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Gouveia D, Mandigers P, Cherubini GB. Bromide: the good, the bad, and the ugly of the oldest antiseizure medication. Front Vet Sci 2024; 11:1433191. [PMID: 38988980 PMCID: PMC11233540 DOI: 10.3389/fvets.2024.1433191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Accepted: 06/12/2024] [Indexed: 07/12/2024] Open
Abstract
Bromide is the first effective antiseizure medication used in human medicine since the XIX century. Initially met with skepticism, bromide quickly gained enthusiasm within the medical field until being largely replaced by newer antiseizure medications with significantly fewer adverse effects in people. In veterinary medicine, bromide continues to be used in the management of epileptic patients for over 30 years, yet adverse effects can impact owners and patients alike. We sought to provide the general practitioner and veterinary neurologist with insightful information on both the positive and negative attributes of bromide, explore factors that may influence its desirability as an antiseizure medication in specific veterinary cases and elucidate its current role in modern epilepsy treatment for veterinary patients. It's also our endeavor to discuss the current use as an alternative or add-on with other known antiseizure medications and potential future studies that might enhance our understanding and use of this medication.
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Affiliation(s)
- Diogo Gouveia
- Dick White Referrals – Linnaeus, Cambridgeshire, United Kingdom
| | - Paul Mandigers
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands
| | - Giunio Bruto Cherubini
- Department of Veterinary Sciences, Veterinary Teaching Hospital “Mario Modenato”, University of Pisa, Pisa, Italy
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2
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Järvelä V, Hamze M, Komulainen-Ebrahim J, Rahikkala E, Piispala J, Kallio M, Kangas SM, Nickl T, Huttula M, Hinttala R, Uusimaa J, Medina I, Immonen EV. A novel pathogenic SLC12A5 missense variant in epilepsy of infancy with migrating focal seizures causes impaired KCC2 chloride extrusion. Front Mol Neurosci 2024; 17:1372662. [PMID: 38660387 PMCID: PMC11039960 DOI: 10.3389/fnmol.2024.1372662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 03/19/2024] [Indexed: 04/26/2024] Open
Abstract
The potassium-chloride co-transporter 2, KCC2, is a neuron-specific ion transporter that plays a multifunctional role in neuronal development. In mature neurons, KCC2 maintains a low enough intracellular chloride concentration essential for inhibitory neurotransmission. During recent years, pathogenic variants in the KCC2 encoding gene SLC12A5 affecting the functionality or expression of the transporter protein have been described in several patients with epilepsy of infancy with migrating focal seizures (EIMFS), a devastating early-onset developmental and epileptic encephalopathy. In this study, we identified a novel recessively inherited SLC12A5 c.692G>A, p. (R231H) variant in a patient diagnosed with severe and drug-resistant EIMFS and profound intellectual disability. The functionality of the variant was assessed in vitro by means of gramicidin-perforated patch-clamp experiments and ammonium flux assay, both of which indicated a significant reduction in chloride extrusion. Based on surface immunolabeling, the variant showed a reduction in membrane expression. These findings implicate pathogenicity of the SLC12A5 variant that leads to impaired inhibitory neurotransmission, increasing probability for hyperexcitability and epileptogenesis.
