1
|
Liao K, Zeng H, Yang X, He D, Wang B, Yuan J. KCNK5 Regulating Potassium Efflux and Inducing Pyroptosis in Corneal Epithelial Cells Through TNFSF10-Mediated Autophagy in Dry Eye. Invest Ophthalmol Vis Sci 2024; 65:34. [PMID: 38236186 PMCID: PMC10807492 DOI: 10.1167/iovs.65.1.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 01/03/2024] [Indexed: 01/19/2024] Open
Abstract
Purpose The purpose of this study was to elucidate the involvement of potassium two pore domain channel subfamily K member 5 (KCNK5)-mediated potassium efflux in the pathogenesis of dry eye and to unravel the underlying molecular mechanisms. Methods To induce experimental dry eye in adult wild-type C57BL/6 mice, scopolamine was administered via subcutaneous injection, and the mice were subjected to desiccating stress. To create an in vitro model of dry eye, desiccation stress was applied to the human corneal epithelial cell line (HCE-T). Intracellular potassium concentration was quantified using inductively coupled plasma mass spectrometry. Cellular death was assessed through lactate dehydrogenase assays. Gene expression profiling was conducted through both RNA sequencing and quantitative real-time PCR. Protein analysis was carried out through Western blotting and immunofluorescence staining. Assessment of the corneal epithelial defect area was conducted through fluorescein sodium staining. Tear secretion was quantified using the phenol red cotton thread method. Results Potassium efflux was observed to further facilitate corneal epithelial pyroptosis. KCNK5 exhibited upregulation in both in vivo and in vitro models of dry eye. The overexpression of KCNK5 was observed to induce potassium efflux and activate the NLR family pyrin domain containing 3 (NLRP3) inflammasome-mediated pyroptosis in vitro. Silencing KCNK5 effectively mitigated pyroptosis in dry eye. Additionally, the overexpression of KCNK5 results in the downregulation of TNF superfamily member 10 (TNFSF10) and subsequent impairment of autophagy. TNFSF10 supplementation could promote autophagy and mitigate pyroptosis in dry eye. Conclusions The upregulation of KCNK5 mediates TNFSF10 to impair autophagy and induce pyroptosis in dry eye. Consequently, targeting KCNK5 may represent a novel and promising approach to therapeutic intervention in the management of dry eye.
Collapse
Affiliation(s)
- Kai Liao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Hao Zeng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xue Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Dalian He
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Bowen Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Jin Yuan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| |
Collapse
|
2
|
Jiang Q, Li C, Zeng W, Xu H, Li J, Zhang T, Deng G, Wang Y. Inhibition of Connexin 36 attenuates HMGB1-mediated depressive-like behaviors induced by chronic unpredictable mild stress. Brain Behav 2022; 12:e2470. [PMID: 35089644 PMCID: PMC8865165 DOI: 10.1002/brb3.2470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 11/30/2021] [Accepted: 12/08/2021] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND High mobility group box 1 (HMGB1) released by neurons and microglia was demonstrated to be an important mediator in depressive-like behaviors induced by chronic unpredictable mild stress (CUMS), which could lead to the imbalance of two different metabolic approaches in kynurenine pathway (KP), thus enhancing glutamate transmission and exacerbating depressive-like behaviors. Evidence showed that HMGB1 signaling might be regulated by Connexin (Cx) 36 in inflammatory diseases of central nervous system (CNS). Our study aimed to further explore the role of Cx36 in depressive-like behaviors and its relationship with HMGB1. METHODS After 4-week chronic stress, behavioral tests were conducted to evaluate depressive-like behaviors, including sucrose preference test (SPT), tail suspension test (TST), forced swimming test (FST), and open field test (OFT). Western blot analysis and immunofluorescence staining were used to observe the expression and location of Cx36. Enzyme-linked immunosorbent assay (ELISA) was adopted to detect the concentrations of inflammatory cytokines. And the excitability and inward currents of hippocampal neurons were recorded by whole-cell patch clamping. RESULTS The expression of Cx36 was significantly increased in hippocampal neurons of mice exposed to CUMS, while treatment with glycyrrhizinic acid (GZA) or quinine could both down-regulate Cx36 and alleviate depressive-like behaviors. The proinflammatory cytokines like HMGB1, tumor necrosis factor alpha (TNF-α), and interleukin-1β (IL-1β) were all elevated by CUMS, and application of GZA and quinine could decrease them. In addition, the enhanced excitability and inward currents of hippocampal neurons induced by lipopolysaccharide (LPS) could be reduced by either GZA or quinine. CONCLUSIONS Inhibition of Cx36 in hippocampal neurons might attenuates HMGB1-mediated depressive-like behaviors induced by CUMS through down-regulation of the proinflammatory cytokines and reduction of the excitability and intracellular ion overload.
Collapse
Affiliation(s)
- Qian Jiang
- Department of PsychiatryFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Chao‐Ran Li
- Department of Nautical PsychologyFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Wen‐Feng Zeng
- Department of Nautical PsychologyFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Hui‐Jing Xu
- Department of PsychiatryFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Jia‐Mei Li
- Department of Stress MedicineFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Ting Zhang
- Department of Nautical PsychologyFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Guang‐Hui Deng
- Department of PsychiatryFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| | - Yun‐Xia Wang
- Department of Nautical PsychologyFaculty of PsychologySecond Military Medical UniversityShanghaiP. R. China
| |
Collapse
|
3
|
Chen YJ, Ma KY, Du SS, Zhang ZJ, Wu TL, Sun Y, Liu YQ, Yin XD, Zhou R, Yan YF, Wang RX, He YH, Chu QR, Tang C. Antifungal Exploration of Quinoline Derivatives against Phytopathogenic Fungi Inspired by Quinine Alkaloids. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:12156-12170. [PMID: 34623798 DOI: 10.1021/acs.jafc.1c05677] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Enlightened from our previous work of structural simplification of quinine and innovative application of natural products against phytopathogenic fungi, lead structure 2,8-bis(trifluoromethyl)-4-quinolinol (3) was selected to be a candidate and its diversified design, synthesis, and antifungal evaluation were carried out. All of the synthesized compounds Aa1-Db1 were evaluated for their antifungal activity against four agriculturally important fungi, Botrytis cinerea, Fusarium graminearum, Rhizoctonia solani, and Sclerotinia sclerotiorum. Results showed that compounds Ac3, Ac4, Ac7, Ac9, Ac12, Bb1, Bb10, Bb11, Bb13, Cb1. and Cb3 exhibited a good antifungal effect, especially Ac12 had the most potent activity with EC50 values of 0.52 and 0.50 μg/mL against S. sclerotiorum and B. cinerea, respectively, which were more potent than those of the lead compound 3 (1.72 and 1.89 μg/mL) and commercial fungicides azoxystrobin (both >30 μg/mL) and 8-hydroxyquinoline (2.12 and 5.28 μg/mL). Moreover, compound Ac12 displayed excellent in vivo antifungal activity, which was comparable in activity to the commercial fungicide boscalid. The preliminary mechanism revealed that compound Ac12 might cause an abnormal morphology of cell membranes, an increase in membrane permeability, and release of cellular contents. These results indicated that compound Ac12 displayed superior in vitro and in vivo fungicidal activities and could be a potential fungicidal candidate against plant fungal diseases.
