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Kristensen AS, Andersen J, Jørgensen TN, Sørensen L, Eriksen J, Loland CJ, Strømgaard K, Gether U. SLC6 neurotransmitter transporters: structure, function, and regulation. Pharmacol Rev 2011; 63:585-640. [PMID: 21752877 DOI: 10.1124/pr.108.000869] [Citation(s) in RCA: 601] [Impact Index Per Article: 46.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.
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Affiliation(s)
- Anders S Kristensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark.
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252
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Hanada T, Hashizume Y, Tokuhara N, Takenaka O, Kohmura N, Ogasawara A, Hatakeyama S, Ohgoh M, Ueno M, Nishizawa Y. Perampanel: A novel, orally active, noncompetitive AMPA-receptor antagonist that reduces seizure activity in rodent models of epilepsy. Epilepsia 2011; 52:1331-40. [DOI: 10.1111/j.1528-1167.2011.03109.x] [Citation(s) in RCA: 278] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Ngomba RT, Santolini I, Salt TE, Ferraguti F, Battaglia G, Nicoletti F, van Luijtelaar G. Metabotropic glutamate receptors in the thalamocortical network: strategic targets for the treatment of absence epilepsy. Epilepsia 2011; 52:1211-22. [PMID: 21569017 DOI: 10.1111/j.1528-1167.2011.03082.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Metabotropic glutamate (mGlu) receptors are positioned at synapses of the thalamocortical network that underlie the development of spike-and-wave discharges (SWDs) associated with absence epilepsy. The modulatory role of individual mGlu receptor subtypes on excitatory and inhibitory synaptic transmission in the cortico-thalamo-cortical circuitry makes subtype-selective mGlu receptor ligands potential candidates as novel antiabsence drugs. Some of these compounds are under clinical development for the treatment of numerous neurologic and psychiatric disorders, and might be soon available for clinical studies in patients with absence seizures refractory to conventional medications. Herein we review the growing evidence that links mGlu receptors to the pathophysiology of pathologic SWDs moving from the anatomic localization and function of distinct mGlu receptor subtypes in the cortico-thalamo-cortical network to in vivo studies in mouse and rat models of absence epilepsy.
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Abstract
It is well admitted now that gliosis participates in epileptogenesis, particularly in symptomatic focal epilepsies, like temporal lobe epilepsy. Indeed, astrocytic and microglial activation was shown to release numerous inflammatory factors that modify neuronal excitability or contribute to neuronal loss. These redundant processes maintain chronic epilepsy. However, other sources of inflammation exist. Several studies pointed out the epileptogenicity of blood-brain barrier disruption due to the leakage of leukocytes and serum proteins, triggering inflammatory and immune responses which disturb the neuronal environment. Recently, it was proposed that peripheral inflammation plays a key-role in epilepsy, mainly mediated by circulating cytokines which promote leukocyte extravasation.
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Affiliation(s)
- Mireille Lerner-Natoli
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U661, UM1, UM2, 141 rue de la Cardonille, 34094 Montpellier Cedex 9, France.
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256
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Beaumont M, Maccaferri G. Is connexin36 critical for GABAergic hypersynchronization in the hippocampus? J Physiol 2011; 589:1663-80. [PMID: 21300748 PMCID: PMC3099022 DOI: 10.1113/jphysiol.2010.201491] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 02/07/2011] [Indexed: 11/08/2022] Open
Abstract
Synchronous bursting of cortical GABAergic interneurons is important in epilepsies associated with excitatory GABAergic signalling. If electrical coupling was critical for the generation of this pathological activity, then the development of selective blockers of connexin36-based interneuronal gap junctions could be of therapeutic value. We have addressed this issue in the 4-aminopyridine model of epilepsy in vitro by comparing GABAergic epileptiform currents and their sensitivity to gap junction blockers in wild-type vs. connexin36 knockout mice. Although electrical coupling was abolished in stratum lacunosum-moleculare interneurons from knockout animals, epileptiform currents were not eliminated. Furthermore, epileptiform currents propagated similarly across hippocampal layers in the two genotypic groups. Blockade of electrical coupling with carbenoxolone suppressed amplitude, frequency and half-width of the epileptiform currents both in wild-type and in knockout animals, whereas mefloquine had no effects. Carbenoxolone also depressed responses to exogenous and synaptic GABA application onto interneurons. We conclude that, in the 4-aminopyridine model of epilepsy in vitro, connexin36 is not critical for the generation of epileptiform discharges in GABAergic networks and that the observed antiepileptic effects of carbenoxolone are likely to be due to blockade of GABAA receptors and not of connexin36-based gap junctions. Lastly, because of its chemical structure and its effects on amplitude and kinetics of GABAergic currents, we tested the hypothesis that carbenoxolone acted via specific sites on GABAA receptors, such as the one mediating the effects of the neurosteroid pregnenolone sulfate, or the allosteric regulatory site of benzodiazepines/β-carbolines. Our results suggest that neither of these is involved.
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Affiliation(s)
- Michael Beaumont
- Northwestern University Interdepartmental Neuroscience Program, Department of Physiology, Feinberg School of Medicine, 303 E Chicago Ave, Tarry Blg Rm 5-707, Chicago, IL 60611, USA
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Woode E, Poku RA, Abotsi WK. Anticonvulsant Effects of a Leaf Extract of Ficus exasperata Vahl (Moraceae) in Mice. INT J PHARMACOL 2011. [DOI: 10.3923/ijp.2011.405.409] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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258
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Lasoń W, Dudra-Jastrzębska M, Rejdak K, Czuczwar SJ. Basic mechanisms of antiepileptic drugs and their pharmacokinetic/pharmacodynamic interactions: an update. Pharmacol Rep 2011; 63:271-92. [DOI: 10.1016/s1734-1140(11)70497-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 03/14/2011] [Indexed: 01/20/2023]
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259
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Hildebrand ME, Smith PL, Bladen C, Eduljee C, Xie JY, Chen L, Fee-Maki M, Doering CJ, Mezeyova J, Zhu Y, Belardetti F, Pajouhesh H, Parker D, Arneric SP, Parmar M, Porreca F, Tringham E, Zamponi GW, Snutch TP. A novel slow-inactivation-specific ion channel modulator attenuates neuropathic pain. Pain 2011; 152:833-843. [PMID: 21349638 DOI: 10.1016/j.pain.2010.12.035] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 12/08/2010] [Accepted: 12/20/2010] [Indexed: 11/29/2022]
Abstract
Voltage-gated ion channels are implicated in pain sensation and transmission signaling mechanisms within both peripheral nociceptors and the spinal cord. Genetic knockdown and knockout experiments have shown that specific channel isoforms, including Na(V)1.7 and Na(V)1.8 sodium channels and Ca(V)3.2 T-type calcium channels, play distinct pronociceptive roles. We have rationally designed and synthesized a novel small organic compound (Z123212) that modulates both recombinant and native sodium and calcium channel currents by selectively stabilizing channels in their slow-inactivated state. Slow inactivation of voltage-gated channels can function as a brake during periods of neuronal hyperexcitability, and Z123212 was found to reduce the excitability of both peripheral nociceptors and lamina I/II spinal cord neurons in a state-dependent manner. In vivo experiments demonstrate that oral administration of Z123212 is efficacious in reversing thermal hyperalgesia and tactile allodynia in the rat spinal nerve ligation model of neuropathic pain and also produces acute antinociception in the hot-plate test. At therapeutically relevant concentrations, Z123212 did not cause significant motor or cardiovascular adverse effects. Taken together, the state-dependent inhibition of sodium and calcium channels in both the peripheral and central pain signaling pathways may provide a synergistic mechanism toward the development of a novel class of pain therapeutics.
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Affiliation(s)
- Michael E Hildebrand
- Zalicus Pharmaceuticals, 301-2389 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3 Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada T2N 4N1 Department of Pharmacology and Anesthesiology, University of Arizona, Tucson, AZ 85724, USA Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC, Canada V6T 1Z4
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260
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Chauhan K, Sheth N, Ranpariya V, Parmar S. Anticonvulsant activity of solasodine isolated from Solanum sisymbriifolium fruits in rodents. PHARMACEUTICAL BIOLOGY 2011; 49:194-199. [PMID: 21062107 DOI: 10.3109/13880209.2010.508499] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
CONTEXT Solanum sisymbriifolium Lam. (Solanaceae), commonly known as sticky nightshade, is traditionally used for central nervous system (CNS) disorders. Although solasodine has been isolated from this plant, little is known about its anticonvulsant and CNS depressant actions. OBJECTIVE We investigated anticonvulsant and CNS depressant effects of solasodine isolated from S. sisymbriifolium using several experimental models. MATERIALS AND METHODS Swiss albino mice (n=6) were employed for pentylenetetrazole (PTZ) and picrotoxin (PCT)-induced convulsions and thiopental-induced sleep time. Different groups of Wistar albino rats (n=6) were subjected to maximal electroshock (MES) test. Solasodine, a steroidal glycoalkaloid, was isolated from dried fruits of S. sisymbriifolium and identified by GC-MS. RESULTS The results showed that intraperitoneal (i.p.) injection of solasodine (25 mg/kg) significantly delayed (p < 0.01) latency of hind limb tonic extensor (HLTE) phase in the PCT-induced convulsions. In the MES model, solasodine significantly reduced (p < 0.001) duration of HLTE at 25, 50, and 100 mg/kg, i.p. in a dose-dependent manner. Interestingly, solasodine did not produce any significant reduction in PTZ-induced convulsions. Prior treatment of solasodine (25, 50, and 100 mg/kg, i.p.) significantly potentiated thiopental-provoked sleep in a dose-dependent manner (p < 0.001). DISCUSSION AND CONCLUSION Our study, for the first time, shows potent anticonvulsant and CNS depressant activities of solasodine. It is likely that solasodine, in part, is responsible for the anticonvulsant and sedative properties of S. sisymbriifolium. The future study should focus on the exact mechanism of action of solasodine.
