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Perucca E, Bialer M, White HS. New GABA-Targeting Therapies for the Treatment of Seizures and Epilepsy: I. Role of GABA as a Modulator of Seizure Activity and Recently Approved Medications Acting on the GABA System. CNS Drugs 2023; 37:755-779. [PMID: 37603262 PMCID: PMC10501955 DOI: 10.1007/s40263-023-01027-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/06/2023] [Indexed: 08/22/2023]
Abstract
γ-Aminobutyric acid (GABA) is the most prevalent inhibitory neurotransmitter in the mammalian brain and has been found to play an important role in the pathogenesis or the expression of many neurological diseases, including epilepsy. Although GABA can act on different receptor subtypes, the component of the GABA system that is most critical to modulation of seizure activity is the GABAA-receptor-chloride (Cl-) channel complex, which controls the movement of Cl- ions across the neuronal membrane. In the mature brain, binding of GABA to GABAA receptors evokes a hyperpolarising (anticonvulsant) response, which is mediated by influx of Cl- into the cell driven by its concentration gradient between extracellular and intracellular fluid. However, in the immature brain and under certain pathological conditions, GABA can exert a paradoxical depolarising (proconvulsant) effect as a result of an efflux of chloride from high intracellular to lower extracellular Cl- levels. Extensive preclinical and clinical evidence indicates that alterations in GABAergic inhibition caused by drugs, toxins, gene defects or other disease states (including seizures themselves) play a causative or contributing role in facilitating or maintaning seizure activity. Conversely, enhancement of GABAergic transmission through pharmacological modulation of the GABA system is a major mechanism by which different antiseizure medications exert their therapeutic effect. In this article, we review the pharmacology and function of the GABA system and its perturbation in seizure disorders, and highlight how improved understanding of this system offers opportunities to develop more efficacious and better tolerated antiseizure medications. We also review the available data for the two most recently approved antiseizure medications that act, at least in part, through GABAergic mechanisms, namely cenobamate and ganaxolone. Differences in the mode of drug discovery, pharmacological profile, pharmacokinetic properties, drug-drug interaction potential, and clinical efficacy and tolerability of these agents are discussed.
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Affiliation(s)
- Emilio Perucca
- Department of Medicine (Austin Health), The University of Melbourne, Melbourne, VIC, Australia.
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia.
- Melbourne Brain Centre, 245 Burgundy Street, Heidelberg, VIC, 3084, Australia.
| | - Meir Bialer
- Institute of Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
- David R. Bloom Center for Pharmacy, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - H Steve White
- Department of Pharmacy, School of Pharmacy, University of Washington, Seattle, WA, USA
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A Computational Model to Investigate GABA-Activated Astrocyte Modulation of Neuronal Excitation. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2020; 2020:8750167. [PMID: 33014120 PMCID: PMC7512075 DOI: 10.1155/2020/8750167] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 08/14/2020] [Accepted: 08/28/2020] [Indexed: 11/18/2022]
Abstract
Gamma-aminobutyric acid (GABA) is critical for proper neural network function and can activate astrocytes to induce neuronal excitability; however, the mechanism by which astrocytes transform inhibitory signaling to excitatory enhancement remains unclear. Computational modeling can be a powerful tool to provide further understanding of how GABA-activated astrocytes modulate neuronal excitation. In the present study, we implemented a biophysical neuronal network model to investigate the effects of astrocytes on excitatory pre- and postsynaptic terminals following exposure to increasing concentrations of external GABA. The model completely describes the effects of GABA on astrocytes and excitatory presynaptic terminals within the framework of glutamatergic gliotransmission according to neurophysiological findings. Utilizing this model, our results show that astrocytes can rapidly respond to incoming GABA by inducing Ca2+ oscillations and subsequent gliotransmitter glutamate release. Elevation in GABA concentrations not only naturally decreases neuronal spikes but also enhances astrocytic glutamate release, which leads to an increase in astrocyte-mediated presynaptic release and postsynaptic slow inward currents. Neuronal excitation induced by GABA-activated astrocytes partly counteracts the inhibitory effect of GABA. Overall, the model helps to increase knowledge regarding the involvement of astrocytes in neuronal regulation using simulated bath perfusion of GABA, which may be useful for exploring the effects of GABA-type antiepileptic drugs.