Collapse
Affiliation(s)
- Yong-Jia Chen
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Kun-Yuan Ma
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Sha-Sha Du
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Zhi-Jun Zhang
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Tian-Lin Wu
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Yu Sun
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Ying-Qian Liu
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Xiao-Dan Yin
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Rui Zhou
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Yin-Fang Yan
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Ren-Xuan Wang
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Ying-Hui He
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Qing-Ru Chu
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Chen Tang
- School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China
| |
Collapse
|
4
|
Wang G, Wu X. The potential antiepileptogenic effect of neuronal Cx36 gap junction channel blockage. Transl Neurosci 2021; 12:46-51. [PMID: 33604079 PMCID: PMC7876775 DOI: 10.1515/tnsci-2021-0008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 12/14/2020] [Accepted: 01/08/2021] [Indexed: 12/21/2022] Open
Abstract
Epilepsy is one of the most prevalent neurological disorders and can result in neuronal injury and degeneration. Consequently, research into new antiepileptic drugs capable of providing protection against neuronal injury and degeneration is extremely important. Neuronal Cx36 gap junction channels have been found to play an important role in epilepsy; thus, pharmacological interference using Cx36 gap junction channel blockers may be a promising strategy for disrupting the synchronization of neurons during seizure activity and protecting neurons. Based on these promising findings, several in vivo and in vitro studies are ongoing and the first encouraging results have been published. The results bring hope that neurons can be protected from injury and degeneration in patients with epilepsy, which is currently impossible.
Collapse
Affiliation(s)
- Guangliang Wang
- Department of Cardiology, Far Eastern Horizon Hospital, Linghai, Liaoning, People's Republic of China
| | - Xuemei Wu
- Department of Pediatric Neurology, First Hospital of Jilin University, 1 Xinmin Street, Changchun 130000, Jilin, People's Republic of China
| |
Collapse
|
5
|
Li Q, Li QQ, Jia JN, Liu ZQ, Zhou HH, Mao XY. Targeting gap junction in epilepsy: Perspectives and challenges. Biomed Pharmacother 2018; 109:57-65. [PMID: 30396092 DOI: 10.1016/j.biopha.2018.10.068] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/08/2018] [Accepted: 10/12/2018] [Indexed: 12/21/2022] Open
Abstract
Gap junctions (GJs) are multiple cellular intercellular connections that allow ions to pass directly into the cytoplasm of neighboring cells. Electrical coupling mediated by GJs plays a role in the generation of highly synchronous electrical activity. Accumulative investigations show that GJs in the brain are involved in the generation, synchronization and maintenance of seizure events. At the same time, GJ blockers exert potent curative potential on epilepsy in vivo or in vitro. This review aims to shed light on the role of GJs in epileptogenesis. Targeting GJs is likely to be served as a novel therapeutic approach on epileptic patients.
Collapse
Affiliation(s)
- Qin Li
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Qiu-Qi Li
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Ji-Ning Jia
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Zhao-Qian Liu
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Hong-Hao Zhou
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Xiao-Yuan Mao
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China.
| |
Collapse
|
6
|
Zou L, Xue Y, Jones M, Heinbockel T, Ying M, Zhan X. The Effects of Quinine on Neurophysiological Properties of Dopaminergic Neurons. Neurotox Res 2017; 34:62-73. [PMID: 29285614 DOI: 10.1007/s12640-017-9855-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 11/28/2017] [Accepted: 12/14/2017] [Indexed: 10/18/2022]
Abstract
Quinine is an antimalarial drug that is toxic to the auditory system by commonly inducing hearing loss and tinnitus, presumably due to its ototoxic effects on disruption of cochlear hair cells and blockade of ion channels of neurons in the auditory system. To a lesser extent, quinine also causes ataxia, tremor, and dystonic reactions. As dopaminergic neurons are implicated to play a role in all of these diseases, we tested the toxicity of quinine on induced dopaminergic (iDA) neurons derived from human pluripotent stem cells (iPSCs) and primary dopaminergic (DA) neurons of substantia nigra from mice brain slices. Patch clamp recordings and combined drug treatments were performed to examine key physiological properties of the DA neurons. We found that quinine (12.5-200 μM) depolarized the resting membrane potential and attenuated the amplitudes of rebound spikes induced by hyperpolarization. Action potentials were also broadened in spontaneously spiking neurons. In addition to quinine attenuating hyperpolarization-dependent conductance, the tail currents following withdrawal of hyperpolarizing currents were also attenuated. Taken together, we found that iPSC-derived DA neurons recapitulated all the tested physiological properties of human DA neurons, and quinine had distinct effects on the physiology of both iDA and primary DA neurons. This toxicity of quinine may be the underlying mechanism for the movement disorders of cinchonism or quinism and may play a role in tinnitus modulation.
Collapse
Affiliation(s)
- Li Zou
- Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC, USA
| | - Yingchao Xue
- Department of Neurology, Hugo W. Moser Research Institute at Kennedy Krieger, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael Jones
- Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC, USA
| | - Thomas Heinbockel
- Department of Anatomy, Howard University College of Medicine, Washington, DC, USA
| | - Mingyao Ying
- Department of Neurology, Hugo W. Moser Research Institute at Kennedy Krieger, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Xiping Zhan
- Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC, USA.
| |
Collapse
|
7
|
Perkins KL, Arranz AM, Yamaguchi Y, Hrabetova S. Brain extracellular space, hyaluronan, and the prevention of epileptic seizures. Rev Neurosci 2017; 28:869-892. [PMID: 28779572 PMCID: PMC5705429 DOI: 10.1515/revneuro-2017-0017] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 06/03/2017] [Indexed: 01/08/2023]
Abstract
Mutant mice deficient in hyaluronan (HA) have an epileptic phenotype. HA is one of the major constituents of the brain extracellular matrix. HA has a remarkable hydration capacity, and a lack of HA causes reduced extracellular space (ECS) volume in the brain. Reducing ECS volume can initiate or exacerbate epileptiform activity in many in vitro models of epilepsy. There is both in vitro and in vivo evidence of a positive feedback loop between reduced ECS volume and synchronous neuronal activity. Reduced ECS volume promotes epileptiform activity primarily via enhanced ephaptic interactions and increased extracellular potassium concentration; however, the epileptiform activity in many models, including the brain slices from HA synthase-3 knockout mice, may still require glutamate-mediated synaptic activity. In brain slice epilepsy models, hyperosmotic solution can effectively shrink cells and thus increase ECS volume and block epileptiform activity. However, in vivo, the intravenous administration of hyperosmotic solution shrinks both brain cells and brain ECS volume. Instead, manipulations that increase the synthesis of high-molecular-weight HA or decrease its breakdown may be used in the future to increase brain ECS volume and prevent seizures in patients with epilepsy. The prevention of epileptogenesis is also a future target of HA manipulation. Head trauma, ischemic stroke, and other brain insults that initiate epileptogenesis are known to be associated with an early decrease in high-molecular-weight HA, and preventing that decrease in HA may prevent the epileptogenesis.
Collapse
Affiliation(s)
- Katherine L. Perkins
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Amaia M. Arranz
- VIB Center for Brain and Disease Research, 3000 Leuven, Belgium; and KU Leuven Department for Neurosciences, Leuven Institute for Neurodegenerative Disorders (LIND) and Universitaire Ziekenhuizen Leuven, University of Leuven, 3000 Leuven, Belgium
| | - Yu Yamaguchi
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, USA
| | - Sabina Hrabetova
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
| |
Collapse
|
8
|
Li X, Zhang HJ, Wang Q, Zhang DW, Wu D, Li W, Quan ZS. Current Study of the Mechanism of Action of the Potential Anti-Epileptic Agent Q808. Molecules 2017; 22:molecules22071134. [PMID: 28686214 PMCID: PMC6152255 DOI: 10.3390/molecules22071134] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 07/01/2017] [Indexed: 11/23/2022] Open
Abstract
Our previous study showed that the anticonvulsant Q808 might be effective against seizures induced by maximal electroshock, pentylenetetrazole (PTZ), isoniazid (ISO), thiosemicarbazide (THIO), and 3-mercaptopropionic acid (3-MP). In the present study, we explored the possible mechanism of action of Q808. Results obtained with high-performance liquid chromatography (HPLC) suggest that Q808 may affect neurotransmitter content in the brain, by specifically increasing GABA content in the rat hippocampus at doses of 40 mg/kg and 80 mg/kg, and by reducing the content of glutamate and glutamine in the rat thalamus at a dose of 80 mg/kg. Intriguingly, there were no changes in the neurotransmitter content in the cortex in response to Q808. In vitro brain slice electrophysiological studies showed that 10−5 M Q808 enhanced the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in corn cells of the CA1 area of the hippocampus, and had no effect on the amplitude of sIPSCs, the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs), or γ-aminobutyric acid (GABA) receptor-mediated currents in primary cultured hippocampal neurons. These findings suggest that the antiepileptic activity of Q808 may be due to its ability to increase the amount of GABA between synapses, without affecting the function of GABA receptors.