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Affiliation(s)
- Kinjal Chauhan
- Department of Pharmaceutical Sciences, Saurashtra University, Rajkot, Gujarat, India
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261
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Abstract
This article discusses seven newly available antiepileptic drugs (AEDs) and agents in phase III development. Lacosamide, licensed as an adjunctive treatment for partial-onset seizures, primarily acts by enhancing sodium channel slow inactivation. At daily doses of 200-600 mg, the drug significantly reduced partial-onset seizures in adults with refractory epilepsy. The most common adverse effects are CNS related. Rufinamide, available as adjunctive treatment for seizures associated with Lennox-Gastaut syndrome, has an unclear mechanism of action, although it does block voltage-dependent sodium channels. Coadministration of valproic acid significantly increases rufinamide circulating concentrations. The drug has been shown to have efficacy for partial-onset, primary generalized tonic-clonic, tonic-atonic, absence and atypical absence seizures. Adverse effects are mainly somnolence, nausea and vomiting. Eslicarbazepine acetate, a carbamazepine analogue, was recently licensed as adjunctive treatment for partial-onset seizures. Eslicarbazepine acetate acts at voltage-gated sodium channels, although the precise mechanism of action is unclear. The drug had efficacy for partial-onset seizures in three randomized, double-blind, placebo-controlled studies, using 400, 800 or 1200 mg/day. Adverse effects include dizziness and somnolence. Retigabine (ezogabine) exerts its anticonvulsant effect through the opening of neuronal voltage-gated potassium channels. Following significant seizure reduction rates at dosages of 600, 900 and 1200 mg/day, license applications have been submitted for its use as adjunctive treatment for patients with partial-onset seizures. Dose-related adverse effects include somnolence, confusion and dizziness. Brivaracetam is the n-propyl analogue of levetiracetam. Mixed results have been obtained in phase III studies in patients with partial-onset seizures, and further trials in children, patients with photosensitive epilepsy and patients with partial-onset seizures are ongoing. Dizziness, headache and somnolence are the most common adverse effects reported. Perampanel was designed as an AMPA-type glutamate receptor antagonist. Following encouraging results from phase II studies in patients with refractory partial-onset seizures, recruitment for phase III trials is almost complete. Ganaxolone is a neurosteroid with potent antiepileptic activity that modulates GABA(A) receptors in the CNS. Ganaxolone has shown promise in a variety of seizure types. Dizziness and somnolence have been reported in some patients. The availability of new AEDs has widened the choices for clinicians treating patients with epilepsy. However, given the minimal improvement in prognosis and disappointing efficacy outcomes in double-blind, placebo-controlled, dose-ranging regulatory trials, it seems unlikely that these novel agents will have a major impact on outcomes for people with epilepsy.
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Affiliation(s)
- Linda J Stephen
- Epilepsy Unit, Division of Cardiovascular and Medical Sciences, Western Infirmary, Glasgow, Scotland
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262
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Gomes CV, Kaster MP, Tomé AR, Agostinho PM, Cunha RA. Adenosine receptors and brain diseases: neuroprotection and neurodegeneration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1380-99. [PMID: 21145878 DOI: 10.1016/j.bbamem.2010.12.001] [Citation(s) in RCA: 303] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 11/30/2010] [Accepted: 12/01/2010] [Indexed: 02/06/2023]
Abstract
Adenosine acts in parallel as a neuromodulator and as a homeostatic modulator in the central nervous system. Its neuromodulatory role relies on a balanced activation of inhibitory A(1) receptors (A1R) and facilitatory A(2A) receptors (A2AR), mostly controlling excitatory glutamatergic synapses: A1R impose a tonic brake on excitatory transmission, whereas A2AR are selectively engaged to promote synaptic plasticity phenomena. This neuromodulatory role of adenosine is strikingly similar to the role of adenosine in the control of brain disorders; thus, A1R mostly act as a hurdle that needs to be overcame to begin neurodegeneration and, accordingly, A1R only effectively control neurodegeneration if activated in the temporal vicinity of brain insults; in contrast, the blockade of A2AR alleviates the long-term burden of brain disorders in different neurodegenerative conditions such as ischemia, epilepsy, Parkinson's or Alzheimer's disease and also seem to afford benefits in some psychiatric conditions. In spite of this qualitative agreement between neuromodulation and neuroprotection by A1R and A2AR, it is still unclear if the role of A1R and A2AR in the control of neuroprotection is mostly due to the control of glutamatergic transmission, or if it is instead due to the different homeostatic roles of these receptors related with the control of metabolism, of neuron-glia communication, of neuroinflammation, of neurogenesis or of the control of action of growth factors. In spite of this current mechanistic uncertainty, it seems evident that targeting adenosine receptors might indeed constitute a novel strategy to control the demise of different neurological and psychiatric disorders.
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Affiliation(s)
- Catarina V Gomes
- Center for Neurosciences of Coimbra, University of Coimbra, Coimbra, Portugal
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263
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Abstract
To investigate the epistatic interactions involved in antiepileptic drug (AED) resistance, 26 coding single-nucleotide polymorphisms (SNPs) were selected from 16 candidate genes. A total of 200 patients with drug-resistant localization-related epilepsy and 200 patients with drug-responsive localization-related epilepsy were genotyped individually for the SNPs. Rather than using the traditional parametric statistical method, a new statistical method, multifactor dimensionality reduction (MDR), was used to determine whether gene-gene interactions increase the risk of AED resistance. The MDR method indicated that a combination of four SNPs (rs12658835 and rs35166395 from GABRA1, rs2228622 from EAAT3 and rs2304725 from GAT3) was the best model for predicting susceptibility to AED resistance with a statistically significant testing accuracy of 0.625 (P < 0.001) and cross-validation consistency of 10/10. This best model had an odds ratio of 3.68 with a significant 95% confidence interval of 2.32-5.85 (P < 0.0001). Our results may provide meaningful information on the mechanism underlying AED resistance and, to the best of our knowledge, this is the first report of evidence for gene-gene interactions underlying AED resistance.
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264
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Progress report on new antiepileptic drugs: A summary of the Tenth Eilat Conference (EILAT X). Epilepsy Res 2010; 92:89-124. [DOI: 10.1016/j.eplepsyres.2010.09.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/25/2010] [Accepted: 09/12/2010] [Indexed: 01/09/2023]
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265
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Siniscalchi A, Gallelli L, De Sarro G. Use of antiepileptic drugs for hyperkinetic movement disorders. Curr Neuropharmacol 2010; 8:359-66. [PMID: 21629443 PMCID: PMC3080592 DOI: 10.2174/157015910793358187] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 04/23/2010] [Accepted: 04/30/2010] [Indexed: 11/23/2022] Open
Abstract
Many studies investigated the use of antiepileptic drugs (AEDs) in several neurological diseases other than epilepsy. These neurological disorders, usually, involve neuronal excitability through the modulating of ion channels, receptors and intracellular signaling pathways, and are the targets of the AEDs. This article provides a review of the clinical efficacy of both conventional and newer AEDs in hyperkinetic movement disorders. Some of these indications for AEDs have been established, while others are under investigation. The modulation of GABAergic transmission may explain the neuronal hyper-excitability that underlies some forms of hyperkinetic movement disorders. So, AEDs able to increase GABAergic neurotransmission may play a role in hyperkinetic movement disorders treatment. Therefore, AEDs could represent a useful therapeutic option in the management of hyperkinetic movement disorders where the available treatments are ineffective.
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Affiliation(s)
- A Siniscalchi
- Department of Neuroscience, Neurology Division, Annunziata Hospital, Cosenza, Italy
| | - L Gallelli
- Pharmacology, Department of Experimental and Clinical Medicine, Faculty of Medicine, University Magna Graecia of Catanzaro, Clinical Pharmacology Unit, Mater Domini University Hospital, Catanzaro, Italy
| | - G De Sarro
- Pharmacology, Department of Experimental and Clinical Medicine, Faculty of Medicine, University Magna Graecia of Catanzaro, Clinical Pharmacology Unit, Mater Domini University Hospital, Catanzaro, Italy
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266
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Affiliation(s)
- Martin J Brodie
- Epilepsy Unit, Western Infirmary, Glasgow G11 6NT, Scotland, UK.
