1
|
Kariuki SM, Wagner RG, Gunny R, D'Arco F, Kombe M, Ngugi AK, White S, Odhiambo R, Cross JH, Sander JW, Newton CRJC. Magnetic resonance imaging findings in Kenyans and South Africans with active convulsive epilepsy: An observational study. Epilepsia 2024; 65:165-176. [PMID: 37964464 DOI: 10.1111/epi.17829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 11/10/2023] [Accepted: 11/10/2023] [Indexed: 11/16/2023]
Abstract
OBJECTIVE Focal epilepsy is common in low- and middle-income countries. The frequency and nature of possible underlying structural brain abnormalities have, however, not been fully assessed. METHODS We evaluated the possible structural causes of epilepsy in 331 people with epilepsy (240 from Kenya and 91 from South Africa) identified from community surveys of active convulsive epilepsy. Magnetic resonance imaging (MRI) scans were acquired on 1.5-Tesla scanners to determine the frequency and nature of any underlying lesions. We estimated the prevalence of these abnormalities using Bayesian priors (from an earlier pilot study) and observed data (from this study). We used a mixed-effect modified Poisson regression approach with the site as a random effect to determine the clinical features associated with neuropathology. RESULTS MRI abnormalities were found in 140 of 240 (modeled prevalence = 59%, 95% confidence interval [CI]: 53%-64%) of people with epilepsy in Kenya, and in 62 of 91 (modeled prevalence = 65%, 95% CI: 57%-73%) in South Africa, with a pooled modeled prevalence of 61% (95% CI: 56%-66%). Abnormalities were common in those with a history of adverse perinatal events (15/23 [65%, 95% CI: 43%-84%]), exposure to parasitic infections (83/120 [69%, 95% CI: 60%-77%]) and focal electroencephalographic features (97/142 [68%, 95% CI: 60%-76%]), but less frequent in individuals with generalized electroencephalographic features (44/99 [44%, 95% CI: 34%-55%]). Most abnormalities were potentially epileptogenic (167/202, 82%), of which mesial temporal sclerosis (43%) and gliosis (34%) were the most frequent. Abnormalities were associated with co-occurrence of generalized non-convulsive seizures (relative risk [RR] = 1.12, 95% CI: 1.04-1.25), lack of family history of seizures (RR = 0.91, 0.86-0.96), convulsive status epilepticus (RR = 1.14, 1.08-1.21), frequent seizures (RR = 1.12, 1.04-1.20), and reported use of anti-seizure medication (RR = 1.22, 1.18-1.26). SIGNIFICANCE MRI identified pathologies are common in people with epilepsy in Kenya and South Africa. Mesial temporal sclerosis, the most common abnormality, may be amenable to surgical correction. MRI may have a diagnostic value in rural Africa, but future longitudinal studies should examine the prognostic role.
Collapse
Affiliation(s)
- Symon M Kariuki
- Neurosciences Unit, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Psychiatry, University of Oxford, Oxford, UK
| | - Ryan G Wagner
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Roxana Gunny
- Department of Neuroradiology, Great Ormond Street Hospital, London, UK
| | - Felice D'Arco
- Department of Neuroradiology, Great Ormond Street Hospital, London, UK
| | - Martha Kombe
- Neurosciences Unit, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Anthony K Ngugi
- Department of Population Health, Medical College, Aga Khan University of East Africa, Nairobi, Kenya
| | | | - Rachael Odhiambo
- Department of Population Health, Medical College, Aga Khan University of East Africa, Nairobi, Kenya
| | - J Helen Cross
- Developmental Neurosciences, UCL, NIHR BRC Great Ormond Street Institute of Child Health, London, UK
| | - Josemir W Sander
- Department of Clinical & Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
- Chalfont Centre for Epilepsy, Chalfont St Peter, UK
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands
- Department of Neurology, West China Hospital, Chengdu, China
- Institute of Brain Science & Brain-Inspired Technology, Sichuan University, Chengdu, China
| | - Charles R J C Newton
- Neurosciences Unit, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Psychiatry, University of Oxford, Oxford, UK
| |
Collapse
|
2
|
de Curtis M, Rossetti AO, Verde DV, van Vliet EA, Ekdahl CT. Brain pathology in focal status epilepticus: evidence from experimental models. Neurosci Biobehav Rev 2021; 131:834-846. [PMID: 34517036 DOI: 10.1016/j.neubiorev.2021.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 09/02/2021] [Accepted: 09/05/2021] [Indexed: 12/01/2022]
Abstract
Status Epilepticus (SE) is often a neurological emergency characterized by abnormally sustained, longer than habitual seizures. The new ILAE classification reports that SE "…can have long-term consequences including neuronal death, neuronal injury…depending on the type and duration of seizures". While it is accepted that generalized convulsive SE exerts detrimental effects on the brain, it is not clear if other forms of SE, such as focal non-convulsive SE, leads to brain pathology and contributes to long-term deficits in patients. With the available clinical and experimental data, it is hard to discriminate the specific action of the underlying SE etiologies from that exerted by epileptiform activity. This information is highly relevant in the clinic for better treatment stratification, which may include both medical and surgical intervention for seizure control. Here we review experimental studies of focal SE, with an emphasis on focal non-convulsive SE. We present a repertoire of brain pathologies observed in the most commonly used animal models and attempt to establish a link between experimental findings and human condition(s). The extensive literature on focal SE animal models suggest that the current approaches have significant limitations in terms of translatability of the findings to the clinic. We highlight the need for a more stringent description of SE features and brain pathology in experimental studies in animal models, to improve the accuracy in predicting clinical translation.
