100-110. [PMID: 28390894 DOI: 10.1016/j.neuropharm.2017.04.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 03/23/2017] [Accepted: 04/03/2017] [Indexed: 01/11/2023]
Abstract
Methylene blue (MB) is commonly used in diagnostic procedures and is also used to treat various medical conditions. Neurological effects of MB have been reported in clinical observations and experimental studies. Thus the modulation of GABAA receptor function by MB was investigated. Whole-cell GABA-activated currents were recorded from HEK293 cells expressing various GABAA receptor subunit configurations. MB inhibition of GABA currents was apparent at 3 μM, and it had an IC50 of 31 μM in human α1β2γ2 receptors. The MB action was rapid and reversible. MB inhibition was not mediated via the picrotoxin site, as a mutation (T6'F of the β2 subunit) known to confer resistance to picrotoxin had no effect on MB-induced inhibition. Blockade of GABAA receptors by MB was demonstrated across a range of receptors expressing varying subunits, including those expressed at extrasynaptic sites. The sensitivity of α1β2 receptors to MB was similar to that observed in α1β2γ2 receptors, indicating that MB's action via the benzodiazepine or Zn2+ site is unlikely. MB-induced inhibition of GABA response was competitive with respect to GABA. Furthermore, mutation of α1 F64 to A and β2 Y205 to F in the extracellular N-terminus, both residues which are known to comprise GABA binding pocket, remarkably diminished MB inhibition of GABA currents. These data suggest that MB inhibits GABAA receptor function by direct or allosteric interaction with the GABA binding site. Finally, in mouse hippocampal CA1 pyramidal neurons, MB inhibited GABA-activated currents as well as GABAergic IPSCs. We demonstrate that MB directly inhibits GABAA receptor function, which may underlie some of the effects of MB on the CNS.
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Affiliation(s)
- Zhenglan Chen
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Ran Liu
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Shao-Hua Yang
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Glenn H Dillon
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Renqi Huang
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States.
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Dussor G. ASICs as therapeutic targets for migraine. Neuropharmacology 2015; 94:64-71. [PMID: 25582295 PMCID: PMC4458434 DOI: 10.1016/j.neuropharm.2014.12.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 11/26/2014] [Accepted: 12/04/2014] [Indexed: 01/05/2023]
Abstract
Migraine is the most common neurological disorder and one of the most common chronic pain conditions. Despite its prevalence, the pathophysiology leading to migraine is poorly understood and the identification of new therapeutic targets has been slow. Several processes are currently thought to contribute to migraine including altered activity in the hypothalamus, cortical-spreading depression (CSD), and afferent sensory input from the cranial meninges. Decreased extracellular pH and subsequent activation of acid-sensing ion channels (ASICs) may contribute to each of these processes and may thus play a role in migraine pathophysiology. Although few studies have directly examined a role of ASICs in migraine, studies directly examining a connection have generated promising results including efficacy of ASIC blockers in both preclinical migraine models and in human migraine patients. The purpose of this review is to discuss the pathophysiology thought to contribute to migraine and findings that implicate decreased pH and/or ASICs in these events, as well as propose issues to be resolved in future studies of ASICs and migraine. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.
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Affiliation(s)
- Greg Dussor
- The University of Texas at Dallas, School of Behavioral and Brain Sciences, GR-41, 800 West Campbell Road, Richardson, TX, 75080, USA.
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