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267
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Design, syntheses, and SAR of 2,8-diazaspiro[4.5]decanones as T-type calcium channel antagonists. Bioorg Med Chem Lett 2010; 20:6375-8. [DOI: 10.1016/j.bmcl.2010.09.098] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 09/14/2010] [Accepted: 09/16/2010] [Indexed: 11/17/2022]
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268
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Juge N, Gray JA, Omote H, Miyaji T, Inoue T, Hara C, Uneyama H, Edwards RH, Nicoll RA, Moriyama Y. Metabolic control of vesicular glutamate transport and release. Neuron 2010; 68:99-112. [PMID: 20920794 DOI: 10.1016/j.neuron.2010.09.002] [Citation(s) in RCA: 288] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2010] [Indexed: 12/16/2022]
Abstract
Fasting has been used to control epilepsy since antiquity, but the mechanism of coupling between metabolic state and excitatory neurotransmission remains unknown. Previous work has shown that the vesicular glutamate transporters (VGLUTs) required for exocytotic release of glutamate undergo an unusual form of regulation by Cl(-). Using functional reconstitution of the purified VGLUTs into proteoliposomes, we now show that Cl(-) acts as an allosteric activator, and the ketone bodies that increase with fasting inhibit glutamate release by competing with Cl(-) at the site of allosteric regulation. Consistent with these observations, acetoacetate reduced quantal size at hippocampal synapses and suppresses glutamate release and seizures evoked with 4-aminopyridine in the brain. The results indicate an unsuspected link between metabolic state and excitatory neurotransmission through anion-dependent regulation of VGLUT activity.
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Affiliation(s)
- Narinobu Juge
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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269
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Zuliani V, Fantini M, Nigam A, Stables JP, Patel MK, Rivara M. Anticonvulsant activity of 2,4(1H)-diarylimidazoles in mice and rats acute seizure models. Bioorg Med Chem 2010; 18:7957-65. [PMID: 20943396 DOI: 10.1016/j.bmc.2010.09.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 08/30/2010] [Accepted: 09/14/2010] [Indexed: 11/17/2022]
Abstract
2,4(1H)-Diarylimidazoles have been previously shown to inhibit hNa(V)1.2 sodium (Na) channel currents. Since many of the clinically used anticonvulsants are known to inhibit Na channels as an important mechanism of their action, these compounds were tested in two acute rodent seizure models for anticonvulsant activity (MES and scMet) and for sedative and ataxic side effects. Compounds exhibiting antiepileptic activity were further tested to establish a dose response curve (ED(50)). The experimental data identified four compounds with anticonvulsant activity in the MES acute seizure rodent model (compound 10, ED(50)=61.7mg/kg; compound 13, ED(50)=46.8mg/kg, compound 17, ED(50)=129.5mg/kg and compound 20, ED(50)=136.7mg/kg). Protective indexes (PI=TD(50)/ED(50)) ranged from 2.1 (compound 10) to greater than 3.6 (compounds 13, 17 and 20). All four compounds were shown to inhibit hNa(V)1.2 in a dose dependant manner. Even if a correlation between sodium channel inhibition and anticonvulsant activity was unclear, these studies identify four Na channel antagonists with anticonvulsant activity, providing evidence that these derivatives could be potential drug candidates for development as safe, new and effective antiepileptic drugs (AEDs).
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Affiliation(s)
- Valentina Zuliani
- Dipartimento Farmaceutico, Università degli Studi di Parma, V.le G.P. Usberti, 27/A, I-43124 Parma, Italy.
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270
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Mao X, Guo F, Yu J, Min D, Wang Z, Xie N, Chen T, Shaw C, Cai J. Up-regulation of GABA transporters and GABA(A) receptor α1 subunit in tremor rat hippocampus. Neurosci Lett 2010; 486:150-5. [PMID: 20851161 DOI: 10.1016/j.neulet.2010.09.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Revised: 09/01/2010] [Accepted: 09/11/2010] [Indexed: 12/15/2022]
Abstract
The loss of GABAergic neurotransmission has been closely linked with epileptogenesis. The modulation of the synaptic activity occurs both via the removal of GABA from the synaptic cleft and by GABA transporters (GATs) and by modulation of GABA receptors. The tremor rat (TRM; tm/tm) is the parent strain of the spontaneously epileptic rat (SER; zi/zi, tm/tm), which exhibits absence-like seizure after 8 weeks of age. However, there are no reports that can elucidate the effects of GATs and GABA(A) receptors (GABARs) on TRMs. The present study was conducted to detect GATs and GABAR α1 subunit in TRMs hippocampus at mRNA and protein levels. In this study, total synaptosomal GABA content was significantly decreased in TRMs hippocampus compared with control Wistar rats by high performance liquid chromatography (HPLC); mRNA and protein expressions of GAT-1, GAT-3 and GABAR α1 subunit were all significantly increased in TRMs hippocampus by real time PCR and Western blot, respectively; GAT-1 and GABAR α1 subunit proteins were localized widely in TRMs and control rats hippocampus including CA1, CA3 and dentate gyrus (DG) regions whereas only a wide distribution of GAT-3 was observed in CA1 region by immunohistochemistry. These data demonstrate that excessive expressions of GAT-1 as well as GAT-3 and GABAR α1 subunit in TRMs hippocampus may provide the potential therapeutic targets for genetic epilepsy.
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Affiliation(s)
- Xiaoyuan Mao
- Department of Pharmaceutical Toxicology, School of Pharmaceutical Science, China Medical University, Shenyang 110001, China
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271
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Gerlach AC, Krajewski JL. Antiepileptic Drug Discovery and Development: What Have We Learned and Where Are We Going? Pharmaceuticals (Basel) 2010; 3:2884-2899. [PMID: 27713381 PMCID: PMC4034102 DOI: 10.3390/ph3092884] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 08/25/2010] [Accepted: 09/01/2010] [Indexed: 11/16/2022] Open
Abstract
Current marketed antiepileptic drugs (AEDs) consist of a variety of structural classes with different mechanisms of action. These agents typically have non-overlapping efficacy and side-effect profiles presenting multiple treatment options for the patient population. However, approximately 30% of seizure sufferers fail to respond to current therapies often because poorly tolerated side-effects limit adequate dosing. The scope of this review is to summarize selected advances in 2nd and 3rd generation AEDs as well as compounds in development with novel mechanisms of action.
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272
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Lewis RW, Mabry J, Polisar JG, Eagen KP, Ganem B, Hess GP. Dihydropyrimidinone positive modulation of delta-subunit-containing gamma-aminobutyric acid type A receptors, including an epilepsy-linked mutant variant. Biochemistry 2010; 49:4841-51. [PMID: 20450160 DOI: 10.1021/bi100119t] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gamma-aminobutyric acid type A receptors (GABA(A) receptors) are ligand-gated chloride channels that play a central role in signal transmission within the mammalian central nervous system. Compounds that modulate specific GABA(A) receptor subtypes containing the delta-subunit are scarce but would be valuable research tools and starting points for potential therapeutic agents. Here we report a class of dihydropyrimidinone (DHPM) heterocycles that preferentially potentiate peak currents of recombinant GABA(A) receptor subtypes containing the delta-subunit expressed in HEK293T cells. Using the three-component Biginelli reaction, 13 DHPMs with structural features similar to those of the barbiturate phenobarbital were synthesized; one DHPM used (monastrol) is commercially available. An up to approximately 3-fold increase in the current from recombinant alpha1beta2delta receptors was observed with the DHPM compound JM-II-43A or monastrol when co-applied with saturating GABA concentrations, similar to the current potentiation observed with the nonselective potentiating compounds phenobarbital and tracazolate. No agonist activity was observed for the DHPMs at the concentrations tested. A kinetic model was used in conjunction with dose-dependent measurements to calculate apparent dissociation constant values for JM-II-43A (400 muM) and monastrol (200 microM) at saturating GABA concentrations. We examined recombinant receptors composed of combinations of subunits alpha1, alpha4, alpha5, alpha6, beta2, beta3, gamma2L, and delta with JM-II-43A to demonstrate the preference for potentiation of delta-subunit-containing receptors. Lastly, reduced currents from receptors containing the mutated delta(E177A) subunit, described by Dibbens et al. [(2004) Hum. Mol. Genet. 13, 1315-1319] as a heritable susceptibility allele for generalized epilepsy with febrile seizures plus, are also potentiated by these DHPMs.
