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Shao M, Yu H, Santhakumar V, Yu J. Antiepileptogenic and neuroprotective effect of mefloquine after experimental status epilepticus. Epilepsy Res 2023; 198:107257. [PMID: 37989006 DOI: 10.1016/j.eplepsyres.2023.107257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 10/30/2023] [Accepted: 11/06/2023] [Indexed: 11/23/2023]
Abstract
Acquired temporal lobe epilepsy (TLE) characterized by spontaneous recurrent seizures (SRS) and hippocampal inhibitory neuron dysfunction is often refractory to current therapies. Gap junctional or electrical coupling between inhibitory neurons has been proposed to facilitate network synchrony and intercellular molecular exchange suggesting a role in both seizures and neurodegeneration. While gap junction blockers can limit acute seizures, whether blocking neuronal gap junctions can modify development of chronic epilepsy has not been examined. This study examined whether mefloquine, a selective blocker of Connexin 36 gap junctions which are well characterized in inhibitory neurons, can limit epileptogenesis and related cellular and behavioral pathology in a model of acquired TLE. A single, systemic dose of mefloquine administered early after pilocarpine-induced status epilepticus (SE) in rat reduced both development of SRS and behavioral co-morbidities. Immunostaining for interneuron subtypes identified that mefloquine treatment likely reduced delayed inhibitory neuronal loss after SE. Uniquely, parvalbumin expressing neurons in the hippocampal dentate gyrus appeared relatively resistant to early cell loss after SE. Functionally, whole cell patch clamp recordings revealed that mefloquine treatment preserved inhibitory synaptic drive to projection neurons one week and one month after SE. These results demonstrate that mefloquine, a drug already approved for malaria prophylaxis, is potentially antiepileptogenic and can protect against progressive interneuron loss and behavioral co-morbidities of epilepsy.
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Affiliation(s)
- Mingting Shao
- Department of Neurosurgery, the First Affiliated Hospital of Bengbu Medical College, Bengbu, China; Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, China
| | - Hang Yu
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, China
| | - Vijayalakshmi Santhakumar
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Jiandong Yu
- Department of Neurosurgery, the First Affiliated Hospital of Bengbu Medical College, Bengbu, China.
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2
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Salcedo-Arellano MJ, Johnson MD, McLennan YA, Hwang YH, Juarez P, McBride EL, Pantoja AP, Durbin-Johnson B, Tassone F, Hagerman RJ, Martínez-Cerdeño V. Brain Metabolomics in Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS). Cells 2023; 12:2132. [PMID: 37681866 PMCID: PMC10487256 DOI: 10.3390/cells12172132] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 08/08/2023] [Accepted: 08/15/2023] [Indexed: 09/09/2023] Open
Abstract
The course of pathophysiological mechanisms involved in fragile X-associated tremor/ataxia syndrome (FXTAS) remains largely unknown. Previous proteomics and metabolomics studies conducted in blood samples collected from FMR1 premutation carriers with FXTAS reported abnormalities in energy metabolism, and precursors of gluconeogenesis showed significant changes in plasma expression levels in FMR1 premutation carriers who developed FXTAS. We conducted an analysis of postmortem human brain tissues from 44 donors, 25 brains with FXTAS, and 19 matched controls. We quantified the metabolite relative abundance in the inferior temporal gyrus and the cerebellum using untargeted mass spectrometry (MS)-based metabolomics. We investigated how the metabolite type and abundance relate to the number of cytosine-guanine-guanine (CGG) repeats, to markers of neurodegeneration, and to the symptoms of FXTAS. A metabolomic analysis identified 191 primary metabolites, the data were log-transformed and normalized prior to the analysis, and the relative abundance was compared between the groups. The changes in the relative abundance of a set of metabolites were region-specific with some overlapping results; 22 metabolites showed alterations in the inferior temporal gyrus, while 21 showed differences in the cerebellum. The relative abundance of cytidine was decreased in the inferior temporal gyrus, and a lower abundance was found in the cases with larger CGG expansions; oleamide was significantly decreased in the cerebellum. The abundance of 11 metabolites was influenced by changes in the CGG repeat number. A histological evaluation found an association between the presence of microhemorrhages in the inferior temporal gyrus and a lower abundance of 2,5-dihydroxypyrazine. Our study identified alterations in the metabolites involved in the oxidative-stress response and bioenergetics in the brains of individuals with FXTAS. Significant changes in the abundance of cytidine and oleamide suggest their potential as biomarkers and therapeutic targets for FXTAS.
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Affiliation(s)
- Maria Jimena Salcedo-Arellano
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, Sacramento, CA 95616, USA; (M.J.S.-A.); (F.T.); (R.J.H.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
| | - Michael D. Johnson
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
| | - Yingratana A. McLennan
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
| | - Ye Hyun Hwang
- Department of Biochemistry and Molecular Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (Y.H.H.); (F.T.)
| | - Pablo Juarez
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
| | - Erin Lucille McBride
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
| | - Adriana P. Pantoja
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
| | - Blythe Durbin-Johnson
- Division of Biostatistics, Department of Public Health Sciences, UC Davis School of Medicine, Sacramento, CA 95817, USA;
| | - Flora Tassone
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, Sacramento, CA 95616, USA; (M.J.S.-A.); (F.T.); (R.J.H.); (V.M.-C.)
- Department of Biochemistry and Molecular Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (Y.H.H.); (F.T.)
| | - Randi J. Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, Sacramento, CA 95616, USA; (M.J.S.-A.); (F.T.); (R.J.H.); (V.M.-C.)
- Department of Pediatrics, UC Davis School of Medicine, Sacramento, CA 95817, USA;
| | - Verónica Martínez-Cerdeño
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, Sacramento, CA 95616, USA; (M.J.S.-A.); (F.T.); (R.J.H.); (V.M.-C.)
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children Northern California, Sacramento, CA 95817, USA; (M.J.S.-A.); (M.D.J.); (Y.A.M.); (P.J.); (E.L.M.); (A.P.P.); (V.M.-C.)
