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Citraro R, Bosco F, Di Gennaro G, Tallarico M, Guarnieri L, Gallelli L, Rania V, Siniscalchi A, De Sarro G, Leo A. An In Vivo Electroencephalographic Analysis of the Effect of Riluzole against Limbic and Absence Seizure and Comparison with Glutamate Antagonists. Pharmaceutics 2023; 15:2006. [PMID: 37514193 PMCID: PMC10386681 DOI: 10.3390/pharmaceutics15072006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/20/2023] [Accepted: 07/20/2023] [Indexed: 07/30/2023] Open
Abstract
BACKGROUND Riluzole (RLZ) has demonstrated neuroprotective effects in several neurological disorders. These neuroprotective effects seem to be mainly due to its ability to inhibit the excitatory glutamatergic neurotransmission, acting on different targets located both at the presynaptic and postsynaptic levels. METHODS In the present study, we evaluated the effects of Riluzole (RLZ) against limbic seizures, induced by AMPA, kainate, and NMDA receptor agonists in Sprague-Dawley rats, and in a well-validated genetic model of absence epilepsy, the WAG/Rij rat. Furthermore, in this latter model, we also studied the effect of RLZ in co-administration with the competitive NMDA receptor antagonist, CPP, or the non-competitive AMPA receptor antagonist, THIQ-10c, on spike-wave discharges (SWDs) in WAG/Rij rats, to understand the potential involvement of AMPA and NMDA receptors in the anti-absence effect of RLZ. RESULTS In Sprague-Dawley rats, RLZ pretreatment significantly reduced the limbic seizure severity induced by glutamatergic agonists, suggesting an antagonism of RLZ mainly on NMDA rather than non-NMDA receptors. RLZ also reduced SWD parameters in WAG/Rij rats. Interestingly, the co-administration of RLZ with CPP did not increase the anti-absence activity of RLZ in this model, advocating a competitive effect on the NMDA receptor. In contrast, the co-administration of RLZ with THIQ-10c induced an additive effect against absence seizure in WAG/Rij rats. CONCLUSIONS these results suggest that the antiepileptic effects of RLZ, in both seizure models, can be mainly due to the antagonism of the NMDA glutamatergic receptors.
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Affiliation(s)
- Rita Citraro
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
- Research Center FAS@UMG, Department of Health Science, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Francesca Bosco
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Gianfranco Di Gennaro
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Martina Tallarico
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Lorenza Guarnieri
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Luca Gallelli
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
- Research Center FAS@UMG, Department of Health Science, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Vincenzo Rania
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Antonio Siniscalchi
- Department of Neurology and Stroke Unit, Annunziata Hospital of Cosenza, 87100 Cosenza, Italy
| | - Giovambattista De Sarro
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
- Research Center FAS@UMG, Department of Health Science, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
| | - Antonio Leo
- Section of Pharmacology, Science of Health Department, School of Medicine, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
- Research Center FAS@UMG, Department of Health Science, University "Magna Graecia" of Catanzaro, 88100 Catanzaro, Italy
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Oztas B, Sahin D, Kir H, Kuskay S, Ates N. Effects of leptin, ghrelin and neuropeptide y on spike-wave discharge activity and certain biochemical parameters in WAG/Rij rats with genetic absence epilepsy. J Neuroimmunol 2020; 351:577454. [PMID: 33333420 DOI: 10.1016/j.jneuroim.2020.577454] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 11/26/2020] [Accepted: 12/06/2020] [Indexed: 12/14/2022]
Abstract
This study aimed to evaluate the effects of leptin, ghrelin and neuropeptide-Y on the development of nonconvulsive seizure activity and their role on combating oxidative stress and cytokines produced by the systemic immune response in the WAG/Rij rat model for genetic absence epilepsy. Current study showed that all three peptides aggravated spike wave discharges activity and affected the oxidative stress in WAG/Rij rats without any significant changes in the levels of IL-1β, IL-6 and TNF-α except leptin that only induced an increment in the concentration of IL-1β. Our results support the modulatory role of these endogenous peptides on absence epilepsy.
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Affiliation(s)
- Berrin Oztas
- Kocaeli University, Faculty of Medicine, Department of Biochemistry, Kocaeli, Turkey
| | - Deniz Sahin
- Kocaeli University, Faculty of Medicine, Department of Physiology, Kocaeli, Turkey.
| | - Hale Kir
- Kocaeli University, Faculty of Medicine, Department of Biochemistry, Kocaeli, Turkey
| | - Sevinc Kuskay
- Kocaeli University, Faculty of Medicine, Department of Biochemistry, Kocaeli, Turkey
| | - Nurbay Ates
- Kocaeli University, Faculty of Medicine, Department of Physiology, Kocaeli, Turkey
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Barad Z, Grattan DR, Leitch B. NMDA Receptor Expression in the Thalamus of the Stargazer Model of Absence Epilepsy. Sci Rep 2017; 7:42926. [PMID: 28220891 PMCID: PMC5318904 DOI: 10.1038/srep42926] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/16/2017] [Indexed: 11/09/2022] Open
Abstract
In the stargazer mouse model of absence epilepsy, altered corticothalamic excitation of reticular thalamic nucleus (RTN) neurons has been suggested to contribute to abnormal synchronicity in the corticothalamic-thalamocortical circuit, leading to spike-wave discharges, the hallmark of absence seizures. AMPA receptor expression and function are decreased in stargazer RTN, due to a mutation of AMPAR auxiliary subunit stargazin. It is unresolved and debated, however, if decreased excitation of RTN is compatible with epileptogenesis. We tested the hypothesis that relative NMDAR expression may be increased in RTN and/or thalamic synapses in stargazers using Western blot on dissected thalamic nuclei and biochemically isolated synapses, as well as immunogold cytochemistry in RTN. Expression of main NMDAR subunits was variable in stargazer RTN and relay thalamus; however, mean expression values were not statistically significantly different compared to controls. Furthermore, no systematic changes in synaptic NMDAR levels could be detected in stargazer thalamus. In contrast, AMPAR subunits were markedly decreased in both nucleus-specific and synaptic preparations. Thus, defective AMPAR trafficking in stargazer thalamus does not appear to lead to a ubiquitous compensatory increase in total and synaptic NMDAR expression, suggesting that elevated NMDAR function is not mediated by changes in protein expression in stargazer mice.
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Affiliation(s)
- Z Barad
- Department of Anatomy, Otago School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - D R Grattan
- Department of Anatomy, Otago School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Centre for Neuroendocrinology, Dunedin, New Zealand
| | - B Leitch
- Department of Anatomy, Otago School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
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4
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Russo E, Citraro R, Constanti A, Leo A, Lüttjohann A, van Luijtelaar G, De Sarro G. Upholding WAG/Rij rats as a model of absence epileptogenesis: Hidden mechanisms and a new theory on seizure development. Neurosci Biobehav Rev 2016; 71:388-408. [DOI: 10.1016/j.neubiorev.2016.09.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Revised: 09/19/2016] [Indexed: 02/06/2023]
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5
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Karimzadeh F, Soleimani M, Mehdizadeh M, Jafarian M, Mohamadpour M, Kazemi H, Joghataei MT, Gorji A. Diminution of the NMDA receptor NR2B subunit in cortical and subcortical areas of WAG/Rij rats. Synapse 2013; 67:839-46. [PMID: 23754322 DOI: 10.1002/syn.21687] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Accepted: 05/21/2013] [Indexed: 12/27/2022]
Abstract
Modulation of glutamatergic NMDA receptors affects the synchronization of spike discharges in in WAG/Rij rats, a valid genetic animal model of absence epilepsy. In this study, we describe the alteration of NR2B subunit of NMDA receptors expression in WAG/Rij rats in different somatosensory cortical layers and in hippocampal CA1 area. Experimental groups were divided into four groups of six rats of both WAG/Rij and Wistar strains with 2 and 6 months of age. The distribution of NR2B receptors was assessed by immunohistochemical staining in WAG/Rij and compared with age-matched Wistar rats. The expression of NR2B subunit was significantly decreased in different somatosensory cortical layers in 2- and 6-month-old WAG/Rij rats. In addition, the distribution of NR2B in hippocampal CA1 area was lower in 6-month-old WAG/Rij compared with age-matched Wistar rats. The reduction of NR2B receptors in different brain areas points to disturbance of glutamate receptors expression in cortical and subcortical areas in WAG/Rij rats. An altered subunit assembly of NMDA receptors may underlie cortical hyperexcitability in absence epilepsy.