Collapse
Affiliation(s)
- Xiang Li
- Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, College of Life Sciences, Jilin University, No. 2699 Qianjin Street, Changchun 130012, China.
| | - Hong-Jian Zhang
- Key Laboratory of Natural Resources and Functional Molecules of the Changbai Mountain, Affiliated Ministry of Education, College of Pharmacy, Yanbian University, Yanji 133002, China.
| | - Qing Wang
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Dian-Wen Zhang
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Di Wu
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Wei Li
- Academy of Chinese Medical Sciences of Jilin Province, Changchun 130012, China.
| | - Zhe-Shan Quan
- Key Laboratory of Natural Resources and Functional Molecules of the Changbai Mountain, Affiliated Ministry of Education, College of Pharmacy, Yanbian University, Yanji 133002, China.
| |
Collapse
|
9
|
Wang L, Dufour S, Valiante TA, Carlen PL. Extracellular Potassium and Seizures: Excitation, Inhibition and the Role of Ih. Int J Neural Syst 2016; 26:1650044. [PMID: 27464853 DOI: 10.1142/s0129065716500441] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Seizure activity leads to increases in extracellular potassium concentration ([K[Formula: see text]]o), which can result in changes in neuronal passive and active membrane properties as well as in population activities. In this study, we examined how extracellular potassium modulates seizure activities using an acute 4-AP induced seizure model in the neocortex, both in vivo and in vitro. Moderately elevated [K[Formula: see text]]o up to 9[Formula: see text]mM prolonged seizure durations and shortened interictal intervals as well as depolarized the neuronal resting membrane potential (RMP). However, when [K[Formula: see text]]o reached higher than 9[Formula: see text]mM, seizure like events (SLEs) were blocked and neurons went into a depolarization-blocked state. Spreading depression was never observed as the blockade of ictal events could be reversed within 1-2[Formula: see text]min after the raised [K[Formula: see text]]o was changed back to control levels. This concentration-dependent dual effect of [K[Formula: see text]]o was observed using in vivo and in vitro mouse brain preparations as well as in human neocortical tissue resected during epilepsy surgery. Blocking the Ih current, mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, modulated the elevated [K[Formula: see text]]o influence on SLEs by promoting the high [K[Formula: see text]]o inhibitory actions. These results demonstrate biphasic actions of raised [K[Formula: see text]]o on neuronal excitability and seizure activity.
Collapse
Affiliation(s)
- Lihua Wang
- 1 Departments of Medicine (Neurology) and Physiology, University Health Network, University of Toronto, Toronto, M5T 2S8, Ontario, Canada
| | - Suzie Dufour
- 1 Departments of Medicine (Neurology) and Physiology, University Health Network, University of Toronto, Toronto, M5T 2S8, Ontario, Canada
| | - Taufik A Valiante
- 2 Division of Neurosurgery, Department of Surgery, University Health Network, University of Toronto, Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, M5T 2S8, Ontario, Canada
| | - Peter L Carlen
- 3 Departments of Medicine (Neurology) and Physiology, University Health Network, University of Toronto, Institute of Biomaterials and Biomedical Engineering University of Toronto, Toronto, M5T 2S8, Ontario, Canada
| |
Collapse
|
10
|
In vitro seizure like events and changes in ionic concentration. J Neurosci Methods 2015; 260:33-44. [PMID: 26300181 DOI: 10.1016/j.jneumeth.2015.08.014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/06/2015] [Accepted: 08/12/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND In vivo, seizure like events are associated with increases in extracellular K(+) concentration, decreases in extracellular Ca(2+) concentration, diphasic changes in extracellular sodium, chloride, and proton concentration, as well as changes of extracellular space size. These changes point to mechanisms underlying the induction, spread and termination of seizure like events. METHODS We investigated the potential role of alterations of the ionic environment on the induction of seizure like events-considering a review of the literature and own experimental work in animal and human slices. RESULTS Increasing extracellular K(+) concentration, lowering extracellular Mg(2+) concentration, or lowering extracellular Ca(2+) concentration can induce seizure like events. In human tissue from epileptic patients, elevation of K(+) concentration induces seizure like events in the dentate gyrus and subiculum. A combination of elevated K(+) concentration and 4-AP or bicuculline can induce seizure like events in neocortical tissue. CONCLUSIONS These protocols provide insight into the mechanisms involved in seizure initiation, spread and termination. Moreover, pharmacological studies as well as studies on mechanisms underlying pharmacoresistance are feasible.
Collapse
|
11
|
Antiepileptic properties of Quinine: A systematic review. Ann Neurosci 2014; 19:14-20. [PMID: 25205956 PMCID: PMC4117066 DOI: 10.5214/ans.0972.7531.180404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 01/31/2012] [Accepted: 02/07/2012] [Indexed: 11/28/2022] Open
Abstract
Background Quinine has anti-epileptic properties in animals. However, in humans this has not been systematically investigated. Purpose To examine the available research evidence on the effects of quinine on seizures in adults or children. Methods We searched online databases for published and unpublished studies in any language from January 1966 to March 2011. We considered randomized controlled trials (RCTs) evaluating the use of quinine in comparison to other drugs in humans with malaria or other conditions, and that reported the prevalence of seizures. Random effects meta-analysis was used to pool effect estimates in order to determine the effect of quinine on the prevalence of seizures. Results We identified six randomized controlled trials on severe malaria. Quinine was compared to the artemisinin derivatives in all trials. A total of 8,244 patients were included. In the meta-analysis, there was no significant effect of quinine on the prevalence of seizures when compared to the artemisinin derivatives (Odds ratio (OR) =0.90, 95% Confidence Interval (95%CI) =0.63-1.30). There was significant heterogeneity (I2=66%, Chi-square=17.44, p=0.008). Subgroup analysis showed that quinine significantly reduced seizures when compared to artemether (OR = 0.66, 95%CI = 0.49-0.88) but when compared to artesunate, prevalence of seizures increased significantly (OR = 1.24, 95%CI = 1.05-1.47). Conclusion There is no sufficient evidence to conclude that quinine has any antiepileptic properties in humans.
Collapse
|
12
|
Abstract
Cramps are painful sensations caused by intense involuntary contractions of skeletal muscles, mostly in the calves, usually lasting from a few seconds to several minutes. Although cramps are mostly idiopathic, theycan bea symptom of other forms of myalgia, restless legs syndrome or spasticity. Especially nocturnal cramps can cause considerable distress for patients requiring fast pain reduction and effective prophylaxis. Stretching the calf muscles helps preventing nocturnal cramps. Pharmacological treatment of leg cramps includes magnesium and quinine.