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3
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Quint WH, Tadema KCD, de Vrieze E, Lukowicz RM, Broekman S, Winkelman BHJ, Hoevenaars M, de Gruiter HM, van Wijk E, Schaeffel F, Meester-Smoor M, Miller AC, Willemsen R, Klaver CCW, Iglesias AI. Loss of Gap Junction Delta-2 (GJD2) gene orthologs leads to refractive error in zebrafish. Commun Biol 2021; 4:676. [PMID: 34083742 PMCID: PMC8175550 DOI: 10.1038/s42003-021-02185-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 05/04/2021] [Indexed: 12/20/2022] Open
Abstract
Myopia is the most common developmental disorder of juvenile eyes, and it has become an increasing cause of severe visual impairment. The GJD2 locus has been consistently associated with myopia in multiple independent genome-wide association studies. However, despite the strong genetic evidence, little is known about the functional role of GJD2 in refractive error development. Here, we find that depletion of gjd2a (Cx35.5) or gjd2b (Cx35.1) orthologs in zebrafish, cause changes in the biometry and refractive status of the eye. Our immunohistological and scRNA sequencing studies show that Cx35.5 (gjd2a) is a retinal connexin and its depletion leads to hyperopia and electrophysiological changes in the retina. These findings support a role for Cx35.5 (gjd2a) in the regulation of ocular biometry. Cx35.1 (gjd2b) has previously been identified in the retina, however, we found an additional lenticular role. Lack of Cx35.1 (gjd2b) led to a nuclear cataract that triggered axial elongation. Our results provide functional evidence of a link between gjd2 and refractive error. Quint et al. use zebrafish lines deficient in one of two orthologs of the Gap Junction Delta-2 (GJD2) gene, which is associated with myopia by genome-wide association studies. They link gjd2 with refractive error and report evidence to suggest that gjd2a plays a role in ocular biometry whilst gjd2b, previously found in the retina, possesses an additional lenticular role.
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Affiliation(s)
- Wim H Quint
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands. .,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands.
| | - Kirke C D Tadema
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Erik de Vrieze
- Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands
| | - Rachel M Lukowicz
- Institute of Neuroscience, University of Oregon, Eugene, United States
| | - Sanne Broekman
- Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands
| | - Beerend H J Winkelman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Cerebellar Coordination and Cognition, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Melanie Hoevenaars
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Erwin van Wijk
- Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands
| | - Frank Schaeffel
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.,Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland
| | - Magda Meester-Smoor
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Adam C Miller
- Institute of Neuroscience, University of Oregon, Eugene, United States
| | - Rob Willemsen
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Caroline C W Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland.,Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Adriana I Iglesias
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands. .,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands.
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4
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Kim J, Augustine GJ. Molecular Layer Interneurons: Key Elements of Cerebellar Network Computation and Behavior. Neuroscience 2020; 462:22-35. [PMID: 33075461 DOI: 10.1016/j.neuroscience.2020.10.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/02/2020] [Accepted: 10/05/2020] [Indexed: 02/05/2023]
Abstract
Molecular layer interneurons (MLIs) play an important role in cerebellar information processing by controlling Purkinje cell (PC) activity via inhibitory synaptic transmission. A local MLI network, constructed from both chemical and electrical synapses, is organized into spatially structured clusters that amplify feedforward and lateral inhibition to shape the temporal and spatial patterns of PC activity. Several recent in vivo studies indicate that such MLI circuits contribute not only to sensorimotor information processing, but also to precise motor coordination and cognitive processes. Here, we review current understanding of the organization of MLI circuits and their roles in the function of the mammalian cerebellum.
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Affiliation(s)
- Jinsook Kim
- Lee Kong Chian School of Medicine Nanyang Technological University Singapore 308238, Singapore
| | - George J Augustine
- Lee Kong Chian School of Medicine Nanyang Technological University Singapore 308238, Singapore.
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5
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Poklis JL, Gonek MM, Wolf CE, Akbarali HI, Dewey WL. Analysis of carbenoxolone by ultra-high-performance liquid chromatography tandem mass spectrometry in mouse brain and blood after systemic administration. Biomed Chromatogr 2018; 33:e4465. [PMID: 30548295 DOI: 10.1002/bmc.4465] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 11/24/2018] [Accepted: 12/05/2018] [Indexed: 11/09/2022]
Abstract
Carbenoxolone is a derivative of glycyrrhetinic acid found in the root of Glycyrrhiza glabra, colloquially known as licorice. It has been used as a treatment for peptic and oral ulcers. In recent years, carbenoxolone has been utilized in basic research for its ability to block gap junctional communication. Better understanding the distribution of carbenoxolone after systemic administration can lead to a better understanding of its potential sites of action. Presented is an ultra high-performance liquid chromatography tandem mass spectrometer (UHPLC-MS/MS) method for the identification and quantification of carbenoxolone in mouse blood and brain tissue. Twenty mice were injected intraperitoneally with 25 mg/kg carbenoxolone and brain tissue and blood were collected for analysis. Blood concentrations (mean ± SD) at 15, 30, 60 and 120 min were determined to be (n = 5) 5394 ± 778, 2636 ± 836, 1564 ± 541 and 846 ± 252 ng/mL, respectively. Brain concentrations (mean ± SD) at 15, 30, 60 and 120 mins were determined to be (n = 5) 171 ± 62, 102 ± 35, 55 ± 10 and 27 ± 9 ng/g, respectively. The analysis of these specimens at the four different time points resulted in blood and brain half-lives in mice of ~43 and 41 min, respectively. The UHPLC-MS/MS method was determined to be sensitive and robust for quantification of carbenoxolone.
