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Spontaneous Ultraslow Na + Fluctuations in the Neonatal Mouse Brain. Cells 2019; 9:cells9010102. [PMID: 31906100 PMCID: PMC7016939 DOI: 10.3390/cells9010102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/18/2019] [Accepted: 12/24/2019] [Indexed: 12/12/2022] Open
Abstract
In the neonate forebrain, network formation is driven by the spontaneous synchronized activity of pyramidal cells and interneurons, consisting of bursts of electrical activity and intracellular Ca2+ oscillations. By employing ratiometric Na+ imaging in tissue slices obtained from animals at postnatal day 2-4 (P2-4), we found that 20% of pyramidal neurons and 44% of astrocytes in neonatal mouse hippocampus also exhibit transient fluctuations in intracellular Na+. These occurred at very low frequencies (~2/h), were exceptionally long (~8 min), and strongly declined after the first postnatal week. Similar Na+ fluctuations were also observed in the neonate neocortex. In the hippocampus, Na+ elevations in both cell types were diminished when blocking action potential generation with tetrodotoxin. Neuronal Na+ fluctuations were significantly reduced by bicuculline, suggesting the involvement of GABAA-receptors in their generation. Astrocytic signals, by contrast, were neither blocked by inhibition of receptors and/or transporters for different transmitters including GABA and glutamate, nor of various Na+-dependent transporters or Na+-permeable channels. In summary, our results demonstrate for the first time that neonatal astrocytes and neurons display spontaneous ultraslow Na+ fluctuations. While neuronal Na+ signals apparently largely rely on suprathreshold GABAergic excitation, astrocytic Na+ signals, albeit being dependent on neuronal action potentials, appear to have a separate trigger and mechanism, the source of which remains unclear at present.
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Iqbal F, Thompson AJ, Riaz S, Pehar M, Rice T, Syed NI. Anesthetics: from modes of action to unconsciousness and neurotoxicity. J Neurophysiol 2019; 122:760-787. [PMID: 31242059 DOI: 10.1152/jn.00210.2019] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Modern anesthetic compounds and advanced monitoring tools have revolutionized the field of medicine, allowing for complex surgical procedures to occur safely and effectively. Faster induction times and quicker recovery periods of current anesthetic agents have also helped reduce health care costs significantly. Moreover, extensive research has allowed for a better understanding of anesthetic modes of action, thus facilitating the development of more effective and safer compounds. Notwithstanding the realization that anesthetics are a prerequisite to all surgical procedures, evidence is emerging to support the notion that exposure of the developing brain to certain anesthetics may impact future brain development and function. Whereas the data in support of this postulate from human studies is equivocal, the vast majority of animal research strongly suggests that anesthetics are indeed cytotoxic at multiple brain structure and function levels. In this review, we first highlight various modes of anesthetic action and then debate the evidence of harm from both basic science and clinical studies perspectives. We present evidence from animal and human studies vis-à-vis the possible detrimental effects of anesthetic agents on both the young developing and the elderly aging brain while discussing potential ways to mitigate these effects. We hope that this review will, on the one hand, invoke debate vis-à-vis the evidence of anesthetic harm in young children and the elderly, and on the other hand, incentivize the search for better and less toxic anesthetic compounds.
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Affiliation(s)
- Fahad Iqbal
- Vi Riddell Pain Program, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew J Thompson
- Vi Riddell Pain Program, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Neuroscience, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
| | - Saba Riaz
- Vi Riddell Pain Program, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Marcus Pehar
- Vi Riddell Pain Program, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Tiffany Rice
- Department of Anesthesiology, Perioperative and Pain Medicine, Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada
| | - Naweed I Syed
- Vi Riddell Pain Program, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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Wang CZ, Ma J, Xu YQ, Jiang SN, Chen TQ, Yuan ZL, Mao XY, Zhang SQ, Liu LY, Fu Y, Yu YC. Early-generated interneurons regulate neuronal circuit formation during early postnatal development. eLife 2019; 8:44649. [PMID: 31120418 PMCID: PMC6533056 DOI: 10.7554/elife.44649] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 05/07/2019] [Indexed: 01/01/2023] Open
Abstract
A small subset of interneurons that are generated earliest as pioneer neurons are the first cohort of neurons that enter the neocortex. However, it remains largely unclear whether these early-generated interneurons (EGIns) predominantly regulate neocortical circuit formation. Using inducible genetic fate mapping to selectively label EGIns and pseudo-random interneurons (pRIns), we found that EGIns exhibited more mature electrophysiological and morphological properties and higher synaptic connectivity than pRIns in the somatosensory cortex at early postnatal stages. In addition, when stimulating one cell, the proportion of EGIns that influence spontaneous network synchronization is significantly higher than that of pRIns. Importantly, toxin-mediated ablation of EGIns after birth significantly reduce spontaneous network synchronization and decrease inhibitory synaptic formation during the first postnatal week. These results suggest that EGIns can shape developing networks and may contribute to the refinement of neuronal connectivity before the establishment of the adult neuronal circuit.