Collapse
|
13
|
Gigout S, Louvel J, Rinaldi D, Martin B, Pumain R. Thalamocortical relationships and network synchronization in a new genetic model "in mirror" for absence epilepsy. Brain Res 2013; 1525:39-52. [PMID: 23743261 DOI: 10.1016/j.brainres.2013.05.044] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 05/25/2013] [Accepted: 05/27/2013] [Indexed: 11/19/2022]
Abstract
Electroencephalographic generalized spike and wave discharges (SWD), the hallmark of human absence seizures, are generated in thalamocortical networks. However, the potential alterations in these networks in terms of the efficacy of the reciprocal synaptic activities between the cortex and the thalamus are not known in this pathology. Here, the efficacy of these reciprocal connections is assessed in vitro in thalamocortical slices obtained from BS/Orl mice, which is a new genetic model of absence epilepsy. These mice show spontaneous SWD, and their features can be compared to that of BR/Orl mice, which are free of SWD. In addition, since gap junctions may modulate the efficacy of these connections, their implications in pharmacologically-induced epileptiform discharges were studied in the same slices. The thalamus and neocortex were independently stimulated and the electrically-evoked responses in both structures were recorded from the same slice. The synaptic efficacy of thalamocortical and corticothalamic connections were assessed by measuring the dynamic range of synaptic field potential changes in response to increasing stimulation strengths. The connection efficacy was weaker in epileptic mice however, this decrease in efficacy was more pronounced in thalamocortical afferents, thus introducing an imbalance in the reciprocal connections between the cortex and thalamus. However, short-term facilitation of the thalamocortical responses were increased in epileptic mice compared to non-epileptic animals. These features may favor occurrence of rhythmical activities in thalamocortical networks. In addition, carbenoxolone (a gap junction blocker) decreased the cumulative duration of 4-aminopyridine-induced ictal-like activities, with a slower time course in epileptic mice. However, the 4-aminopyridine-induced GABA-dependent negative potentials, which appeared to trigger the ictal-like activities, remained. Our results show that the balance of the reciprocal connections between the thalamus and cortex is altered in favor of the corticothalamic connections in epileptic mice, and suggest that gap junctions mediate a stronger cortical synchronization in this strain.
Collapse
Affiliation(s)
- Sylvain Gigout
- Epilepsie de l'Enfant et Plasticité Cérébrale, INSERM U 663, Paris, France.
| | | | | | | | | |
Collapse
|
14
|
Chang WP, Wu JJS, Shyu BC. Thalamic modulation of cingulate seizure activity via the regulation of gap junctions in mice thalamocingulate slice. PLoS One 2013; 8:e62952. [PMID: 23690968 PMCID: PMC3653920 DOI: 10.1371/journal.pone.0062952] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 03/26/2013] [Indexed: 11/19/2022] Open
Abstract
The thalamus is an important target for deep brain stimulation in the treatment of seizures. However, whether the modulatory effect of thalamic inputs on cortical seizures occurs through the modulation of gap junctions has not been previously studied. Therefore, we tested the effects of different gap junction blockers and couplers in a drug-resistant seizure model and studied the role of gap junctions in the thalamic modulation on cortical seizures. Multielectrode array and calcium imaging were used to record the cortical seizures induced by 4-aminopyridine (250 µM) and bicuculline (5-50 µM) in a novel thalamocingulate slice preparation. Seizure-like activity was significantly attenuated by the pan-gap junction blockers carbenoxolone and octanol and specific neuronal gap junction blocker mefloquine. The gap junction coupler trimethylamine significantly enhanced seizure-like activity. Gap junction blockers did not influence the initial phase of seizure-like activity, but they significantly decreased the amplitude and duration of the maintenance phase. The development of seizures is regulated by extracellular potassium concentration. Carbenoxolone partially restored the amplitude and duration after removing the thalamic inputs. A two-dimensional current source density analysis showed that the sink and source signals shifted to deeper layers after removing the thalamic inputs during the clonic phase. These results indicate that the regulatory mechanism of deep brain stimulation in the thalamus occurs partially though gap junctions.
Collapse
Affiliation(s)
- Wei-Pang Chang
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - José Jiun-Shian Wu
- Institute of Zoology, National Taiwan University, Taipei, Taiwan, Republic of China
| | - Bai-Chuang Shyu
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China
- Institute of Biomedical Science, Academia Sinica, Taipei, Taiwan, Republic of China
- * E-mail:
| |
Collapse
|
15
|
Abstract
Epilepsy is a common neurological disorder characterized by periodic and unpredictable seizures. Gap junctions have recently been proposed to be involved in the generation, synchronization and maintenance of seizure events. The present review mainly summarizes recent reports concerning the contribution of gap junctions to the pathophysiology of epilepsy, together with the regulation of connexin after clinical and experimental seizure activity. The anticonvulsant effects of gap junction blockers both in vitro and in vivo suggest that the gap junction is a candidate target for the development of antiepileptic drugs. It is also of interest that the roles of neuronal and astrocytic gap junctions in epilepsy have been investigated independently, based on evidence from pharmacological manipulations and connexin-knockout mice. Further studies using more specific manipulations of gap junctions in different cell types and in human epileptic tissue are needed to fully uncover the role of gap junctions in epilepsy.
Collapse
Affiliation(s)
- Miao-Miao Jin
- Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Chen Zhong
- Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058 China
| |
Collapse
|
16
|
Mwita C, Mwai L, Newton C. Antiepileptic properties of quinine: A systematic review. JBI LIBRARY OF SYSTEMATIC REVIEWS 2011; 9:1999-2022. [PMID: 27819948 DOI: 10.11124/01938924-201109480-00001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
EXECUTIVE SUMMARY Background: Quinine has been found to have anti-epileptic properties in animals. However, in humans this has not been systematically investigated. If quinine has antiepileptic properties in humans, it may reduce the neurological sequelae associated with acute seizures in severe malaria and promote its choice over other antimalarial drugs in treating severe falciparum malaria. OBJECTIVE The review objective was to examine available research evidence on the effects of quinine on seizures in adults or children who present with seizures or who develop seizures in the course of treatment. INCLUSION CRITERIA Participants: This review considered adult and child patients who were prescribed using quinine for malaria, arthritis, nocturnal leg cramps, arrhythmia and systemic lupus erythematosus. INTERVENTION This review evaluated the use of quinine in comparison to other drugs used for malaria, arthritis, nocturnal leg cramps, arrhythmia and systemic lupus erythematosus. OUTCOMES The primary outcome of interest for this review was the proportion of participants who had seizures after the administration of quinine, compared with those who were not given quinine.Types of Studies: This review considered randomised controlled trials. SEARCH STRATEGY We searched online databases for published and unpublished studies written in English and identified articles using predefined criteria.Methodological Quality: Papers selected for retrieval were assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument. DATA EXTRACTION/SYNTHESIS The data extracted included specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. A standardized data extraction tool was used. A random effects model was used to statistically pool data in meta-analysis, in order to determine the effect of quinine on prevalence of seizures in comparison to other drugs. RESULTS We identified six randomized controlled trials on severe malaria. Quinine was compared to the artemisinin derivatives in all trials. A total of 8,244 patients were included. In the meta-analysis, there was no significant effect of quinine on the prevalence of seizures (Odds ratio=0.90 95% Confidence Interval=0.63-1.30). There was significant heterogeneity (Chi-squared=17.44, p=0.008). DISCUSSION This is the first review on the antiepileptic effect of quinine in humans. However, this effect is not demonstrated in patients with malaria. A dose-response effect may be responsible for the absence of antiepileptic properties of quinine in humans. The results of the review are confounded by the fact that all the studies reviewed were conducted in patients with malaria, and quinine was only compared against artemisinin compounds which may have neurological effects. Further, incidence of seizures could not be assessed in this review. CONCLUSIONS There is not sufficient evidence to conclude that quinine has any antiepileptic properties. A dose-response effect may be responsible for the absence of antiepileptic properties of quinine in humans with severe malaria. IMPLICATIONS FOR PRACTICE This review provides data that may influence choice of antimalarial drugs in resource poor settings. IMPLICATIONS FOR RESEARCH This review identifies the need for further studies on the antiepileptic properties of quinine with sufficient power, designed to capture seizure prevalence and incidence as outcomes, that have the ability to control for confounders appropriately and that can explore the dose-response effect of quinine on seizures.
