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2.
Exp Neurol ; 318: 50-60, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31022385

RESUMO

The contribution of glial transporters to glutamate movement across the membrane has been identified as a potential target for anti-seizure therapies. Two such glutamate transporters, GLT-1 and system xc-, are expressed on glial cells, and modulation of their expression and function have been identified as a means by which seizures, neuronal injury, and gliosis can be reduced in models of brain injury. While GLT-1 is responsible for the majority of glutamate uptake in the brain, system xc- releases glutamate in the extracellular cleft in exchange for cystine and represents as such the major source of hippocampal extracellular glutamate. Using the Theiler's Murine Encephalomyelitis Virus (TMEV) model of viral-induced epilepsy, we have taken two well-studied approaches, one pharmacological, one genetic, to investigate the potential role(s) of GLT-1 and system xc- in TMEV-induced pathology. Our findings suggest that the methods we utilized to modulate these glial transporters, while effective in other models, are not sufficient to reduce the number or severity of behavioral seizures in TMEV-infected mice. However, genetic knockout of xCT, the specific subunit of system xc-, may have cellular effects, as we observed a slight decrease in neuronal injury caused by TMEV and an increase in astrogliosis in the CA1 region of the hippocampus. Furthermore, xCT knockout caused an increase in GLT-1 expression selectively in the cortex. These findings have significant implications for both the characterization of the TMEV model as well as for future efforts to discover novel and effective anti-seizure drugs.

3.
J Neurosci ; 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30504280

RESUMO

Astrocyte expression of metabotropic glutamate receptor 5 (mGluR5) is consistently observed in resected tissue from patients with epilepsy and is equally prevalent in animal models of epilepsy. However, little is known about the functional signaling properties or downstream consequences of astrocyte mGluR5 activation during epilepsy development. In the rodent brain, astrocyte mGluR5 expression is developmentally regulated and confined in expression/function to the first weeks of life, with similar observations made in human control tissue. Herein, we demonstrate that mGluR5 expression and function dramatically increase in a mouse model of temporal lobe epilepsy (TLE). Interestingly, in both male and female mice, mGluR5 function persists in the astrocyte throughout the process of epileptogenesis following status epilepticus. However, mGluR5 expression and function is transient in animals that do not develop epilepsy over an equivalent time period, suggesting that patterns of mGluR5 expression may signify continuing epilepsy development or its resolution. We demonstrate that during epileptogenesis, astrocytes re-acquire mGluR5-dependent calcium transients following agonist application or synaptic glutamate release-a feature of astrocyte-neuron communication absent since early development. Finally, we find that the selective and conditional knockout of mGluR5 signaling from astrocytes during epilepsy development slows the rate of glutamate clearance through astrocyte glutamate transporters under high-frequency stimulation conditions, a feature that suggests astrocyte mGluR5 expression during epileptogenesis may recapitulate earlier developmental roles in regulating glutamate transporter function.SIGNIFICANCE STATEMENTIn development, astrocyte mGluR5 signaling plays a critical role in regulating structural and functional interactions between astrocytes and neurons at the tripartite synapse. Notably, mGluR5 signaling is a positive regulator of astrocyte glutamate transporter expression and function-an essential component of excitatory signaling regulation in hippocampus. After early development, astrocyte mGluR5 expression is downregulated, but re-emerges in animal models of TLE development and patient epilepsy samples. We explored the hypothesis that astrocyte mGluR5 re-emergence recapitulates earlier developmental roles during TLE acquisition. Our work demonstrates that astrocytes with mGluR5 signaling during TLE development perform faster glutamate uptake in hippocampus, revealing a previously unexplored role for astrocyte mGluR5 signaling in hypersynchronous pathology.