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Affiliation(s)
- Fariba Karimzadeh
- Tehran University of Medical Sciences, Tehran, Iran; Shefa Neuroscience Research Centre, Tehran, Iran
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Kovács Z, Slézia A, Bali ZK, Kovács P, Dobolyi A, Szikra T, Hernádi I, Juhász G. Uridine modulates neuronal activity and inhibits spike-wave discharges of absence epileptic Long Evans and Wistar Albino Glaxo/Rijswijk rats. Brain Res Bull 2013; 97:16-23. [PMID: 23707857 DOI: 10.1016/j.brainresbull.2013.05.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 04/20/2013] [Accepted: 05/06/2013] [Indexed: 01/09/2023]
Abstract
Pharmacological and functional data suggest the existence of uridine (Urd) receptors in the central nervous system (CNS). In the present study, simultaneous extracellular single unit recording and microiontophoretic injection of the pyrimidine nucleoside Urd was used to provide evidence for the presence of Urd-sensitive neurons in the thalamus and the cerebral cortex of Long Evans rats. Twenty-two neurons in the thalamus (24% of recorded neurons) and 17 neurons in the cortex (55%) responded to the direct iontophoresis of Urd. The majority of Urd-sensitive neurons in the thalamus and cortex (82% and 59%, respectively) increased their firing rate in response to Urd. In contrary, adenosine (Ado) and uridine 5'-triphosphate (UTP) decreased the firing rate of all responding neurons in the thalamus, and the majority of responding neurons in the cortex (83% and 87%, respectively). Functional relevance of Urd-sensitive neurons was investigated in spontaneously epileptic freely moving Long Evans and Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. Intraperitoneal (i.p.) injection of 500mg/kg Urd decreased epileptic activity (210-270min after injection) in both rat strains. Intraperitoneal administration of 1000mg/kg Urd decreased the number of spike-wave discharges (SWDs) between 150-270min and 90-270min in Long Evans and WAG/Rij rats, respectively. The effect of Urd was long-lasting in both rat strains as the higher dose significantly decreased the number of SWDs even 24h after Urd injection. The present results suggest that Urd-sensitive neurons in the thalamus and the cerebral cortex may play a role in the antiepileptic action of Urd possibly via modulation of thalamocortical neuronal circuits.
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Affiliation(s)
- Zsolt Kovács
- Department of Zoology, University of West Hungary, Savaria Campus, Károlyi Gáspár tér 4, Szombathely 9700, Hungary.
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Bazyan AS, van Luijtelaar G. Neurochemical and behavioral features in genetic absence epilepsy and in acutely induced absence seizures. ISRN NEUROLOGY 2013; 2013:875834. [PMID: 23738145 PMCID: PMC3664506 DOI: 10.1155/2013/875834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 02/06/2013] [Indexed: 02/08/2023]
Abstract
The absence epilepsy typical electroencephalographic pattern of sharp spikes and slow waves (SWDs) is considered to be due to an interaction of an initiation site in the cortex and a resonant circuit in the thalamus. The hyperpolarization-activated cyclic nucleotide-gated cationic I h pacemaker channels (HCN) play an important role in the enhanced cortical excitability. The role of thalamic HCN in SWD occurrence is less clear. Absence epilepsy in the WAG/Rij strain is accompanied by deficiency of the activity of dopaminergic system, which weakens the formation of an emotional positive state, causes depression-like symptoms, and counteracts learning and memory processes. It also enhances GABAA receptor activity in the striatum, globus pallidus, and reticular thalamic nucleus, causing a rise of SWD activity in the cortico-thalamo-cortical networks. One of the reasons for the occurrence of absences is that several genes coding of GABAA receptors are mutated. The question arises: what the role of DA receptors is. Two mechanisms that cause an infringement of the function of DA receptors in this genetic absence epilepsy model are proposed.
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Affiliation(s)
- A. S. Bazyan
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Science, Russian Federation, 5A Butlerov Street, Moscow 117485, Russia
| | - G. van Luijtelaar
- Biological Psychology, Donders Centre for Cognition, Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands
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8
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D'Amore V, Santolini I, van Rijn CM, Biagioni F, Molinaro G, Prete A, Conn PJ, Lindsley CW, Zhou Y, Vinson PN, Rodriguez AL, Jones CK, Stauffer SR, Nicoletti F, van Luijtelaar G, Ngomba RT. Potentiation of mGlu5 receptors with the novel enhancer, VU0360172, reduces spontaneous absence seizures in WAG/Rij rats. Neuropharmacology 2012; 66:330-8. [PMID: 22705340 DOI: 10.1016/j.neuropharm.2012.05.044] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 05/25/2012] [Accepted: 05/29/2012] [Indexed: 11/27/2022]
Abstract
Absence epilepsy is generated by the cortico-thalamo-cortical network, which undergoes a finely tuned regulation by metabotropic glutamate (mGlu) receptors. We have shown previously that potentiation of mGlu1 receptors reduces spontaneous occurring spike and wave discharges (SWDs) in the WAG/Rij rat model of absence epilepsy, whereas activation of mGlu2/3 and mGlu4 receptors produces the opposite effect. Here, we have extended the study to mGlu5 receptors, which are known to be highly expressed within the cortico-thalamo-cortical network. We used presymptomatic and symptomatic WAG/Rij rats and aged-matched ACI rats. WAG/Rij rats showed a reduction in the mGlu5 receptor protein levels and in the mGlu5-receptor mediated stimulation of polyphosphoinositide hydrolysis in the ventrobasal thalamus, whereas the expression of mGlu5 receptors was increased in the somatosensory cortex. Interestingly, these changes preceded the onset of the epileptic phenotype, being already visible in pre-symptomatic WAG/Rij rats. SWDs in symptomatic WAG/Rij rats were not influenced by pharmacological blockade of mGlu5 receptors with MTEP (10 or 30 mg/kg, i.p.), but were significantly decreased by mGlu5 receptor potentiation with the novel enhancer, VU0360172 (3 or 10 mg/kg, s.c.), without affecting motor behaviour. The effect of VU0360172 was prevented by co-treatment with MTEP. These findings suggest that changes in mGlu5 receptors might lie at the core of the absence-seizure prone phenotype of WAG/Rij rats, and that mGlu5 receptor enhancers are potential candidates to the treatment of absence epilepsy. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.
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Affiliation(s)
- V D'Amore
- I.R.C.C.S., NEUROMED, Neuropharmacology Unit, Parco Tecnologico, Località Camerelle 86077, Pozzilli, Isernia, Italy
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9
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Kovács Z, Czurkó A, Kékesi KA, Juhász G. Intracerebroventricularly administered lipopolysaccharide enhances spike–wave discharges in freely moving WAG/Rij rats. Brain Res Bull 2011; 85:410-6. [DOI: 10.1016/j.brainresbull.2011.05.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 03/19/2011] [Accepted: 05/08/2011] [Indexed: 12/15/2022]
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10
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Bazyan AS, Segal OL. Hyperpolarization-activated I h pacemaker channel in the mammalian brain. NEUROCHEM J+ 2010. [DOI: 10.1134/s181971241004001x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Inaba Y, D'Antuono M, Bertazzoni G, Biagini G, Avoli M. Diminished presynaptic GABA(B) receptor function in the neocortex of a genetic model of absence epilepsy. Neurosignals 2009; 17:121-31. [PMID: 19176980 DOI: 10.1159/000197864] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Accepted: 07/11/2008] [Indexed: 11/19/2022] Open
Abstract
Changes in GABA(B) receptor subunit expression have been recently reported in the neocortex of epileptic WAG/Rij rats that are genetically prone to experience absence seizures. These alterations may lead to hyperexcitability by downregulating the function of presynaptic GABA(B) receptors in neocortical networks as suggested by a reduction in paired-pulse depression. Here, we tested further this hypothesis by analyzing the effects induced by the GABA(B) receptor agonist baclofen (0.1-10 microM) on the inhibitory events recorded in vitro from neocortical slices obtained from epileptic (>180 day-old) WAG/Rij and age-matched, non-epileptic control (NEC) rats. We found that higher doses of baclofen were required to depress pharmacologically isolated, stimulus-induced IPSPs generated by WAG/Rij neurons as compared to NEC. We also obtained similar evidence by comparing the effects of baclofen on the rate of occurrence of synchronous GABAergic events recorded by WAG/Rij and NEC neocortical slices treated with 4-aminopyridine + glutamatergic receptor antagonists. In conclusion, these data highlight a decreased function of presynaptic GABA(B) receptors in the WAG/Rij rat neocortex. We propose that this alteration may contribute to neocortical hyperexcitability and thus to absence seizures.