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Affiliation(s)
- Justin L Poklis
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - Maciej M Gonek
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - Carl E Wolf
- Department of Pathology, Virginia Commonwealth University, Richmond, VA, USA
| | - Hamid I Akbarali
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - William L Dewey
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
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6
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Protein Kinase C Enhances Electrical Synaptic Transmission by Acting on Junctional and Postsynaptic Ca 2+ Currents. J Neurosci 2018; 38:2796-2808. [PMID: 29440551 DOI: 10.1523/jneurosci.2619-17.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/15/2018] [Accepted: 02/02/2018] [Indexed: 11/21/2022] Open
Abstract
By synchronizing neuronal activity, electrical transmission influences the coordination, pattern, and/or frequency of firing. In the hemaphroditic marine-snail, Aplysia calfornica, the neuroendocrine bag cell neurons use electrical synapses to synchronize a 30 min afterdischarge of action potentials for the release of reproductive hormone. During the afterdischarge, protein kinase C (PKC) is activated, although its impact on bag cell neuron electrical transmission is unknown. This was investigated here by monitoring electrical synapses between paired cultured bag cell neurons using dual whole-cell recording. Voltage clamp revealed a largely voltage-independent junctional current, which was enhanced by treating with a PKC activator, PMA, before recording. We also examined the transfer of presynaptic action potential-like waveforms (generated in voltage clamp) to the postsynaptic cell (measured in current clamp). For control pairs, the presynaptic spike-like waveforms mainly evoked electrotonic potentials; however, when PKC was triggered, these stimuli consistently produced postsynaptic action potentials. To assess whether this involved changes to postsynaptic responsiveness, single bag cell neurons were injected with junctional-like current mimicking that evoked by a presynaptic action potential. Unlike control neurons, which were less likely to spike, cells in PMA always fired action potentials to the junctional-like current. Furthermore, PKC activation increased a postsynaptic voltage-gated Ca2+ current, which was recruited even by modest depolarization associated with an electrotonic potential. Whereas PKC inhibits gap junctions in most systems, bag cell neurons are rather unique, as the kinase potentiates the electrical synapse; in turn, this synergizes with augmented postsynaptic Ca2+ current to promote synchronous firing.SIGNIFICANCE STATEMENT Electrical coupling is a fundamental form of communication. For the bag cell neurons of Aplysia, electrical synapses coordinate a prolonged burst of action potentials known as the afterdischarge. We looked at how protein kinase C, which is upregulated with the afterdischarge, influences information transfer across the synapse. The kinase activation increased junctional current, a remarkable finding given that this enzyme is largely considered inhibitory for gap junctions. There was also an augmentation in the ability of a presynaptic neuron to provoke postsynaptic action potentials. This increased excitability was, in part, due to enhanced postsynaptic voltage-dependent Ca2+ current. Thus, protein kinase C improves the fidelity of electrotonic transmission and promotes synchronous firing by modulating both junctional and membrane conductances.
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Coulon P, Landisman CE. The Potential Role of Gap Junctional Plasticity in the Regulation of State. Neuron 2017; 93:1275-1295. [PMID: 28334604 DOI: 10.1016/j.neuron.2017.02.041] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 01/20/2017] [Accepted: 02/22/2017] [Indexed: 11/19/2022]
Abstract
Electrical synapses are the functional correlate of gap junctions and allow transmission of small molecules and electrical current between coupled neurons. Instead of static pores, electrical synapses are actually plastic, similar to chemical synapses. In the thalamocortical system, gap junctions couple inhibitory neurons that are similar in their biochemical profile, morphology, and electrophysiological properties. We postulate that electrical synaptic plasticity among inhibitory neurons directly interacts with the switching between different firing patterns in a state-dependent and type-dependent manner. In neuronal networks, electrical synapses may function as a modifiable resonance feedback system that enables stable oscillations. Furthermore, the plasticity of electrical synapses may play an important role in regulation of state, synchrony, and rhythmogenesis in the mammalian thalamocortical system, similar to chemical synaptic plasticity. Based on their plasticity, rich diversity, and specificity, electrical synapses are thus likely to participate in the control of consciousness and attention.
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Affiliation(s)
- Philippe Coulon
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA 98101, USA.
| | - Carole E Landisman
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA 98101, USA.
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Wang LJ, Ma KT, Shi WY, Wang YZ, Zhao L, Chen XY, Li XZ, Jiang XW, Zhang ZS, Li L, Si JQ. Enhanced gap junctional channel activity between vascular smooth muscle cells in cerebral artery of spontaneously hypertensive rats. Clin Exp Hypertens 2017; 39:295-305. [PMID: 28513236 DOI: 10.1080/10641963.2016.1235181] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The aim of the present study is to investigate the effects of hypertension on the gap junctions between vascular smooth muscle cells (VSMCs) in the cerebral arteries (CAs) of spontaneously hypertensive rats (SHRs). The functions of gap junctions in the CAs of VSMCs in SHRs and control normotensive Wistar-Kyoto (WKY) rats were studied using whole-cell patch clamp recordings and pressure myography, and the expression levels of connexins were analyzed using reverse transcription-quantitative polymerase chain reaction and Western blot analyses. Whole-cell patch clamp measurements revealed that the membrane capacitance and conductance of in situ VSMCs in the CAs were significantly greater in SHRs than in WKY rats, suggesting that gap junction coupling is enhanced between VSMCs in the CAs of SHRs. Application of the endothelium-independent vasoconstrictors KCl or phenylephrine (PE) stimulated a greater vasoconstriction in the CAs of SHRs than in those of WKY rats. The EC50 value of KCl was 24.9 mM (n = 14) and 36.9 mM (n=12) for SHRs and WKY rats, respectively. The EC50 value of PE was 0.9 µM (n = 7) and 2.2 µM (n = 7) for SHRs and WKY rats, respectively. Gap junction inhibitors 18β-glycyrrhetinic acid (18β-GA), niflumic acid (NFA), and 2-aminoethoxydiphenyl borate (2-APB) attenuated KCl-induced vasoconstriction in SHRs and WKY rats. The mRNA and protein expression levels of the gap junction protein connexin 45 (Cx45) were significantly higher in the CAs of SHRs than in those of WKY rats. Phosphorylated Cx43 protein expression was significantly higher in the CAs of SHRs than in those of WKY rats, despite the total Cx43 mRNA and protein expression levels in the cerebral artery (CA) exhibiting no significant difference between SHRs and WKY rats. Increases in the expression of Cx45 and phosphorylation of Cx43 may promote gap junction communication among VSMCs in the CAs of SHRs, which may enhance the contractile response of the CA to vasoconstrictors.