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Affiliation(s)
- Ryan W Lewis
- Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, New York 14853-2703, USA
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273
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Netoff T, Beverlin B. Dynamical effects of antiepileptic drugs on neurons affect network synchronizability. BMC Neurosci 2010. [PMCID: PMC3090778 DOI: 10.1186/1471-2202-11-s1-o10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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274
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Nasreddine W, Beydoun A, Atweh S, Abou-Khalil B. Emerging drugs for partial onset seizures. Expert Opin Emerg Drugs 2010; 15:415-31. [DOI: 10.1517/14728214.2010.492394] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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275
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Potschka H. Modulating P-glycoprotein regulation: future perspectives for pharmacoresistant epilepsies? Epilepsia 2010; 51:1333-47. [PMID: 20477844 DOI: 10.1111/j.1528-1167.2010.02585.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Enhanced brain efflux of antiepileptic drugs by the blood-brain barrier transporter P-glycoprotein is discussed as one mechanism contributing to pharmacoresistance of epilepsies. P-glycoprotein overexpression has been proven to occur as a consequence of seizure activity. Therefore, blocking respective signaling events should help to improve brain penetration and efficacy of P-glycoprotein substrates. A series of recent studies revealed key signaling factors involved in seizure-associated transcriptional activation of P-glycoprotein. These data suggested several interesting targets, including the N-methyl-d-aspartate (NMDA) receptor, the inflammatory enzyme cyclooxygenase-2, and the prostaglandin E2 EP1 receptor. These targets have been further evaluated in rodent models, demonstrating that targeting these factors can control P-glycoprotein expression, improve antiepileptic drug brain penetration, and help to overcome pharmacoresistance. In general, the approach offers particular advantages over transporter inhibition as it preserves basal transporter function. In this review the different strategies for blocking P-glycoprotein upregulation, including their therapeutic promise and drawbacks are discussed. Moreover, pros and cons of the approach are compared to those of alternative strategies to overcome transporter-associated resistance. Regarding future perspectives of the novel approach, there is an obvious need to more clearly define the clinical relevance of transporter overexpression. In this context current efforts are discussed, including the development of imaging tools that allow an evaluation of P-glycoprotein function in individual patients.
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Affiliation(s)
- Heidrun Potschka
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University, Munich, Germany.
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276
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Zuliani V, Rivara M, Fantini M, Costantino G. Sodium channel blockers for neuropathic pain. Expert Opin Ther Pat 2010; 20:755-79. [DOI: 10.1517/13543771003774118] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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277
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Bagdy G, Riba P, Kecskeméti V, Chase D, Juhász G. Headache-type adverse effects of NO donors: vasodilation and beyond. Br J Pharmacol 2010; 160:20-35. [PMID: 20331608 DOI: 10.1111/j.1476-5381.2010.00643.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Although nitrate therapy, used in the treatment of cardiovascular disorders, is frequently associated with side-effects, mainly headaches, the summaries of product characteristics of nitrate-containing medicines do not report detailed description of headaches and even do not highlight the possibility of nitrate-induced migraine. Two different types of nitrate-induced headaches have been described: (i) immediate headaches that develop within the first hour of the application, are mild or medium severity without characteristic symptoms for migraine, and ease spontaneously; and (ii) delayed, moderate or severe migraine-type headaches (occurring mainly in subjects with personal or family history of migraine), that develop 3-6 h after the intake of nitrates, with debilitating, long-lasting symptoms including nausea, vomiting, photo- and/or phono-phobia. These two types of headaches are remarkably different, not only in their timing and symptoms, but also in the persons who are at risk. Recent studies provide evidence that the two headache types are caused by different mechanisms: immediate headaches are connected to vasodilation caused by nitric oxide (NO) release, while migraines are triggered by other actions such as the release of calcitonin gene-related peptide or glutamate, or changes in ion channel function mediated by cyclic guanosine monophosphate or S-nitrosylation. Migraines usually need anti-attack medication, such as triptans, but these drugs are contraindicated in most medical conditions that are treated using nitrates. In conclusion, these data recommend the correction of summaries of nitrate product characteristics, and also suggest a need to develop new types of anti-migraine drugs, effective in migraine attacks, that could be used in patients with risk for angina pectoris.
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Affiliation(s)
- G Bagdy
- Department of Pharmacodynamics, Faculty of Pharmacy, Semmelweis University, Budapest, Hungary.
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278
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Li C, Xu B, Wang WW, Yu XJ, Zhu J, Yu HM, Han D, Pei DS, Zhang GY. Coactivation of GABA receptors inhibits the JNK3 apoptotic pathway via disassembly of GluR6-PSD-95-MLK3 signaling module in KA-induced seizure. Epilepsia 2010; 51:391-403. [PMID: 19694794 DOI: 10.1111/j.1528-1167.2009.02270.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
PURPOSE Past work has demonstrated that kainic acid (KA)-induced seizures could cause the enhancement of excitation and lead to neuronal death in rat hippocampus. To counteract such an imbalance between excitation and inhibition, we designed experiments by activating the inhibitory gamma-aminobutyric acid (GABA) receptor to investigate whether such activation suppresses the excitatory glutamate signaling induced by KA and to elucidate the underlying molecular mechanisms. METHODS Muscimol coapplied with baclofen was intraperitoneally administrated to the rats 40 min before KA injection by intracerebroventricular infusion. Subsequently we used a series of methods including immunoprecipitation, immunoblotting, histologic analysis, and immunohistochemistry to analyze the interaction, expression, and phosphorylation of relevant proteins as well as the survival of the CA1/CA3 pyramidal neurons. RESULTS Coadministration of muscimol and baclofen exerted neuroprotection against neuron death induced by KA; inhibited the increased assembly of the GluR6-PSD-95-MLK3 module induced by KA; and suppressed the activation of MLK3, MKK7, and JNK3. DISCUSSION Taken together, we demonstrate that coactivation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module induced by KA. This provides a new insight into the therapeutic approach to epileptic seizure.
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Affiliation(s)
- Chong Li
- Research Center of Biochemistry and Molecular Biology, Provincial Key Laboratory of Brain Disease Bioinformation, Xuzhou Medical College, Xuzhou, Jiangsu, China
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279
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Abstract
In the last fifteen years, new antiepileptic medications have been offered for the treatment of patients with epilepsy. Nevertheless, despite optimal medical treatment, up to 30% of patients still experience recurrent seizures and the challenge for new, more efficacious and better-tolerated drugs continues. New antiepileptic drugs include the evolution of pre-existing drugs and new compounds identified through the investigation of additional molecular targets, such as SV2A synaptic vesicle protein, voltage-gated potassium channels, ionotropic and metabotropic glutamate receptors, and gap junctions. This paper reviews the available information on various classes of molecules that are in the pipeline as well as on the innovative approaches to the treatment of epilepsy.
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Affiliation(s)
- Pasquale Striano
- Muscular & Neurodegenerative Diseases Unit, Institute G. Gaslini, Genova, Italy
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280
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de Groot M, Toering ST, Boer K, Spliet WGM, Heimans JJ, Aronica E, Reijneveld JC. Expression of synaptic vesicle protein 2A in epilepsy-associated brain tumors and in the peritumoral cortex. Neuro Oncol 2010; 12:265-73. [PMID: 20167814 DOI: 10.1093/neuonc/nop028] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Synaptic vesicle protein 2A (SV2A) has been identified as the binding site for the antiepileptic drug levetiracetam and is thought to decrease neuronal excitability. Since knockout of SV2A in mice leads to seizures, we hypothesized that a reduction in SV2A expression promotes seizure generation in epilepsy-associated brain tumors. We compared the SV2A expression and distribution in surgically removed tumor tissue (n = 63) and peritumoral cortex (n = 31) of patients with glial and glioneuronal tumors to normal control cortex obtained at autopsy in nonbrain tumor patients (n = 6). Additionally, we compared the SV2A expression and distribution in tumor patients with epilepsy (n = 39) with SV2A expression in tumor patients without epilepsy (n = 24). Immunohistochemistry in control cortex demonstrated strong and diffuse SV2A immunoreactivity (IR) throughout all cortical layers. Similar strong SV2A IR (with the same diffuse distribution pattern) was observed in the peritumoral cortical specimens in both patients with and without epilepsy. Modest SV2A IR was observed within the tumor area. The SV2A-positive cells detected within the tumor area were mainly entrapped neurons. Oligodendrogliomas and glioneuronal tumors displayed variable SV2A neuropil staining. In ganglioglioma (GG), strong SV2A IR was present along the dysplastic neuronal cell borders and processes. In both GG and dysembryoplastic neuroepithelial tumors, SV2A IR was occasionally observed within the neuronal perikarya. We found no differences in SV2A expression in the peritumoral cortex between the patients with and without epilepsy, which suggests that the role of SV2A in epileptogenesis in patients with glial tumors is questionable. The distinct pattern of SV2A IR in glioneuronal tumors suggests a redistribution of SV2A.
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Affiliation(s)
- Marjolein de Groot
- Department Of Neurology, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, The Netherlands.