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Affiliation(s)
- Yugi Inaba
- Montreal Neurological Institute and Departments of Neurology and Neurosurgery, and Physiology, McGill University, Montréal, Que., Canada
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Citraro R, Russo E, Gratteri S, Di Paola ED, Ibbadu GF, Curinga C, Gitto R, Chimirri A, Donato G, De Sarro G. Effects of non-competitive AMPA receptor antagonists injected into some brain areas of WAG/Rij rats, an animal model of generalized absence epilepsy. Neuropharmacology 2006; 51:1058-67. [PMID: 16901515 DOI: 10.1016/j.neuropharm.2006.06.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 05/24/2006] [Accepted: 06/29/2006] [Indexed: 10/24/2022]
Abstract
CFM-2 [1-(4-aminophenyl)-3,5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin-4-one] and THIQ-10c [N-acetyl-1-(4-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline], are two non-competitive 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid (AMPA) receptor antagonists, which demonstrated to antagonize generalized tonic-clonic seizures in different animal models. We have evaluated the effects of such compounds in a genetic animal model of absence epilepsy, the WAG/Rij rat. Animals were focally microinjected into specific brain areas of the cortico-thalamic circuit in order to evaluate the effects of these compounds on the number and duration of epileptic spike-wave discharges (SWDs) and better characterize the role of AMPA neurotransmission in this animal model. The focal microinjection of the two AMPA antagonists into some thalamic nuclei (ventralis posteromedialis (VPM), reticularis (NRT), ventralis posterolateralis (VPL) and the primary somatosensory forelimb region (S1FL)) was, generally, not able to significantly modify the occurrence of SWDs. Whereas, both compounds were able to reduce the number and duration of SWDs dose-dependently when microinjected into the peri-oral region of the primary somatosensory cortex (S1po). These findings suggest that AMPA receptor antagonists might play a role in absence epilepsies and that it might depend on the involvement of specific neuronal areas.
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Affiliation(s)
- Rita Citraro
- Section of Pharmacology, Department of Experimental and Clinical Medicine, Faculty of Medicine and Surgery, University of Catanzaro, School of Medicine at Catanzaro, Policlinico Mater Domini, Via Tommaso Campanella, 115, 88100 Catanzaro, Italy
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Alexander GM, Godwin DW. Metabotropic glutamate receptors as a strategic target for the treatment of epilepsy. Epilepsy Res 2006; 71:1-22. [PMID: 16787741 DOI: 10.1016/j.eplepsyres.2006.05.012] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Accepted: 05/16/2006] [Indexed: 12/31/2022]
Abstract
Epilepsy is a chronic neurological disorder that has many known types, including generalized epilepsies that involve cortical and subcortical structures. A proportion of patients have seizures that are resistant to traditional anti-epilepsy drugs, which mainly target ion channels or postsynaptic receptors. This resistance to conventional therapies makes it important to identify novel targets for the treatment of epilepsy. Given the involvement of the neurotransmitter glutamate in the etiology of epilepsy, targets that control glutamatergic neurotransmission are of special interest. The metabotropic glutamate receptors (mGluRs) are of a family of eight G-protein-coupled receptors that serve unique regulatory functions at synapses that use the neurotransmitter glutamate. Their distribution within the central nervous system provides a platform for both presynaptic control of glutamate release, as well as postsynaptic control of neuronal responses to glutamate. In recent years, substantial efforts have been made towards developing selective agonists and antagonists which may be useful for targeting specific receptor subtypes in an attempt to harness the therapeutic potential of these receptors. We examine the possibility of intervening at these receptors by considering the specific example of absence seizures, a form of generalized, non-convulsive seizure that involves the thalamus. Views of the etiology of absence seizures have evolved over time from the "centrencephalic" concept of a diffuse subcortical pacemaker toward the "cortical focus" theory in which cortical hyperexcitability leads the thalamus into the 3-4 Hz rhythms that are characteristic of absence seizures. Since the cortex communicates with the thalamus via a massive glutamatergic projection, ionotropic glutamate receptor (iGluR) blockade has held promise, but the global nature of iGluR intervention has precluded the clinical effectiveness of drugs that block iGluRs. In contrast, mGluRs, because they modulate iGluRs at glutamatergic synapses only under certain conditions, may quell seizure activity by selectively reducing hyperactive glutamatergic synaptic communication within the cortex and thalamus without significantly affecting normal response rates. In this article, we review the circuitry and events leading to absence seizure generation within the corticothalamic network, we present a comprehensive review of the synaptic location and function of mGluRs within the thalamus and cerebral cortex, and review the current knowledge of mGluR modulation and seizure generation. We conclude by reviewing the potential advantages of Group II mGluRs, specifically mGluR2, in the treatment of both convulsive and non-convulsive seizures.
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Affiliation(s)
- Georgia M Alexander
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Citraro R, Russo E, Di Paola ED, Ibbadu GF, Gratteri S, Marra R, De Sarro G. Effects of some neurosteroids injected into some brain areas of WAG/Rij rats, an animal model of generalized absence epilepsy. Neuropharmacology 2006; 50:1059-71. [PMID: 16631210 DOI: 10.1016/j.neuropharm.2006.02.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Revised: 01/30/2006] [Accepted: 02/20/2006] [Indexed: 10/24/2022]
Abstract
Neurosteroids are synthesized in the brain and have been demonstrated to modulate various cerebral functions. Allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one), a naturally occurring neurosteroid, and ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one), a synthetic derivative, are two neurosteroids acting as positive allosteric modulators of the GABA(A) receptor complex acting on a specific steroid recognition site. Both agents antagonize generalized tonic-clonic seizures in various animal models of epilepsy. Pregnenolone sulphate (3beta-hydroxy-5alpha-pregnen-20-one 3-sulphate; PS) is a negative allosteric modulator of GABA(A) receptors and a positive modulator of the NMDA receptors. We have evaluated the effects of such compounds in a genetic animal model of absence epilepsy, the WAG/Rij rat. Animals were chronically implanted with five frontoparietal cortical electrodes for electrocorticogram (EEG) recordings and bilateral guide cannulae into specific brain areas of the cortico-thalamic circuit in order to evaluate the effects of these compounds on the number and duration of epileptic spike-wave discharges (SWDs). The focal and bilateral microinjection of the two GABA(A) positive modulators into some thalamic nuclei (nucleus ventralis posteromedialis, nucleus reticularis thalami, nucleus ventralis posterolateralis was usually able to significantly worsen the occurrence of SWDs in WAG/Rij rats. Whereas both compounds were able to reduce the number and duration of SWDs when microinjected into the peri-oral region of the primary somatosensory cortex. The effects of PS were more complex depending on both the dose and the site of administration, generally, at low doses in thalamic nuclei and cortex, PS induced an increase of absence activity and a reduction at higher doses. These findings suggest that neurosteroids might play a role in absence epilepsies and that it might depend on the involvement of specific neuronal areas.