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Affiliation(s)
- Viivi Järvelä
- Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
| | - Mira Hamze
- INMED, INSERM, Aix-Marseille University, Marseille, France
| | - Jonna Komulainen-Ebrahim
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
- Department of Children and Adolescents, Division of Pediatric Neurology, Oulu University Hospital, Oulu, Finland
| | - Elisa Rahikkala
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
- Department of Clinical Genetics, Oulu University Hospital, Oulu, Finland
| | - Johanna Piispala
- Department of Clinical Neurophysiology, Oulu University Hospital, Oulu, Finland
| | - Mika Kallio
- Department of Clinical Neurophysiology, Oulu University Hospital, Oulu, Finland
| | - Salla M. Kangas
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
| | - Tereza Nickl
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
- Laboratory of Transgenic Models of Diseases, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
| | - Marko Huttula
- Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland
| | - Reetta Hinttala
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
- Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Johanna Uusimaa
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
- Department of Children and Adolescents, Division of Pediatric Neurology, Oulu University Hospital, Oulu, Finland
| | - Igor Medina
- INMED, INSERM, Aix-Marseille University, Marseille, France
| | - Esa-Ville Immonen
- Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
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3
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Chen Y, Compton RG. A bespoke reagent-free amperometric bromide sensor for seawater. Talanta 2023. [DOI: 10.1016/j.talanta.2022.124019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Derieux C, Léauté A, Brugoux A, Jaccaz D, Terrier C, Pin JP, Kniazeff J, Le Merrer J, Becker JAJ. Chronic sodium bromide treatment relieves autistic-like behavioral deficits in three mouse models of autism. Neuropsychopharmacology 2022; 47:1680-1692. [PMID: 35418620 PMCID: PMC9283539 DOI: 10.1038/s41386-022-01317-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 03/07/2022] [Accepted: 03/21/2022] [Indexed: 12/15/2022]
Abstract
Autism Spectrum Disorders (ASD) are neurodevelopmental disorders whose diagnosis relies on deficient social interaction and communication together with repetitive behavior. To date, no pharmacological treatment has been approved that ameliorates social behavior in patients with ASD. Based on the excitation/inhibition imbalance theory of autism, we hypothesized that bromide ions, long used as an antiepileptic medication, could relieve core symptoms of ASD. We evaluated the effects of chronic sodium bromide (NaBr) administration on autistic-like symptoms in three genetic mouse models of autism: Oprm1-/-, Fmr1-/- and Shank3Δex13-16-/- mice. We showed that chronic NaBr treatment relieved autistic-like behaviors in these three models. In Oprm1-/- mice, these beneficial effects were superior to those of chronic bumetanide administration. At transcriptional level, chronic NaBr in Oprm1 null mice was associated with increased expression of genes coding for chloride ions transporters, GABAA receptor subunits, oxytocin and mGlu4 receptor. Lastly, we uncovered synergistic alleviating effects of chronic NaBr and a positive allosteric modulator (PAM) of mGlu4 receptor on autistic-like behavior in Oprm1-/- mice. We evidenced in heterologous cells that bromide ions behave as PAMs of mGlu4, providing a molecular mechanism for such synergy. Our data reveal the therapeutic potential of bromide ions, alone or in combination with a PAM of mGlu4 receptor, for the treatment of ASDs.
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Affiliation(s)
- Cécile Derieux
- grid.464126.30000 0004 0385 4036Physiologie de la Reproduction et des Comportements, INRAE UMR0085, CNRS UMR7247, IFCE, Université de Tours, Inserm, 37380 Nouzilly, France ,grid.12366.300000 0001 2182 6141UMR1253, iBrain, Université de Tours, Inserm, CNRS, Faculté des Sciences et Techniques, Parc de Grandmont, 37200 Tours, France ,grid.121334.60000 0001 2097 0141Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, Inserm, 34094 Montpellier, France
| | - Audrey Léauté
- grid.464126.30000 0004 0385 4036Physiologie de la Reproduction et des Comportements, INRAE UMR0085, CNRS UMR7247, IFCE, Université de Tours, Inserm, 37380 Nouzilly, France
| | - Agathe Brugoux
- grid.464126.30000 0004 0385 4036Physiologie de la Reproduction et des Comportements, INRAE UMR0085, CNRS UMR7247, IFCE, Université de Tours, Inserm, 37380 Nouzilly, France ,grid.12366.300000 0001 2182 6141UMR1253, iBrain, Université de Tours, Inserm, CNRS, Faculté des Sciences et Techniques, Parc de Grandmont, 37200 Tours, France
| | - Déborah Jaccaz
- Unité Expérimentale de Physiologie Animale de l’Orfrasière, INRAE UE0028, 37380 Nouzilly, France
| | - Claire Terrier
- grid.464126.30000 0004 0385 4036Physiologie de la Reproduction et des Comportements, INRAE UMR0085, CNRS UMR7247, IFCE, Université de Tours, Inserm, 37380 Nouzilly, France ,grid.12366.300000 0001 2182 6141UMR1253, iBrain, Université de Tours, Inserm, CNRS, Faculté des Sciences et Techniques, Parc de Grandmont, 37200 Tours, France
| | - Jean-Philippe Pin
- grid.121334.60000 0001 2097 0141Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, Inserm, 34094 Montpellier, France
| | - Julie Kniazeff
- grid.121334.60000 0001 2097 0141Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, Inserm, 34094 Montpellier, France
| | - Julie Le Merrer
- Physiologie de la Reproduction et des Comportements, INRAE UMR0085, CNRS UMR7247, IFCE, Université de Tours, Inserm, 37380, Nouzilly, France. .,UMR1253, iBrain, Université de Tours, Inserm, CNRS, Faculté des Sciences et Techniques, Parc de Grandmont, 37200, Tours, France.