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281
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Gitto R, De Luca L, Ferro S, Agnello S, Russo E, De Sarro G, Chimirri A. Synthesis and Structure-Active Relationship of 1-Aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline Anticonvulsants. Chem Pharm Bull (Tokyo) 2010; 58:1602-5. [DOI: 10.1248/cpb.58.1602] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | | | | | | | - Emilio Russo
- Dipartimento di Medicina Sperimentale e Clinica, Università Magna Græcia
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282
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Abstract
Schizophrenia is a disorder in which disturbances in the integration of emotion with cognition plays a central role and probably involves several different regions, including the dorsolateral prefrontal cortex, the rostral anterior cingulate cortex, the hippocampal formation, and basolateral amygdala (BLA). Recent brain imaging studies have reported changes in volume, whereas postmortem studies point to dysfunction of the GABA and glutamate systems in these regions. Microarray-based profiles indicate that complex changes in the expression of genes associated with synaptic transmission and ion channels are involved in GABA cell dysfunction in schizophrenics. Molecular abnormalities vary considerably on the basis of sector and layer, suggesting that the unique connectivity of intrinsic and extrinsic afferents may critical in regulating the activity of genes in specific subpopulations of GABA cells. Projections of the BLA may be of particular importance to the induction of abnormal circuitry in schizophrenia, as their ingrowth during late adolescence and early adulthood may help to 'trigger' the onset of illness in susceptible individuals. A preponderance of cellular and molecular abnormalities has been found in the stratum oriens (SO) of sectors CA3/2 in which BLA afferents provide a robust innervation. These observations have lead to the development of a rodent model for the study of abnormal circuitry in this disorder. For example, single-cell recordings in hippocampal slices exposed to increased activation from the BLA have shown decreases in GABA currents in pyramidal neurons in SO of CA3/2, but not CA1, and support the validity of this model. Overall, the postmortem studies of neural circuitry abnormalities in schizophrenia are beginning to implicate specific cellular, molecular, and electrophysiological mechanism in specific subtypes of cortical neurons defined by their afferent and efferent connectivity within key corticolimbic regions.
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Affiliation(s)
- Francine M Benes
- Program in Structural and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA.
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283
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Fritsch B, Stott JJ, Donofrio JJ, Rogawski MA. Treatment of early and late kainic acid-induced status epilepticus with the noncompetitive AMPA receptor antagonist GYKI 52466. Epilepsia 2010; 51:108-17. [PMID: 19682025 PMCID: PMC4535693 DOI: 10.1111/j.1528-1167.2009.02205.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Benzodiazepines such as diazepam may fail to effectively treat status epilepticus because benzodiazepine-sensitive GABA(A) receptors are progressively internalized with continued seizure activity. Ionotropic glutamate receptors, including AMPA receptors, are externalized, so that AMPA receptor antagonists, which are broad-spectrum anticonvulsants, could be more effective treatments for status epilepticus. We assessed the ability of the noncompetitive AMPA receptor antagonist GYKI 52466 to protect against kainic acid-induced status epilepticus in mice. METHODS Groups of animals treated with kainic acid received GYKI 52466 (50 mg/kg followed in 15 min by 50 mg/kg) or diazepam (25 mg/kg followed in 20 min by 12.5 mg/kg) beginning at 5 min of continuous seizure activity or 25 min later. The duration of seizure activity was determined by EEG recording from epidural cortical electrodes. RESULTS Both GYKI 52466 and diazepam rapidly terminated electrographic and behavioral seizures when administered early. However, diazepam-treated animals exhibited more seizure recurrences. With late administration, GYKI 52466 also rapidly terminated seizures and they seldom recurred, whereas diazepam was slow to produce seizure control and recurrences were common. Although both treatments caused sedation, GYKI 52466-treated animals retained neurological responsiveness whereas diazepam-treated animals did not. GYKI 52466 did not affect blood pressure whereas diazepam caused a sustained drop in mean arterial pressure. DISCUSSION Noncompetitive AMPA receptor antagonists represent a promising approach for early treatment of status epilepticus; they may also be effective at later times when there is refractoriness to benzodiazepines.
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Affiliation(s)
- Brita Fritsch
- Epilepsy Research Section, National Institute for Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
- Department of Neurology, University of Freiburg, Freiburg, Germany
| | - Jeffrey J. Stott
- Epilepsy Research Section, National Institute for Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Joy Joelle Donofrio
- Epilepsy Research Section, National Institute for Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Michael A. Rogawski
- Epilepsy Research Section, National Institute for Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
- Department of Neurology, School of Medicine, University of California, Davis, Sacramento, California, U.S.A
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284
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Higgins GA, Breysse N, Undzys E, Derksen DR, Jeffrey M, Scott BW, Xin T, Roucard C, Bressand K, Depaulis A, Burnham WM. Comparative study of five antiepileptic drugs on a translational cognitive measure in the rat: relationship to antiepileptic property. Psychopharmacology (Berl) 2010; 207:513-27. [PMID: 19841906 DOI: 10.1007/s00213-009-1682-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Accepted: 09/21/2009] [Indexed: 12/31/2022]
Abstract
RATIONALE Antiepileptic drugs (AEDs) have been available for many years; yet, new members of this class continue to be identified and developed due to the limitations of existing drugs, which include a propensity for cognitive impairment. However, there is little preclinical information about the cognitive effects they produce, which clinically include deficits in attention and slowing of reaction time. OBJECTIVES The purpose of this study was to profile two first-generation AEDs, phenytoin and valproate, and three second-generation AEDs, levetiracetam, pregabalin and lacosamide. Initially, each drug was examined across a range of well characterised preclinical seizure tests, and then each drug was evaluated in the five-choice serial reaction time test (5-CSRTT) based on efficacious doses from the seizure tests. MATERIALS AND METHODS Each AED was tested for anti-seizure efficacy in either (1) the maximal electroshock seizure test, (2) s.c. PTZ seizure test, (3) amygdala-kindled seizures and (4) the genetic absence epilepsy rat of Strasbourg model of absence seizures. On completion of these studies, each drug was tested in rats trained to asymptotic performance in the 5-CSRTT (0.5 s SD, 5 s ITI, 100 trials). Male rats were used in all studies. RESULTS Each AED was active in at least one of the seizure tests, although only valproate was active in each test. In the 5-CSRT test, all drugs with the exception of levetiracetam, significantly slowed reaction time and increased omissions. Variable effects were seen on accuracy. The effect on omissions was reversed by increasing stimulus duration from 0.5 to 5 s, supporting a drug-induced attention deficit. Levetiracetam had no negative effect on performance; indeed, reaction time was slightly increased (i.e. faster). CONCLUSIONS These results highlight somewhat similar effects of phenytoin, valproate, pregabalin and lacosamide on attention and reaction time, and comparison to efficacious doses from the seizure tests support the view that there may be a better separation with the newer AEDs. Levetiracetam had no detrimental effect in the 5-CSRTT, which may be consistent with clinical experience where the drug is considered to be well tolerated amongst the AED class.
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Affiliation(s)
- Guy A Higgins
- NPS Pharmaceuticals, 101 College Street, Toronto, Canada.
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285
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The antiepileptic drug zonisamide inhibits MAO-B and attenuates MPTP toxicity in mice: clinical relevance. Exp Neurol 2009; 221:329-34. [PMID: 19948168 DOI: 10.1016/j.expneurol.2009.11.018] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 11/06/2009] [Accepted: 11/21/2009] [Indexed: 11/23/2022]
Abstract
Zonisamide is an FDA-approved antiepileptic drug that blocks voltage-dependent Na(+) channels and T-type Ca(2+) channels and improves clinical outcome in Parkinson's disease (PD) patients when used as an adjunct to other PD therapies. Zonisamide also modifies dopamine (DA) activity, provides protection in ischemia models and influences antioxidant systems. Thus, we tested it for its ability to protect DA neurons in a mouse model of PD and investigated mechanisms underlying its protection. Concurrent treatment of mice with zonisamide and 1-methyl-4-phenyl-1,2,3,6-tetraydropyridine (MPTP) attenuated the reduction in striatal contents of DA, its metabolite DOPAC and tyrosine hydroxylase (TH). We also discovered that zonisamide inhibited monoamine oxidase B (MAO-B) activity in vitro with an IC(50) of 25 muM, a concentration that is well within the therapeutic range used for treating epilepsy in humans. Moreover, the irreversible binding of systemically administered selegiline to MAO-B in mouse brain was attenuated by zonisamide as measured by ex vivo assays. Zonisamide treatment alone did not produce any lasting effects on ex vivo MAO-B activity, indicating that it is a reversible inhibitor of the enzyme. Consistent with the effects of zonisamide on MAO-B, the striatal content of 1-methyl-4-phenylpyridinium (MPP(+)), which is derived from the administered MPTP via MAO-B actions, was substantially reduced in mice treated with MPTP and zonisamide. The potency and reversibility with which zonisamide blocks MAO-B may contribute to the ability of the drug to improve clinical symptoms in PD patients. The results also suggest that caution in its use may be necessary, especially when administered with other drugs, in the treatment of epilepsy or PD.
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286
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Quintans-Júnior LJ, Silva DA, Siqueira JS, Araújo AA, Guimarães AG, Araújo RA, Araújo DA, Souza MDFV, Gutierrez SJ, Barbosa-Filho JM, Almeida RN. Anticonvulsant property of N-salicyloyltryptamine: evidence of enhance of central GABAergic neurotransmission. ACTA ACUST UNITED AC 2009. [DOI: 10.1590/s1676-26492009000400005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
AIM: In the present study we verified the anticonvulsant properties of the new tryptamine analogue, N-salicyloyltryptamine (NST), in rodents. METHODS AND RESULTS: In the evaluation of the anticonvulsant activity, NST protected the animals from the incidence of seizures induced by pentylenetetrazole (PTZ) and picrotoxin (PIC), in doses of 100 and 200 mg/kg. NST (100 and 200 mg/kg, i.p.) significantly eliminated the extensor reflex of maximal electric-induced seizure tests in 40% of the experimental animals. However, in the PTZ model FLU (10 mg/kg, i.p.), an antagonist of the benzodiazepine (BZD) site in the GABA A-BZD receptor complex, inhibited the prolongation of seizure latency induced by NST. CONCLUSION: Our results demonstrated an anticonvulsant activity of the new analogue that could be, at least in part, associated to the involvement of the GABAergic mechanism.