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Affiliation(s)
- Rita Citraro
- Section of Pharmacology, Department of Experimental and Clinical Medicine, Faculty of Medicine and Surgery, University of Catanzaro, Policlinico Mater Domini, Via T. Campanella, 115, 88100 Catanzaro, Italy
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D'Antuono M, Inaba Y, Biagini G, D'Arcangelo G, Tancredi V, Avoli M. Synaptic hyperexcitability of deep layer neocortical cells in a genetic model of absence seizures. GENES BRAIN AND BEHAVIOR 2006; 5:73-84. [PMID: 16436191 DOI: 10.1111/j.1601-183x.2005.00146.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
We used sharp-electrode, intracellular recordings in an in vitro brain slice preparation to study the excitability of neocortical neurons located in the deep layers (>900 microm from the pia) of epileptic (180-210-days old) Wistar Albino Glaxo/Rijswijk (WAG/Rij) and age-matched, non-epileptic control (NEC) rats. Wistar Albino Glaxo/Rijswijk rats represent a genetic model of absence seizures associated with generalized spike and wave (SW) discharges in vivo. When filled with neurobiotin, these neurons had a typical pyramidal shape with extensive apical and basal dendritic trees; moreover, WAG/Rij and NEC cells had similar fundamental electrophysiological and repetitive firing properties. Sequences of excitatory postsynaptic potentials (EPSPs) and hyperpolarizing inhibitory postsynaptic potentials (IPSPs) were induced in both the strains by electrical stimuli delivered to the underlying white matter or within the neocortex; however, in 24 of 55 regularly firing WAG/Rij cells but only in 2 of 25 NEC neurons, we identified a late EPSP that (1) led to action potential discharge and (2) was abolished by the N-methyl-D-aspartate (NMDA) receptor antagonist 3,3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonate (20 microM; n = 8/8 WAG/Rij cells). Finally, we found that the fast and slow components of the stimulus-induced IPSPs recorded during the application of glutamatergic receptor antagonists had similar reversal potentials in the two strains, while the peak conductance of the fast IPSP was significantly reduced in WAG/Rij cells. These findings document an increase in synaptic excitability that is mediated by NMDA receptors, in epileptic WAG/Rij rat neurons located in neocortical deep layers. We propose that this mechanism may be instrumental for initiating and maintaining generalized SW discharges in vivo.
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Affiliation(s)
- M D'Antuono
- Dipartimento di Fisiologia Umana e Farmacologia V. Erspamer, Università di Roma La Sapienza, Roma, Italy
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16
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Veatch LM, Becker HC. Lorazepam and MK-801 effects on behavioral and electrographic indices of alcohol withdrawal sensitization. Brain Res 2006; 1065:92-106. [PMID: 16313888 DOI: 10.1016/j.brainres.2005.10.047] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 10/10/2005] [Accepted: 10/15/2005] [Indexed: 11/22/2022]
Abstract
Repeated cycles of chronic ethanol exposure and withdrawal result in sensitization of withdrawal-related CNS hyperexcitability that generally reflects an imbalance in activity of GABA and glutamate systems. Many pharmacological treatments for ethanol withdrawal target neuroadaptive changes in GABA and glutamate neurotransmission. The present study utilized a mouse model of repeated withdrawals to evaluate the ability of lorazepam and MK-801 treatments to antagonize behavioral and electroencephalographic (EEG) measures of sensitized withdrawal seizure activity. Adult male C3H/He mice received chronic intermittent ethanol vapor exposure in inhalation chambers (16 h/day) and during each withdrawal cycle, separate groups of mice were evaluated for handling-induced convulsions (HIC) or abnormal EEG (high-voltage "brief spindle episodes" (BSE)) activity. Lorazepam (0.5-1.0 mg/kg) or MK-801 (0.1-0.3 mg/kg) treatment at 1 h into each of three withdrawal cycles reduced behavioral (HIC) and electrographic (BSE) signs of seizure activity in a dose-related fashion compared to vehicle-treated mice. During a subsequent untreated withdrawal, mice previously treated with lorazepam or MK-801 for earlier withdrawals exhibited reduced HIC activity during the acute phase but exacerbated HIC activity during the protracted phase of this final (fourth) withdrawal cycle. Both lorazepam and MK-801 treatment conditions resulted in enhanced BSE activity during the entire fourth (untreated) withdrawal episode. Collectively, these results suggest that while treatment of repeated ethanol withdrawals with a benzodiazepine (lorazepam) or an NMDA receptor antagonist (MK-801) may have some initial benefits in ameliorating the development of sensitized withdrawal excitability, such treatment may also render subjects more vulnerable to seizure activity at later time points.
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Affiliation(s)
- Lynn M Veatch
- Charleston Alcohol Research Center, Center for Drug and Alcohol Programs, Department of Psychiatry and Behavioral Sciences, 67 President Street, IOP-4N, Medical University of South Carolina, Charleston, 29425, USA
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Schridde U, van Luijtelaar G. Corticosterone increases spike-wave discharges in a dose- and time-dependent manner in WAG/Rij rats. Pharmacol Biochem Behav 2005; 78:369-75. [PMID: 15219779 DOI: 10.1016/j.pbb.2004.04.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Revised: 04/14/2004] [Accepted: 04/26/2004] [Indexed: 11/22/2022]
Abstract
Corticosteroids mediate seizure activity in different epilepsy models or epilepsies. However, for childhood absence epilepsy, a nonconvulsive type of epilepsy, direct evidence for corticosteroid seizure modulation is lacking. Thus, in the present study, we analysed the acute systemic effects of different doses of the corticosteroid corticosterone on seizure activity in a well-validated animal model of childhood absence epilepsy, the WAG/Rij rat. We found a time- and dose-dependent increase in the number of spike-wave discharges (SWD) in the EEG, with 500 microg/kg of corticosterone causing a 327% increase in discharges compared to baseline 15-30 min after administration. No treatment effects were found on mean duration of SWD and behavior. Our data indicate that corticosterone in a physiologically relevant dose can aggravate absence seizures in a rapid but transient way. Regarding the time course of the effect, we suggest that corticosterone is acting nongenomically, possibly via a temporary increase of excitatory amino acids.
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Affiliation(s)
- Ulrich Schridde
- NICI, Department of Biological Psychology, University of Nijmegen, P.O. Box 9104, 6500 HE, Nijmegen, The Netherlands.
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18
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D'Arcangelo G, D'Antuono M, Biagini G, Warren R, Tancredi V, Avoli M. Thalamocortical oscillations in a genetic model of absence seizures. Eur J Neurosci 2002; 16:2383-93. [PMID: 12492433 DOI: 10.1046/j.1460-9568.2002.02411.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We used field potential recordings in an in vitro thalamocortical slice preparation to compare the rhythmic oscillations generated by reciprocally connected networks of the thalamus and cerebral cortex obtained from epileptic (> 160 days old) WAG/Rij and age-matched, nonepileptic control (NEC) rats. To increase neuronal excitability, and thus to elicit spontaneous field potential activity in vitro, we applied medium containing: (i) zero [Mg2+]; (ii) high [K+] (8.25 mm); or (iii) low concentrations of the K+ channel blocker 4-aminopyridine (4AP, 0.5-1 micro m). Of these procedures, only the last was effective in triggering oscillatory activity that depended on the type of tissue. Thus, during 4AP application: (i) sequences of fast (intraburst frequency 9.5-16.1 Hz) and slower (5-8.9 Hz) field potential oscillations (FPOs) were recorded in WAG/Rij slices (n = 23), but (ii) only fast FPOs were seen in NEC slices (n = 7). Slower FPOs in WAG/Rij slices reflected a larger degree of thalamocortical synchronization than fast FPOs, and disappeared after surgical separation of cortex and thalamus (n = 5); under these conditions fast FPOs continued to occur in thalamus only. In addition, fast and slower FPOs disappeared in all areas of the WAG/Rij slice during thalamic application of the excitatory amino acid receptor antagonist kynurenic acid (n = 3), while fast FPOs continued to occur in thalamus when kynurenic acid was applied to the cortex (n = 4). Bath application of the N-methyl-D-aspartic acid (NMDA) receptor antagonist 3,3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonate (CPP) abolished slower FPOs in WAG/Rij cortex and thalamus (n = 6) without infuencing fast FPOs recorded in WAG/Rij (n = 6) or NEC slices (n = 4). Moreover, cortical application of CPP (n = 6) abated slower FPOs although they persisted following CPP application to the thalamus (n = 7). Our data demonstrate that highly synchronized, slower FPOs can occur during 4AP application in WAG/Rij but not in NEC slices. This activity, which may represent an in vitro hallmark of thalamocortical epileptogenicity, requires the function of reciprocally connected thalamic and cortical networks and depends on cortical NMDA receptor-mediated mechanisms.
