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Carta E, Chung SK, James VM, Robinson A, Gill JL, Remy N, Vanbellinghen JF, Drew CJG, Cagdas S, Cameron D, Cowan FM, Del Toro M, Graham GE, Manzur AY, Masri A, Rivera S, Scalais E, Shiang R, Sinclair K, Stuart CA, Tijssen MAJ, Wise G, Zuberi SM, Harvey K, Pearce BR, Topf M, Thomas RH, Supplisson S, Rees MI, Harvey RJ. Mutations in the GlyT2 gene (SLC6A5) are a second major cause of startle disease. J Biol Chem 2012; 287:28975-85. [PMID: 22700964 PMCID: PMC3436555 DOI: 10.1074/jbc.m112.372094] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/11/2012] [Indexed: 11/06/2022] Open
Abstract
Hereditary hyperekplexia or startle disease is characterized by an exaggerated startle response, evoked by tactile or auditory stimuli, leading to hypertonia and apnea episodes. Missense, nonsense, frameshift, splice site mutations, and large deletions in the human glycine receptor α1 subunit gene (GLRA1) are the major known cause of this disorder. However, mutations are also found in the genes encoding the glycine receptor β subunit (GLRB) and the presynaptic Na(+)/Cl(-)-dependent glycine transporter GlyT2 (SLC6A5). In this study, systematic DNA sequencing of SLC6A5 in 93 new unrelated human hyperekplexia patients revealed 20 sequence variants in 17 index cases presenting with homozygous or compound heterozygous recessive inheritance. Five apparently unrelated cases had the truncating mutation R439X. Genotype-phenotype analysis revealed a high rate of neonatal apneas and learning difficulties associated with SLC6A5 mutations. From the 20 SLC6A5 sequence variants, we investigated glycine uptake for 16 novel mutations, confirming that all were defective in glycine transport. Although the most common mechanism of disrupting GlyT2 function is protein truncation, new pathogenic mechanisms included splice site mutations and missense mutations affecting residues implicated in Cl(-) binding, conformational changes mediated by extracellular loop 4, and cation-π interactions. Detailed electrophysiology of mutation A275T revealed that this substitution results in a voltage-sensitive decrease in glycine transport caused by lower Na(+) affinity. This study firmly establishes the combination of missense, nonsense, frameshift, and splice site mutations in the GlyT2 gene as the second major cause of startle disease.
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Affiliation(s)
- Eloisa Carta
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Seo-Kyung Chung
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Victoria M. James
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Angela Robinson
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Jennifer L. Gill
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Nathalie Remy
- Human Genetics, Liège University Hospital, B-4000 Liège, Belgium
| | | | - Cheney J. G. Drew
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Sophie Cagdas
- Department of Child Neuropsychiatry, C Poma Hospital, 46100 Mantova, Italy
| | - Duncan Cameron
- Department of Paediatrics, Glan Clwyd Hospital, Rhyl LL18 5UJ, United Kingdom
| | - Frances M. Cowan
- Department of Paediatrics, Imperial College, London W12 0HS, United Kingdom
| | - Mireria Del Toro
- Servicio de Neurologia Pediatrica, Hospital General Universitari Vall d'Hebron, 08035 Barcelona, Spain
| | - Gail E. Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada
| | - Adnan Y. Manzur
- Department of Paediatric Neurology, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom
| | - Amira Masri
- Department of Paediatrics, University of Jordan, 11941 Amman, Jordan
| | - Serge Rivera
- Service de Pédiatrie, Centre Hospitalier de la Côte Basque, 64109 Bayonne, France
| | - Emmanuel Scalais
- Neurologie Pédiatrique, Centre Hospitalier de Luxembourg, L-1210 Luxembourg
| | - Rita Shiang
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia 23298-0033
| | - Kate Sinclair
- Queensland Paediatric Rehabilitation Service, Royal Children's Hospital, Herston 4029, Australia
| | | | - Marina A. J. Tijssen
- Department of Neurology, University Medical Centre Groningen, 9713 GZ, Groningen, The Netherlands
| | - Grahame Wise
- Sydney Children's Hospital, Randwick NSW 2031, Australia
| | - Sameer M. Zuberi
- Paediatric Neurosciences Research Group, Royal Hospital for Sick Children, Glasgow G3 8SJ, United Kingdom
| | - Kirsten Harvey
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Brian R. Pearce
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Maya Topf