Collapse
Affiliation(s)
- Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto NeurologicoCarlo Besta, Milano, Italy.
| | - Andrea O Rossetti
- Department of Clinical Neuroscience, University Hospital (CHUV) and University of Lausanne, Lausanne, Switzerland
| | - Diogo Vila Verde
- Epilepsy Unit, Fondazione IRCCS Istituto NeurologicoCarlo Besta, Milano, Italy
| | - Erwin A van Vliet
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Science Park 904, P.O. Box 94246, 1090 GE, Amsterdam, the Netherlands; Amsterdam UMC, University of Amsterdam, Department of (Neuro)Pathology, Amsterdam Neuroscience, Meibergdreef 9, Amsterdam, the Netherlands
| | - Christine T Ekdahl
- Division of Clinical Neurophysiology, Lund University, Sweden; Lund Epilepsy Center, Dept Clinical Sciences, Lund University, Sweden
| |
Collapse
|
3
|
Cavarsan CF, Malheiros J, Hamani C, Najm I, Covolan L. Is Mossy Fiber Sprouting a Potential Therapeutic Target for Epilepsy? Front Neurol 2018; 9:1023. [PMID: 30555406 PMCID: PMC6284045 DOI: 10.3389/fneur.2018.01023] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 11/13/2018] [Indexed: 11/13/2022] Open
Abstract
Mesial temporal lobe epilepsy (MTLE) caused by hippocampal sclerosis is one of the most frequent focal epilepsies in adults. It is characterized by focal seizures that begin in the hippocampus, sometimes spread to the insulo-perisylvian regions and may progress to secondary generalized seizures. Morphological alterations in hippocampal sclerosis are well defined. Among them, hippocampal sclerosis is characterized by prominent cell loss in the hilus and CA1, and abnormal mossy fiber sprouting (granular cell axons) into the dentate gyrus inner molecular layer. In this review, we highlight the role of mossy fiber sprouting in seizure generation and hippocampal excitability and discuss the response of alternative treatment strategies in terms of MFS and spontaneous recurrent seizures in models of TLE (temporal lobe epilepsy).
Collapse
Affiliation(s)
- Clarissa F Cavarsan
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Jackeline Malheiros
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Clement Hamani
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil.,Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada
| | - Imad Najm
- Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Luciene Covolan
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil.,Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States
| |
Collapse
|
4
|
Monti G, Tondelli M, Giovannini G, Bedin R, Nichelli PF, Trenti T, Meletti S, Chiari A. Cerebrospinal fluid tau proteins in status epilepticus. Epilepsy Behav 2015; 49:150-4. [PMID: 25958230 DOI: 10.1016/j.yebeh.2015.04.030] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 04/15/2015] [Accepted: 04/16/2015] [Indexed: 10/23/2022]
Abstract
Tau protein is a phosphorylated microtubule-associated protein, principally localized at neuronal level in the central nervous system (CNS). Tau levels in the cerebrospinal fluid (CSF) are considered to index both axonal and neuronal damage. To date, however, no study has specifically evaluated the CSF levels of tau proteins in patients with status epilepticus (SE). We evaluated these established biomarkers of neuronal damage in patients with SE who received a lumbar puncture during SE between 2007 and 2014. Status epilepticus cases due to acute structural brain damage, including CNS infection, were excluded. Clinical, biological, therapeutic, and follow-up data were collected. Group comparison between patients stratified according to SE response to antiepileptic drugs (AEDs), disability, and epilepsy outcomes were performed. Twenty-eight patients were considered for the analyses (mean age 56 years): 14 patients had abnormally high CSF t-tau level, six patients had abnormally high CSF p-tau level, and only three patients had abnormally low Aβ1-42 level. Cerebrospinal fluid t-tau value was higher in patients who developed a refractory SE compared to patients with seizures controlled by AED. Cerebrospinal fluid t-tau values were positively correlated with SE duration and were higher in patients treated with propofol anesthesia compared to patients that had not received this treatment. Patients with higher CSF t-tau had higher risk of developing disability (OR = 32.5, p = 0.004) and chronic epilepsy (OR = 12; p = 0.016) in comparison with patients with lower CSF t-tau level. Our results suggest that CSF t-tau level might be proposed as a biomarker of SE severity and prognosis. Prospective studies are needed to evaluate the effects of propofol on tau pathology in this setting. This article is part of a Special Issue entitled "Status Epilepticus".