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Affiliation(s)
- Li-Jie Wang
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China
| | - Ke-Tao Ma
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,b The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University , Shihezi , China
| | - Wen-Yan Shi
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,c Department of Physiology , Huazhong University of Science and Technology of Basic Medical Sciences , Wuhan , China
| | - Ying-Zi Wang
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China
| | - Lei Zhao
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,b The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University , Shihezi , China
| | - Xin-Yan Chen
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China
| | - Xin-Zhi Li
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,b The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University , Shihezi , China
| | - Xue-Wei Jiang
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China
| | - Zhong-Shuang Zhang
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,b The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University , Shihezi , China
| | - Li Li
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,b The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University , Shihezi , China
| | - Jun-Qiang Si
- a Department of Physiology , Medical College of Shihezi University , Shihezi , China.,b The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University , Shihezi , China.,c Department of Physiology , Huazhong University of Science and Technology of Basic Medical Sciences , Wuhan , China.,d Department of Physiology , Wuhan University School of Basic Medical Sciences , Wuhan , China
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9
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Lavrov I, Fox L, Shen J, Han Y, Cheng J. Gap Junctions Contribute to the Regulation of Walking-Like Activity in the Adult Mudpuppy (Necturus Maculatus). PLoS One 2016; 11:e0152650. [PMID: 27023006 PMCID: PMC4811563 DOI: 10.1371/journal.pone.0152650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 03/17/2016] [Indexed: 12/03/2022] Open
Abstract
Although gap junctions are widely expressed in the developing central nervous system, the role of electrical coupling of neurons and glial cells via gap junctions in the spinal cord in adults is largely unknown. We investigated whether gap junctions are expressed in the mature spinal cord of the mudpuppy and tested the effects of applying gap junction blocker on the walking-like activity induced by NMDA or glutamate in an in vitro mudpuppy preparation. We found that glial and neural cells in the mudpuppy spinal cord expressed different types of connexins that include connexin 32 (Cx32), connexin 36 (Cx36), connexin 37 (Cx37), and connexin 43 (Cx43). Application of a battery of gap junction blockers from three different structural classes (carbenexolone, flufenamic acid, and long chain alcohols) substantially and consistently altered the locomotor-like activity in a dose-dependent manner. In contrast, these blockers did not significantly change the amplitude of the dorsal root reflex, indicating that gap junction blockers did not inhibit neuronal excitability nonselectively in the spinal cord. Taken together, these results suggest that gap junctions play a significant modulatory role in the spinal neural networks responsible for the generation of walking-like activity in the adult mudpuppy.
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Affiliation(s)
- Igor Lavrov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia
| | - Lyle Fox
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jun Shen
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Yingchun Han
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jianguo Cheng
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- * E-mail:
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10
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Koo J, Choe HK, Kim HD, Chun SK, Son GH, Kim K. Effect of Mefloquine, a Gap Junction Blocker, on Circadian Period2 Gene Oscillation in the Mouse Suprachiasmatic Nucleus Ex Vivo. Endocrinol Metab (Seoul) 2015; 30:361-70. [PMID: 25491783 PMCID: PMC4595362 DOI: 10.3803/enm.2015.30.3.361] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 07/31/2014] [Accepted: 10/17/2014] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND In mammals, the master circadian pacemaker is localized in an area of the ventral hypothalamus known as the suprachiasmatic nucleus (SCN). Previous studies have shown that pacemaker neurons in the SCN are highly coupled to one another, and this coupling is crucial for intrinsic self-sustainability of the SCN central clock, which is distinguished from peripheral oscillators. One plausible mechanism underlying the intercellular communication may involve direct electrical connections mediated by gap junctions. METHODS We examined the effect of mefloquine, a neuronal gap junction blocker, on circadian Period 2 (Per2) gene oscillation in SCN slice cultures prepared from Per2::luciferase (PER2::LUC) knock-in mice using a real-time bioluminescence measurement system. RESULTS Administration of mefloquine causes instability in the pulse period and a slight reduction of amplitude in cyclic PER2::LUC expression. Blockade of gap junctions uncouples PER2::LUC-expressing cells, in terms of phase transition, which weakens synchrony among individual cellular rhythms. CONCLUSION These findings suggest that neuronal gap junctions play an important role in synchronizing the central pacemaker neurons and contribute to the distinct self-sustainability of the SCN master clock.
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Affiliation(s)
- Jinmi Koo
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Han Kyoung Choe
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Hee Dae Kim
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Sung Kook Chun
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Gi Hoon Son
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Legal Medicine, Korea University College of Medicine, Seoul, Korea
| | - Kyungjin Kim
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea.
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11
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Modelling the Effects of Electrical Coupling between Unmyelinated Axons of Brainstem Neurons Controlling Rhythmic Activity. PLoS Comput Biol 2015; 11:e1004240. [PMID: 25954930 PMCID: PMC4425518 DOI: 10.1371/journal.pcbi.1004240] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 03/15/2015] [Indexed: 11/19/2022] Open
Abstract
Gap junctions between fine unmyelinated axons can electrically couple groups of brain neurons to synchronise firing and contribute to rhythmic activity. To explore the distribution and significance of electrical coupling, we modelled a well analysed, small population of brainstem neurons which drive swimming in young frog tadpoles. A passive network of 30 multicompartmental neurons with unmyelinated axons was used to infer that: axon-axon gap junctions close to the soma gave the best match to experimentally measured coupling coefficients; axon diameter had a strong influence on coupling; most neurons were coupled indirectly via the axons of other neurons. When active channels were added, gap junctions could make action potential propagation along the thin axons unreliable. Increased sodium and decreased potassium channel densities in the initial axon segment improved action potential propagation. Modelling suggested that the single spike firing to step current injection observed in whole-cell recordings is not a cellular property but a dynamic consequence of shunting resulting from electrical coupling. Without electrical coupling, firing of the population during depolarising current was unsynchronised; with coupling, the population showed synchronous recruitment and rhythmic firing. When activated instead by increasing levels of modelled sensory pathway input, the population without electrical coupling was recruited incrementally to unpatterned activity. However, when coupled, the population was recruited all-or-none at threshold into a rhythmic swimming pattern: the tadpole “decided” to swim. Modelling emphasises uncertainties about fine unmyelinated axon physiology but, when informed by biological data, makes general predictions about gap junctions: locations close to the soma; relatively small numbers; many indirect connections between neurons; cause of action potential propagation failure in fine axons; misleading alteration of intrinsic firing properties. Modelling also indicates that electrical coupling within a population can synchronize recruitment of neurons and their pacemaker firing during rhythmic activity. Some groups of nerve cells in the brain are connected to each other electrically where their processes make contact and form specialized “gap” junctions. The simplest function of electrical connections is to make activity propagate faster by avoiding the delays resulting from chemical messengers at synaptic connections. In other cases, especially in higher brain regions where more spread out nerve cells may be connected by their axons, the function of electrical coupling is less clear. To understand this type of electrical connection better we have built computer models of a group of electrically coupled nerve cells in the brain which control swimming in very young frog tadpoles. We show that the coupling can be indirect, via other members of the group, and can profoundly influence the properties of the nerve cells which would be recorded during real experiments. The main role of the coupling is to synchronise the firing of the group so they are all recruited together when the tadpole is stimulated and then fire in a rhythm suitable to drive swimming movements. The results from this simple animal raise issues which will help to understand coupling in more complex brains.