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Affiliation(s)
- Giovanna D'Arcangelo
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801, University St., Montréal, QC, H3A B, Canada
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19
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Budziszewska B, Van Luijtelaar G, Coenen AM, Leśkiewicz M, Lasoń W. Effects of neurosteroids on spike-wave discharges in the genetic epileptic WAG/Rij rat. Epilepsy Res 1999; 33:23-9. [PMID: 10022363 DOI: 10.1016/s0920-1211(98)00067-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Effects of i.p. administration of the neurosteroids, allopregnanolone and pregnenolone sulfate, were studied in WAG/Rij rats, a genetic model for generalized absence epilepsy. EEG recordings showed that allopregnanolone, a positive modulator of the GABA(A) receptor, in doses ranging from 5 to 20 mg/kg, increased dose-dependently the number- and total duration of spike-wave discharges. Pregnenolone sulfate, a positive modulator of NMDA receptors, also increased those parameters, though only at the highest dose used (100 mg/kg). Significant changes in spike-wave discharges occurred during the first hour post-injection and were not accompanied with behavioral alterations. The obtained data indicate that both these neurosteroids aggravate the spike-wave activity. This finding contrasts with the anti-convulsant effects of some neurosteroids and they point to a different pharmacological profile of epilepsy with convulsive or non-convulsive seizures.
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Affiliation(s)
- B Budziszewska
- Department of Endocrinology, Institute of Pharmacology, Polish Academy of Sciences, Kraków
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20
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Danober L, Deransart C, Depaulis A, Vergnes M, Marescaux C. Pathophysiological mechanisms of genetic absence epilepsy in the rat. Prog Neurobiol 1998; 55:27-57. [PMID: 9602499 DOI: 10.1016/s0301-0082(97)00091-9] [Citation(s) in RCA: 403] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Generalized non-convulsive absence seizures are characterized by the occurrence of synchronous and bilateral spike and wave discharges (SWDs) on the electroencephalogram, that are concomitant with a behavioral arrest. Many similarities between rodent and human absence seizures support the use of genetic rodent models, in which spontaneous SWDs occur. This review summarizes data obtained on the neurophysiological and neurochemical mechanisms of absence seizures with special emphasis on the Genetic Absence Epilepsy Rats from Strasbourg (GAERS). EEG recordings from various brain regions and lesion experiments showed that the cortex, the reticular nucleus and the relay nuclei of the thalamus play a predominant role in the development of SWDs. Neither the cortex, nor the thalamus alone can sustain SWDs, indicating that both structures are intimely involved in the genesis of SWDs. Pharmacological data confirmed that both inhibitory and excitatory neurotransmissions are involved in the genesis and control of absence seizures. Whether the generation of SWDs is the result of an excessive cortical excitability, due to an unbalance between inhibition and excitation, or excessive thalamic oscillations, due to abnormal intrinsic neuronal properties under the control of inhibitory GABAergic mechanisms, remains controversial. The thalamo-cortical activity is regulated by several monoaminergic and cholinergic projections. An alteration of the activity of these different ascending inputs may induce a temporary inadequation of the functional state between the cortex and the thalamus and thus promote SWDs. The experimental data are discussed in view of these possible pathophysiological mechanisms.
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Affiliation(s)
- L Danober
- INSERM U 398, Neurobiologie et Neuropharmacologie des épilepsies généralisées, Faculté de Médecine, Strasbourg, France.
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Aizawa M, Ito Y, Fukuda H. Pharmacological profiles of generalized absence seizures in lethargic, stargazer and gamma-hydroxybutyrate-treated model mice. Neurosci Res 1997; 29:17-25. [PMID: 9293489 DOI: 10.1016/s0168-0102(97)00066-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We examined the pharmacological profiles of generalized absence seizures in three mouse models: two mutant strains with spontaneous absence seizures, lethargic and stargazer, and ddY mice (GHB model) in which absence seizures were induced by administering gamma-butyrolactone (GBL), a prodrug of gamma-hydroxybutyric acid (GHB). A typical antiabsence drug, ethosuximide (200 mg/kg), attenuated absence seizure behavior, spike and wave and paroxysmal discharges (SWDs and PDs) in each model. P-[3-Aminopropyl]-P-diethoxymethylphosphinic acid (CGP 35348), a selective gamma-aminobutyric acid (GABA)B antagonist (200 mg/kg), suppressed absence seizure behavior, SWDs and PDs at least as effectively as ethosuximide (200 mg/kg) in lethargic and GHB model mice. P-[3-Aminopropyl]-P-cyclohexylmethylphosphinic acid (CGP 46381) was more effective than CGP 35348 and ethosuximide in these models. Although the antiabsence effect of CGP 46381 was as strong as that of ethosuximide (200 mg/kg) in stargazer mice, CGP 35348 (200-400 mg/kg) was weaker than ethosuximide. (+)-5-Methyl-10,11-dihydro-5H-dibenzo[a,b]cyclohepten-5,10-imine hydrogen maleate (MK-801), a non-competitive N-methyl-D-aspartate (NMDA) antagonist (0.5 mg/kg), had no effects on SWDs and PDs in lethargic or GHB model mice. Although MK-801 (0.5 mg/kg) suppressed SWDs significantly in stargazer mice, irregular electroencephalographic patterns were observed. These results suggest that GABAB receptors play a significant role in the pathogenesis of generalized absence seizures in these models, although the mechanism involved in stargazer mice differ from that in the other two.
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Affiliation(s)
- M Aizawa
- Department of Pharmacology, College of Pharmacy, Nihon University, Chiba, Japan
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22
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Hallak M, Irtenkauf SM, Cotton DB. Effect of magnesium sulfate on excitatory amino acid receptors in the rat brain. I. N-methyl-D-aspartate receptor channel complex. Am J Obstet Gynecol 1996; 175:575-81. [PMID: 8828416 DOI: 10.1053/ob.1996.v175.a74408] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Our purpose was to determine the effect of peripherally administered magnesium sulfate on the N-methyl-D-aspartate receptor channel complex in the rat central nervous system. STUDY DESIGN Six rats were injected intraperitoneally with 270 mg/kg magnesium sulfate, followed by 27 mg/kg every 20 minutes for 4 hours. Controls (n = 6) received saline solution. Six rats received intraperitoneal injections of magnesium sulfate (270 mg/kg) every 4 hours for 24 hours and 6 received saline solution. Six rats received intraperitoneal magnesium sulfate (270 mg/kg) every 12 hours for 2 weeks and 6 received saline solution. Rats were subsequently perfused and killed and their brains dissected and frozen. Cryostate sections were taken, labeled in vitro by one of three ligands for autoradiography assay, and mounted on tritium-sensitive film for 4 weeks. The ligands were tritiated glutamate agonist, N-methyl-D-aspartate binding site; tritiated glycine agonist, glycine binding site; and tritiated MK-801 noncompetitive antagonist, channel site. Optical density measurements of binding of 11 brain regions on each section were performed with an image analyzing system. RESULTS N-methyl-D-aspartate receptor binding in the hippocampus was higher than in all other brain regions in all three experiments. Systemic administration of magnesium sulfate for 24 hours resulted in reduced tritiated glutamate binding, whereas long-term administration (2 weeks) resulted in significantly decreased tritiated glycine binding in all brain regions sampled. Binding of tritiated MK-801 was significantly increased in both short- and intermediate-term administration of magnesium sulfate. CONCLUSIONS These data suggest that short-term magnesium sulfate administration results in increased inhibition of the ion channel. This effect is also continued with prolonged treatment, along with decreased sensitivity of the N-methyl-D-aspartate receptor channel complex to its agonists glutamate and glycine. This proposed time-dependent, twofold effect may provide insight into the mechanisms of magnesium sulfate's central anticonvulsant effect.