Collapse
Affiliation(s)
- Giulia Monti
- Department of Biomedical, Metabolic, and Neural Science, University of Modena and Reggio Emilia, Modena, Italy; Neurology Unit, NOCSAE Hospital, AUSL Modena, Italy
| | - Manuela Tondelli
- Department of Biomedical, Metabolic, and Neural Science, University of Modena and Reggio Emilia, Modena, Italy; Neurology Unit, NOCSAE Hospital, AUSL Modena, Italy
| | - Giada Giovannini
- Department of Biomedical, Metabolic, and Neural Science, University of Modena and Reggio Emilia, Modena, Italy; Neurology Unit, NOCSAE Hospital, AUSL Modena, Italy
| | | | - Paolo F Nichelli
- Department of Biomedical, Metabolic, and Neural Science, University of Modena and Reggio Emilia, Modena, Italy; Neurology Unit, NOCSAE Hospital, AUSL Modena, Italy
| | - Tommaso Trenti
- Clinical Pathology-Toxicology, NOCSAE Hospital, ASL Modena, Italy
| | - Stefano Meletti
- Department of Biomedical, Metabolic, and Neural Science, University of Modena and Reggio Emilia, Modena, Italy; Neurology Unit, NOCSAE Hospital, AUSL Modena, Italy.
| | | |
Collapse
|
5
|
|
6
|
|
7
|
Costa-Ferro ZSM, Vitola AS, Pedroso MF, Cunha FB, Xavier LL, Machado DC, Soares MBP, Ribeiro-dos-Santos R, DaCosta JC. Prevention of seizures and reorganization of hippocampal functions by transplantation of bone marrow cells in the acute phase of experimental epilepsy. Seizure 2010; 19:84-92. [PMID: 20080419 DOI: 10.1016/j.seizure.2009.12.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 12/11/2009] [Accepted: 12/17/2009] [Indexed: 12/24/2022] Open
Abstract
In this study, we investigated the therapeutic potential of bone marrow mononuclear cells (BMCs) in a model of epilepsy induced by pilocarpine in rats. BMCs obtained from green fluorescent protein (GFP) transgenic mice or rats were transplanted intravenously after induction of status epilepticus (SE). Spontaneous recurrent seizures (SRS) were monitored using Racine's seizure severity scale. All of the rats in the saline-treated epileptic control group developed SRS, whereas none of the BMC-treated epileptic animals had seizures in the short term (15 days after transplantation), regardless of the BMC source. Over the long-term chronic phase (120 days after transplantation), only 25% of BMC-treated epileptic animals had seizures, but with a lower frequency and duration compared to the epileptic control group. The density of hippocampal neurons in the brains of animals treated with BMCs was markedly preserved. At hippocampal Schaeffer collateral-CA1 synapses, long-term potentiation was preserved in BMC-transplanted rats compared to epileptic controls. The donor-derived GFP(+) cells were rarely found in the brains of transplanted epileptic rats. In conclusion, treatment with BMCs can prevent the development of chronic seizures, reduce neuronal loss, and influence the reorganization of the hippocampal neuronal network.