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Nardone R, Sebastianelli L, Brigo F, Golaszewski S, Trinka E, Pucks-Faes E, Saltuari L, Versace V. Effects of intrathecal baclofen therapy in subjects with disorders of consciousness: a reappraisal. J Neural Transm (Vienna) 2020; 127:1209-1215. [PMID: 32710152 DOI: 10.1007/s00702-020-02233-8] [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: 04/08/2020] [Accepted: 07/14/2020] [Indexed: 01/16/2023]
Abstract
Baclofen is a structural analogue of gamma-amino-butyric acid (GABA), which reduces spastic hypertonia of striated muscle due to a mechanism of GABAB-ergic inhibition of mono- and polysynaptic reflexes at the spinal level. There are reports of patients with severe disorders of consciousness that presented a substantial improvement following intrathecal baclofen (ITB) administration for severe spasticity. The neural mechanisms underlying the clinical recovery after ITB have not yet been clarified. Baclofen could modulate sleep-wake cycles that may be dysregulated and thus interfere with alertness and awareness. The diminished proprioceptive and nociceptive sensory inputs may relieve thalamo-cortical neural networks involved in maintaining the consciousness of the self and the world. ITB treatment might also promote the recovery of an impaired GABAergic cortical tone, restoring the balance between excitatory and inhibitory cortical activity. Furthermore, glutamatergic synapses are directly or indirectly modulated by GABAB-ergic receptors. Neurophysiological techniques (such as transcranial magnetic stimulation, electroencephalography, or the combination of both) can be helpful to explore the effects of intrathecal or oral baclofen on the modulation of neural cortical circuits in humans with disorders of consciousness.
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Affiliation(s)
- Raffaele Nardone
- Department of Neurology, Hospital of Merano (SABES-ASDAA), Merano-Meran, Italy. .,Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria. .,Spinal Cord Injury and Tissue Regeneration Center, Salzburg, Austria. .,Karl Landsteiner Institut für Neurorehabilitation und Raumfahrtneurologie, Salzburg, Austria.
| | - Luca Sebastianelli
- Department of Neurorehabilitation, Hospital of Vipiteno, Vipiteno, Italy.,Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
| | - Francesco Brigo
- Department of Neurology, Hospital of Merano (SABES-ASDAA), Merano-Meran, Italy.,Department of Neuroscience, Biomedicine and Movement Science, University of Verona, Verona, Italy
| | - Stefan Golaszewski
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.,Karl Landsteiner Institut für Neurorehabilitation und Raumfahrtneurologie, Salzburg, Austria
| | - Eugen Trinka
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.,Centre for Cognitive Neurosciences Salzburg, Salzburg, Austria.,University for Medical Informatics and Health Technology, UMIT, Hall in Tirol, Austria
| | | | - Leopold Saltuari
- Department of Neurorehabilitation, Hospital of Vipiteno, Vipiteno, Italy.,Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
| | - Viviana Versace
- Department of Neurology, Hospital of Merano (SABES-ASDAA), Merano-Meran, Italy.,Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
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Werner FM, Coveñas R. Classical neurotransmitters and neuropeptides involved in generalized epilepsy in a multi-neurotransmitter system: How to improve the antiepileptic effect? Epilepsy Behav 2017; 71:124-129. [PMID: 25819950 DOI: 10.1016/j.yebeh.2015.01.038] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Revised: 01/27/2015] [Accepted: 01/28/2015] [Indexed: 12/20/2022]
Abstract
Here, we describe in generalized epilepsies the alterations of classical neurotransmitters and neuropeptides acting at specific subreceptors. In order to consider a network context rather than one based on focal substrates and in order to make the interaction between neurotransmitters and neuropeptides and their specific subreceptors comprehensible, neural networks in the hippocampus, thalamus, and cerebral cortex are described. In this disease, a neurotransmitter imbalance between dopaminergic and serotonergic neurons and between presynaptic GABAergic neurons (hypoactivity) and glutaminergic neurons (hyperactivity) occurs. Consequently, combined GABAA agonists and NMDA antagonists could furthermore stabilize the neural networks in a multimodal pharmacotherapy. The antiepileptic effect and the mechanisms of action of conventional and recently developed antiepileptic drugs are reviewed. The GASH:Sal animal model can contribute to examine the efficacy of antiepileptic drugs. The issues of whether the interaction of classical neurotransmitters with other subreceptors (5-HT7, metabotropic 5 glutaminergic, A2A adenosine, and alpha nicotinic 7 cholinergic receptors) or whether the administration of agonists/antagonists of neuropeptides might improve the therapeutic effect of antiepileptic drugs should be addressed. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".