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Affiliation(s)
- M Hallak
- Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, MI 48235, USA
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23
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Koerner C, Danober L, Boehrer A, Marescaux C, Vergnes M. Thalamic NMDA transmission in a genetic model of absence epilepsy in rats. Epilepsy Res 1996; 25:11-9. [PMID: 8886657 DOI: 10.1016/0920-1211(96)00015-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In the selected strain of GAERS Wistar rats (Genétic Absence Epilepsy Rats from Strasbourg), all animals present spontaneously recurrent absence seizures characterized by bilateral and synchronous generalized spike-and-wave discharges (SWD) accompanied by behavioural arrest. SWD depend on a thalamo-cortical network connecting the reticular and relay nuclei of the thalamus and their cortical projection areas. This loop involves both GABAergic and glutamatergic synapses. In the present study, we investigated the implication of NMDA transmission in the genesis of absence seizures in GAERS. Intra-peritoneal or intra-cerebroventricular injections of NMDA, the competitive NMDA antagonist CGP 40116, the non-competitive NMDA antagonist (+)-MK 801 and the antagonist of the glycine modulatory site 5,7-dichlorokynurenic acid dose-dependently suppressed SWD. Bilateral infusions of the same drugs in the lateral relay nuclei of the thalamus had similar suppressive effects. Intra-cerebroventricular or intrathalamic administration of D-serine, an agonist of the glycine modulatory site, had no effect on SWD. These data show that NMDA neurotransmission, especially within the thalamus, plays a major role in the control of absence seizures in GAERs. Disregulation of NMDA-mediated transmission by NMDA or antagonists, interacting with various sites of the receptor complex, may suppress the thalamo-cortical oscillatory activity which underlies SWD.
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Affiliation(s)
- C Koerner
- Unité INSERM 398, Faculté de Médecine, Strasbourg, France
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24
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Przewłocka B, Lasoń W, Machelska H, van Luijtelaar G, Coenen A, Przewłocki R. Kappa opioid receptor agonists suppress absence seizures in WAG/Rij rats. Neurosci Lett 1995; 186:131-4. [PMID: 7777181 DOI: 10.1016/0304-3940(95)11303-e] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Involvement of the kappa opioid receptor in the regulation of epileptic activity was studied in WAG/Rij rats, a genetic model of absence epilepsy. I.c.v. administration of the kappa agonists U50,488H (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzeneacetamide), U69,593 (5 alpha, 7 alpha, 8 beta)-(-)-N-methyl-(1-pyrrolidinyl)-1- oxaspiro(4,5)dec-8-yl)benzeneacetamide) or PD117,302 ((+/-)-trans-N-methyl-N-[2-(1-pyrrolidinyl)- cyclohexyl]benzo[b]thiophene-4-acetamide), 50 and 150 micrograms/5 microliter each, dose-dependently decreased the number and mean duration of spike wave discharges (SWD). Peripheral administration of U50,488H (10 and 30 mg/kg s.c.) also attenuated the seizure activity in this model. The specific kappa opioid receptor antagonist nor-binaltorphimine (Nor-BNI, 10 micrograms/5 microliters i.c.v., 18 h before EEG registration) moderately increased the number of SWD, which suggests that endogenous opioids acting through kappa receptors may tonically inhibit the seizure activity in these rats. In addition, the enhancement of an absence-like seizure activity induced by the specific mu opioid receptor agonist D-Ala2-N-methyl-Phe4-Gly5-ol-enkephalin (DAMGO, 0.7 microgram/5 microliters i.c.v.) was also attenuated in rats pretreated with U50,488H, U69,593 or PD117,302. These data indicate that activation of the kappa opioid receptor exerts an inhibitory effect on absence-like seizure activity in WAG/Rij rats.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
- Amino Acid Sequence
- Animals
- Anticonvulsants/pharmacology
- Dose-Response Relationship, Drug
- Electroencephalography/drug effects
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalins/pharmacology
- Epilepsy, Absence/drug therapy
- Epilepsy, Absence/genetics
- Epilepsy, Absence/physiopathology
- Injections, Intraventricular
- Injections, Subcutaneous
- Male
- Molecular Sequence Data
- Naltrexone/administration & dosage
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Pyrroles/pharmacology
- Pyrrolidines/administration & dosage
- Pyrrolidines/pharmacology
- Rats
- Rats, Inbred Strains
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, mu/agonists
- Thiophenes/pharmacology
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Affiliation(s)
- B Przewłocka
- Neuropeptide Research Department, Institute of Pharmacology, Polish Academy of Sciences, Kraków
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25
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Prevett MC, Lammertsma AA, Brooks DJ, Bartenstein PA, Patsalos PN, Fish DR, Duncan JS. Benzodiazepine-GABAA receptors in idiopathic generalized epilepsy measured with [11C]flumazenil and positron emission tomography. Epilepsia 1995; 36:113-21. [PMID: 7821267 DOI: 10.1111/j.1528-1157.1995.tb00969.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The neurochemical basis of absence seizures and the mechanism of their suppression by valproate (VPA) are uncertain. We used positron emission tomography (PET) to determine whether an abnormality of [11C]flumazenil binding to benzodiazepine (BZD)-GABAA receptors exists in patients with childhood and juvenile absence epilepsy and to examine the effects of VPA on [11C]flumazenil binding. The regional cerebral volume of distribution (Vd) of [11C]flumazenil in patients not treated with VPA was not different from that in normal controls; Vd was lower in patients treated with VPA, and the number of receptors available for binding was significantly reduced in such patients as compared with normal controls. There was no evidence of a primary abnormality of the BZD-GABAA receptor in childhood and juvenile absence epilepsy (CAE/JAE), but the data suggest that treatment with VPA is associated with a reduction in [11C]flumazenil binding that may be relevant to its mode of action in CAE/JAE.
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Affiliation(s)
- M C Prevett
- MRC Cyclotron Unit, Hammersmith Hospital, London, England
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26
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Banerjee PK, Snead OC. Thalamic NMDA receptors in the gamma-hydroxybutyrate model of absence seizures: a cerebral microinjection study in rats. Neuropharmacology 1995; 34:43-53. [PMID: 7623963 DOI: 10.1016/0028-3908(94)00134-e] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The possible role of thalamic NMDA receptors in the generation of experimental absence-like seizures was studied in rats. Bilaterally synchronous spike wave discharges were induced by gamma-hydroxybutyric acid (GHB) and were recorded simultaneously from different thalamic nuclei and the layers I-IV of frontoparietal cortex. Bilateral infusions of NMDA into thalamic mediodorsal nucleus, the intralaminar central lateral/paracentral nucleus, ventroposterolateral, or reticular nucleus of the thalamus in conscious rats, prior to GHB administration suppressed GHB-induced SWD in a dose dependent manner. However, no such suppression of GHB-induced SWD was observed when NMDA infusions were made into the above thalamic sites after the onset or development of GHB-induced SWD. Pretreatment with high doses of competitive (CGP 43487) or non-competitive NMDA receptor antagonists (MK-801 and ketamine) also dose dependently suppressed GHB-induced SWD. Both MK-801 and CGP 43487 dose dependently antagonized NMDA-mediated inhibition of GHB-induced SWD activity but at lower doses did not produce significant inhibition of GHB-induced SWD. The anti-SWD effects of NMDA, MK-801 and ketamine but not CGP 43487 were more pronounced in the mediodorsal and intralaminar thalamic nuclei than in the ventroposterolateral or reticular nucleus of thalamus. Because low doses of NMDA antagonists failed to disrupt the generation of seizures in the GHB model, these findings do not support a role for thalamic NMDA receptors in the pathogenesis of absence-like seizures induced by gamma-hydroxybutyric acid.