4.
Epilepsia ; 59(11): 2035-2048, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30328622

RESUMO

OBJECTIVE: Approximately 30% of patients with epilepsy are refractory to existing antiseizure drugs (ASDs). Given that the properties of the central nervous systems of these patients are likely to be altered due to their epilepsy, tissues from rodents that have undergone epileptogenesis might provide a therapeutically relevant disease substrate for identifying compounds capable of attenuating pharmacoresistant seizures. To facilitate the development of such a model, this study describes the effects of classical glutamate receptor antagonists and 20 ASDs on recurrent epileptiform discharges (REDs) in brain slices derived from the kainate-induced status epilepticus model of temporal lobe epilepsy (KA-rats). METHODS: Horizontal brain slices containing the medial entorhinal cortex (mEC) were prepared from KA-rats, and REDs were recorded from the superficial layers. 6-cyano-7-nitroquinoxaline-2,3-dione, (2R)-amino-5-phosphonovaleric acid, tetrodotoxin, or ASDs were bath applied for 20 minutes. Concentration-dependent effects and half maximal effective concentration values were determined for RED duration, frequency, and amplitude. RESULTS: ASDs targeting sodium and potassium channels (carbamazepine, eslicarbazepine, ezogabine, lamotrigine, lacosamide, phenytoin, and rufinamide) attenuated REDs at concentrations near their average therapeutic plasma concentrations. γ-aminobutyric acid (GABA)ergic synaptic transmission-modulating ASDs (clobazam, midazolam, phenobarbital, stiripentol, tiagabine, and vigabatrin) attenuated REDs only at higher concentrations and, in some cases, prolonged RED durations. ASDs with other/mixed mechanisms of action (bumetanide, ethosuximide, felbamate, gabapentin, levetiracetam, topiramate, and valproate) and glutamate receptor antagonists weakly or incompletely inhibited RED frequency, increased RED duration, or had no significant effects. SIGNIFICANCE: Taken together, these data suggest that epileptiform activity recorded from the superficial layers of the mEC in slices obtained from KA-rats is differentially sensitive to existing ASDs. The different sensitivities of REDs to these ASDs may reflect persistent molecular, cellular, and/or network-level changes resulting from disease. These data are expected to serve as a foundation upon which future therapeutics may be differentiated and assessed for potentially translatable efficacy in patients with refractory epilepsy.

5.
Epilepsy Behav ; 78: 302-312, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29097123

RESUMO

There is common agreement that many disorders of the central nervous system are 'complex', that is, there are many potential factors that influence the development of the disease, underlying mechanisms, and successful treatment. Most of these disorders, unfortunately, have no cure at the present time, and therapeutic strategies often have debilitating side effects. Interestingly, some of the 'complexities' of one disorder are found in another, and the similarities are often network defects. It seems likely that more discussions of these commonalities could advance our understanding and, therefore, have clinical implications or translational impact. With this in mind, the Fourth International Halifax Epilepsy Conference and Retreat was held as described in the prior paper, and this companion paper focuses on the second half of the meeting. Leaders in various subspecialties of epilepsy research were asked to address aging and dementia or psychosis in people with epilepsy (PWE). Commonalities between autism, depression, aging and dementia, psychosis, and epilepsy were the focus of the presentations and discussion. In the last session, additional experts commented on new conceptualization of translational epilepsy research efforts. Here, the presentations are reviewed, and salient points are highlighted.

6.
Epilepsy Curr ; 17(5): 293-298, 2017 Sep-Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29225544

RESUMO

Epilepsy is a chronic neurological disorder caused by abnormal changes in the functions of neuronal circuits and manifested by seizures. It affects patients of all age, substantially worsens the quality of life for the patients as well as their families, and imposes a huge economic burden on the healthcare system. Historically, efforts for discovering and developing antiseizure therapies have been focused on modulating the functions of receptors, transporters, and enzymes expressed by neurons. These drug development efforts have paid off, as we have over 25 antiseizure drugs available in the clinic. However, these drugs mainly provide symptomatic relief from seizures and often cause serious adverse effects. Importantly, almost one-third of patients with epilepsy do not have their seizures adequately controlled by available drugs. To address this problem, researchers are investigating cellular and molecular mechanisms fundamental to the optimal function of neuronal circuits. Evidence shows that disruptions in these mechanisms cause impairment in neuroglial interactions, uncontrolled inflammation, aberrant synaptogenesis, and neurodegeneration in genetic and acquired epilepsies. Many novel therapeutic targets have been identified to target these mechanisms for developing new antiseizure drugs. In addition, the field is exploring new drug targets which may impede the development of epilepsy. We have summarized some of these novel targets in this brief review.