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, London WC1E 7HX, United Kingdom
| | - Rhys H. Thomas
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
- Wales Epilepsy Research Network, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Stéphane Supplisson
- Institut de Biologie de l'Ecole Normale Supérieure, Paris 75000, France
- Institut National de la Santé et de la Recherche Médicale, U1024, Paris 75000, France, and
- CNRS, UMR 8197, Paris 75000, France
| | - Mark I. Rees
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
- Wales Epilepsy Research Network, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Robert J. Harvey
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
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Davies JS, Chung SK, Thomas RH, Robinson A, Hammond CL, Mullins JGL, Carta E, Pearce BR, Harvey K, Harvey RJ, Rees MI. The glycinergic system in human startle disease: a genetic screening approach. Front Mol Neurosci 2010; 3:8. [PMID: 20407582 PMCID: PMC2854534 DOI: 10.3389/fnmol.2010.00008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 03/08/2010] [Indexed: 11/17/2022] Open
Abstract
Human startle disease, also known as hyperekplexia (OMIM 149400), is a paroxysmal neurological disorder caused by defects in glycinergic neurotransmission. Hyperekplexia is characterised by an exaggerated startle reflex in response to tactile or acoustic stimuli which first presents as neonatal hypertonia, followed in some with episodes of life-threatening infantile apnoea. Genetic screening studies have demonstrated that hyperekplexia is genetically heterogeneous with several missense and nonsense mutations in the postsynaptic glycine receptor (GlyR) alpha1 subunit gene (GLRA1) as the primary cause. More recently, missense, nonsense and frameshift mutations have also been identified in the glycine transporter GlyT2 gene, SLC6A5, demonstrating a presynaptic component to this disease. Further mutations, albeit rare, have been identified in the genes encoding the GlyR beta subunit (GLRB), collybistin (ARHGEF9) and gephyrin (GPHN) - all of which are postsynaptic proteins involved in orchestrating glycinergic neurotransmission. In this review, we describe the clinical ascertainment aspects, phenotypic considerations and the downstream molecular genetic tools utilised to analyse both presynaptic and postsynaptic components of this heterogeneous human neurological disorder. Moreover, we will describe how the ancient startle response is the preserve of glycinergic neurotransmission and how animal models and human hyperekplexia patients have provided synergistic evidence that implicates this inhibitory system in the control of startle reflexes.
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Affiliation(s)
- Jeff S Davies
- Institute of Life Science, School of Medicine, Swansea University Singleton Park, Swansea, UK
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Harvey RJ, Carta E, Pearce BR, Chung SK, Supplisson S, Rees MI, Harvey K. A critical role for glycine transporters in hyperexcitability disorders. Front Mol Neurosci 2008; 1:1. [PMID: 18946534 PMCID: PMC2526004 DOI: 10.3389/neuro.02.001.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 01/30/2008] [Indexed: 11/13/2022] Open
Abstract
Defects in mammalian glycinergic neurotransmission result in a complex motor disorder characterized by neonatal hypertonia and an exaggerated startle reflex, known as hyperekplexia (OMIM 149400). This affects newborn children and is characterized by noise or touch-induced seizures that result in muscle stiffness and breath-holding episodes. Although rare, this disorder can have serious consequences, including brain damage and/or sudden infant death. The primary cause of hyperekplexia is missense and non-sense mutations in the glycine receptor (GlyR) α1 subunit gene (GLRA1) on chromosome 5q33.1, although we have also discovered rare mutations in the genes encoding the GlyR β subunit (GLRB) and the GlyR clustering proteins gephyrin (GPNH) and collybistin (ARHGEF9). Recent studies of the Na+/Cl−-dependent glycine transporters GlyT1 and GlyT2 using mouse knockout models and human genetics have revealed that mutations in GlyT2 are a second major cause of hyperekplexia, while the phenotype of the GlyT1 knockout mouse resembles a devastating neurological disorder known as glycine encephalopathy (OMIM 605899). These findings highlight the importance of these transporters in regulating the levels of synaptic glycine.