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12
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Rabinowitch I, Schafer WR. Engineering new synaptic connections in the C. elegans connectome. WORM 2015; 4:e992668. [PMID: 26430564 PMCID: PMC4588382 DOI: 10.4161/21624054.2014.992668] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 11/21/2014] [Accepted: 11/24/2014] [Indexed: 01/14/2023]
Abstract
Most of what we currently know about how neural circuits work we owe to methods based on the electrical or optical recording of neural activity. This is changing dramatically. First, the advent of optogenetic techinques has enabled precise manipulation of the activity of specific neurons. Second, the development of super-resolution methods for obtaining detailed maps of synaptic connectivity has paved the way for uncovering the connectomes of entire brains or brain regions. We describe a third and complementary new strategy for investigating and manipulating neural circuits: the artificial insertion of new synapses into existing neural circuits using genetic engineering tools. We have successfully accomplished this in C. elegans. Thus, In addition to being the first animal with an entirely mapped connectome, C. elegans is now also the first animal to have an editable connectome. Variations on this approach may be applicable in more complex nervous systems.
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Affiliation(s)
- Ithai Rabinowitch
- Basic Sciences Division; Fred Hutchinson Cancer Research Center ; Seattle, WA USA
| | - William R Schafer
- Cell Biology Division; MRC Laboratory of Molecular Biology ; Cambridge, UK
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13
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Dargaei Z, Colmers PLW, Hodgson HM, Magoski NS. Electrical coupling between Aplysia bag cell neurons: characterization and role in synchronous firing. J Neurophysiol 2014; 112:2680-96. [PMID: 25185820 DOI: 10.1152/jn.00494.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In neuroendocrine cells, hormone release often requires a collective burst of action potentials synchronized by gap junctions. This is the case for the electrically coupled bag cell neurons in the reproductive system of the marine snail, Aplysia californica. These neuroendocrine cells are found in two clusters, and fire a synchronous burst, called the afterdischarge, resulting in neuropeptide secretion and the triggering of ovulation. However, the physiology and pharmacology of the bag cell neuron electrical synapse are not completely understood. As such, we made dual whole cell recordings from pairs of electrically coupled cultured bag cell neurons. The junctional current was nonrectifying and not influenced by postsynaptic voltage. Furthermore, junctional conductance was voltage independent and, not surprisingly, strongly correlated with coupling coefficient magnitude. The electrical synapse also acted as a low-pass filter, although under certain conditions, electrotonic potentials evoked by presynaptic action potentials could drive postsynaptic spikes. If coupled neurons were stimulated to spike simultaneously, they presented a high degree of action potential synchrony compared with not-coupled neurons. The electrical synapse failed to pass various intracellular dyes, but was permeable to Cs(+), and could be inhibited by niflumic acid, meclofenamic acid, or 5-nitro-2-(3-phenylpropylamino)benzoic acid. Finally, extracellular and sharp-electrode recording from the intact bag cell neuron cluster showed that these pharmacological uncouplers disrupted both electrical coupling and afterdischarge generation in situ. Thus electrical synapses promote bag cell neuron firing synchrony and may allow for electrotonic spread of the burst through the network, ultimately contributing to propagation of the species.
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Affiliation(s)
- Zahra Dargaei
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Phillip L W Colmers
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Heather M Hodgson
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Neil S Magoski
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
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14
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Rewiring neural circuits by the insertion of ectopic electrical synapses in transgenic C. elegans. Nat Commun 2014; 5:4442. [PMID: 25026983 PMCID: PMC4109004 DOI: 10.1038/ncomms5442] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 06/17/2014] [Indexed: 12/13/2022] Open
Abstract
Neural circuits are functional ensembles of neurons that are selectively interconnected by chemical or electrical synapses. Here we describe a synthetic biology approach to the study of neural circuits, whereby new electrical synapses can be introduced in novel sites in the neuronal circuitry to reprogram behaviour. We added electrical synapses composed of the vertebrate gap junction protein Cx36 between Caenorhabditis elegans chemosensory neurons with opposite intrinsic responses to salt. Connecting these neurons by an ectopic electrical synapse led to a loss of lateral asymmetry and altered chemotaxis behaviour. In a second example, introducing Cx36 into an inhibitory chemical synapse between an olfactory receptor neuron and an interneuron changed the sign of the connection from negative to positive, and abolished the animal’s behavioural response to benzaldehyde. These data demonstrate a synthetic strategy to rewire behavioural circuits by engineering synaptic connectivity in C. elegans. Neural circuits are functional ensembles of neurons that are selectively interconnected by chemical or electrical synapses. Here the authors describe an approach to the study of neural circuits in C. elegans whereby electrical synapses are introduced between previously unconnected neurons to reprogram behaviour.
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15
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Kim J, Lee S, Tsuda S, Zhang X, Asrican B, Gloss B, Feng G, Augustine GJ. Optogenetic mapping of cerebellar inhibitory circuitry reveals spatially biased coordination of interneurons via electrical synapses. Cell Rep 2014; 7:1601-1613. [PMID: 24857665 DOI: 10.1016/j.celrep.2014.04.047] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 02/10/2014] [Accepted: 04/21/2014] [Indexed: 11/26/2022] Open
Abstract
We used high-speed optogenetic mapping technology to examine the spatial organization of local inhibitory circuits formed by cerebellar interneurons. Transgenic mice expressing channelrhodopsin-2 exclusively in molecular layer interneurons allowed us to focally photostimulate these neurons, while measuring resulting responses in postsynaptic Purkinje cells. This approach revealed that interneurons converge upon Purkinje cells over a broad area and that at least seven interneurons form functional synapses with a single Purkinje cell. The number of converging interneurons was reduced by treatment with gap junction blockers, revealing that electrical synapses between interneurons contribute substantially to the spatial convergence. Remarkably, gap junction blockers affected convergence in sagittal slices, but not in coronal slices, indicating a sagittal bias in electrical coupling between interneurons. We conclude that electrical synapse networks spatially coordinate interneurons in the cerebellum and may also serve this function in other brain regions.