7.
Neurobiol Dis ; 105: 221-234, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28624414

RESUMO

Memory deficits have a significant impact on the quality of life of patients with epilepsy and currently no effective treatments exist to mitigate this comorbidity. While these cognitive comorbidities can be associated with varying degrees of hippocampal cell death and hippocampal sclerosis, more subtle changes in hippocampal physiology independent of cell loss may underlie memory dysfunction in many epilepsy patients. Accordingly, animal models of epilepsy or epileptic processes exhibiting memory deficits in the absence of cell loss could facilitate novel therapy discovery. Mouse corneal kindling is a cost-effective and non-invasive model of focal to bilateral tonic-clonic seizures that may exhibit memory deficits in the absence of cell loss. Therefore, we tested the hypothesis that corneal kindled C57BL/6 mice exhibit spatial pattern processing and memory deficits in a task reliant on DG function and that these impairments would be concurrent with physiological remodeling of the DG as opposed to overt neuron loss. Following corneal kindling, C57BL/6 mice exhibited deficits in a DG-associated spatial memory test - the metric task. Compatible with this finding, we also discovered saturated, and subsequently impaired, LTP of excitatory synaptic transmission at the perforant path to DGC synapse. This saturation of LTP was consistent with evidence suggesting that perforant path to DGC synapses in kindled mice had previously experienced LTP-like changes to their synaptic weights: increased postsynaptic depolarizations in response to equivalent presynaptic input and significantly larger amplitude AMPA receptor mediated spontaneous EPSCs. Additionally, there was evidence for kindling-induced changes in the intrinsic excitability of DGCs: reduced threshold to population spikes under extracellular recording conditions and significantly increased membrane resistances observed in DGCs. Importantly, quantitative immunohistochemical analysis revealed hippocampal astrogliosis in the absence of overt neuron loss. These changes in spatial pattern processing and memory deficits in corneal kindled mice represent a novel model of seizure-induced cognitive dysfunction associated with pathophysiological remodeling of excitatory synaptic transmission and granule cell excitability in the absence of overt cell loss.


Assuntos
Giro Denteado/patologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Transtornos da Memória/etiologia , Neurônios/patologia , Convulsões/complicações , Convulsões/patologia , Animais , Aprendizagem por Associação , Biofísica , Morte Celular/fisiologia , Córnea/inervação , Modelos Animais de Doenças , Estimulação Elétrica , Proteína Glial Fibrilar Ácida/metabolismo , Gliose/etiologia , Técnicas In Vitro , Excitação Neurológica/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Técnicas de Patch-Clamp , Fosfopiruvato Hidratase/metabolismo , Sinapses/fisiologia
8.
Neurochem Res ; 42(7): 1939-1948, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28478594

RESUMO

Cannabidiol (CBD) is a cannabinoid component of marijuana that has no significant activity at cannabinoid receptors or psychoactive effects. There is considerable interest in CBD as a therapy for epilepsy. Almost a third of epilepsy patients are not adequately controlled by clinically available anti-seizure drugs (ASDs). Initial studies appear to demonstrate that CBD preparations may be a useful treatment for pharmacoresistant epilepsy. The National Institute of Neurological Disorders and Stroke (NINDS) funded Epilepsy Therapy Screening Program (ETSP) investigated CBD in a battery of seizure models using a refocused screening protocol aimed at identifying pharmacotherapies to address the unmet need in pharmacoresistant epilepsy. Applying this new screening workflow, CBD was investigated in mouse 6 Hz 44 mA, maximal electroshock (MES), corneal kindling models and rat MES and lamotrigine-resistant amygdala kindling models. Following intraperitoneal (i.p.) pretreatment, CBD produced dose-dependent protection in the acute seizure models; mouse 6 Hz 44 mA (ED50 164 mg/kg), mouse MES (ED50 83.5 mg/kg) and rat MES (ED50 88.9 mg/kg). In chronic models, CBD produced dose-dependent protection in the corneal kindled mouse (ED50 119 mg/kg) but CBD (up to 300 mg/kg) was not protective in the lamotrigine-resistant amygdala kindled rat. Motor impairment assessed in conjunction with the acute seizure models showed that CBD exerted seizure protection at non-impairing doses. The ETSP investigation demonstrates that CBD exhibits anti-seizure properties in acute seizure models and the corneal kindled mouse. However, further preclinical and clinical studies are needed to determine the potential for CBD to address the unmet needs in pharmacoresistant epilepsy.