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Affiliation(s)
- Robert J Harvey
- Department of Pharmacology, The School of Pharmacy London, UK
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Rees MI, Harvey K, Pearce BR, Chung SK, Duguid IC, Thomas P, Beatty S, Graham GE, Armstrong L, Shiang R, Abbott KJ, Zuberi SM, Stephenson JBP, Owen MJ, Tijssen MAJ, van den Maagdenberg AMJM, Smart TG, Supplisson S, Harvey RJ. Mutations in the gene encoding GlyT2 (SLC6A5) define a presynaptic component of human startle disease. Nat Genet 2006; 38:801-6. [PMID: 16751771 PMCID: PMC3204411 DOI: 10.1038/ng1814] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Accepted: 05/05/2006] [Indexed: 11/08/2022]
Abstract
Hyperekplexia is a human neurological disorder characterized by an excessive startle response and is typically caused by missense and nonsense mutations in the gene encoding the inhibitory glycine receptor (GlyR) alpha1 subunit (GLRA1). Genetic heterogeneity has been confirmed in rare sporadic cases, with mutations affecting other postsynaptic glycinergic proteins including the GlyR beta subunit (GLRB), gephyrin (GPHN) and RhoGEF collybistin (ARHGEF9). However, many individuals diagnosed with sporadic hyperekplexia do not carry mutations in these genes. Here we show that missense, nonsense and frameshift mutations in SLC6A5 (ref. 8), encoding the presynaptic glycine transporter 2 (GlyT2), also cause hyperekplexia. Individuals with mutations in SLC6A5 present with hypertonia, an exaggerated startle response to tactile or acoustic stimuli, and life-threatening neonatal apnea episodes. SLC6A5 mutations result in defective subcellular GlyT2 localization, decreased glycine uptake or both, with selected mutations affecting predicted glycine and Na+ binding sites.
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Affiliation(s)
- Mark I Rees
- School of Medicine, University of Wales Swansea, Singleton Park, West Glamorgan SA2 8PP, UK.
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Harvey K, Duguid IC, Alldred MJ, Beatty SE, Ward H, Keep NH, Lingenfelter SE, Pearce BR, Lundgren J, Owen MJ, Smart TG, Lüscher B, Rees MI, Harvey RJ. The GDP-GTP exchange factor collybistin: an essential determinant of neuronal gephyrin clustering. J Neurosci 2004; 24:5816-26. [PMID: 15215304 PMCID: PMC6729214 DOI: 10.1523/jneurosci.1184-04.2004] [Citation(s) in RCA: 195] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Glycine receptors (GlyRs) and specific subtypes of GABA(A) receptors are clustered at synapses by the multidomain protein gephyrin, which in turn is translocated to the cell membrane by the GDP-GTP exchange factor collybistin. We report the characterization of several new variants of collybistin, which are created by alternative splicing of exons encoding an N-terminal src homology 3 (SH3) domain and three alternate C termini (CB1, CB2, and CB3). The presence of the SH3 domain negatively regulates the ability of collybistin to translocate gephyrin to submembrane microaggregates in transfected mammalian cells. Because the majority of native collybistin isoforms appear to harbor the SH3 domain, this suggests that collybistin activity may be regulated by protein-protein interactions at the SH3 domain. We localized the binding sites for collybistin and the GlyR beta subunit to the C-terminal MoeA homology domain of gephyrin and show that multimerization of this domain is required for collybistin-gephyrin and GlyR-gephyrin interactions. We also demonstrate that gephyrin clustering in recombinant systems and cultured neurons requires both collybistin-gephyrin interactions and an intact collybistin pleckstrin homology domain. The vital importance of collybistin for inhibitory synaptogenesis is underlined by the discovery of a mutation (G55A) in exon 2 of the human collybistin gene (ARHGEF9) in a patient with clinical symptoms of both hyperekplexia and epilepsy. The clinical manifestation of this collybistin missense mutation may result, at least in part, from mislocalization of gephyrin and a major GABA(A) receptor subtype.
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Affiliation(s)
- Kirsten Harvey
- Department of Pharmacology, The School of Pharmacy, London WC1N 1AX, United Kingdom.