| | - Jerome A. J. Becker
- grid.464126.30000 0004 0385 4036Physiologie de la Reproduction et des Comportements, INRAE UMR0085, CNRS UMR7247, IFCE, Université de Tours, Inserm, 37380 Nouzilly, France ,grid.12366.300000 0001 2182 6141UMR1253, iBrain, Université de Tours, Inserm, CNRS, Faculté des Sciences et Techniques, Parc de Grandmont, 37200 Tours, France
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Mazzoleni S, Bassani S. PCDH19 interplay with GABA(A) receptors: a window to DEE9 pathogenetic mechanisms. Neural Regen Res 2021; 17:803-805. [PMID: 34472478 PMCID: PMC8530141 DOI: 10.4103/1673-5374.322455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Sara Mazzoleni
- Institute of Neuroscience, CNR, Milan; Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate (MI), Italy
| | - Silvia Bassani
- Institute of Neuroscience, CNR; NeuroMI Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy
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6
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Sabir M, Tan YY, Aris A, Mani AR. The role of endogenous bromotyrosine in health and disease. Free Radic Res 2019; 53:1019-1034. [PMID: 31530194 DOI: 10.1080/10715762.2019.1668560] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bromotyrosine is a stable by-product of eosinophil peroxidase activity, a result of eosinophil activation during an inflammatory immune response. The elevated presence of bromotyrosine in tissue, blood, and urine in medical conditions involving eosinophil activation has highlighted the potential role of bromotyrosine as a medical biomarker. This is highly beneficial in a paediatric setting as a urinary noninvasive biomarker. However, bromotyrosine and its derivatives may exert biological effects, such as protective effects in the brain and pathogenic effects in the thyroid. Understanding these pathways may yield therapeutic advancements in medicine. In this review, we summarize the existing evidence present in literature relating to bromotyrosine formation and metabolism, identify the biological actions of bromotyrosine and evaluate the feasibility of bromotyrosine as a medical biomarker.