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Affiliation(s)
- Chang-Zheng Wang
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Jian Ma
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
| | - Ye-Qian Xu
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Shao-Na Jiang
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Tian-Qi Chen
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Zu-Liang Yuan
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Xiao-Yi Mao
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Shu-Qing Zhang
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Lin-Yun Liu
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Yinghui Fu
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Yong-Chun Yu
- Jing'an District Centre Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
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The Pharmacological Assessment of GABA A Receptor Activation in Experimental Febrile Seizures in Mice. eNeuro 2019; 6:eN-TNWR-0429-18. [PMID: 31058209 PMCID: PMC6498421 DOI: 10.1523/eneuro.0429-18.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Revised: 01/01/2019] [Accepted: 01/04/2019] [Indexed: 01/07/2023] Open
Abstract
Hyperthermia-induced febrile seizures (FSs) are the most common seizures during childhood, and prolonged complex FSs can result in the development of epilepsy. Currently, GABAA receptor modulators such as benzodiazepines and barbiturates are used as medications for FSs with the aim of enhancing GABA-mediated inhibition of neuronal activity. However, it is still up for debate whether these enhancers of GABAergic neurotransmission could depolarize immature neurons with relatively higher levels of the intracellular Cl− in the developing brain during FSs. Here, we performed simultaneous video-local field potential monitoring to determine whether benzodiazepines and barbiturates affect the phenotypes of FSs in postnatal day (P)11 and P14 mice. We found that low-dose administration of diazepam decreased the incidence of clonic seizures at P11. We also found that high-dose administration of diazepam and pentobarbital exacerbated the behavioral and electrophysiological phenotypes of the induction phase of experimental FSs at P11 but not at P14. We further found that the deteriorated phenotypes at P11 were suppressed when Na+K+2Cl− cotransporter isoform 1 (NKCC1), which mediates Cl− influx, was blocked by treatment with the diuretic bumetanide. Though our findings do not exclude the involvement of sedation effect of high-dose GABAA receptor modulators in worsening experimental FSs at P11, pharmacological enhancement of GABAergic signaling could aggravate seizure activity in the early phase of FSs.
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Reid CA, Rollo B, Petrou S, Berkovic SF. Can mutation‐mediated effects occurring early in development cause long‐term seizure susceptibility in genetic generalized epilepsies? Epilepsia 2018; 59:915-922. [DOI: 10.1111/epi.14077] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Christopher Alan Reid
- The Florey Institute for Neuroscience and Mental Health The University of Melbourne Parkville Victoria Australia
| | - Ben Rollo
- The Florey Institute for Neuroscience and Mental Health The University of Melbourne Parkville Victoria Australia
| | - Steven Petrou
- The Florey Institute for Neuroscience and Mental Health The University of Melbourne Parkville Victoria Australia
| | - Samuel F. Berkovic
- Department of Medicine Epilepsy Research Centre Austin Health University of Melbourne Heidelberg Victoria Australia
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Griguoli M, Cherubini E. Early Correlated Network Activity in the Hippocampus: Its Putative Role in Shaping Neuronal Circuits. Front Cell Neurosci 2017; 11:255. [PMID: 28878628 PMCID: PMC5572250 DOI: 10.3389/fncel.2017.00255] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 08/08/2017] [Indexed: 12/02/2022] Open
Abstract
Synchronized neuronal activity occurring at different developmental stages in various brain structures represents a hallmark of developmental circuits. This activity, which differs in its specific patterns among animal species may play a crucial role in de novo formation and in shaping neuronal networks. In the rodent hippocampus in vitro, the so-called giant depolarizing potentials (GDPs) constitute a primordial form of neuronal synchrony preceding more organized forms of activity such as oscillations in the theta and gamma frequency range. GDPs are generated at the network level by the interaction of the neurotransmitters glutamate and GABA which, immediately after birth, exert both a depolarizing and excitatory action on their targets. GDPs are triggered by GABAergic interneurons, which in virtue of their extensive axonal branching operate as functional hubs to synchronize large ensembles of cells. Intrinsic bursting activity, driven by a persistent sodium conductance and facilitated by the low expression of Kv7.2 and Kv7.3 channel subunits, responsible for IM, exerts a permissive role in GDP generation. Here, we discuss how GDPs are generated in a probabilistic way when neuronal excitability within a local circuit reaches a certain threshold and how GDP-associated calcium transients act as coincident detectors for enhancing synaptic strength at emerging GABAergic and glutamatergic synapses. We discuss the possible in vivo correlate of this activity. Finally, we debate recent data showing how, in several animal models of neuropsychiatric disorders including autism, a GDPs dysfunction is associated to morphological alterations of neuronal circuits and behavioral deficits reminiscent of those observed in patients.