Assuntos
Anticonvulsivantes/uso terapêutico , Canabidiol/uso terapêutico , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos/métodos , Epilepsia/tratamento farmacológico , Convulsões/tratamento farmacológico , Animais , Canabidiol/farmacologia , Relação Dose-Resposta a Droga , Eletrochoque/efeitos adversos , Epilepsia/induzido quimicamente , Epilepsia/fisiopatologia , Excitação Neurológica/efeitos dos fármacos , Excitação Neurológica/fisiologia , Lamotrigina , Masculino , Camundongos , Pentilenotetrazol/toxicidade , Ratos , Ratos Sprague-Dawley , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Triazinas/farmacologia , Triazinas/uso terapêutico
9.
eNeuro ; 4(2)2017 Mar-Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28497109

RESUMO

Central nervous system infection can induce epilepsy that is often refractory to established antiseizure drugs. Previous studies in the Theiler's murine encephalomyelitis virus (TMEV)-induced mouse model of limbic epilepsy have demonstrated the importance of inflammation, especially that mediated by tumor necrosis factor-α (TNFα), in the development of acute seizures. TNFα modulates glutamate receptor trafficking via TNF receptor 1 (TNFR1) to cause increased excitatory synaptic transmission. Therefore, we hypothesized that an increase in TNFα signaling after TMEV infection might contribute to acute seizures. We found a significant increase in both mRNA and protein levels of TNFα and the protein expression ratio of TNF receptors (TNFR1:TNFR2) in the hippocampus, a brain region most likely involved in seizure initiation, after TMEV infection, which suggests that TNFα signaling, predominantly through TNFR1, may contribute to limbic hyperexcitability. An increase in hippocampal cell-surface glutamate receptor expression was also observed during acute seizures. Although pharmacological inhibition of TNFR1-mediated signaling had no effect on acute seizures, several lines of genetically modified animals deficient in either TNFα or TNFRs had robust changes in seizure incidence and severity after TMEV infection. TNFR2-/- mice were highly susceptible to developing acute seizures, suggesting that TNFR2-mediated signaling may provide beneficial effects during the acute seizure period. Taken together, the present results suggest that inflammation in the hippocampus, caused predominantly by TNFα signaling, contributes to hyperexcitability and acute seizures after TMEV infection. Pharmacotherapies designed to suppress TNFR1-mediated or augment TNFR2-mediated effects of TNFα may provide antiseizure and disease-modifying effects after central nervous system infection.


Assuntos
Hipocampo/metabolismo , Convulsões/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Modelos Animais de Doenças , Epilepsia do Lobo Temporal/virologia , Hipocampo/virologia , Camundongos Endogâmicos C57BL , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Convulsões/patologia , Convulsões/virologia , Transdução de Sinais , Lobo Temporal/patologia , Theilovirus
10.
Neurochem Res ; 42(7): 1995-2010, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28508174

RESUMO

The series of experiments herein evaluated prototype drugs representing different mechanisms of antiseizure, antinociceptive or antidepressant action in a battery of preclinical pain models in adult male CF#1 mice (formalin, writhing, and tail flick) and Sprague Dawley rats partial sciatic nerve ligation (PSNL). In the formalin assay, phenytoin (PHT, 6 mg/kg), sodium valproate (VPA, 300 mg/kg), amitriptyline (AMI, 7.5 and 15 mg/kg), gabapentin (GBP, 30 and 70 mg/kg), tiagabine (TGB, 5 and 15 mg/kg), and acetominophen (APAP, 250 and 500 mg/kg) reduced both phases of the formalin response to ≤ 25% of vehicle-treated mice. In the acetic acid induced writhing assay, VPA (300 mg/kg), ethosuximide (ETX, 300 mg/kg), morphine (MOR, 5 & 10 mg/kg), GBP (10, 30, and 60 mg/kg), TGB (15 mg/kg), levetiracetam (LEV, 300 mg/kg), felbamate (FBM, 80 mg/kg) and APAP (250 mg/kg) reduced writhing to ≤ 25% of vehicle-treated mice. In the tail flick test, MOR (1.25-5 mg/kg), AMI (15 mg/kg) and TGB (5 mg/kg) demonstrated significant antinociceptive effects. Finally, carbamazepine (CBZ, 20 and 50 mg/kg), VPA, MOR (2 and 4 mg/kg), AMI (12 mg/kg), TPM (100 mg/kg), lamotrigine (LTG, 40 mg/kg), GBP (60 mg/kg), TGB (15 mg/kg), FBM (35 mg/kg), and APAP (250 mg/kg) were effective in the PSNL model. Thus, TGB was the only prototype compound with significant analgesic effects in each of the four models, while AMI, GBP, APAP, and MOR each improved three of the four pain phenotypes. This study highlights the importance evaluating novel targets in a variety of pain phenotypes.