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Affiliation(s)
- Felix-Martin Werner
- Höhere Berufsfachschule für Altenpflege und Ergotherapie der Euro Akademie Pößneck, Pößneck, Germany; Institute of Neurosciences of Castilla y León (INCYL), Laboratory of Neuroanatomy of the Peptidergic Systems (Lab. 14), University of Salamanca, Salamanca, Spain.
| | - Rafael Coveñas
- Institute of Neurosciences of Castilla y León (INCYL), Laboratory of Neuroanatomy of the Peptidergic Systems (Lab. 14), University of Salamanca, Salamanca, Spain.
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Mareš P. Proconvulsant action of two GABA(B) receptor antagonists is age-dependent. Physiol Res 2013; 62:S109-14. [PMID: 24329690 DOI: 10.33549/physiolres.932599] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Antagonists of GABA(B) receptors are expected to have proconvulsant action also in developing brain. Two antagonists (CGP55845 and CGP46381) were tested in a model of cortical epileptic afterdischarges (ADs) in 12-, 18- and 25-day-old rat pups with implanted electrodes. CGP55845 was dissolved in dimethylsulfoxide and the results demonstrated marked proconvulsant action of this solvent which masked possible action of the antagonist. Water soluble antagonist CGP46381 led to marked potentiation of ADs in 12-day-old animals, its action decreased with age, it was negligible in 25-day-old rats. Our results demonstrated important inhibitory role of GABA(B) receptors at very early stages of maturation.
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Affiliation(s)
- P Mareš
- Department of Developmental Epileptology, Institute of Physiology AS CR, Prague, Czech Republic.
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Mareš P, Tichá K, Mikulecká A. Anticonvulsant and behavioral effects of GABA(B) receptor positive modulator CGP7930 in immature rats. Epilepsy Behav 2013; 28:113-20. [PMID: 23708148 DOI: 10.1016/j.yebeh.2013.04.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Revised: 04/09/2013] [Accepted: 04/15/2013] [Indexed: 01/14/2023]
Abstract
Possible anticonvulsant action of GABAB receptor positive allosteric modulator CGP7930 was studied in cortical epileptic afterdischarges (ADs) in rat pups 12, 18, and 25 days old. Afterdischarges were induced by six series of stimulation of sensorimotor cortex, and CGP7930 (20 or 40 mg/kgi.p.) was administered after the first AD. In addition, the effects of CGP7930 on sensorimotor performance and behavior in open field and elevated plus maze were assessed. CGP7930 decreased duration of ADs in 12-day-old but not in older rats. Motor phenomena (movements accompanying stimulation and clonic seizures) were not changed. CGP7930 only moderately affected sensorimotor performance, altered slightly spontaneous behavior in the open field, and did not influence behavior in the elevated plus maze in terms of an adaptive form of learning or anxiety-like behavior. Marked anticonvulsant action with subtle deficits in sensorimotor performance in 12-day-old rats suggests a possible use of CGP7930 as an age-specific anticonvulsant.
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Affiliation(s)
- Pavel Mareš
- Department of Developmental Epileptology, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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Mareš P. Anticonvulsant action of GABAB receptor positive modulator CGP7930 in immature rats. Epilepsy Res 2012; 100:49-54. [DOI: 10.1016/j.eplepsyres.2012.01.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 01/07/2012] [Accepted: 01/15/2012] [Indexed: 12/30/2022]
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Tabashidze N, Mareš P. GABA-A receptors play a minor role in cortical epileptic afterdischarges in immature rats. Brain Res 2011; 1412:102-7. [PMID: 21824607 DOI: 10.1016/j.brainres.2011.07.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 07/14/2011] [Accepted: 07/14/2011] [Indexed: 10/18/2022]
Abstract
The role of inhibitory γ-aminobutyric acid-A (GABA-A) system in the cortical epileptic afterdischarges (ADs) was studied at three different developmental stages of rats. Animals 12, 18 and 25days old with implanted epidural electrodes were pretreated with bicuculline (1 and 2mg/kgi.p.) and 15min later repeatedly stimulated with low frequency trains with stepwise increasing current intensity. Bicuculline only exceptionally decreased threshold current intensities necessary for elicitation of movements directly bound to stimulation, spike-and wave ADs, clonic seizures and transition into a limbic type of ADs. Duration of ADs was not systematically affected by either dose of bicuculline. In contrast, transcallosal evoked potentials exhibited under the influence of bicuculline steeper curve expressing relation between intensity of stimuli and amplitude of responses. In contrast to GABA-B receptors, GABA-A receptors do not play an important role in generation and arrest of cortical epileptic ADs in immature rats.