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Affiliation(s)
- Marilena Griguoli
- European Brain Research Institute (EBRI) "Fondazione Rita Levi-Montalcini"Rome, Italy
| | - Enrico Cherubini
- European Brain Research Institute (EBRI) "Fondazione Rita Levi-Montalcini"Rome, Italy.,Department of Neuroscience, International School for Advanced StudiesTrieste, Italy
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Zhang JQ, Xu WY, Xu CQ. Neonatal Propofol and Etomidate Exposure Enhance Inhibitory Synaptic Transmission in Hippocampal Cornus Ammonis 1 Pyramidal Neurons. Chin Med J (Engl) 2017; 129:2714-2724. [PMID: 27824005 PMCID: PMC5126164 DOI: 10.4103/0366-6999.193459] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Background: Propofol and etomidate are the most important intravenous general anesthetics in the current clinical use and that mediate gamma-aminobutyric acid's (GABAergic) synaptic transmission. However, their long-term effects on GABAergic synaptic transmission induced by neonatal propofol or etomidate exposure remain unclear. We investigated the long-term GABAergic neurotransmission alterations, following neonatal propofol and etomidate administration. Methods: Sprague-Dawley rat pups at postnatal days 4–6 were underwent 6-h-long propofol-induced or 5-h-long etomidate-induced anesthesia. We performed whole-cell patch-clamp recording from pyramidal cells in the cornus ammonis 1 area of acute hippocampal slices of postnatal 80–90 days. Spontaneous and miniature inhibitory GABAergic currents (spontaneous inhibitory postsynaptic currents [sIPSCs] and miniature inhibitory postsynaptic currents [mIPSCs]) and their kinetic characters were measured. The glutamatergic tonic effect on inhibitory transmission and the effect of bumetanide on neonatal propofol exposure were also examined. Results: Neonatal propofol exposure significantly increased the frequency of mIPSCs (from 1.87 ± 0.35 Hz to 3.43 ± 0.51 Hz, P < 0.05) and did not affect the amplitude of mIPSCs and sIPSCs. Both propofol and etomidate slowed the decay time of mIPSCs kinetics (168.39 ± 27.91 ms and 267.02 ± 100.08 ms vs. 68.18 ± 12.43 ms; P < 0.05). Bumetanide significantly blocked the frequency increase and reversed the kinetic alteration of mIPSCs induced by neonatal propofol exposure (3.01 ± 0.45 Hz and 94.30 ± 32.56 ms). Conclusions: Neonatal propofol and etomidate exposure has long-term effects on inhibitory GABAergic transmission. Propofol might act at pre- and post-synaptic GABA receptor A (GABAA) receptors within GABAergic synapses and impairs the glutamatergic tonic input to GABAergic synapses; etomidate might act at the postsynaptic site.