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Affiliation(s)
- Mariam Sabir
- UCL Division of Medicine, Royal Free Campus, University College London , London , UK
| | - Yen Yi Tan
- UCL Division of Medicine, Royal Free Campus, University College London , London , UK
| | - Aleena Aris
- UCL Division of Medicine, Royal Free Campus, University College London , London , UK
| | - Ali R Mani
- UCL Division of Medicine, Royal Free Campus, University College London , London , UK
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7
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Combs MD, Edwards SH, Scherpenhuizen JM, Narayan EJ, Kessell AE, Ramsay J, Piltz J, Raidal SR, Quinn JC. Treatment with potassium bromide mitigates ataxia and reduces tremor in lambs with perennial ryegrass toxicosis. N Z Vet J 2019; 67:287-294. [PMID: 31248334 DOI: 10.1080/00480169.2019.1637300] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Aims: To assess the use of potassium bromide (KBr) as a therapeutic intervention for perennial ryegrass toxicosis (PRGT) in lambs fed ryegrass seed containing lolitrem B. Methods: Male lambs aged 10-12 months (n = 43) were assigned to receive ryegrass seed containing lolitrem B, at a dose of 0.16 mg/kg/day (Groups 2, 3 and 4), or lucerne chaff and molasses (Groups 1 and 5). Lambs in Groups 2 and 3 were observed for clinical signs and gait changes until defined signs of PGRT were observed, when they were transferred, with lambs in Group 1, to the Testing phase of the trial. Lambs in Group 3 were then treated with a single oral dose of 300 mg/kg bromide. Lambs in Groups 4 and 5 received KBr daily from the start of the trial (540 mg/kg bromide over 3 days then 20 mg/kg daily) and were transferred to the Testing phase after 18 days. Clinical examination and gait assessment, and surface electromyography of the triceps muscle, measuring root-mean-square (RMS) voltages, were carried out on Days 0, 1 and 2 of the Testing phase followed by necropsy, histopathology, measurement of concentrations of bromide in serum and CSF and faecal cortisol metabolites (FCM). Results: In Group 3 lambs, mean composite gait scores decreased between Testing phase Day 0 and Days 1 and 2 (p < 0.001), but increased in lambs in Group 2 between Day 0 and Day 2 (p = 0.015). Scores for lambs in Group 3 on Day 2 were lower than for lambs in Group 2 (p < 0.001). Mean RMS voltages on Day 2 were higher in lambs in Group 2 than Group 3 (p = 0.045). Mean concentrations of bromide in serum were >800 µg/mL in lambs in Groups 3 and 4 on Day 2. Concentrations of FCM were higher in lambs from Group 2 than in Groups 1 or 5, but were similar in Groups 2, 3 and 4. Histopathological findings in the cerebellum of lambs from Groups 2, 3 and 4 were similar, showing pyknosis of neurons within the granular layer of the cerebellum and Purkinje neuron proximal axonal spheroid formation. Conclusions and clinical relevance: A single oral dose of 300 mg/kg bromide in lambs with neurological signs of PRGT resulted in reduced composite gait scores and reduced RMS voltages, indicating a significant improvement in clinical signs of ataxia, movement disorder and muscle tremor associated with the neurotoxic effects of lolitrem B.
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Affiliation(s)
- M D Combs
- School of Animal and Veterinary Sciences, Charles Sturt University , Wagga Wagga , Australia
| | - S H Edwards
- School of Animal and Veterinary Sciences, Charles Sturt University , Wagga Wagga , Australia
| | - J M Scherpenhuizen
- School of Animal and Veterinary Sciences, Charles Sturt University , Wagga Wagga , Australia
| | - E J Narayan
- School of Science and Health, Western Sydney University , Penrith , Australia
| | - A E Kessell
- Veterinary Diagnostic Laboratory, City University of Hong Kong , Hong Kong
| | - J Ramsay
- School of Animal and Veterinary Sciences, Charles Sturt University , Wagga Wagga , Australia
| | - J Piltz
- New South Wales Department of Primary Industries , Wagga Wagga , Australia
| | - S R Raidal
- School of Animal and Veterinary Sciences, Charles Sturt University , Wagga Wagga , Australia
| | - J C Quinn
- School of Animal and Veterinary Sciences, Charles Sturt University , Wagga Wagga , Australia
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Kang JQ. Defects at the crossroads of GABAergic signaling in generalized genetic epilepsies. Epilepsy Res 2017; 137:9-18. [PMID: 28865303 DOI: 10.1016/j.eplepsyres.2017.08.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 08/14/2017] [Accepted: 08/22/2017] [Indexed: 12/16/2022]