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287
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Higgins GA, Breysse N, Undzys E, Kuo C, Joharchi N, Derksen DR, Xin T, Isaac M, Slassi M. The anti-epileptic drug lacosamide (Vimpat) has anxiolytic property in rodents. Eur J Pharmacol 2009; 624:1-9. [PMID: 19818346 DOI: 10.1016/j.ejphar.2009.09.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Revised: 09/10/2009] [Accepted: 09/28/2009] [Indexed: 01/04/2023]
Abstract
Lacosamide ((R)-2-acetamido-N-benzyl-3-methoxypropionamide; formerly harkoseride, SPM 927; Vimpat), has been recently approved by US and European regulatory authorities for use as add-on therapy for partial-onset seizures in adults. Because a number of anti-epileptic drugs are used to treat conditions beyond epilepsy, including anxiety, in the present study we investigated the anxiolytic potential of lacosamide in a conditioned emotional response (CER) model in rat, and the mouse marble burying assay. In each test lacosamide produced a significant effect consistent with anxiolysis, i.e. lacosamide increased suppression ratio in the CER test, and reduced the number of marbles buried in the marble burying assay. The doses necessary for an anxiolytic effect were higher than those necessary for efficacy in seizure tests conducted in the same species. For example in the mouse, the lacosamide oral ED(50) in the maximal electroshock seizure (MES) and 6 Hz tests was 5.3 and 9.6 mg/kg respectively, and the minimal effective dose in the marble burying assay was 30 mg/kg. In both seizure and anxiety tests, the (S)-enantiomer of lacosamide was inactive suggesting a similar mechanism of action, possibly use-dependent inhibition of sodium channel function (Errington et al., 2008). Efficacy in the CER model was equivalent to diazepam and pregabalin (Lyrica). In tests of side-effects, lacosamide had no effect on choice accuracy in the delayed match to position task of working memory, although at the 30 mg/kg dose, response rates and response latencies were significantly affected. In sum, the present results identify for the first time, an anxiolytic potential of lacosamide.
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Affiliation(s)
- Guy A Higgins
- NPS Pharmaceuticals, 101 College Street, Toronto, ON M5G 0A3, Canada.
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288
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Boehlen A, Kunert A, Heinemann U. Effects of XE991, retigabine, losigamone and ZD7288 on kainate-induced theta-like and gamma network oscillations in the rat hippocampus in vitro. Brain Res 2009; 1295:44-58. [PMID: 19699191 DOI: 10.1016/j.brainres.2009.08.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Revised: 08/02/2009] [Accepted: 08/09/2009] [Indexed: 11/19/2022]
Abstract
Ion currents such as M-currents (I(M)), persistent sodium currents (I(NaP)) and H-currents (I(h)) have been observed in a variety of brain regions, including the hippocampal formation, where storage and retrieval of information are facilitated by oscillatory network activities. They have been suggested to play an important role in neuronal excitability, synaptic transmission, membrane oscillatory activity, and in shaping resonance. Resonance and membrane potential oscillations have been implied in the generation of theta but not gamma oscillations. Here, we performed extracellular field potential recordings in hippocampal slices from adult rats and applied either the I(M) blocker XE991, the I(M) activator retigabine, the I(NaP) blocker losigamone or the I(h) inhibitor ZD7288 to test if these currents contribute to the generation of network oscillations. Kainate application induced network theta-like frequency oscillations in coronal slices as well as network gamma frequency oscillations in horizontal slices, and these remained stable for up to 3h. Power spectrum analysis revealed that all agents dose-dependently reduced the network oscillations in both frequency bands in areas CA3 and CA1. In contrast, the peak oscillation frequency was affected differentially. These results confirm that theta-like frequency oscillations are induced in longitudinal slices while gamma frequency oscillations dominate in horizontal slices. They also suggest that modifying neuronal excitability and transmitter release alters hippocampal network oscillations which are thought to be crucial for memory processing.
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Affiliation(s)
- Anne Boehlen
- Institute of Neurophysiology, Johannes Müller-Center of Physiology, Charité-Universitätsmedizin Berlin, Tucholskystrasse 2, 10117 Berlin, Germany
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289
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Li P, Bandyopadhyaya AK, Covey DF, Steinbach JH, Akk G. Hydrogen bonding between the 17beta-substituent of a neurosteroid and the GABA(A) receptor is not obligatory for channel potentiation. Br J Pharmacol 2009; 158:1322-9. [PMID: 19702782 DOI: 10.1111/j.1476-5381.2009.00390.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Potentiating neurosteroids are some of the most efficacious modulators of the mammalian GABA(A) receptor. One of the crucial interactions may be between the C20 ketone group (D-ring substituent at C17) of the neurosteroid, and the N407 and Y410 residues in the M4 domain of the receptor. In this study, we examined the contribution of hydrogen bonding between 17beta-substituents on the steroid D-ring and the GABA(A) receptor to potentiation by neurosteroids. EXPERIMENTAL APPROACH Whole-cell and single-channel recordings were made from HEK 293 cells transiently expressing wild-type and mutant alpha1beta2gamma2L GABA(A) receptors. KEY RESULTS A steroid with a 17beta-carbonitrile group (3alpha5alpha18nor17betaCN) was a potent and efficacious potentiator of the GABA(A) receptor. Potentiation was also shown by a cyclosteroid in which C21 and the C18 methyl group of (3alpha,5alpha)-3-hydroxypregnan-20-one are connected within a six-membered ring containing a double bond as a hydrogen bond acceptor (3alpha5alphaCDNC12), a steroid containing a 17beta-ethyl group on the D-ring (3alpha5alpha17betaEt) and a steroid lacking a 17beta-substituent on the D-ring (3alpha5alpha17H). Single-channel kinetic analysis indicates that the kinetic mechanism of action is the same for the neurosteroid 3alpha5alphaP, 3alpha5alpha18nor17betaCN, 3alpha5alphaCDNC12, 3alpha5alpha17betaEt and 3alpha5alpha17H. Interestingly, 3alpha5alpha17betaEt, at up to 3 microM, was incapable of potentiating the alpha1N407A/Y410F double mutant receptor. CONCLUSIONS AND IMPLICATIONS Hydrogen bonding between the steroid 17beta-substituent and the GABA(A) receptor is not a critical requirement for channel potentiation. The alpha1N407/Y410 residues are important for neurosteroid potentiation for reasons other than hydrogen bonding between steroid and receptor.
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Affiliation(s)
- Ping Li
- Department of Anesthesiology, Washington University in St Louis, St Louis, MO 63110, USA
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290
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Epileptogenic potential of mefloquine chemoprophylaxis: a pathogenic hypothesis. Malar J 2009; 8:188. [PMID: 19656408 PMCID: PMC2736201 DOI: 10.1186/1475-2875-8-188] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Accepted: 08/05/2009] [Indexed: 12/01/2022] Open
Abstract
Background Mefloquine has historically been considered safe and well-tolerated for long-term malaria chemoprophylaxis, but prescribing it requires careful attention in order to rule out contraindications to its use. Contraindications include a history of certain neurological conditions that might increase the risk of seizure and other adverse events. The precise pathophysiological mechanism by which mefloquine might predispose those with such a history to seizure remains unclear. Presentation of the hypothesis Studies have demonstrated that mefloquine at doses consistent with chemoprophylaxis accumulates at high levels in brain tissue, which results in altered neuronal calcium homeostasis, altered gap-junction functioning, and contributes to neuronal cell death. This paper reviews the scientific evidence associating mefloquine with alterations in neuronal function, and it suggests the novel hypothesis that among those with the prevalent EPM1 mutation, inherited and mefloquine-induced impairments in neuronal physiologic safeguards might increase risk of GABAergic seizure during mefloquine chemoprophylaxis. Testing and implications of the hypothesis Consistent with case reports of tonic-clonic seizures occurring during mefloquine chemoprophylaxis among those with family histories of epilepsy, it is proposed here that a new contraindication to mefloquine use be recognized for people with EPM1 mutation and for those with a personal history of myoclonus or ataxia, or a family history of degenerative neurologic disorder consistent with EPM1. Recommendations and directions for future research are presented.