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Webster MT, Pearce BR, Bowen DM, Francis PT. The effects of perturbed energy metabolism on the processing of amyloid precursor protein in PC12 cells. J Neural Transm (Vienna) 1998; 105:839-53. [PMID: 9869322 DOI: 10.1007/s007020050098] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The mismetabolism of amyloid precursor protein (APP), favouring the production of A beta, is considered to be central to the pathogenesis of Alzheimer's disease (AD). However it remains to be established whether the causative factor is the reported toxicity of A beta or reduced production of secretory derivatives of APP which may have trophic or neuroprotective properties. One possible contributory factor to an imbalance in APP metabolism is the impaired cellular energy availability described in AD. The aim of this study was to investigate processing of APP-like proteins following inhibition of oxidative energy metabolism in PC12 cells. Under these conditions, intracellular and secreted APP-like proteins were significantly reduced. Treatment of energy perturbed cells with the lysosomotropic agent chloroquine restored intracellular concentrations of APP-like proteins to the control range, while the secretion was completely restored by activation of protein kinase C. These findings raise the possibility that energy related metabolic stress may lead to altered metabolism of APP-like proteins favouring a potentially amyloidogenic pathway. Furthermore, the observation that activation of PKC is able to overcome this potentially pathogenic process has important implications for treatment of AD with the current generation of cholinomimetic drugs, suggesting that such drugs may slow disease progression as well as improve cognitive dysfunction.
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Affiliation(s)
- M T Webster
- Dementia Research Laboratory, Biochemical Neuropharmacology Group, UMDS, London, United Kingdom
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Webster MT, Groome N, Francis PT, Pearce BR, Sherriff FE, Thinakaran G, Felsenstein KM, Wasco W, Tanzi RE, Bowen DM. A novel protein, amyloid precursor-like protein 2, is present in human brain, cerebrospinal fluid and conditioned media. Biochem J 1995; 310 ( Pt 1):95-9. [PMID: 7646477 PMCID: PMC1135859 DOI: 10.1042/bj3100095] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A monoclonal antibody, 3B11, was raised to a novel protein, amyloid precursor-like protein 2, which did not recognize amyloid precursor protein. Multiple bands were detected in human brain fractions and cell lysate by Western blotting, indicating the presence of isoforms, 3B11 immunoreactivity was also detected in cerebrospinal fluid and conditioned medium, indicating that the protein is secreted. Immunocytochemistry revealed 3B11 immunoreactivity in sections of human brain.
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Affiliation(s)
- M T Webster
- Miriam Marks Department of Neurochemistry, Institute of Neurology, London, U.K
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Biggs CS, Pearce BR, Fowler LJ, Whitton PS. Effect of isonicotinic acid hydrazide on extracellular amino acids and convulsions in the rat: reversal of neurochemical and behavioural deficits by sodium valproate. J Neurochem 1994; 63:2197-201. [PMID: 7964739 DOI: 10.1046/j.1471-4159.1994.63062197.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have studied the effect of isonicotinic acid hydrazide (INH), a convulsant agent, on the extracellular levels of amino acids in the hippocampus, and the effect of sodium valproate (VPA) administration in INH-treated rats. INH (250 mg/kg) caused a rapid and sustained decrease in basal levels of GABA, and during this period convulsions of increasing severity were observed. Basal levels of glutamine, taurine, aspartate, and glutamate were unchanged by INH. When VPA was coadministered with INH, basal GABA levels were increased and no convulsions were observed. When transmitter release was evoked using 100 mM K+, the increase in dialysate GABA observed in INH-treated animals was less than that seen in controls and convulsions increased in frequency. K(+)-evoked release of glutamate and aspartate tended to be higher following INH treatment, and in the case of aspartate, this increase was significant. VPA reversed the changes in evoked release of glutamate and aspartate, and release of GABA was considerably greater than that seen in control or INH-treated rats. No drug effect on evoked changes in taurine or glutamine level was seen. These are the first data to show decreased extracellular GABA in conjunction with convulsions in freely moving animals in vivo.