Abstract
Seizure disorders are very common and affect 3% of the general population. The recurrent unprovoked seizures that are also called epilepsies are highly diverse as to both underlying genetic basis and clinic presentations. Recent genetic advances and sequencing technologies indicate that many epilepsies previously thought to be without known causes, or idiopathic generalized epilepsies (IGEs), are virtually genetic epilepsy as they are caused by genetic variations. IGEs are estimated to account for ∼15-20% of all epilepsies. Initially IGEs were primarily considered channelopathies, because the first genetic defects identified in IGEs involved ion channel genes. However, new findings indicate that mutations in many non ion channel genes are also involved in addition to those in ion channel genes. Interestingly, mutations in many genes associated with epilepsy affect GABAergic signaling, a major biological pathway in epilepsy. Additionally, many antiepileptic drugs work via enhancing GABAergic signaling. Hence, the review will focus on the mutations that impair GABAergic signaling and selectively discuss the newly identified STXBP1, PRRT2, and DNM1 in addition to those long-established epilepsy ion channel genes that also impair GABAergic signaling like SCN1A and GABAA receptor subunit genes. GABAergic signaling includes the pre- and post- synaptic mechanisms. Some mutations, such as STXBP1, PRRT2, DNM1, and SCN1A, impair GABAergic signaling mainly via pre-synaptic mechanisms while those mutations in GABAA receptor subunit genes impair GABAergic signaling via post-synaptic mechanisms. Nevertheless, these findings suggest impaired GABAergic signaling is a converging pathway of defects for many ion channel or non ion channel mutations associated with genetic epilepsies.
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Affiliation(s)
- Jing-Qiong Kang
- Departments of Neurology, Vanderbilt University Medical Center, Nashville, TN, 37232-8552, USA; Affiliated Hospital of Nantong University, Jiangsu, 226001, China; Vanderbilt Brain Institute, Vanderbilt Kennedy Center of Human Development, Vanderbilt University, Nashville, TN, 37232-8522, USA.
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9
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Quast TA, Combs MD, Edwards SH. Pharmacokinetics of bromide in adult sheep following oral and intravenous administration. Aust Vet J 2015; 93:20-5. [DOI: 10.1111/avj.12285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2013] [Indexed: 11/29/2022]
Affiliation(s)
- TA Quast
- School of Animal and Veterinary Science; Charles Sturt University; Wagga Wagga New South Wales Australia
| | - MD Combs
- School of Animal and Veterinary Science; Charles Sturt University; Wagga Wagga New South Wales Australia
| | - SH Edwards
- School of Animal and Veterinary Science; Charles Sturt University; Wagga Wagga New South Wales Australia
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10
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Combined effect of bumetanide, bromide, and GABAergic agonists: an alternative treatment for intractable seizures. Epilepsy Behav 2011; 20:147-9. [PMID: 21167788 DOI: 10.1016/j.yebeh.2010.10.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Revised: 10/26/2010] [Accepted: 10/27/2010] [Indexed: 11/22/2022]
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Zahran EM, Hua Y, Li Y, Flood AH, Bachas LG. Triazolophanes: a new class of halide-selective ionophores for potentiometric sensors. Anal Chem 2010; 82:368-75. [PMID: 19994863 DOI: 10.1021/ac902132d] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Triazolophanes, cyclic compounds containing 1,2,3-triazole units, are a new class of host molecules that demonstrate strong interactions with halides. These molecules are designed with a preorganized cavity that interacts through hydrogen bonding with spherical anions, such as chloride and bromide. We have explored the use of one such triazolophane as a halide-selective ionophore in poly(vinyl chloride) (PVC) membrane electrodes. Different membrane compositions were evaluated to identify concentrations of the ionophore, plasticizer, and lipophilic additive that give rise to the best chloride and bromide selectivity. The lipophilicity of the plasticizer was found to have a great impact on the electrode response. Additionally, the concentration of the lipophilic additive was found to be critical for optimal response. The utility of a triazolophane-based electrode was demonstrated by quantification of bromide in horse serum samples.