Collapse
Affiliation(s)
- Zaquer S M Costa-Ferro
- Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Palmio J, Suhonen J, Keränen T, Hulkkonen J, Peltola J, Pirttilä T. Cerebrospinal fluid tau as a marker of neuronal damage after epileptic seizure. Seizure 2009; 18:474-7. [PMID: 19428269 DOI: 10.1016/j.seizure.2009.04.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 04/02/2009] [Accepted: 04/09/2009] [Indexed: 10/20/2022] Open
Abstract
PURPOSE Whether repeated brief seizures can cause neuronal damage is controversial. Cerebrospinal fluid (CSF) total tau (T-tau) and phosphorylated tau (P-tau) measurements have been suggested for the diagnosis of Alzheimer's disease, and T-tau may also be a marker of axonal damage and neuronal degeneration. We studied T-tau and P-tau levels and P-tau/T-tau ratio in CSF after epileptic seizures in order to determine whether they are increased after seizures. METHODS A total of 54 patients with tonic-clonic or partial secondarily generalized seizures due to various etiologies were studied and CSF obtained within 48h after the seizure. RESULTS There were no statistical differences in the levels of T-tau (p=0.09, ANOVA) or P-tau (p=0.60) between different etiologic groups or controls. No patients with epilepsy of unknown origin had abnormal CSF T-tau whereas 11 patients with acute or remote symptomatic seizures had abnormal T-tau levels and the P-tau/T-tau ratio showed significant differences between the groups and controls (p=0.003). CONCLUSIONS Epileptic seizures with unknown etiology did not increase CSF tau levels. Abnormal tau levels were associated with either acute or remote symptomatic seizures with known etiology. The presence of elevated CSF tau increases the probability of symptomatic cause in a patient with a seizure.
Collapse
Affiliation(s)
- Johanna Palmio
- Department of Neurology, University of Tampere, FIN-33014 Tampere, Finland.
| | | | | | | | | | | |
Collapse
|
9
|
Voss LJ, Sleigh JW, Barnard JPM, Kirsch HE. The Howling Cortex: Seizures and General Anesthetic Drugs. Anesth Analg 2008; 107:1689-703. [PMID: 18931234 DOI: 10.1213/ane.0b013e3181852595] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
10
|
Boison D. The adenosine kinase hypothesis of epileptogenesis. Prog Neurobiol 2007; 84:249-62. [PMID: 18249058 DOI: 10.1016/j.pneurobio.2007.12.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 11/02/2007] [Accepted: 12/05/2007] [Indexed: 02/07/2023]
Abstract
Current therapies for epilepsy are largely symptomatic and do not affect the underlying mechanisms of disease progression, i.e. epileptogenesis. Given the large percentage of pharmacoresistant chronic epilepsies, novel approaches are needed to understand and modify the underlying pathogenetic mechanisms. Although different types of brain injury (e.g. status epilepticus, traumatic brain injury, stroke) can trigger epileptogenesis, astrogliosis appears to be a homotypic response and hallmark of epilepsy. Indeed, recent findings indicate that epilepsy might be a disease of astrocyte dysfunction. This review focuses on the inhibitory neuromodulator and endogenous anticonvulsant adenosine, which is largely regulated by astrocytes and its key metabolic enzyme adenosine kinase (ADK). Recent findings support the "ADK hypothesis of epileptogenesis": (i) Mouse models of epileptogenesis suggest a sequence of events leading from initial downregulation of ADK and elevation of ambient adenosine as an acute protective response, to changes in astrocytic adenosine receptor expression, to astrocyte proliferation and hypertrophy (i.e. astrogliosis), to consequential overexpression of ADK, reduced adenosine and - finally - to spontaneous focal seizure activity restricted to regions of astrogliotic overexpression of ADK. (ii) Transgenic mice overexpressing ADK display increased sensitivity to brain injury and seizures. (iii) Inhibition of ADK prevents seizures in a mouse model of pharmacoresistant epilepsy. (iv) Intrahippocampal implants of stem cells engineered to lack ADK prevent epileptogenesis. Thus, ADK emerges both as a diagnostic marker to predict, as well as a prime therapeutic target to prevent, epileptogenesis.
Collapse
Affiliation(s)
- Detlev Boison
- R.S. Dow Neurobiology Laboratories, Legacy Research, Portland, OR 97232, USA.
| |
Collapse
|
11
|
Gröhn O, Pitkänen A. Magnetic resonance imaging in animal models of epilepsy-noninvasive detection of structural alterations. Epilepsia 2007; 48 Suppl 4:3-10. [PMID: 17767570 DOI: 10.1111/j.1528-1167.2007.01236.x] [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] [Indexed: 11/28/2022]
Abstract
Small animal magnetic resonance imaging (MRI) has opened a window through which brain abnormalities can be observed over time in rodents noninvasively. We review MRI studies done during epileptogenesis triggered by status epilepticus in rat. Most of these studies have used quantitative T2, diffusion, and/or volumetric MRI. The goal has been to identify the distribution and severity of structural lesions during the epileptogenic process, that is, soon after status epilepticus, during epileptogenesis, and after the appearance of spontaneous seizures. Data obtained demonstrate that MRI can be used to associate the development of brain pathology with the evolution of clinical phenotype. MRI can also be used to select animals to preclinical studies based on the severity and/or distribution of brain damage, thus making the study population more homogeneous, for example, for assessment of novel antiepileptogenic or neuroprotective treatments. Importantly, follow-up data collected emphasize interindividual differences in the dynamics of development of abnormalities that could have remained undetected in a typical histologic analysis providing a snapshot to brain pathology. A great future challenge is to take advantage of interanimal variability in MRI in the development of surrogate markers for epilepsy or its comorbidities such as memory impairment. Understanding of molecular and cellular mechanisms underlying changes in various MRI techniques will help to better understand complex progressive pathological processes associated with epileptogenesis and epilepsy.