Collapse
Affiliation(s)
- Clifford Mwita
- 1. Centre for Geographic Medicine Research (Coast), Kenya Medical Research Institute (KEMRI)/ Wellcome Trust Research Programme 2. Joanna Briggs Institute Affiliate Center in Kenya 3. Neurosciences Unit, Institute of Child Health, University College London, United Kingdom 4. Departement of Psychiatry, University of Oxford, Oxford, United Kingdom
| | | | | |
Collapse
|
17
|
Altered intrinsic properties of neuronal subtypes in malformed epileptogenic cortex. Brain Res 2010; 1374:116-28. [PMID: 21167139 DOI: 10.1016/j.brainres.2010.12.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 12/03/2010] [Accepted: 12/08/2010] [Indexed: 02/06/2023]
Abstract
Neuronal intrinsic properties control action potential firing rates and serve to define particular neuronal subtypes. Changes in intrinsic properties have previously been shown to contribute to hyperexcitability in a number of epilepsy models. Here we examined whether a developmental insult producing the cortical malformation of microgyria altered the identity or firing properties of layer V pyramidal neurons and two interneuron subtypes. Trains of action potentials were elicited with a series of current injection steps during whole cell patch clamp recordings. Cells in malformed cortex identified as having an apical dendrite had firing patterns similar to control pyramidal neurons. The duration of the second action potential in the train was increased in paramicrogyral (PMG) pyramidal cells, suggesting that these cells may be in an immature state, as was previously found for layer II/III pyramidal neurons. Based on stereotypical firing patterns and other intrinsic properties, fast-spiking (FS) and low threshold-spiking (LTS) interneuron subpopulations were clearly identified in both control and malformed cortex. Most intrinsic properties measured in malformed cortex were unchanged, suggesting that subtype identity is maintained. However, LTS interneurons in lesioned cortex had increased maximum firing frequency, decreased initial afterhyperpolarization duration, and increased total adaptation ratio compared to control LTS cells. FS interneurons demonstrated decreased maximum firing frequencies in malformed cortex compared to control FS cells. These changes may increase the efficacy of LTS while decreasing the effectiveness of FS interneurons. These data indicate that differential alterations of individual neuronal subpopulations may endow them with specific characteristics that promote epileptogenesis.
Collapse
|
18
|
Medina-Ceja L, Ventura-Mejía C. Differential effects of trimethylamine and quinine on seizures induced by 4-aminopyridine administration in the entorhinal cortex of vigilant rats. Seizure 2010; 19:507-13. [PMID: 20685138 DOI: 10.1016/j.seizure.2010.07.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 06/30/2010] [Accepted: 07/09/2010] [Indexed: 11/25/2022] Open
Abstract
In vivo and in vitro evidence from animals suggesting that gap junctions (GJs) play a role in the spreading of epileptiform activity. We have examined the influence of the gap junction opener trimethylamine (TMA) and the connexin 36 (Cx36) gap junctional blocker, quinine, on epileptiform activity induced by 4-aminopyridine (4-AP) in the rat entorhinal cortex (EC) and the CA1 hippocampal region. A cannula and surface electrodes were implanted into the brain to administer drugs and to monitor electrical activity. Injection of 4-AP (10 nmol) produced epileptiform discharge trains of high amplitude and frequency associated with seizure behavior rated between 0 and 3 in the Racine scale. In the presence of TMA (500 nmol), 4-AP produced distinct epileptiform patterns with continuous, long epileptiform discharges of high amplitude and frequency associated with seizure behavior of 0, 1, 3 and 5 during the first 30 min post-drug administration that diminished after 90 min. Quinine injection (35 pmol) into the EC of seizing animals decreased the amplitude and frequency of the discharge trains in the EC and CA1 regions, which were completely blocked after 34 min. Indeed, the seizure behavior of the animals was completely blocked in five of the six rats 53.2s after quinine administration. We suggest that the intensity of the proepileptic effect of TMA on epileptiform activity depends on the time and route of drug administration, and that neural Cx36-dependent GJs are important structures in the generation of epileptiform activity, as well as in the seizure behavior induced by 4-AP.
Collapse
Affiliation(s)
- Laura Medina-Ceja
- Department of Cellular and Molecular Biology, University of Guadalajara, 45110 Guadalajara, Jalisco, Mexico.
| | | |
Collapse
|
19
|
Kraglund N, Andreasen M, Nedergaard S. Differential influence of non-synaptic mechanisms in two in vitro models of epileptic field bursts. Brain Res 2010; 1324:85-95. [PMID: 20153738 DOI: 10.1016/j.brainres.2010.02.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 02/01/2010] [Accepted: 02/04/2010] [Indexed: 12/26/2022]
Abstract
Non-synaptic interactions are known to promote epileptiform activity through mechanisms that have primarily been studied in one particular in vitro model (low Ca(2+) model). Here we characterize another non-synaptic model, where ictal-like field bursts are induced in the CA1 area of rat hippocampal slices by exposure to Cs(+) (4-5mM) together with blockers of fast chemical synaptic transmission, and compare it with the low Ca(2+) model. The Cs-induced field bursts were blocked by 1 microM tetrodotoxin, but persisted in the presence of 200 microM Cd(2+) or 300 microM Ni(2+). Hyperosmotic condition (addition of 30 mM sucrose), reduced burst amplitude, but, unlike field bursts induced by 0mM Ca(2+)/5.25 mM K(+), sucrose had no effect on frequency or duration. Intracellular alkalinization-acidification sequence induced by NH(4)Cl potentiated and blocked, respectively, the field bursts. Octanol (100-250 microM) blocked all activity in most experiments. A quantitative comparison of three gap junction antagonists (carbenoxolone (100 microM), quinidine (100-250 microM), and endothelin-3 (1-2 microM)) indicated that gap junction communication is implicated in both models. However, endothelin-3 had selective effect on the low Ca(2+)-induced field burst. The data suggest that extracellular space-dependent processes, including field effects, significantly contribute to ongoing field burst activity, whereas initiation of a field burst can occur with or without the aid of such interactions, depending on the level of neuronal excitability. Gap junctions seem to have a general role in initiating field bursts. However, the contribution to this effect from neuronal versus glial connexin types differs in the two epileptic models studied.
Collapse
Affiliation(s)
- Nikolaj Kraglund
- Department of Physiology and Biophysics, Aarhus University, Arhus C, Denmark
| | | | | |
Collapse
|
20
|
Voss LJ, Jacobson G, Sleigh JW, Steyn-Ross A, Steyn-Ross M. Excitatory effects of gap junction blockers on cerebral cortex seizure-like activity in rats and mice. Epilepsia 2009; 50:1971-8. [PMID: 19486358 DOI: 10.1111/j.1528-1167.2009.02087.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE The role of gap junctions in seizures is an area of intense research. Many groups have reported anticonvulsant effects of gap junction blockade, strengthening the case for a role for gap junctions in ictogenesis. The cerebral cortex is underrepresented in this body of research. We have investigated the effect of gap junction blockade on seizure-like activity in rat and mouse cerebral cortex slices. METHODS Seizure-like activity was induced by perfusing with low-magnesium artificial cerebrospinal fluid. The effect of three gap junction blockers was investigated in rat cortical slices; quinine (200 and 400 microm), quinidine (100 and 200 microm), and carbenoxolone (100 and 200 microm). In addition, the effect of mefloquine was investigated in wild-type mice and connexin36 knockout mice. The data were analyzed for the effect on frequency and amplitude of seizure-like events. RESULTS Paradoxical excitatory effects on seizure-like activity were observed for all three agents in rat cortical slices. Quinine (200 microm) and carbenoxolone (100 microm) increased both the frequency and amplitude of seizure-like events. Quinidine (100 microm) increased the frequency of events. Higher doses of quinine (400 microm) and carbenoxolone (200 microm) had biphasic excitatory-inhibitory effects. Similar excitatory effects were observed in adult wild-type mouse cortical slices perfused with mefloquine (5 microm or 10 microm), but were absent in slices from connexin36-deficient mice. DISCUSSION In conclusion, we have shown a paradoxical proseizure effect of pharmacologic gap junction blockade in a cortical model of seizure-like activity. We suggest that this effect is probably due to a disruption of inhibitory interneuron coupling secondary to connexin36 blockade.