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Affiliation(s)
- P K Banerjee
- Division of Neurology, Childrens Hospital of Los Angeles, University of Southern California School of Medicine 90027, USA
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27
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Lasoń W, Przewłocka B, Van Luijtelaar G, Coenen A. Proenkephalin and prodynorphin mRNA level in brain of rats with absence epilepsy. Neuropeptides 1994; 27:343-7. [PMID: 7898641 DOI: 10.1016/0143-4179(94)90060-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An in situ hybridization method was used to estimate the proenkephalin (PENK) and prodynorphin (PDYN) mRNA levels in the brain of epileptic 6-month-old WAG/Rij rats in comparison with non-epileptic: 3-month-old WAG/Rij rats, 3-month-old ACI rats and 6-month-old ACI rats. The epileptic rats had a significantly higher level of PENK mRNA in the striatum as compared to non-epileptic controls. The PDYN mRNA level was significantly elevated only in the hippocampus of epileptic rats, whereas age- or strain-related changes in the striatal and cortical PDYN mRNA levels were found in both epileptic and non-epileptic rats. The changes in the biosynthetic activity of endogenous opioid peptide systems may be important for the occurrence of epileptic discharges in these animals.
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Affiliation(s)
- W Lasoń
- Neuropeptide Research Department, Polish Academy of Sciences, Kraków
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28
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Peeters BW, Ramakers GM, Ellenbroek BA, Vossen JM, Coenen AM. Interactions between NMDA and nonNMDA receptors in nonconvulsive epilepsy in the WAG/Rij inbred strain. Brain Res Bull 1994; 33:715-8. [PMID: 7514947 DOI: 10.1016/0361-9230(94)90237-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The interaction between NMDA and nonNMDA receptors was studied in nonconvulsive epilepsy in WAG/Rij rats. Compounds acting on NMDA (NMDA, APH) and nonNMDA (AMPA, GDEE, kainic acid, kynurenic acid) receptors were coinjected intracerebroventricularly. The WAG/Rij rat strain may be an animal model for human nonconvulsive absence epilepsy. The effects on the epilepsy, EEG and behaviour were measured. It appeared that the epilepsy increase, induced by the nonNMDA receptor agonist AMPA, and in a less obvious way, kainic acid, was blocked by the NMDA receptor antagonist APH. The effects of NMDA were completely blocked by the nonNMDA receptor antagonists GDEE and kynurenic acid. These results suggest that there is an interaction between NMDA and nonNMDA receptors. It might be that nonNMDAergic compounds act via activation or inactivation of NMDA receptors and that this latter receptor subtype is the trigger for an epileptic seizure.
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Affiliation(s)
- B W Peeters
- Department of Neuropharmacology, Organon International B.V., Oss, The Netherlands
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Peeters BW, Ramakers GM, Vossen JM, Coenen AM. The WAG/Rij rat model for nonconvulsive absence epilepsy: involvement of nonNMDA receptors. Brain Res Bull 1994; 33:709-13. [PMID: 7514946 DOI: 10.1016/0361-9230(94)90236-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The involvement of AMPA and kainate receptors in nonconvulsive epilepsy was studied by intracerebroventricular injections of AMPA, GDEE, kainic acid and kynurenic acid in WAG/Rij rats. The WAG/Rij rat strain is recognized as an animal model for human absence epilepsy. EEG registrations showed that AMPA (0.1 pmol/5 microliters; 1 pmol/5 microliters; 10 pmol/5 microliters) dose-dependently increased the nonconvulsive absence epilepsy while GDEE (0.2 mumol/5 microliters; 1 mumol/5 microliters; 5 umol/5 microliters) caused a dose-dependent decrease. All effects of GDEE could be blocked by an inactive AMPA dosage. Kainic acid (0.01 nmol/5 microliters; 0.1 nmol/5 microliters; 0.15 nmol/5 microliters) had no effects on the nonconvulsive epilepsy but induced convulsions in the two highest dosages. Kynurenic acid (50 nmol/5 microliters; 100 nmol/5 microliters; 500 nmol/5 microliters) decreased dose-dependently the incidence of nonconvulsive epilepsy. The effect of kynurenic acid could be blocked by a nonconvulsive dosage of kainic acid. These results show that the AMPA and kainate receptor appear to be involved in nonconvulsive epilepsy. Furthermore, blockage of these two receptor subtypes led to an antiepileptic effect without inducing behavioural alterations. Therefore, selective AMPA and kainate receptor antagonists might be potent anti-epileptics.
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Affiliation(s)
- B W Peeters
- Department of Neuropharmacology, Organon International B. V., Oss, The Netherlands
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Hallak M, Berman RF, Irtenkauf SM, Janusz CA, Cotton DB. Magnesium sulfate treatment decreases N-methyl-D-aspartate receptor binding in the rat brain: an autoradiographic study. JOURNAL OF THE SOCIETY FOR GYNECOLOGIC INVESTIGATION 1994; 1:25-30. [PMID: 9419742 DOI: 10.1177/107155769400100106] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE We determined the effect of peripherally administered magnesium sulfate on N-methyl-D-aspartate (NMDA) receptor binding capacity in various regions of the rat brain. METHODS Three separate experiments were performed. 1) Six rats were injected intraperitoneally with 270 mg/kg of magnesium sulfate, followed by 27 mg/kg every 20 minutes for 4 hours; controls (n = 6) received saline. 2) Six rats received intraperitoneal injections of magnesium sulfate (270 mg/kg) every 4 hours for 24 hours, while six received saline. 3) Six rats received intraperitoneal magnesium sulfate (270 mg/kg) every 12 hours for a total of 2 weeks, and six received saline. Rats were subsequently perfused and sacrificed, and their brains were dissected, rinsed, and frozen. Cryostat sections were taken, labeled by in vitro [3H]-CGP 39653, assayed autoradiographically, and mounted on Ultrofilm for 4 weeks. Optical density measurements of binding on each section were performed using an image analyzing system. Eleven brain regions were sampled: 1, 2) frontal and occipital cortex; 3-7) hippocampus--CA-1, CA-3, stratum radiatum, stratum oriens, dentate gyrus; 8) thalamus; 9) hypothalamus; 10) caudate nucleus; and 11) cerebellum. RESULTS The NMDA receptor binding density in the hippocampus was significantly higher than in all other brain regions in all three experiments. In experiment 1, there was no significant effect on NMDA receptor binding. However, prolonged systemic administration of magnesium sulfate for 24 hours resulted in significantly reduced [3H]-CGP binding in all brain regions sampled. After chronic magnesium sulfate administration (2 weeks), the [3H]-CGP binding was still reduced in the cortex and some regions of the hippocampus; however, there was no significant change in other regions. CONCLUSIONS Peripheral treatment with magnesium sulfate results in a significant reduction in the NMDA receptor binding capacity in the rat brain. These results support the hypothesis that magnesium central activity is mediated, at least in part, via the NMDA receptor.
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Affiliation(s)
- M Hallak
- Department of Obstetrics and Gynecology, Wayne State University, Hutzel Hospital, Detroit, MI 48201, USA
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Hallak M, Irtenkauf SM, Janusz CA, Cotton DB. Stimulation and inhibition of N-methyl-D-aspartate receptors in rats: developing a seizure model. Am J Obstet Gynecol 1993; 169:695-700. [PMID: 8372882 DOI: 10.1016/0002-9378(93)90645-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
OBJECTIVE The objective of this study was to develop an experimental rat hippocampal seizure model based on the stimulatory effects of N-methyl-D-aspartate and to determine the inhibitory effects of MK-801 on N-methyl-D-aspartate-induced seizures. STUDY DESIGN Two separate experiments were performed. In the first experiment chemitrode-implanted rats were injected intracranially with increasing doses (5, 10, 20, and 30 micrograms) of N-methyl-D-aspartate into the hippocampus. Various electrophysiologic and behavioral parameters were examined to determine the dose required to reliably elicit hippocampal seizure activity without having toxic effects on the rats. In the second experiment rats were given an intraperitoneal injection of MK-801 (0.5 or 1 mg/kg), followed 20 minutes later by an intracranial injection of N-methyl-D-aspartate (20 or 30 micrograms). The ability of MK-801 to suppress N-methyl-D-aspartate-induced seizure activity was assessed in this experiment. RESULTS Intrahippocampal injection of 20 micrograms of N-methyl-D-aspartate produced the shortest electrical seizure latency (193 +/- 72 seconds, p < 0.01). At this dose seizure was achieved in 80% (four of five of the animals, and the highest numbers of electrical seizures per animal were produced (2.2 +/- 0.8, p < 0.05). The group that received 30 micrograms of N-methyl-D-aspartate had a shorter latency, a longer duration of behavioral seizure and a higher number of behavioral seizures (p < 0.05). However, this group suffered a 60% (three of five) mortality rate. The addition of MK-801 significantly decreased the number of seizures per animal and the total seizure duration (p < 0.05). MK-801 also reduced the latency period. CONCLUSION Intracranial injection of 20 micrograms of N-methyl-D-aspartate produced reliable hippocampal seizure activity without mortality. MK-801 at a dose of 1 mg/kg injected intraperitoneally had significant inhibitory effects on this seizure model.