Collapse
Affiliation(s)
- Olli Gröhn
- Biomedical NMR Research Group, Department of Neurobiology, A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland.
| | | |
Collapse
|
12
|
Bjørnaes H, Stabell KE, Heminghyt E, Røste GK, Bakke SJ. Resective Surgery for Intractable Focal Epilepsy in Patients with Low IQ: Predictors for Seizure Control and Outcome with Respect to Seizures and Neuropsychological and Psychosocial Functioning. Epilepsia 2004; 45:131-9. [PMID: 14738420 DOI: 10.1111/j.0013-9580.2004.34003.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To investigate possible predictive factors for seizure control in a group of children and adults with low IQs (IQ, < or =70) who underwent resective surgery for intractable focal epilepsy and to study outcome with respect to seizures and neuropsychological functioning. We also studied psychosocial outcome in the adult patients. METHODS Thirty-one patients (eight children younger than 18 years) with a Wechsler Full Scale IQ of 70 or less underwent comprehensive neuropsychological assessments before and 2 years after surgery. Adults also completed the Washington Psychosocial Seizure Inventory (WPSI). Univariate analyses were used to identify variables differentiating between patients who became seizure free and those who did not. Pre- and postoperative test results were compared by t test for dependent samples. RESULTS Forty-eight percent of the patients became seizure free, 52% of those with temporal lobe resection and 38% of those with extratemporal resection. Only one variable was predictive for seizure outcome: duration of epilepsy. In one third of the patients, who had the shortest duration of epilepsy (<12 years), 80% became seizure free. Significant improvement was seen regarding vocational adjustment in adults (WPSI). Seizure-free adults improved their Full Scale IQ scores. No cognitive changes were found in seizure-free children or in patients who did not become seizure free. CONCLUSIONS A good seizure outcome was obtained after resective surgery in patients with intractable focal epilepsy and low IQ, provided that treatment was done relatively shortly after onset of epilepsy. No adverse effects were seen on cognitive and psychosocial functioning.
Collapse
|
13
|
Samoilova M, Li J, Pelletier MR, Wentlandt K, Adamchik Y, Naus CC, Carlen PL. Epileptiform activity in hippocampal slice cultures exposed chronically to bicuculline: increased gap junctional function and expression. J Neurochem 2003; 86:687-99. [PMID: 12859682 DOI: 10.1046/j.1471-4159.2003.01893.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Chronic (18 h) exposure of cultured hippocampal slices to the type-A GABA receptor blocker, bicuculline methiodide (BMI) 10 micro m increased the levels of connexin 43 (Cx43) and connexin 32 (Cx32) mRNAs, but not connexin 26 and connexin 36, as demonstrated by RNase protection assays. The levels of Cx43 and Cx32 proteins in membrane fractions detected by western blotting were also significantly increased. Immunoblotting indicated that BMI also promoted a significant expression of the transcription protein c-fos. The rate of fluorescence recovery after photobleaching, an index of gap junctional coupling, was also significantly increased, whereas it was blocked by the gap junctional blocker, carbenoxolone (100 micro m). Extracellular recordings in CA1 stratum pyramidale, performed in BMI-free solution, demonstrated that BMI-exposed cultures possessed synaptic responses characteristic of epileptiform discharges: (i) significantly greater frequency of spontaneous epileptiform discharges, (ii) post-synaptic potentials with multiple population spikes, and (iii) significantly longer duration of primary afterdischarges. Carbenoxolone (100 micro m), but not its inactive analog, oleanolic acid (100 micro m), reversibly inhibited spontaneous and evoked epileptiform discharges. The findings of BMI-induced parallel increases in levels of gap junction expression and function, and the increase in epileptiform discharges, which were sensitive to gap junctional blockers, are consistent with the hypothesis that increased gap junctional communication plays an intrinsic role in the epileptogenic process.
Collapse
Affiliation(s)
- Marina Samoilova
- Bloorview Epilepsy Research Laboratory, Division of Cellular and Molecular Biology, Toronto Western Research Institute, Toronto, Ontario, Canada
| | | | | | | | | | | | | |
Collapse
|