Collapse
Affiliation(s)
- Logan J Voss
- Department of Anesthesiology, Waikato Clinical School, University of Auckland, Waikato Hospital, New Zealand.
| | | | | | | | | |
Collapse
|
21
|
Nassiri-Asl M, Zamansoltani F, Torabinejad B. Antiepileptic effects of quinine in the pentylenetetrazole model of seizure. Seizure 2009; 18:129-32. [DOI: 10.1016/j.seizure.2008.08.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 04/10/2008] [Accepted: 08/08/2008] [Indexed: 11/26/2022] Open
|
22
|
The inhibitory effect of trimethylamine on the anticonvulsant activities of quinine in the pentylenetetrazole model in rats. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:1496-500. [PMID: 18556104 DOI: 10.1016/j.pnpbp.2008.05.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2008] [Revised: 05/06/2008] [Accepted: 05/09/2008] [Indexed: 11/20/2022]
Abstract
Quinine specifically blocks connexin 36 (Cx36), one of the proteins that form gap junction channels. Quinine suppressed ictal epileptiform activity in in vitro and in vivo studies without decreasing neuronal excitability. In this study, we considered the possible mechanism of anticonvulsant effects of quinine (1, 250, 500, 1000 and 2000 microM, i.c.v.) in the pentylenetetrazole (PTZ) model of seizure. Thus, we used trimethylamine (TMA) (0.05 microM, 5 microM, 50 microM), a gap junction channel opener, to examine whether it could reverse the effects of quinine in rats. Intracerebroventricular (i.c.v.) injection of quinine affected generalized tonic-clonic seizure (GTCS) induced by PTZ by increments in seizure onset and reducing seizure duration. Additionally, pretreatment with different doses of TMA (i.c.v.) attenuated the anticonvulsant effects of quinine on the latency and duration of GTCS. It can be concluded that quinine possesses anticonvulsant effects via modulation of gap junction channels, which could contribute to the control of GTCS.
Collapse
|
23
|
An JH, Su Y, Radman T, Bikson M. Effects of glucose and glutamine concentration in the formulation of the artificial cerebrospinal fluid (ACSF). Brain Res 2008; 1218:77-86. [PMID: 18533132 DOI: 10.1016/j.brainres.2008.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 04/03/2008] [Accepted: 04/04/2008] [Indexed: 10/22/2022]
Abstract
The composition of the ACSF is fundamental in controlling the extracellular environment of the brain slice preparation. 'Typical' formulations lack amino acids and contain a higher concentration of glucose (10 mM) than in the cerebrospinal fluid (0.47-4.4 mM). We examined the effects of different concentrations of glutamine, the most abundant amino acid in the CSF, and glucose on rat hippocampal slice physiology. Bipolar paired-pulse stimulation was applied to the Schaffer collaterals and population spikes were monitored in the CA1 pyramidal layer for approximately 1 hour. Addition of glutamine (0.5 mM) to slices superfused with 10 mM of glucose did not enhance population spike amplitude. Higher concentration of glutamine (2-5 mM) resulted in spreading-depression. Decreasing glucose concentration from 10 mM to 5 mM, in the absence of glutamine, attenuated population spikes. Decreasing glucose to 2 mM, in the absence of glutamine, suppressed evoked population spikes. Superfusing brain slices with ACSF containing 'physiological' concentrations of both glucose (2 mM) and glutamine (0.5 mM) similarly suppressed population spikes. In separate experiments, during high-K+ induced epileptiform activity, glutamine (0.5 mM) did not affect the burst duration, frequency or waveform. These results suggest that the concentration of glucose in ACSF should conservatively be 10 mM in order to maximize paired-pulse population responses while the presence of physiological concentration of glutamine (0.5 mM) has minimal effects on paired-pulse responses and high-K+ induced epileptiform activity. These results are discussed in the context of fundamental differences between in vitro brain slice superfusion and in vivo brain perfusion.
Collapse
Affiliation(s)
- Je Hi An
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, USA
| | | | | | | |
Collapse
|
24
|
Päsler D, Gabriel S, Heinemann U. Two-pore-domain potassium channels contribute to neuronal potassium release and glial potassium buffering in the rat hippocampus. Brain Res 2007; 1173:14-26. [PMID: 17850772 DOI: 10.1016/j.brainres.2007.07.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2007] [Revised: 07/02/2007] [Accepted: 07/08/2007] [Indexed: 10/23/2022]
Abstract
Two-pore-domain potassium (K2P) channels have been suggested to be involved in neuronal K+ release and glial K+ uptake. We studied effects of the K2P channel blockers quinine (200 or 500 microM), quinidine (500 microM), and bupivacaine (200 microM) on stimulus-induced and iontophoretically induced transient increases of the extracellular potassium concentration ([K+]o) in area CA1 of rat hippocampal slices, always in presence of AMPA/kainate and NMDA receptor antagonists. Increases in [K+]o evoked by repetitive alvear stimulation (20 Hz) were blocked by quinine and quinidine but amplitudes of population spikes were only modestly reduced. Bupivacaine suppressed both rises in [K+]o and population spikes. In contrast, iontophoretically induced rises in [K+]o were moderately augmented by quinine and quinidine while bupivacaine had no effect. Barium at concentrations of 2 mM which should block both potassium inward rectifier (Kir) and some K2P channels doubled iontophoretically induced rises in [K+]o also in presence of quinine, quinidine, and bupivacaine. The data suggest that quinine/quinidine-sensitive K2P channels mediate K+ release from neurons and possibly contribute to glial K+ buffering.
Collapse
Affiliation(s)
- Dennis Päsler
- Institute for Neurophysiology, Charité - Medical University of Berlin, Tucholskystr. 2, 10117 Berlin, Germany
| | | | | |
Collapse
|
25
|
Fujiwara-Tsukamoto Y, Isomura Y, Imanishi M, Fukai T, Takada M. Distinct types of ionic modulation of GABA actions in pyramidal cells and interneurons during electrical induction of hippocampal seizure-like network activity. Eur J Neurosci 2007; 25:2713-25. [PMID: 17459104 DOI: 10.1111/j.1460-9568.2007.05543.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
It has recently been shown that electrical stimulation in normal extracellular fluid induces seizure-like afterdischarge activity that is always preceded by GABA-dependent slow depolarization. These afterdischarge responses are synchronous among mature hippocampal neurons and driven by excitatory GABAergic input. However, the differences in the mechanisms whereby the GABAergic signals in pyramidal cells and interneurons are transiently converted from hyperpolarizing to depolarizing (and even excitatory) have remained unclear. To clarify the network mechanisms underlying this rapid GABA conversion that induces afterdischarges, we examined the temporal changes in GABAergic responses in pyramidal cells and/or interneurons of the rat hippocampal CA1 area in vitro. The extents of slow depolarization and GABA conversion were much larger in the pyramidal cell group than in any group of interneurons. Besides GABA(A) receptor activation, neuronal excitation by ionotropic glutamate receptors enhanced GABA conversion in the pyramidal cells and consequent induction of afterdischarge. The slow depolarization was confirmed to consist of two distinct phases; an early phase that depended primarily on GABA(A)-mediated postsynaptic Cl- accumulation, and a late phase that depended on extracellular K+ accumulation, both of which were enhanced by glutamatergic neuron excitation. Moreover, extracellular K+ accumulation augmented each oscillatory response of the afterdischarge, probably by further Cl- accumulation through K+-coupled Cl- transporters. Our findings suggest that the GABA reversal potential may be elevated above their spike threshold predominantly in the pyramidal cells by biphasic Cl- intrusion during the slow depolarization in GABA- and glutamate-dependent fashion, leading to the initiation of seizure-like epileptiform activity.