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Affiliation(s)
- Jia-Qiang Zhang
- Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL 32611, USA; Department of Anesthesiology, The People's Hospital of Zhengzhou University, Zhengzhou, Henan 450003, China,
| | - Wan-Ying Xu
- Department of Neurobiology, Wake Forest University, Winston-Salem, NC 27106, USA
| | - Chang-Qing Xu
- Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL 32611, USA
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Krawczyk M, Ramani M, Dian J, Florez CM, Mylvaganam S, Brien J, Reynolds J, Kapur B, Zoidl G, Poulter MO, Carlen PL. Hippocampal hyperexcitability in fetal alcohol spectrum disorder: Pathological sharp waves and excitatory/inhibitory synaptic imbalance. Exp Neurol 2016; 280:70-9. [PMID: 26996134 DOI: 10.1016/j.expneurol.2016.03.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Revised: 02/29/2016] [Accepted: 03/13/2016] [Indexed: 01/01/2023]
Abstract
Prenatal alcohol exposure (PAE) can lead to long-lasting neurological alterations that may predispose individuals to seizures and neurobehavioral dysfunction. To date, there exists limited information regarding the underlying pathophysiological mechanisms. The hippocampal CA3 region generates excitatory population activity, called sharp waves (SPWs), that provide an ideal model to study perturbations in neuronal excitability at the network and cellular levels. In the present study, we utilized a mouse model of PAE and used dual extracellular and whole-cell patch-clamp recordings from CA3 hippocampal pyramidal cells to evaluate the effect of 1st trimester-equivalent ethanol exposure (10% v/v) on SPW activity and excitatory/inhibitory balance. We observed that PAE significantly altered in vitro SPW waveforms, with an increased duration and amplitude, when compared to controls. In addition, PAE slices exhibited reduced pharmacological inhibition by the GABA-A receptor antagonist bicuculline (BMI) on SPW activity, and increased population spike paired-pulse ratios, all indicative of network disinhibition within the PAE hippocampus. Evaluation of PAE CA3 pyramidal cell activity associated with SPWs, revealed increased action potential cell firing, which was accompanied by an imbalance of excitatory/inhibitory synaptic drive, shifted in favor of excitation. Moreover, we observed intrinsic changes in CA3 pyramidal activity in PAE animals, including increased burst firing and instantaneous firing rate. This is the first study to provide evidence for hippocampal dysfunction in the ability to maintain network homeostasis and underlying cellular hyperexcitability in a model of PAE. These circuit and cellular level alterations may contribute to the increased propensity for seizures and neurobehavioral dysfunction observed in patients with a history of PAE.
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Affiliation(s)
- Michal Krawczyk
- Division of Fundamental Neurobiology, Toronto Western Research Institute, UHN, Toronto, ON, Canada.
| | - Meera Ramani
- Division of Fundamental Neurobiology, Toronto Western Research Institute, UHN, Toronto, ON, Canada
| | - Josh Dian
- Division of Fundamental Neurobiology, Toronto Western Research Institute, UHN, Toronto, ON, Canada
| | - Carlos M Florez
- Division of Fundamental Neurobiology, Toronto Western Research Institute, UHN, Toronto, ON, Canada
| | - Shanthini Mylvaganam
- Division of Fundamental Neurobiology, Toronto Western Research Institute, UHN, Toronto, ON, Canada
| | - James Brien
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - James Reynolds
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Bhushan Kapur
- Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, Toronto, ON, Canada
| | - Georg Zoidl
- Department of Biology, York University, Toronto, ON, Canada; Department of Psychology, York University, Toronto, ON, Canada
| | - Michael O Poulter
- Robarts Research Institute and Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Peter L Carlen
- Division of Fundamental Neurobiology, Toronto Western Research Institute, UHN, Toronto, ON, Canada; Department of Medicine (Neurology), University of Toronto, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada
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Puskarjov M, Kahle KT, Ruusuvuori E, Kaila K. Pharmacotherapeutic targeting of cation-chloride cotransporters in neonatal seizures. Epilepsia 2014; 55:806-18. [PMID: 24802699 PMCID: PMC4284054 DOI: 10.1111/epi.12620] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2014] [Indexed: 12/15/2022]
Abstract
Seizures are a common manifestation of acute neurologic insults in neonates and are often resistant to the standard antiepileptic drugs that are efficacious in children and adults. The paucity of evidence-based treatment guidelines, coupled with a rudimentary understanding of disease pathogenesis, has made the current treatment of neonatal seizures empiric and often ineffective, highlighting the need for novel therapies. Key developmental differences in γ-aminobutyric acid (GABA)ergic neurotransmission between the immature and mature brain, and trauma-induced alterations in the function of the cation-chloride cotransporters (CCCs) NKCC1 and KCC2, probably contribute to the poor efficacy of standard antiepileptic drugs used in the treatment of neonatal seizures. Although CCCs are attractive drug targets, bumetanide and other existing CCC inhibitors are suboptimal because of pharmacokinetic constraints and lack of target specificity. Newer approaches including isoform-specific NKCC1 inhibitors with increased central nervous system penetration, and direct and indirect strategies to enhance KCC2-mediated neuronal chloride extrusion, might allow therapeutic modulation of the GABAergic system for neonatal seizure treatment. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.