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291
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Tonic GABAergic inhibition of sympathetic preganglionic neurons: a novel substrate for sympathetic control. J Neurosci 2009; 28:12445-52. [PMID: 19020037 DOI: 10.1523/jneurosci.2951-08.2008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The sympathetic tone is primarily defined by the level of activity of the sympathetic preganglionic neurons. We report a novel inhibitory influence on sympathetic activity, that of tonic GABAergic inhibition which could have a profound global effect on sympathetic outflow. Recording from identified SPNs in the intermediolateral cell column (IML) of rat spinal cord slices, application of the GABA receptor antagonist bicuculline, but not gabazine, elicited a change in voltage that lasted for the duration of application. This response was mediated by a direct effect on SPNs since it persisted in tetrodotoxin and low Ca(2+)/high Mg(2+) and the amplitude of responses were related to Cl(-) concentration in patch solutions. Such tonic inhibitory responses were not observed in interneurons, the other neuronal type in the IML, although ongoing IPSPs were antagonized in these neurons. The effects of bicuculline were enhanced by diazepam but not zolpidem or the GABA modulators THIP and THDOC suggesting a role for alpha5 subunits. PCR using primers for the alpha5 and delta subunits indicated the presence of alpha5, but not delta subunits in the IML. Firing rates of SPNs were enhanced by bicuculline and decreased by diazepam indicating that this tonic inhibition has a profound effect on the excitability of SPNs. These data indicate a novel influence for controlling the activity of SPNs regardless of their function.
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292
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2,4(5)-Diarylimidazoles as inhibitors of hNaV1.2 sodium channels: Pharmacological evaluation and structure–property relationships. Bioorg Med Chem 2009; 17:3642-8. [DOI: 10.1016/j.bmc.2009.03.067] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 03/27/2009] [Accepted: 03/31/2009] [Indexed: 11/17/2022]
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293
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Giustizieri M, Armogida M, Berretta N, Federici M, Piccirilli S, Mercuri NB, Nistico R. Differential effect of carbamazepine and oxcarbazepine on excitatory synaptic transmission in rat hippocampus. Synapse 2009; 62:783-9. [PMID: 18655118 DOI: 10.1002/syn.20556] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In this study, we have compared the effects of two structurally related compounds carbamazepine (CBZ) and oxcarbazepine (OXC), both in current use for the treatment of epilepsy and bipolar disorder, on fast excitatory transmission in rat hippocampal slices. Using electrophysiological recordings, we have investigated the effects of CBZ and OXC on repetitive action potential discharge of CA1 pyramidal neurons demonstrating that both compounds produced firing inhibition with similar IC(50) values. Moreover, we show that bath applied CBZ (0.01-1 mM) exerted a concentration-dependent decrease in the amplitude of the field excitatory postsynaptic potentials with an IC(50) of approximately 194.3 microM. When OXC was used at the same concentrations, the concentration-response curve was shifted to the right (IC(50) of approximately 711.07 microM). In addition, we demonstrated that CBZ and OXC reduced, to a different extent, both evoked excitatory postsynaptic currents and NMDA-, AMPA-, and KA-mediated inward currents, CBZ being more potent than OXC. These data highlight distinct presynaptic and postsynaptic sites of action for both compounds and suggest that CBZ, by markedly depressing postsynaptic ionotropic glutamate receptors-mediated responses, may produce more severe cognitive and memory impairment. Thus, we assume that relatively high doses of OXC could be better tolerated than therapeutically equivalent doses of CBZ, justifying the preferential use of OXC as first-line treatment in the therapy of neurological and psychiatric disorders, particularly when compared with CBZ.
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Affiliation(s)
- Michela Giustizieri
- Laboratory of Experimental Neurology, Fondazione Santa Lucia IRCCS, Rome, Italy
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294
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Reddy DS, Rogawski MA. Neurosteroid replacement therapy for catamenial epilepsy. Neurotherapeutics 2009; 6:392-401. [PMID: 19332335 PMCID: PMC2682439 DOI: 10.1016/j.nurt.2009.01.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2008] [Accepted: 01/09/2009] [Indexed: 11/22/2022] Open
Abstract
Perimenstrual catamenial epilepsy, the cyclical occurrence of seizure exacerbations near the time of menstruation, affects a high proportion of women of reproductive age with drug-refractory epilepsy. Enhanced seizure susceptibility in perimenstrual catamenial epilepsy is believed to be due to the withdrawal of the progesterone-derived GABA(A) receptor modulating neurosteroid allopregnanolone as a result of the fall in progesterone at the time of menstruation. Studies in a rat pseudopregnancy model of catamenial epilepsy indicate that after neurosteroid withdrawal there is enhanced susceptibility to chemoconvulsant seizures. There is also a transitory increase in the frequency of spontaneous seizures in epileptic rats that had experienced pilocarpine-induced status epilepticus. In the catamenial epilepsy model, there is a marked reduction in the antiseizure potency of anticonvulsant drugs, including benzodiazepines and valproate, but an increase in the anticonvulsant potency and protective index of neurosteroids such as allopregnanolone and the neurosteroid analog ganaxolone. The enhanced seizure susceptibility and benzodiazepine-resistance subsequent to neurosteroid withdrawal may be related to reduced expression and altered kinetics of synaptic GABA(A) receptors and increased expression of GABA(A) receptor subunits (such as alpha4) that confer benzodiazepine insensitivity. The enhanced potency of neurosteroids may be due to a relative increase after neurosteroid withdrawal in the expression of neurosteroid-sensitive delta-subunit-containing perisynaptic or extrasynaptic GABA(A) receptors. Positive allosteric modulatory neurosteroids and synthetic analogs such as ganaxolone may be administered to prevent catamenial seizure exacerbations, in what we call neurosteroid replacement therapy.
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Affiliation(s)
- Doodipala S. Reddy
- grid.412408.bDepartment of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M Health Science Center, 228 Reynolds Medical Building, 77843-1114 College Station, TX
| | - Michael A. Rogawski
- Department of Neurology, School of Medicine, University of California, Davis, 4860 Y Street, Suite 3700, 95817-2307 Sacramento, CA
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295
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Chen Z, Chen S, Chen L, Zhou J, Dai Q, Yang L, Li X, Zhou L. Long-term increasing co-localization of SCN8A and ankyrin-G in rat hippocampal cornu ammonis 1 after pilocarpine induced status epilepticus. Brain Res 2009; 1270:112-20. [PMID: 19306853 DOI: 10.1016/j.brainres.2009.03.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 03/01/2009] [Accepted: 03/03/2009] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels (VGSC) are important determinants of neuronal excitability which are implicated in the pathogenesis of epilepsy. Ankyrin-G contributes to the distribution and regulation of VGSC. Here we investigated the alterations of the two alpha-subunits SCN8A and SCN1A and their adapter ankyrin-G in the hippocampal cornu ammonis 1 (CA1) of rats after pilocarpine induced status epilepticus (PISE), compared to the sham-control group (C1) and blank-control group (C2). Significant increase of SCN8A mRNA (41.08% increase compared to C1, P<0.001; 30.88% increase compared to C2, P=0.011) was detected 60 days after PISE. At D1 SCN8A mRNA reduced but no significant changes were detected when compared to controls (one-way ANOVA, F=1.232, P=0.276). After measuring the optical density of Western blot, we detected significant differences between the levels of SCN8A protein in different groups but no difference between the protein levels of SCN1A at D1 and D60 after pilocarpine treatment compared to the control. At D60 the relative copies of ankyrin-G mRNA on internal control beta-actin in PISE group increased significantly compared to C1 and C2 (one-way ANOVA, F=16.537, P<0.001). Significantly increase of ankyrin-G immunoreactivity in Western blot from the PISE group 1 day and 60 days after PISE was observed, compared to the controls (one-way ANOVA, F=24.255 at D1, P<0.001; F=29.280 at D60, P<0.001). After analyzing the double-stained cells counting, we detected significant differences between the numbers of SCN8A+/ankyrin-G+ immunoreactive cells in different groups in acute and chronic period following PISE (two way-ANOVA, F(group)=37.905, P<0.001; F(day)=45.310, P<0.001). The data revealed that both SCN8A and ankyrin-G increased significantly in the CA1 subfield of the rat hippocampus 60 days following pilocarpine induced status epilepticus and co-localized with each other.
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Affiliation(s)
- Ziyi Chen
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, 58th Zhongshan 2nd Road, Guangzhou, PR China
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296
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Gisabella B, Cunningham MG, Bolshakov VY, Benes FM. Amygdala-dependent regulation of electrical properties of hippocampal interneurons in a model of schizophrenia. Biol Psychiatry 2009; 65:464-72. [PMID: 19027103 DOI: 10.1016/j.biopsych.2008.09.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Revised: 09/11/2008] [Accepted: 09/12/2008] [Indexed: 11/29/2022]
Abstract
BACKGROUND Schizophrenia (SZ) involves dysfunction of gamma-aminobutyric acid (GABA)ergic transmission in the hippocampus (HIPP), particularly in sector CA2/3. Previous work using a rodent model of postmortem abnormalities in SZ demonstrated that activation of the basolateral amygdala (BLA) results in decreases of GABA currents in pyramidal neurons of CA2/3 but not CA1. In addition, a decrease of GABA cells has been reported in postmortem studies of the HIPP in SZ. In the present work we tested the hypothesis that BLA activation in this rodent model of SZ leads to changes in the electrical properties of interneurons located in sector CA2/3. METHODS Patch clamp recordings in HIPP slices were performed in rat HIPP slices after 15 days of infusion of picrotoxin into the BLA. The intrinsic and firing properties and hyperpolarization-activated currents (Ih) of interneurons were measured in stratum oriens (SO) of CA2/3 and CA1. RESULTS The BLA activation was associated with a lower resting membrane potential and an increased action potential firing rate in interneurons of CA2/3 but not CA1. Recordings from interneurons further demonstrated an increase of currents associated with hyperpolarization-activated cationic channels (Ih), which help to control neuronal firing rates and oscillatory rhythms. CONCLUSIONS Taken together, these results suggest that the enhanced BLA activity is capable of increasing the excitability of interneurons in SO of CA2/3 and might contribute to GABAergic dysfunction in SZ.