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Affiliation(s)
- N Tabashidze
- Department of Developmental Epileptology, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, CZ-14220,Prague, Czech Republic
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Mareš P. GABA-B receptor antagonist CGP 35348 interferes with an arrest of cortical epileptic afterdischarges in developing rats. Epilepsy Res 2010; 92:125-33. [DOI: 10.1016/j.eplepsyres.2010.08.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 08/19/2010] [Accepted: 08/22/2010] [Indexed: 01/13/2023]
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Pometlová M, Kubová H, Mares P. Effects of 2-chloroadenosine on cortical epileptic afterdischarges in immature rats. Pharmacol Rep 2010; 62:62-7. [PMID: 20360616 DOI: 10.1016/s1734-1140(10)70243-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 07/17/2010] [Indexed: 11/29/2022]
Abstract
Adenosine may represent an endogenous anticonvulsant in the brain. This study focused on the possible anticonvulsant action of an adenosine agonist, 2-chloroadenosine, against cortical epileptic afterdischarges (ADs) in immature rats. Three age groups of rat pups with implanted electrodes were studied: 12-, 18- and 25-days-old. The compound, 2-chloroadenosine, was injected after the first successful stimulation at doses of 1, 4 or 10 mg/kg intraperitoneally, and stimulation at the same intensity was repeated three more times. Movements directly elicited by stimulation, as well as clonic seizures accompanying electroencephalography (EEG) ADs, were markedly suppressed in only the 18-day-old animals. The effects in the 12- and especially the 25-day-old rats were moderate. The duration of the ADs decreased in all three age groups with 2-chloroadenosine treatment, and the shortest AD duration was seen in the treated, 12-day-old rats. The AD suppression also lasted longer in this age group than it did in the older animals. After a brief suppression of the second AD, the treated, 25-day-old group exhibited a significant AD rebound during the third and fourth stimulations. Taken together, our data show that 2-chloroadenosine exhibits an anticonvulsant effect that is dose- and age-dependent.
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Affiliation(s)
- Marie Pometlová
- Charles University, Third Medical School, Department of Normal, Pathological and Clinical Physiology, Ke Karlovu 4, CZ-12000 Prague 2, Czech Republic
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Mareš P, Stehlíková M. Anticonvulsant doses of ganaxolone do not compromise motor performance in immature rats. Neurosci Lett 2010; 469:396-9. [DOI: 10.1016/j.neulet.2009.12.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 11/06/2009] [Accepted: 12/11/2009] [Indexed: 11/26/2022]
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Szczurowska E, Mareš P. Controversial action of positive modulator of subtype 7 of metabotropic glutamate receptors AMN082 on cortical epileptic afterdischarges in immature rats. Eur J Pharmacol 2009; 623:37-40. [DOI: 10.1016/j.ejphar.2009.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 08/30/2009] [Accepted: 09/08/2009] [Indexed: 10/20/2022]
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Lojková-Janečková D, Ng J, Mareš P. Antagonists of group I metabotropic glutamate receptors and cortical afterdischarges in immature rats. Epilepsia 2009; 50:2123-9. [DOI: 10.1111/j.1528-1167.2009.02091.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
Seizures have been recognized to occur in multiple sclerosis (MS) since early descriptions of the disease. Various studies have attempted to determine the incidence and prevalence of seizures in MS; although they differ in the reported prevalence, seizures do appear to be more common in MS cohorts than in the general population. The pathological underpinning of seizures in MS remains indeterminate. Cortical and subcortical demyelination and inflammation may explain the increased frequency of seizures in MS, although this hypothetical correlation remains to be proven. Management of seizures in MS is similar to the management of seizures in other patients. Consideration of the underlying neurological deficits related to MS may be necessary, and dosages of antiepileptic drugs should be adjusted if increased sensitivity to the adverse effects of these agents or interaction with other centrally acting medications is suspected. The prognosis of epilepsy in patients with MS remains uncertain, with some studies suggesting a more favourable prognosis than others.
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Affiliation(s)
- Brendan J. Kelley
- Departments of Neurology, University of Cincinnati, Cincinnati, Ohio
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