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Affiliation(s)
- C S Biggs
- Department of Pharmacology, School of Pharmacy, London, England
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Affiliation(s)
- M T Webster
- Institute of Neurology, Queen Square, London
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Biggs CS, Pearce BR, Fowler LJ, Whitton PS. Regional effects of sodium valproate on extracellular concentrations of 5-hydroxytryptamine, dopamine, and their metabolites in the rat brain: an in vivo microdialysis study. J Neurochem 1992; 59:1702-8. [PMID: 1402915 DOI: 10.1111/j.1471-4159.1992.tb11001.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effects of sodium valproate (VPA; 100, 200, and 400 mg/kg, i.p.) on ventral hippocampal and anterior caudate putamen extracellular levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) were examined using in vivo microdialysis. VPA induced dose-related increases in dialysate DA, 3,4-dihydroxyphenylacetic acid, and 5-HT in the ventral hippocampus. Anterior caudate putamen dialysate 5-HT was also dose dependently elevated by the drug, whereas DA levels tended to decrease with increasing VPA dose. In contrast, VPA (200, 400, and 800 mg/kg, i.p.) produced no significant elevation of DA in posterior caudate putamen dialysates, although 5-HT levels were significantly elevated at the 400- and 800-mg/kg doses. In all three regions studied, dialysate concentrations of 5-hydroxyindoleacetic acid and homovanillic acid remained at basal levels following VPA treatments. The results are discussed with regard to the possible anticonvulsant mode of action of VPA.
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Affiliation(s)
- C S Biggs
- Department of Pharmacology, School of Pharmacy, London, England, U.K
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Biggs CS, Pearce BR, Fowler LJ, Whitton PS. The effect of sodium valproate on extracellular GABA and other amino acids in the rat ventral hippocampus: an in vivo microdialysis study. Brain Res 1992; 594:138-42. [PMID: 1467933 DOI: 10.1016/0006-8993(92)91038-g] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We report the effects of i.p. administration of sodium valproate (VPA) on extracellular concentrations of various amino acids in the rat ventral hippocampus studied using in vivo microdialysis, followed by HPLC with fluorometric detection. At the doses used (100, 200 and 400 mg/kg), VPA had no effect on extracellular aspartate, glutamine and taurine, whilst inducing a small, but not statistically significant increase in glutamate at 200 and 400 mg/kg. In contrast, VPA administration produced a biphasic effect on extracellular GABA levels which was dependent on the dose used. At 100 mg/kg, VPA reduced GABA concentrations by 50% when compared to basal. 200 mg/kg VPA had virtually no effect, whilst 400 mg/kg VPA raised extracellular GABA levels to 200% of basal. The results are discussed in relation to the known pharmacological and anticonvulsant actions of VPA.
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Affiliation(s)
- C S Biggs
- Department of Pharmacology, School of Pharmacy, London, UK
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Abstract
The non-competitive N-methyl-D-aspartate receptor antagonist MK-801 was observed to have regionally specific effects on the extracellular concentration of dopamine and its metabolites. In rat anterior striatum, MK-801 transiently decreased extracellular dopamine, in spite of inducing intense circling behaviour which is generally associated with an increase in this neurotransmitter. In contrast, hippocampal extracellular dopamine was increased in a dose-related manner by MK-801. The possible significance of these data is discussed in relation to some of the known behavioural actions of MK-801.
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Affiliation(s)
- P S Whitton
- Department of Pharmacology, School of Pharmacy, London, UK
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13
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Abstract
The effect of MK-801 (0.25 or 0.5 mg/kg) on the extracellular concentration of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in rat hippocampus and striatum was studied using intracerebral dialysis. The dialysate 5-HT concentration was dose-dependently increased by MK-801 in both regions. In the hippocampus, at the higher drug dose a slow increase in the 5-HIAA level was observed, and this became significant 3 h after treatment. In contrast to this, the extracellular 5-HIAA content in the striatum was significantly decreased 150 min after administration of both doses of MK-801. The data are discussed in the light of the known behavioural effects of MK-801 and possible N-methyl-D-aspartic acid receptor regulation of 5-HT release.
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Affiliation(s)
- P S Whitton
- Department of Pharmacology, School of Pharmacy, London, England
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Abstract
A growth cone-enriched fraction isolated from neonatal rat forebrain was shown to accumulate gamma-amino [3H]butyric acid ([3H]-GABA) and [3H]noradrenaline ([3H]NA). Uptake of both neurotransmitters was sodium- and temperature-dependent and exhibited saturation kinetics with Km values of 17.7 microM and 4.5 microM respectively and Vmax values of 114 pmol/min/mg protein and 59 pmol/min/mg protein respectively. Electron microscopic autoradiography showed that about 50% of isolated growth cones can accumulate [3H]GABA. Inhibitor studies showed that beta-alanine was a relatively weak inhibitor of [3H]GABA uptake compared to nipecotic acid and diamino-butyric acid. Growth cone fractions preloaded with [3H]GABA and [3H]NA demonstrated a K+ (25 mM) -induced release of both neurotransmitters. Of the K+-stimulated release of [3H]GABA 50% was Ca2+-dependent, whereas the release of [3H]NA was entirely Ca2+-independent.