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Affiliation(s)
- Barbara Gisabella
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02478, USA
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297
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Toering ST, Boer K, de Groot M, Troost D, Heimans JJ, Spliet WGM, van Rijen PC, Jansen FE, Gorter JA, Reijneveld JC, Aronica E. Expression patterns of synaptic vesicle protein 2A in focal cortical dysplasia and TSC-cortical tubers. Epilepsia 2009; 50:1409-18. [PMID: 19220410 DOI: 10.1111/j.1528-1167.2008.01955.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Synaptic vesicle protein 2A (SV2A), the binding site for the antiepileptic drug (AED) levetiracetam, has been shown to be involved in the control of neuronal excitability. The aim of the study was to define the expression and cell-specific distribution of SV2A in developmental focal lesions associated with medically intractable epilepsy. METHODS SV2A immunocytochemistry and Western blotting was performed in focal cortical dysplasia (FCD type IIB) and cortical tubers from patients with tuberous sclerosis complex (TSC). RESULTS Autopsy and surgical control neocortical specimens were characterized by strong SV2A immunoreactivity throughout all cortical layers, with punctate labeling around the somata and dendrites of neurons. In FCD and cortical tuber specimens less intense, SV2A immunoreactivity was observed in the neuropil. The reduction in expression was confirmed by Western blot analysis. In both FCD and tuber specimens, clusters of punctate labeling were detected along cell borders and processes (perisomatic synapses) of dysplastic neuronal cells localized in both gray and white matter. The large majority of balloon cells in FCD, or giant cells in tubers, did not show punctate labeling around their somata. SV2A immunoreactivity was observed occasionally within the neuronal perikarya. CONCLUSIONS The pattern of SV2A immunoreactivity with reduced neuropil expression and altered cellular and subcellular distribution suggests a possible contribution of SV2A to the epileptogenicity of these malformations of cortical development. Knowledge of the expression pattern of SV2A in epilepsy-associated pathologies may be valuable for the evaluation of the effectiveness of AEDs targeting this protein.
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Affiliation(s)
- Sjoukje T Toering
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
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298
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André VM, Cepeda C, Vinters HV, Huynh M, Mathern GW, Levine MS. Pyramidal cell responses to gamma-aminobutyric acid differ in type I and type II cortical dysplasia. J Neurosci Res 2009; 86:3151-62. [PMID: 18615638 DOI: 10.1002/jnr.21752] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abnormalities in the gamma-aminobutyric acid (GABA)-ergic system could be responsible for seizures in cortical dysplasia (CD). We examined responses of pyramidal neurons to exogenous application of GABA, as well as alterations of GABAergic interneuron number and size in pediatric epilepsy surgery patients with non-CD, type I CD, and type II CD pathologies. We used the dissociated cell preparation for electrophysiology along with immunohistochemistry to identify number and size of GABAergic cells. Pyramidal neurons from type I CD tissue showed increased EC(50) and faster kinetics compared with cells from non-CD and type II CD tissue. Cytomegalic pyramidal neurons showed increased GABA peak currents and decreased peak current densities, longer kinetics, and decreased sensitivity to zolpidem and zinc compared with normal pyramidal cells from non-CD and type I CD. There were fewer but larger glutamic acid decarboxylase (GAD)-containing cells in type II CD tissue with cytomegalic neurons compared with non-CD, type I CD, and type II CD without cytomegalic neurons. In addition, GABA transporters (VGAT and GAT-1) showed increased staining surrounding cytomegalic neurons in type II CD tissue. These results indicate that there are differences in GABA(A) receptor-mediated pyramidal cell responses in type I and type II CD. Alterations in zolpidem and zinc sensitivities also suggest that cytomegalic neurons have altered GABA(A) receptor subunit composition. These findings support the hypothesis that patients with type I and type II CD will respond differently to GABA-mediated antiepileptic drugs and that cytomegalic neurons have features similar to immature neurons with prolonged GABA(A) receptor open channel times.
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Affiliation(s)
- Véronique M André
- Mental Retardation Research Center, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA.
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299
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DeFazio RA, Raval AP, Lin HW, Dave KR, Della-Morte D, Perez-Pinzon MA. GABA synapses mediate neuroprotection after ischemic and epsilonPKC preconditioning in rat hippocampal slice cultures. J Cereb Blood Flow Metab 2009; 29:375-84. [PMID: 18957990 PMCID: PMC2696173 DOI: 10.1038/jcbfm.2008.126] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Delayed neuroprotection against ischemic challenges is conferred by both ischemic preconditioning (IPC) and preconditioning by activation of the epsilon-isoform of protein kinase C (epsilonPKC-PC). In vivo, ischemic preconditioning enhances GABA release and ameliorates glutamate release during lethal cerebral ischemia. We tested the hypothesis that IPC and epsilonPKC-PC confer neuroprotection by GABA synapses in rat organotypic hippocampal slices. Ischemic preconditioning or epsilonPKC-PC was induced with 15 mins oxygen-glucose deprivation (OGD) or psiepsilonRACK, a selective epsilonPKC activator; and test ischemia consisted of 40 mins OGD. At the time of peak neuroprotection (48 h after preconditioning), we recorded GABA(A) receptor-mediated miniature postsynaptic currents (GABA mPSCs) in vulnerable CA1 pyramidal neurons using whole-cell voltage clamp techniques. The frequency and amplitude of GABA mPSCs significantly increased 48 h after IPC. In contrast, epsilonPKC-PC enhanced only the amplitude of GABA mPSCs with no effect on frequency. We next asked if neuroprotection depended on these changes in GABA synapses. Weak antagonism of the GABA(A) receptor with bicuculline (100 nmol/L) decreased the amplitude of GABA mPSCs by 20.9+/-6.1%. When applied during test ischemia, 100 nmol/L bicuculline abolished neuroprotection conferred by either IPC or epsilonPKC-PC. We conclude that neuroprotection conferred by preconditioning depends on functional modifications of GABA synapses.
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Affiliation(s)
- R Anthony DeFazio
- Cerebral Vascular Disease Research Center, Department of Neurology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida 33101, USA.
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300
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Jang SY, Kim MK, Lee KR, Park MS, Kim BC, Cho KH, Lee MC, Kim YS. Gene-to-gene interaction between sodium channel-related genes in determining the risk of antiepileptic drug resistance. J Korean Med Sci 2009; 24:62-8. [PMID: 19270815 PMCID: PMC2650995 DOI: 10.3346/jkms.2009.24.1.62] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 04/28/2008] [Indexed: 11/20/2022] Open
Abstract
The pathogenesis of antiepileptic drug (AED) resistance is multifactorial. However, most candidate gene association studies typically assess the effects of candidate genes independently of each other, which is partly because of the limitations of the parametric-statistical methods for detecting the gene-to-gene interactions. A total of 200 patients with drug-resistant epilepsy and 200 patients with drug-responsive epilepsy were genotyped for 3 representative the single nucleotide polymorphisms (SNPs) of the voltage-gated sodium channel genes (SCN1A, SCN1B, and SCN2A) by polymerase chain reaction and direct sequencing analysis. Besides the typical parametric statistical method, a new statistical method (multifactor dimensionality reduction [MDR]) was used to determine whether gene-to-gene interactions increase the risk of AED resistance. None of the individual genotypes or alleles tested in the present study showed a significant association with AED resistance, regardless of their theoretical functional value. With the MDR method, of three possible 2-locus genotype combinations, the combination of SCN2A-PM with SCN1B-PM was the best model for predicting susceptibility to AED resistance, with a p value of 0.0547. MDR, as an analysis paradigm for investigating multi-locus effects in complex disorders, may be a useful statistical method for determining the role of gene-to-gene interactions in the pathogenesis of AED resistance.
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Affiliation(s)
- Sin-Young Jang
- Department of Neurology, Chonnam National University Medical School, Gwangju, Korea
| | - Myeong-Kyu Kim
- Department of Neurology, Chonnam National University Medical School, Gwangju, Korea
| | - Kee-Ra Lee
- Department of Neurology, Chonnam National University Medical School, Gwangju, Korea
| | - Man-Seok Park
- Department of Neurology, Chonnam National University Medical School, Gwangju, Korea
| | - Byeong-Chae Kim
- Department of Neurology, Chonnam National University Medical School, Gwangju, Korea
| | - Ki-Hyun Cho
- Department of Neurology, Chonnam National University Medical School, Gwangju, Korea
| | - Min-Cheol Lee
- Department of Pathology, Chonnam National University Medical School, Gwangju, Korea
| | - Yo-Sik Kim
- Department of Neurology, Wonkwang University School of Medicine, Iksan, Korea
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