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Affiliation(s)
- Jinsook Kim
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Singapore 637553, Singapore; Laboratory of Synaptic Circuitry, Program in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore; A(∗)STAR/Duke-NUS Neuroscience Research Partnership, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Soojung Lee
- Laboratory of Synaptic Circuitry, Program in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore; A(∗)STAR/Duke-NUS Neuroscience Research Partnership, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Center for Functional Connectomics, Korea Institute of Science and Technology, 39-1 Hawolgokdong, Seongbukgu, Seoul 136-791, Republic of Korea; Department of Maxillofacial Tissue Regeneration, School of Dentistry, Kyung Hee University, Seoul 130-050, Republic of Korea
| | - Sachiko Tsuda
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Singapore 637553, Singapore; Laboratory of Synaptic Circuitry, Program in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore; A(∗)STAR/Duke-NUS Neuroscience Research Partnership, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Xuying Zhang
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Brent Asrican
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Bernd Gloss
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Guoping Feng
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA; McGovern Institute for Brain Research, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - George J Augustine
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Singapore 637553, Singapore; Laboratory of Synaptic Circuitry, Program in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore; A(∗)STAR/Duke-NUS Neuroscience Research Partnership, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; Marine Biological Laboratory, Woods Hole, MA 02543, USA; Center for Functional Connectomics, Korea Institute of Science and Technology, 39-1 Hawolgokdong, Seongbukgu, Seoul 136-791, Republic of Korea; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore.
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16
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Ceriani F, Mammano F. A rapid and sensitive assay of intercellular coupling by voltage imaging of gap junction networks. Cell Commun Signal 2013; 11:78. [PMID: 24144139 PMCID: PMC3819673 DOI: 10.1186/1478-811x-11-78] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022] Open
Abstract
Background A variety of mechanisms that govern connexin channel gating and permeability regulate coupling in gap junction networks. Mutations in connexin genes have been linked to several pathologies, including cardiovascular anomalies, peripheral neuropathy, skin disorders, cataracts and deafness. Gap junction coupling and its patho–physiological alterations are commonly assayed by microinjection experiments with fluorescent tracers, which typically require several minutes to allow dye transfer to a limited number of cells. Comparable or longer time intervals are required by fluorescence recovery after photobleaching experiments. Paired electrophysiological recordings have excellent time resolution but provide extremely limited spatial information regarding network connectivity. Results Here, we developed a rapid and sensitive method to assay gap junction communication using a combination of single cell electrophysiology, large–scale optical recordings and a digital phase–sensitive detector to extract signals with a known frequency from Vf2.1.Cl, a novel fluorescent sensor of plasma membrane potential. Tests performed in HeLa cell cultures confirmed that suitably encoded Vf2.1.Cl signals remained confined within the network of cells visibly interconnected by fluorescently tagged gap junction channels. We used this method to visualize instantly intercellular connectivity over the whole field of view (hundreds of cells) in cochlear organotypic cultures from postnatal mice. A simple resistive network model reproduced accurately the spatial dependence of the electrical signals throughout the cellular network. Our data suggest that each pair of cochlear non−sensory cells of the lesser epithelial ridge is coupled by ~1500 gap junction channels, on average. Junctional conductance was reduced by 14% in cochlear cultures harboring the T5M mutation of connexin30, which induces a moderate hearing loss in connexin30T5M/T5M knock–in mice, and by 91% in cultures from connexin30−/− mice, which are profoundly deaf. Conclusions Our methodology allows greater sensitivity (defined as the minimum magnitude of input signal required to produce a specified output signal having a specified signal−to−noise ratio) and better time resolution compared to classical tracer–based techniques. It permitted us to dynamically visualize intercellular connectivity down to the 10th order in non−sensory cell networks of the developing cochlea. We believe that our approach is of general interest and can be seamlessly extended to a variety of biological systems, as well as to other connexin−related disease conditions.
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Affiliation(s)
| | - Fabio Mammano
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, Padova 35131, Italy.
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Moradi S, Charkhpour M, Ghavimi H, Motahari R, Ghaderi M, Hassanzadeh K. Gap junction blockers: a potential approach to attenuate morphine withdrawal symptoms. J Biomed Sci 2013; 20:77. [PMID: 24143922 PMCID: PMC4015126 DOI: 10.1186/1423-0127-20-77] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 10/14/2013] [Indexed: 11/18/2022] Open
Abstract
Background The exact mechanisms of morphine-induced dependence and withdrawal symptoms remain unclear. In order to identify an agent that can prevent withdrawal syndrome, many studies have been performed. This study was aimed to evaluate the effect of gap junction blockers; carbenoxolone (CBX) or mefloquine (MFQ); on morphine withdrawal symptoms in male rat. Adult male Wistar rats (225 – 275 g) were selected randomly and divided into 10 groups. All groups underwent stereotaxic surgery and in order to induce dependency, morphine was administered subcutaneously) Sc) at an interval of 12 hours for nine continuous days. On the ninth day of the experiment, animals received vehicle or CBX (100, 400, 600 μg/10 μl/rat, icv) or MFQ (50, 100 and 200 μg/10 μl/rat, icv) after the last saline or morphine (Sc) injection. Morphine withdrawal symptoms were precipitated by naloxone hydrochloride 10 min after the treatments. The withdrawal signs including: jumping, rearing, genital grooming, abdomen writhing, wet dog shake and stool weight, were recorded for 60 minutes. Results Results showed that CBX and MFQ decreased all withdrawal signs; and the analysis indicated that they could attenuate the total withdrawal scores significantly. Conclusion Taking together it is concluded that gap junction blockers prevented naloxone-precipitated withdrawal symptoms.
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Affiliation(s)
| | | | | | | | | | - Kambiz Hassanzadeh
- Cellular and Molecular Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran.
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18
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Ma KT, Li XZ, Li L, Jiang XW, Chen XY, Liu WD, Zhao L, Zhang ZS, Si JQ. Role of gap junctions in the contractile response to agonists in the mesenteric artery of spontaneously hypertensive rats. Hypertens Res 2013; 37:110-5. [PMID: 24048484 DOI: 10.1038/hr.2013.120] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 12/24/2022]
Abstract
To investigate the effects of hypertension on the changes in gap junctions between vascular smooth muscle cells (VSMCs) in the mesenteric artery (MA) of spontaneously hypertensive rats (SHRs). Whole-cell patch clamp, pressure myography, real-time quantitative reverse transcription PCR (qRT-PCR), western blot analysis and transmission electron microscopy were used to examine the differences in expression and function of the gap junction between MA VSMCs of SHR and control normotensive Wistar-Kyoto (WKY) rats. (1) Whole-cell patch clamp measurements showed that the membrane capacitance and conductance of in-situ MA VSMCs of SHR were significantly greater than those of WKY rats (P<0.05), suggesting enhanced gap junction coupling between MA VSMCs of SHR. (2) The administration of phenylephrine (PE) and KCl (an endothelium-independent vasoconstrictor) initiated more pronounced vasoconstriction in SHR versus WKY rats (P<0.05). Furthermore, 2-APB (a gap junction inhibitor) attenuated PE- and KCl-induced vasoconstriction, and the inhibitory effects of 2-APB were significantly greater in SHR (P<0.05). (3) The expression of connexin 45 (Cx45) mRNA and protein in the MA was greater in SHR versus WKY rats (P<0.05). The level of phosphorylated Cx43 was significantly higher in SHR versus WKY rats (P<0.05), although the expression of total Cx43 mRNA and protein in the MA was equivalent between SHR and WKY rats. Electron microscopy revealed that the gap junctions were significantly larger in SHR versus WKY rats. Increases in the expression of Cx45 and phosphorylation of Cx43 may contribute to the enhancement of communication across gap junctions between MA VSMCs of SHR, which may increase the contractile response to agonists.