Collapse
Affiliation(s)
- Yoko Fujiwara-Tsukamoto
- Department of System Neuroscience, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan
| | | | | | | | | |
Collapse
|
26
|
Martens KR, De Caigny P, Parvez K, Amarell M, Wong C, Lukowiak K. Stressful stimuli modulate memory formation in Lymnaea stagnalis. Neurobiol Learn Mem 2007; 87:391-403. [PMID: 17126571 DOI: 10.1016/j.nlm.2006.10.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 10/17/2006] [Accepted: 10/18/2006] [Indexed: 11/21/2022]
Abstract
Stress has been shown to be a strong modulator of learning and memory in animals. We employ operant training of aerial respiratory behaviour in our model system, the pond snail Lymnaea stagnalis, to show that application of an acute consistent physical stressor enhances memory formation. A single 30 min operant conditioning training session, which normally results in intermediate-term memory (ITM) persisting 3h, results in long-term memory (LTM) persisting 24h if immediately preceded or followed by a stressor, for example a 30s exposure to 25 mM KCl. Other physical stressors (0.3% quinine-HCl or quick cooling and warming) similarly enhance memory formation. The memory is context specific and is not seen after the application of too much or too little stress. The memory can be extinguished by exposing snails to the hypoxic training environment and withholding reinforcing stimuli. The LTM that results from 30 min of training and stressor exposure is dependent on de novo protein synthesis and gene transcription in a single neuron, RPeD1. Because the soma of RPeD1 must be present for memory augmentation by the application of a stressor we are well placed for future investigations to directly determine the specific molecular alterations by which stress primes the formation of LTM.
Collapse
Affiliation(s)
- Kara R Martens
- Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr NW, Calgary AB, Canada T2P 1N3
| | | | | | | | | | | |
Collapse
|
27
|
Bostanci MO, Bagirici F. Anticonvulsive effects of quinine on penicillin-induced epileptiform activity: an in vivo study. Seizure 2007; 16:166-72. [PMID: 17239627 DOI: 10.1016/j.seizure.2006.11.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2006] [Revised: 10/27/2006] [Accepted: 11/13/2006] [Indexed: 11/30/2022] Open
Abstract
Epilepsy is an important problem in neurological disorders. The common features of all types of epilepsy are the synchronized and uncontrolled discharges of nerve cell assemblies. Recent studies claimed that gap junctions have a critical role in epileptic neuronal events. The aim of present study is to investigate the effects of connexin36 (Cx36) channel blocker quinine on penicillin-induced experimental epilepsy. For this purpose, 4 months old male Wistar rats were used in the present study. Permanent screw electrodes allowing EEG monitoring from conscious animals and permanent cannula providing the administration of the substances to the brain ventricle were placed into the cranium of rats under general anesthesia. At the end of the postoperative recovery period, epileptiform activity was generated by injecting 300 IU crystallized penicillin through the ventricular cannula. When the epileptiform activity, monitored from a digital recording system, reached maximal frequency and amplitude, quinine (200, 400 or 1000 nmol) was administered similar to penicillin. Effects of quinine on epileptiform activity were assessed by both electrophysiological and behavioral analysis. Quinine suppressed epileptiform activity by decreasing the amplitude and frequency of epileptiform spikes and by attenuating the epileptiform behavior. The outcomes of this study suggest that the blockade of Cx36 channels may contribute to the amelioration of epileptic activity.
Collapse
Affiliation(s)
- M Omer Bostanci
- Department of Physiology, Faculty of Medicine, Ondokuz Mayis University, 55139 Samsun, Turkey.
| | | |
Collapse
|
28
|
Margineanu DG, Klitgaard H. The connexin 36 blockers quinine, quinidine and mefloquine inhibit cortical spreading depression in a rat neocortical slice model in vitro. Brain Res Bull 2006; 71:23-8. [PMID: 17113924 DOI: 10.1016/j.brainresbull.2006.07.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Revised: 07/18/2006] [Accepted: 07/19/2006] [Indexed: 11/26/2022]
Abstract
A protocol for inducing cortical spreading depression (SD) on rat neocortical slices in vitro, upon local application of calibrated approximately nl drops of KCl, 3M was used to elicit SD events, recorded at two different points on the slice. This in vitro model was validated by the inhibition of SD episodes by the NMDA antagonist MK-801 (20 microM), the reference SD blocker. Quinine, its stereoisomer quinidine, and mefloquine consistently inhibited the SD episodes. Quinine and quinidine, 100 and 200 microM reduced the duration, while mefloquine, 100 and 200 microM reduced the amplitude of SD events, all in a concentration-dependent manner. These compounds have been reported to block gap junctions, specifically the neuronal connexin (Cx) 36, but they also exert other cellular effects. While further investigation is warranted to settle whether SD inhibition in vitro by quinine, quinidine and mefloquine reflects an involvement of neuronal Cx36 channels in SD generation/propagation, these results bear potential drug-discovery relevance for the migraine with aura.
Collapse
|
29
|
Wang D, Darwish DS, Schreurs BG. Effects of 4-aminopyridine on classical conditioning of the rabbit (Oryctolagus cuniculus) nictitating membrane response. Behav Pharmacol 2006; 17:319-29. [PMID: 16914950 DOI: 10.1097/01.fbp.0000224381.56121.15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A large body of data suggests that potassium channels may play an important role in learning and memory. Previous in-vitro research in a number of species including Hermissenda and the rabbit suggests that a 4-aminopyridine-sensitive transient potassium channel may be involved in classical conditioning. We investigated the effects of in-vivo 4-aminopyridine administration (0.5 mg/kg) on classical conditioning of the rabbit nictitating membrane response using a battery of tests designed to assess the associative, sensory, and motor contributors of 4-aminopyridine to responding. 4-Aminopyridine enhanced both classical conditioning and conditioning-specific reflex modification compared with a saline vehicle control, and these effects had several nonassociative components including an increase in the frequency of responding to both the conditioned and the unconditioned stimuli, suggesting a sensitizing effect of the drug. Although 4-aminopyridine can have peripheral effects, it may also modify cerebellar excitability or hippocampal neurotransmitter balance resulting in heightened responsiveness to stimulation.
Collapse
Affiliation(s)
- Desheng Wang
- Department of Physiology and Pharmacology, Blanchette Rockefeller Neurosciences Institute, West Virginia University School of Medicine, Morgantown, West Virginia 26506, USA
| | | | | |
Collapse
|
30
|
Gigout S, Louvel J, Kawasaki H, D'Antuono M, Armand V, Kurcewicz I, Olivier A, Laschet J, Turak B, Devaux B, Pumain R, Avoli M. Effects of gap junction blockers on human neocortical synchronization. Neurobiol Dis 2006; 22:496-508. [PMID: 16478664 DOI: 10.1016/j.nbd.2005.12.011] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 12/14/2005] [Accepted: 12/19/2005] [Indexed: 11/26/2022] Open
Abstract
Field potentials and intracellular recordings were obtained from human neocortical slices to study the role of gap junctions (GJ) in neuronal network synchronization. First, we examined the effects of GJ blockers (i.e., carbenoxolone, octanol, quinine, and quinidine) on the spontaneous synchronous events (duration = 0.2-1.1 s; intervals of occurrence = 3-27 s) generated by neocortical slices obtained from temporal lobe epileptic patients during application of 4-aminopyridine (4AP, 50 muM) and glutamatergic receptor antagonists. The synchronicity of these potentials (recorded at distances up to 5 mm) was decreased by GJ blockers within 20 min of application, while prolonged GJ blockers treatment at higher doses made them disappear with different time courses. Second, we found that slices from patients with focal cortical dysplasia (FCD) could generate in normal medium spontaneous synchronous discharges (duration = 0.4-8 s; intervals of occurrence = 0.5-90 s) that were (i) abolished by NMDA receptor antagonists and (ii) slowed down by carbenoxolone. Finally, octanol or carbenoxolone blocked 4AP-induced ictal-like discharges (duration = up to 35 s) in FCD slices. These data indicate that GJ play a role in synchronizing human neocortical networks and may implement epileptiform activity in FCD.