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Affiliation(s)
- Martin Puskarjov
- Department of Biosciences and Neuroscience Center, University of HelsinkiHelsinki, Finland
| | - Kristopher T Kahle
- Department of Neurosurgery, Harvard Medical School, Massachusetts General HospitalBoston, Massachusetts, U.S.A
| | - Eva Ruusuvuori
- Department of Biosciences and Neuroscience Center, University of HelsinkiHelsinki, Finland
| | - Kai Kaila
- Department of Biosciences and Neuroscience Center, University of HelsinkiHelsinki, Finland
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Kang SK, Kadam SD. Pre-Clinical Models of Acquired Neonatal Seizures: Differential Effects of Injury on Function of Chloride Co-Transporters. AUSTIN JOURNAL OF CEREBROVASCULAR DISEASE & STROKE 2014; 1:1026. [PMID: 25590049 PMCID: PMC4290373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hypoxic-ischemic encephalopathy [HIE] represents the most common acquired pathology associated with neonatal seizures. HIE-associated neonatal seizures are often difficult to control, due to their refractoriness to traditional anti-seizure agents. Developmentally regulated chloride gradients during early development make the neonatal brain more seizure-susceptible by depolarizing GABAAR-mediated currents, and therefore hindering inhibition by conventional anti-seizure drugs such as phenobarbital [PB] and benzodiazepines. Pharmaco-modulation of chloride co-transporters has become a current field of research in treating refractory neonatal seizures, and the basis of two clinical trials [NCT01434225; NCT00380531]. However, the recent termination of NEMO study [NCT01434225] on bumetanide, an NKCC1 antagonist, suggests that clinical utilization of bumetanide as an adjunct to treat neonatal seizures with PB may not be a viable option. Hence, re-evaluation of bumetanide as an adjunct through pre-clinical studies is warranted. Additionally, the model-specific variability in the efficacy of bumetanide in the pre-clinical models of neonatal seizures highlights the differential consequences of insults used to induce seizures in each pre-clinical model as worth exploration. Injury itself can significantly alter the function of chloride co-transporters, and therefore the efficacy of anti-seizure agents that follow.
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Affiliation(s)
- SK Kang
- Neuroscience Laboratory, Hugo Moser Research Institute, USA
| | - SD Kadam
- Neuroscience Laboratory, Hugo Moser Research Institute, USA
- Department of Neurology, Johns Hopkins University, USA
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Abstract
The γ-aminobutyric acid receptor type A (GABAA receptor) is a ligand-gated chloride channel that mediates major inhibitory functions in the central nervous system. GABAA receptors function mainly as pentamers containing α, β, and either γ or δ subunits. A number of antiepileptic drugs have agonistic effects on GABAA receptors. Hence, dysfunctions of GABAA receptors have been postulated to play important roles in the etiology of epilepsy. In fact, mutations or genetic variations of the genes encoding the α1, α6, β2, β3, γ2, or δ subunits (GABRA1, GABRA6, GABRB2, GABRB3, GABRG2, and GABRD, respectively) have been associated with human epilepsy, both with and without febrile seizures. Epilepsy resulting from mutations is commonly one of following, genetic (idiopathic) generalized epilepsy (e.g., juvenile myoclonic epilepsy), childhood absence epilepsy, genetic epilepsy with febrile seizures, or Dravet syndrome. Recently, mutations of GABRA1, GABRB2, and GABRB3 were associated with infantile spasms and Lennox-Gastaut syndrome. These mutations compromise hyperpolarization through GABAA receptors, which is believed to cause seizures. Interestingly, most of the insufficiencies are not caused by receptor gating abnormalities, but by complex mechanisms, including endoplasmic reticulum (ER)-associated degradation, nonsense-mediated mRNA decay, intracellular trafficking defects, and ER stress. Thus, GABAA receptor subunit mutations are now thought to participate in the pathomechanisms of epilepsy, and an improved understanding of these mutations should facilitate our understanding of epilepsy and the development of new therapies.
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Donnan GA, Paterson DJ. Howard Florey and neuroscience. J Physiol 2013; 591:33-4. [DOI: 10.1113/jphysiol.2012.248963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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