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Affiliation(s)
- M Hallak
- Department of Obstetrics and Gynecology, Wayne State University/Hutzel Hospital, Detroit, MI 48201
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Coenen AM, Drinkenburg WH, Inoue M, van Luijtelaar EL. Genetic models of absence epilepsy, with emphasis on the WAG/Rij strain of rats. Epilepsy Res 1992; 12:75-86. [PMID: 1396543 DOI: 10.1016/0920-1211(92)90029-s] [Citation(s) in RCA: 202] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this review, the main characteristics of genetic models of absence epilepsy, in particular with respect to WAG/Rij rats, are presented. Genetic models are important and relevant, since evidence exists that these models mimic spontaneously occurring human epilepsy more than models in which epilepsy is artificially induced. Genetic models can be divided into models in which seizures are elicited and into those in which epilepsy appears without any sensory stimulation. The majority of genetic models show that absence type of epilepsy; during the last few years, we and others have noticed that rats of various strains exhibit spontaneously occurring spike-wave discharges in the EEG. Among the strains highly affected is the WAG/Rij strain, which is a fully inbred strain. Individuals are homozygous and because of this property, genetic studies are meaningful. Electrophysiological studies have indicated that abnormal discharges in the cortical EEG are generalized and that the hippocampus is not involved. Parts of the thalamus, together with the thalamic reticular nucleus, apparently act as a pacemaker for the abnormal discharges. There is a circadian modulation in the number of spike-wave discharges. Discharges mainly occur during intermediate levels of vigilance such as passive wakefulness and light slow-wave sleep and at transitions of sleep states. Pharmacological studies with clinically effective antiepileptic drugs have shown a close agreement in seizure response between man and rat. Studies with new compounds have emphasized the role of the GABAergic and glutamatergic system in this type of epilepsy. Particularly striking is the role of the GABAergic system. GABA agonists enhance and GABA antagonists reduce the occurrence of spike-wave discharges, which deviates from the effects of GABAergic drugs in non-convulsive epilepsy. Even more striking is the role of the benzodiazepines, generally seen as GABA agonists; these drugs do not act as such in absence epilepsy since they reduce spike-wave discharges. Also good evidence for an involvement of other neurotransmitters such as noradrenaline, dopamine and opioid peptides exists in absence epilepsy. Genetic data obtained from the WAG/Rij model for absence epilepsy show a relatively simple pattern of inheritance with one gene determining whether an individual is epileptic or not, and with other genes regulating the number and duration of seizures. This is in good agreement with the more restricted human data. Cognitive studies have shown two important features of epilepsy in the WAG/Rij strain: modulation of the number of spike-wave discharges by mental or physical activity and on the other hand, the disruption of cognitive activity by spike-wave discharges.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- A M Coenen
- Department of Psychology, University of Nijmegen, Netherlands
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Marescaux C, Vergnes M, Depaulis A. Genetic absence epilepsy in rats from Strasbourg--a review. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1992; 35:37-69. [PMID: 1512594 DOI: 10.1007/978-3-7091-9206-1_4] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have selected a strain of rats and designated it the Genetic Absence Epilepsy Rat from Strasbourg (GAERS). In this strain, 100% of the animals present recurrent generalized non-convulsive seizures characterized by bilateral and synchronous spike-and-wave discharges accompanied with behavioural arrest, staring and sometimes twitching of the vibrissae. Spontaneous SWD (7-11 cps, 300-1,000 microV, 0.5-75 sec) start and end abruptly on a normal background EEG. They usually occur at a mean frequency of 1.5 per min when the animals are in a state of quiet wakefulness. Drugs effective against absence seizures in humans (ethosuccimide, trimethadione, valproate, benzodiazepines) suppress the SWD dose-dependently, whereas drugs specific for convulsive or focal seizures (carbamazepine, phenytoin) are ineffective. SWD are increased by epileptogenic drugs inducing petit mal-like seizures, such as pentylenetetrazol, gamma-hydroxybutyrate, THIP and penicillin. Depth EEG recordings and lesion experiments show that SWD in GAERs depend on cortical and thalamic structures with a possible rhythmic triggering by the lateral thalamus. Most neurotransmitters are involved in the control of SWD (dopamine, noradrenaline, NMDA, acetylcholine), but GABA and gamma-hydroxybutyrate (GHB) seem to play a critical role. SWD are genetically determined with an autosomal dominant inheritance. The variable expression of SWD in offsprings from GAERS x control reciprocal crosses may be due to the existence of multiple genes. Neurophysiological, behavioural, pharmacological and genetic studies demonstrate that spontaneous SWD in GAERS fulfill all the requirements for an experimental model of absence epilepsy. As the mechanisms underlying absence epilepsy in humans are still unknown, the analysis of the genetic thalamocortical dysfunction in GAERS may be fruitful in investigations of the pathogenesis of generalized non-convulsive seizures.
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Affiliation(s)
- C Marescaux
- Service de Neurologie I, C.H.U., Strasbourg, France
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Romettino S, Lazdunski M, Gottesmann C. Anticonvulsant and sleep-waking influences of riluzole in a rat model of absence epilepsy. Eur J Pharmacol 1991; 199:371-3. [PMID: 1915583 DOI: 10.1016/0014-2999(91)90503-i] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Six WAG/Rij rats, an animal model of human absence epilepsy, were injected intraperitoneally with riluzole. At 4 mg/kg, riluzole decreased the number, mean duration and spike-frequency of the spontaneously occurring discharges for 3 h. Riluzole also increased slow wave sleep at the expense of waking. As riluzole at 3 mg/kg decreased the number and spike-frequency of the discharges without inducing a sedative effect, this compound could be of therapeutic interest in human absence epilepsy.
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Affiliation(s)
- S Romettino
- Laboratoire de Psychophysiologie, Faculté des Sciences, Université de Nice-Sophia Antipolis, France
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Ramakers GM, Peeters BW, Vossen JM, Coenen AM. CNQX, a new non-NMDA receptor antagonist, reduces spike wave discharges in the WAG/Rij rat model of absence epilepsy. Epilepsy Res 1991; 9:127-31. [PMID: 1686585 DOI: 10.1016/0920-1211(91)90023-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects on seizures, EEG and behavior of the non-NMDA receptor antagonist CNQX (6-cyano-7-nitroquinoxaline-2,3-dione), were studied in the WAG/Rij rat with absence epilepsy. Intracerebroventricular injections (10, 50, and 100 nmol/5 microliters CNQX) showed that CNQX decreases the number of spike wave discharges in a dose-dependent way. Coinjection of CNQX (100 nmol/5 microliters) and AMPA (0.1 pmol/5 microliters), kainic acid (0.01 nmol/5 microliters) or NMDA (50 pmol/5 microliters) attenuated the CNQX response, indicating that CNQX acts on both non-NMDA and NMDA receptors. The observed effects appear to be specific manipulations of the epilepsy not mediated by behavioral changes.
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Affiliation(s)
- G M Ramakers
- Rudolf Magnus Institute for Pharmacology, University of Utrecht, The Netherlands
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