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Affiliation(s)
- Ke-Tao Ma
- 1] Department of Physiology, Medical College of Shihezi University, Shihezi, PR China [2] The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, PR China
| | - Xin-Zhi Li
- 1] The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, PR China [2] Department of Pathophysiology, Medical College of Shihezi University, Shihezi, PR China
| | - Li Li
- 1] Department of Physiology, Medical College of Shihezi University, Shihezi, PR China [2] The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, PR China
| | - Xue-Wei Jiang
- Department of Physiology, Medical College of Shihezi University, Shihezi, PR China
| | - Xin-Yan Chen
- Department of Physiology, Medical College of Shihezi University, Shihezi, PR China
| | - Wei-Dong Liu
- Department of Physiology, Medical College of Shihezi University, Shihezi, PR China
| | - Lei Zhao
- 1] Department of Physiology, Medical College of Shihezi University, Shihezi, PR China [2] The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, PR China
| | - Zhong-Shuang Zhang
- 1] Department of Physiology, Medical College of Shihezi University, Shihezi, PR China [2] The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, PR China
| | - Jun-Qiang Si
- 1] Department of Physiology, Medical College of Shihezi University, Shihezi, PR China [2] The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, PR China
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Li XZ, Ma KT, Guan BC, Li L, Zhao L, Zhang ZS, Si JQ, Jiang ZG. Fenamates block gap junction coupling and potentiate BKCa channels in guinea pig arteriolar cells. Eur J Pharmacol 2013; 703:74-82. [PMID: 23420003 PMCID: PMC3615131 DOI: 10.1016/j.ejphar.2013.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 02/01/2013] [Accepted: 02/06/2013] [Indexed: 10/27/2022]
Abstract
We determined the actions of the fenamates, flufenamic acid (FFA) and niflumic acid (NFA), on gap junction-mediated intercellular coupling between vascular smooth muscle cells (VSMC) in situ of acutely isolated arteriole segments from the three vascular beds: the spiral modiolar artery (SMA), anterior inferior cerebellar artery (AICA) and mesenteric artery (MA), and on non-junctional membrane channels in dispersed VSMCs. Conventional whole-cell recording methods were used. FFA reversibly suppressed the input conductance (Ginput) or increased the input resistance (Rinput) in a concentration dependent manner, with slightly different IC50s for the SMA, AICA and MA segments (26, 33 and 56 μM respectively, P>0.05). Complete electrical isolation of the recorded VSMC was normally reached at ≥ 300 μM. NFA had a similar effect on gap junction among VSMCs with an IC50 of 40, 48 and 62 μM in SMA, AICA and MA segments, respectively. In dispersed VSMCs, FFA and NFA increased outward rectifier K(+)-current mediated by the big conductance calcium-activated potassium channel (BKCa) in a concentration-dependent manner, with a similar EC50 of ∼300 μM for both FFA and NFA in the three vessels. Iberiotoxin, a selective blocker of the BKCa, suppressed the enhancement of the BKCa by FFA and NFA. The KV blocker 4-AP had no effect on the fenamates-induced K(+)-current enhancement. We conclude that FFA and NFA blocked the vascular gap junction mediated electrical couplings uniformly in arterioles of the three vascular beds, and complete electrical isolation of the recorded VSMC is obtained at ≧300μM; FFA and NFA also activate BKCa channels in the arteriolar smooth muscle cells in addition to their known inhibitory effects on chloride channels.
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Affiliation(s)
- Xin-Zhi Li
- Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, P.R. China
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Ke-Tao Ma
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Bing-Cai Guan
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050017, P.R. China
| | - Li Li
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Lei Zhao
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Zhong-Shuang Zhang
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Jun-Qiang Si
- Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, P.R. China
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Zhi-Gen Jiang
- Oregon Hearing Research Center, NRC04, Oregon Health and Science University, Portland, OR, 97239 USA
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Hur YN, Lee J, Sohn SC, Won CG, Lee HH, Kim DH, Choi SH, Shin KH, Chun BG. Sex Differences in Hippocampal Neuronal Sensitization by Nicotine in M. gerbils. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY 2013; 17:405-9. [PMID: 24227940 PMCID: PMC3823952 DOI: 10.4196/kjpp.2013.17.5.405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/31/2013] [Accepted: 08/13/2013] [Indexed: 11/15/2022]
Abstract
We studied the sex different nicotine effect on evoked population spike amplitudes (ePSA) and connexin (Cx) expression in the hippocampus CA1 area of gerbils. Acute doses of nicotine bitartrate (0.5 mg/kg: NT-0.5) slightly reduced ePSA in males but markedly augmented that in females. Acute NT (5.0 mg/kg) markedly increased the ePSA in all gerbils. Unlike acute NT-0.5, repeated NT-0.5 injection (twice a day for 7 days) significantly increased the ePSA in males and slightly affected the NT-0.5 effect in females. The Cx36 and Cx43 expression levels as well as Cx expressing neuronal populations were significantly increased by repeated NT-0.5 in in both male and female gerbils, and particularly, Cx43 expression was somewhat prominent in females. These results demonstrated a sex difference with respect to the nicotine effect on hippocampal bisynaptic excitability, irrelevant to connexin expression.