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Affiliation(s)
- Elsayed M Zahran
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, USA
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Nakamura F, Suzuki S, Nishimura S, Yagi K, Seino M. Effects of clobazam and its active metabolite on GABA-activated currents in rat cerebral neurons in culture. Epilepsia 1996; 37:728-35. [PMID: 8764810 DOI: 10.1111/j.1528-1157.1996.tb00643.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE The antiepileptic effects of clobazam, a 1,5-benzodiazepine, have been well documented in animal experiments and clinical trials. However, the drug's mechanisms of antiepileptic actions are still undetermined. The purpose of this study was to learn how clobazam and its active metabolite modulate gamma-aminobutyric acid (GABA)-activated currents in rat cerebral neurons in culture. METHODS Whole-cell voltage-clamp recordings were performed on cultured cerebral neurons of the rat. Clobazam or its metabolite N-desmethylclobazam was dissolved in the extracellular solution and applied for 2 s by pressure ejection from a micropipette. To maintain GABA-activated currents, 2 mM Mg adenosine triphosphate (ATP) was added to the intracellular solution. RESULTS GABA elicited outward currents that were mediated by GABAA receptor-coupled Cl- channels. Applying clobazam with 10 microM GABA elicited enhanced outward currents. Flumazenil, an antagonist of the benzodiazepine receptor, inhibited the enhancing effect of clobazam. The enhancement ratio increased as much as 2.28-fold in a dose-dependent manner at a concentration of 3 microM clobazam. However, it started to decrease at a concentration of 10 microM clobazam. The metabolite N-desmethylclobazam was tested in the same manner, and exhibited an identical dose-dependent enhancement of GABA-activated currents. CONCLUSIONS The antiepileptic effects of the 1,5-benzodiazepines are attributed to the enhancement of GABAergic inhibitory neurotransmission. The antiepileptic effects of clobazam are thought to depend mainly on its active metabolite N-desmethylclobazam, which is present in high concentrations in patients who receive long-term clobazam. Clobazam's enhancement of GABA-activated currents was most marked on weaker GABA currents. We therefore infer that clobazam acts more efficiently on tissues in which the release of GABA is diminished.
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Affiliation(s)
- F Nakamura
- National Epilepsy Center, Shizuoka Higashi Hospital, Japan
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Abstract
gamma-Aminobutyric acid (GABA)A receptors for the inhibitory neurotransmitter GABA are likely to be found on most, if not all, neurons in the brain and spinal cord. They appear to be the most complicated of the superfamily of ligand-gated ion channels in terms of the large number of receptor subtypes and also the variety of ligands that interact with specific sites on the receptors. There appear to be at least 11 distinct sites on GABAA receptors for these ligands.
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Affiliation(s)
- G A Johnston
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology, University of Sydney, NSW, Australia
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Abstract
The effect of dietary chloride content (0.2, 0.4 and 1.3 per cent chloride on a dry matter basis) on the disposition of a single oral dose of bromide (14 mg kg-1) was evaluated in normal beagles. Increasing the dietary chloride content from 0.2 to 1.3 per cent resulted in a significant decrease in the mean apparent elimination half-life from 69 +/- 22 days to 24 +/- 7 days. The mean area under the concentration curve (AUC) for dogs fed 1.3 per cent chloride was significantly smaller than the AUC for dogs fed 0.2 per cent chloride. Dietary chloride had no effect on the maximum serum concentrations (Cmax) or on the time (Tmax) to reach the maximum concentrations. The steady-state serum bromide concentrations predicted from the single dose data for daily doses of 14 mg kg-1 of bromide were significantly lower in dogs fed 1.3 per cent chloride (310 +/- 150 mg litre-1) than in dogs fed 0.2 per cent chloride (1950 +/- 1140 mg litre-1). The predicted mean daily doses of bromide necessary to maintain serum levels within the therapeutic range for dogs fed 1.3 per cent chloride (43 +/- 13 mg kg-1) were almost twice as high as the dose estimated for dogs fed 0.4 per cent chloride (22 +/- 3 mg kg-1) and nearly three times as high as the dose estimated for dogs fed 0.2 per cent chloride (15 +/- 4 mg kg-1). These differences were statistically significant (P = 0.002).
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Affiliation(s)
- L A Trepanier
- Department of Pharmacology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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