Collapse
Affiliation(s)
- S Gigout
- INSERM U 573, Paris, 75014 France
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Gigout S, Louvel J, Pumain R. Effects in vitro and in vivo of a gap junction blocker on epileptiform activities in a genetic model of absence epilepsy. Epilepsy Res 2006; 69:15-29. [PMID: 16466906 DOI: 10.1016/j.eplepsyres.2005.12.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 11/28/2005] [Accepted: 12/08/2005] [Indexed: 11/29/2022]
Abstract
We investigated the effects of carbenoxolone (CBX), a gap junctions (GJ) blocker, on epileptiform activities in vivo and in vitro. In a first series of experiments, i.p. CBX decreased the cumulative duration of cortical spike-wave discharges (SWD) in adult Genetic Absence Epilepsy Rats from Strasbourg (GAERS) without reduction in the SW amplitude or frequency. Since SWD are generated in thalamocortical networks, we studied the effect of CBX on thalamic and cortical activities elicited by 4-aminopyridine (4AP) in thalamocortical slices from GAERS or non-epileptic rats (NER). Spontaneous ictal-like activities (ILA) were recorded simultaneously in thalamus and somatosensory cortex. However, experiments where these structures were surgically separated showed that ILA were generated in the cortex and recorded by volume conduction in the thalamus. GABA-dependent negative field potentials were also recorded in the cortex, either isolated or initiating ILA. After bath-applying CBX (100 microM), the frequency and cumulative duration of ILA decreased but less rapidly in GAERS than in NER slices and they disappeared at a time point when GABA-dependent negative potentials remained. These data suggest that GJ do not mediate the 4AP induced interneuronal synchronisation but may be implicated in the spreading of the synchronised activities from interneuronal networks to principal neurones. Our results show that CBX exerts an antiepileptic action in vivo, and that GJ blockers limits spread of synchronised activities in vitro. They may represent an appropriate target for development of new antiepileptic drugs.
Collapse
Affiliation(s)
- S Gigout
- Neurobiologie et Pharmacologie moléculaire, INSERM U 573, 75014 Paris, France
| | | | | |
Collapse
|
32
|
Chao TC, Chen CM. Learning-Induced Synchronization and Plasticity of a Developing Neural Network. J Comput Neurosci 2005; 19:311-24. [PMID: 16502239 DOI: 10.1007/s10827-005-2653-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Revised: 05/17/2005] [Accepted: 05/31/2005] [Indexed: 10/25/2022]
Abstract
Learning-induced synchronization of a neural network at various developing stages is studied by computer simulations using a pulse-coupled neural network model in which the neuronal activity is simulated by a one-dimensional map. Two types of Hebbian plasticity rules are investigated and their differences are compared. For both models, our simulations show a logarithmic increase in the synchronous firing frequency of the network with the culturing time of the neural network. This result is consistent with recent experimental observations. To investigate how to control the synchronization behavior of a neural network after learning, we compare the occurrence of synchronization for four networks with different designed patterns under the influence of an external signal. The effect of such a signal on the network activity highly depends on the number of connections between neurons. We discuss the synaptic plasticity and enhancement effects for a random network after learning at various developing stages.
Collapse
Affiliation(s)
- T C Chao
- Department of Physics, National Taiwan Normal University, Taipei, Taiwan
| | | |
Collapse
|
33
|
Gajda Z, Szupera Z, Blazsó G, Szente M. Quinine, a blocker of neuronal cx36 channels, suppresses seizure activity in rat neocortex in vivo. Epilepsia 2005; 46:1581-91. [PMID: 16190928 DOI: 10.1111/j.1528-1167.2005.00254.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE The selective contribution of neuronal gap junction (GJ) communication via connexin 36 (Cx36) channels to epileptogenesis and to the maintenance and propagation of seizures was investigated in both the primary focus and the mirror focus by using pharmacologic approaches with the 4-aminopyridine in vivo epilepsy model. METHODS ECoG recording was performed on anesthetized adult rats, in which either quinine, a selective blocker of Cx36, or the broad-spectrum GJ blockers carbenoxolone and octanol were applied locally, before the induction or at already active epileptic foci. RESULTS The blockade of Cx36 channels by quinine before the induction of epileptiform activity slightly reduced the epileptogenesis. When quinine was applied after 25-30 repetitions of seizures, a new discharge pattern appeared with frequencies >15 Hz at the initiation of seizures. In spite of the increased number of seizures, the summated ictal activity decreased, because of the significant reduction in the duration of the seizures. The amplitudes of the seizure discharges of all the patterns decreased, with the exception of those with frequencies of 11-12 Hz. The blockade of Cx36 channels and the global blockade of the GJ channels resulted in qualitatively different modifications in ictogenesis. CONCLUSIONS The blockade of Cx36 channels at the already active epileptic focus has an anticonvulsive effect and modifies the manifestation of the 1- to 18-Hz seizure discharges. Our findings indicate that the GJ communication via Cx36 channels is differently involved in the synchronization of the activities of the networks generating seizure discharges with different frequencies. Additionally, we conclude that both neuronal and glial GJ communication contribute to the manifestation and propagation of seizures in the adult rat neocortex.
Collapse
Affiliation(s)
- Zita Gajda
- Department of Comparative Physiology, University of Szeged, Szeged, Hungary
| | | | | | | |
Collapse
|
34
|
Bihi RI, Jefferys JGR, Vreugdenhil M. The role of extracellular potassium in the epileptogenic transformation of recurrent GABAergic inhibition. Epilepsia 2005; 46 Suppl 5:64-71. [PMID: 15987256 DOI: 10.1111/j.1528-1167.2005.01011.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Epileptiform burst-firing can occur in hippocampal area CA1 where recurrent excitation is relatively weak and recurrent inhibition strong. Recent observations suggest that recurrent inhibition can transform into recurrent excitation because of collapse of the chloride gradient. Here we assess the role of potassium in this epileptogenic transformation. METHODS Extracellular field potential recordings, combined with either intracellular recordings from pyramidal neurons or extracellular potassium concentration recordings, were made in vitro from isolated CA1 minislices cut from the rat hippocampus and in vivo from area CA1 in urethane-anesthetized rats. Burst responses were evoked by 5-Hz alveus stimulation. RESULTS The 5-Hz alveus stimulation in vitro caused a transient period of burst responses that was associated with a transient increase in synaptic input in stratum oriens and a transient shift of the reversal potential of the synaptic potential. These changes were related to the transient increase in extracellular potassium concentration in stratum oriens. Observations in vivo confirmed the relation between bursting and extracellular potassium concentration in stratum oriens. CONCLUSIONS Use-dependent increase of extracellular potassium concentration in stratum oriens facilitates the collapse of the chloride gradient in the basal dendrites and transforms gamma-aminobutyric acid (GABA)ergic inhibition into GABAergic excitation, giving rise to burst firing. Improvement of intracellular chloride homeostasis or extracellular potassium homeostasis could reduce epileptogenicity.
Collapse
Affiliation(s)
- Rachid Id Bihi
- Department of Neurophysiology, University of Birmingham, Birmingham, United Kingdom
| | | | | |
Collapse
|