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Affiliation(s)
- Young-Na Hur
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Joon Lee
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Seung-Chan Sohn
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Chung-Gil Won
- Department of Anatomy, College of Veterinary Medicine, Gyeongsang National University, Jinju 660-701, Korea
| | - Hyung-Ha Lee
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Dong-Hoon Kim
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Sang-Hyun Choi
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Kyung-Ho Shin
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
| | - Boe-Gwun Chun
- Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, Korea
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Wu CL, Shih MF, Lai JY, Yang HT, Turner G, Chen L, Chiang AS. Heterotypic Gap Junctions between Two Neurons in the Drosophila Brain Are Critical for Memory. Curr Biol 2011; 21:848-54. [DOI: 10.1016/j.cub.2011.02.041] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 02/24/2011] [Accepted: 02/24/2011] [Indexed: 10/18/2022]
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Zlomuzica A, Reichinnek S, Maxeiner S, Both M, May E, Wörsdörfer P, Draguhn A, Willecke K, Dere E. Deletion of connexin45 in mouse neurons disrupts one-trial object recognition and alters kainate-induced gamma-oscillations in the hippocampus. Physiol Behav 2010; 101:245-53. [PMID: 20471991 DOI: 10.1016/j.physbeh.2010.05.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2009] [Revised: 04/16/2010] [Accepted: 05/07/2010] [Indexed: 10/19/2022]
Abstract
Neuronal gap junctions, allowing fast intercellular electrotonic signal transfer, have been implicated in mechanisms governing learning and memory processes. We have examined conditional neuron-directed (Cx45fl/fl:Nestin-Cre) connexin45 deficient mice in terms of behavioral and electrophysiological correlates of learning and memory. Behavioral habituation to a novel environment and motor learning were not changed in these mice. Novel object recognition after delays of up to 60min was impaired in neuronal Cx45 deficient mice. However, object-place recognition was not significantly different from controls. Analysis of enhanced green fluorescent reporter protein expression controlled by the endogenous mouse Cx45 promoter in the brain of neuronal Cx45 deficient mice suggested that Cx45 is expressed in the perirhinal cortex and the CA3 subregion of the hippocampus. The neuronal Cx45 deficient mice were also examined for aberrations in the generation and synchronization of network oscillations in the hippocampus. General excitability, synaptic short time plasticity, and spontaneous high-frequency oscillations (sharp-wave ripples) in the hippocampus were not different from controls. However, bath stimulation of hippocampal slices with kainate induced significantly lower gamma-oscillation amplitudes in the CA3, but not in the CA1 subfield of the neuronal Cx45 deficient mice. Additionally, they exhibited a significantly larger full width half maximum of the frequency distribution in the CA1 subfield as compared to the controls. In conclusion, the neuron-directed deletion of Cx45 impaired one-trial novel object recognition and altered kainate-induced gamma-oscillations possibly via the disruption of inter-neuronal gap junctional communication in the hippocampus or perirhinal cortex.
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Affiliation(s)
- A Zlomuzica
- Institute of Experimental Psychology, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
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Abdallah CG, Tang CY, Mathew SJ, Martinez J, Hof PR, Perera TD, Shungu DC, Gorman JM, Coplan JD. Diffusion tensor imaging in studying white matter complexity: a gap junction hypothesis. Neurosci Lett 2010; 475:161-4. [PMID: 20371267 DOI: 10.1016/j.neulet.2010.03.070] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/05/2010] [Accepted: 03/29/2010] [Indexed: 01/08/2023]
Abstract
The role of the prefrontal cortex as an executive oversight of posterior brain regions raises the question of the extent to which the anterior regions of the brain interconnect with the posterior regions. The aim of this study is to test the complexity of rostral white matter tracts, which connect anterior and posterior brain regions, in comparison to caudal white matter tracts and the corpus callosum. Diffusion tensor imaging (DTI) is a modality that measures fractional anisotropy (FA). Higher white matter complexity could result in a decrease of FA, possibly through denser intersection of fiber tracts. DTI was used to determine regional FA in 9 healthy bonnet macaques (Macaca radiata). Four regions of interest were included: anterior and posterior limbs of the internal capsule, the occipital lobe white matter, and the corpus callosum. FA of the anterior limbs of the internal capsule was lowest compared to all other regions of interest (Newman-Keuls (N-K); p<0.0001), whereas FA of the corpus callosum was highest (N-K; p<0.0001). The posterior limbs of the internal capsule and the occipital white matter were not distinguishable but exhibited intermediate FA in comparison to the former (N-K; p<0.0001) and the latter (N-K; p<0.0001). The current study demonstrates that FA, a measure of white matter complexity, can vary markedly as a function of region of interest. Moreover, validation of these findings using neurohistological studies and replication in human samples appears warranted.
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Affiliation(s)
- Chadi G Abdallah
- Department of Psychiatry, Division of Neuropsychopharmacology, State University of New York, Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11023, USA.
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Juszczak GR, Swiergiel AH. Properties of gap junction blockers and their behavioural, cognitive and electrophysiological effects: animal and human studies. Prog Neuropsychopharmacol Biol Psychiatry 2009; 33:181-98. [PMID: 19162118 DOI: 10.1016/j.pnpbp.2008.12.014] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 12/22/2008] [Accepted: 12/22/2008] [Indexed: 10/21/2022]
Abstract
Gap junctions play an important role in brain physiology. They synchronize neuronal activity and connect glial cells participating in the regulation of brain metabolism and homeostasis. Gap junction blockers (GJBs) include various chemicals that impair gap junction communication, disrupt oscillatory neuronal activity over a wide range of frequencies, and decrease epileptic discharges. The behavioural and clinical effects of GJBs suggest that gap junctions can be involved in the regulation of locomotor activity, arousal, memory, and breathing. Severe neuropsychiatric side effects suggest the involvement of gap junctions in mechanisms of consciousness. Unfortunately, the available GJBs are not selective and can bind to targets other than gap junctions. Other problems in behavioural studies include the possible adverse effects of GJBs, for example, retinal toxicity and hearing disturbances, changes in blood-brain transport, and the metabolism of other drugs. Therefore, it is necessary to design experiments properly to avoid false, misleading or uninterpretable results. We review the pharmacological properties and electrophysiological, behavioural and cognitive effects of the available gap junction blockers, such as carbenoxolone, glycyrrhetinic acid, quinine, quinidine, mefloquine, heptanol, octanol, anandamide, fenamates, 2-APB, several anaesthetics, retinoic acid, oleamide, spermine, aminosulfonates, and sodium propionate. It is concluded that despite a number of different problems, the currently used gap junction blockers could be useful tools in pharmacology and neuroscience.
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Affiliation(s)
- Grzegorz R Juszczak
- Department of Animal Behaviour, Institute of Genetics and Animal Breeding, Jastrzebiec, ul. Postepu 1, 05-552 Wolka Kosowska, Poland.
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