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Abstract
A subcellular fraction highly enriched in neuronal growth cones was isolated from 5-day-old rat forebrain by a recently described method. The growth cone fraction was shown to have a sodium- and temperature-dependent, high-affinity (Km = 4.4 microM) uptake system for [3H]GABA. Electron microscopic autoradiography confirmed that this uptake was into growth cones since only these structures were heavily labelled with silver grains. High potassium induced the release of newly accumulated [3H]GABA from the growth cone fraction, about half of which was Ca2+-dependent. The presence of uptake and release systems for GABA in growth cones may simply reflect the development of growth cones into nerve terminals. Alternatively, these observations may indicate a role for neurotransmitter release in synaptogenesis.
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Abstract
The binding of [3H]kainic acid to caudate nucleus membranes prepared from brains of examples of Alzheimer's dementia and controls has been determined. No changes were detected in either the affinity or the number of kainate binding sites in the Alzheimer samples compared to control, although there was a large decrease in choline acetyltransferase activity.
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Abstract
We examined the ability of developing cerebellar cell cultures to synthesize a 71,000 MW stress protein (SP71) in response to heat shock and Cd2+ treatment. The induction of SP71 synthesis appeared to be dependent on both the age of the culture and the stressor used. Heat shock induced SP71 synthesis in freshly prepared cells and in cell cultures at each age examined, whereas Cd2+ was effective only in cultures at 7 days of age and older. These findings are discussed with reference to the development of various cell types in these cultures.
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Abstract
The effect of tetanus toxin pretreatment on K+-stimulated [3H]gamma-aminobutyric acid release from neuron-enriched cerebellar cell cultures at various stages during their development in vitro was assessed. Tetanus toxin had little inhibitory effect on immature (1-3-day-old) cultures, but markedly reduced K+-evoked [3H]gamma-aminobutyric acid release from 7- and 14-day-old cultures (approximately 80% inhibition). It is suggested that cerebellar neurons in culture develop tetanus toxin-sensitive transmitter release mechanisms similar to their in vivo counterparts.
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Abstract
We investigated the effect of GABA, muscimol and THIP on the K+ -stimulated and spontaneous release of [3H]GABA from neuron-enriched cell cultures of the rat cerebellum. Each agonist produced significant reductions in evoked [3H]GABA without causing marked changes in spontaneous release. The agonist-induced inhibition of K+ -stimulated [3H]GABA release was reversed by the GABA antagonists bicuculline and picrotoxin. It is suggested that GABAergic neurons in cerebellar cell cultures possess GABA receptors which are involved in the regulation of evoked transmitter release.
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Pearce BR, Dutton GR. K+-stimulated release of endogenous glutamate, GABA and other amino acids from neuron- and glia-enriched cultures of the rat cerebellum. FEBS Lett 1981; 135:215-8. [PMID: 6119230 DOI: 10.1016/0014-5793(81)80980-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Pearce BR, Currie DN, Beale R, Dutton GR. Potassium-stimulated, calcium-dependent release of [3H]GABA from neuron- and glia-enriched cultures of cells dissociated from rat cerebellum. Brain Res 1981; 206:485-9. [PMID: 6260284 DOI: 10.1016/0006-8993(81)90552-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The release of [3H]GABA from cultures of cells dissociated from the rat cerebellum was investigated. The culture system contained a population of neurons (stellate and basket cells) which were capable of accumulating [3H]GABA and releasing it in a calcium-dependent manner in response to 50 mM potassium. In addition, the release of [3H]GABA for cultured astrocytes was found to be insensitive to potassium depolarization.
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Pearce BR, Currie DN, Dutton GR, Hussey RE, Beale R, Pigott R. A simple perfusion chamber for studying neurotransmitter release from cells maintained in monolayer culture. J Neurosci Methods 1981; 3:255-9. [PMID: 6111627 DOI: 10.1016/0165-0270(81)90061-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A perfusion chamber is described for studying the efflux of putative neurotransmitters from CNS cells maintained in monolayer culture. We have used this apparatus to investigate the efflux of newly accumulated [3H]GABA from cell cultures of the early postnatal rat cerebellum.
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