Assuntos
Analgésicos/uso terapêutico , Anticonvulsivantes/uso terapêutico , Antidepressivos/uso terapêutico , Modelos Animais de Doenças , Neuralgia/tratamento farmacológico , Medição da Dor/efeitos dos fármacos , Analgésicos/farmacologia , Animais , Anticonvulsivantes/farmacologia , Antidepressivos/farmacologia , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos/métodos , Masculino , Camundongos , Neuralgia/patologia , Ácidos Nipecóticos/farmacologia , Ácidos Nipecóticos/uso terapêutico , Medição da Dor/métodos , Ratos , Ratos Sprague-Dawley , Roedores , Tiagabina
11.
Epilepsia ; 58(6): 1073-1084, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28449218

RESUMO

OBJECTIVE: The mouse 6 Hz model of psychomotor seizures is a well-established and commonly used preclinical model for antiseizure drug (ASD) discovery. Despite its widespread use both in the identification and differentiation of novel ASDs in mice, a corresponding assay in rats has not been developed. We established a method for 6 Hz seizure induction in rats, with seizure behaviors similar to those observed in mice including head nod, jaw clonus, and forelimb clonus. METHODS: A convulsive current that elicits these seizure behaviors in 97% of rats (CC97 ) was determined using a Probit analysis. Numerous prototype ASDs were evaluated in this model using stimulus intensities of 1.5× and 2× the CC97 , which is comparable to the approach used in the mouse 6 Hz seizure model (e.g., 32 and 44 mA stimulus intensities). The ASDs evaluated include carbamazepine, clobazam, clonazepam, eslicarbazepine, ethosuximide, ezogabine, gabapentin, lacosamide, lamotrigine, levetiracetam, phenobarbital, phenytoin, rufinamide, tiagabine, topiramate, and sodium valproate. Median effective dose (ED50 ) and median toxic (motor impairment) dose (TD50 ) values were obtained for each compound. RESULTS: Compounds that were effective at the 1.5 × CC97 stimulus intensity at protective index (PI) values >1 included clobazam, ethosuximide, ezogabine, levetiracetam, phenobarbital, and sodium valproate. Compounds that were effective at the 2 × CC97 stimulus intensity at PI values >1 included ezogabine, phenobarbital, and sodium valproate. SIGNIFICANCE: In a manner similar to the use of the mouse 6 Hz model, development of a rat 6 Hz test will aid in the differentiation of ASDs, as well as in study design and dose selection for chronic rat models of pharmacoresistant epilepsy. The limited number of established ASDs with demonstrable efficacy at the higher stimulus intensity suggests that, like the mouse 6 Hz 44 mA model, the rat 6 Hz seizure model may be a useful screening tool for pharmacoresistant seizures.


Assuntos
Anticonvulsivantes/uso terapêutico , Modelos Animais de Doenças , Descoberta de Drogas , Eletroencefalografia/efeitos dos fármacos , Epilepsias Parciais/tratamento farmacológico , Epilepsias Parciais/fisiopatologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Avaliação Pré-Clínica de Medicamentos , Estimulação Elétrica , Masculino , Camundongos , Ratos , Ratos Sprague-Dawley , Especificidade da Espécie , Resultado do Tratamento
12.
Neurochem Res ; 42(7): 1904-1918, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28303498

RESUMO

The successful identification of promising investigational therapies for the treatment of epilepsy can be credited to the use of numerous animal models of seizure and epilepsy for over 80 years. In this time, the maximal electroshock test in mice and rats, the subcutaneous pentylenetetrazol test in mice and rats, and more recently the 6 Hz assay in mice, have been utilized as primary models of electrically or chemically-evoked seizures in neurologically intact rodents. In addition, rodent kindling models, in which chronic network hyperexcitability has developed, have been used to identify new agents. It is clear that this traditional screening approach has greatly expanded the number of marketed drugs available to manage the symptomatic seizures associated with epilepsy. In spite of the numerous antiseizure drugs (ASDs) on the market today, the fact remains that nearly 30% of patients are resistant to these currently available medications. To address this unmet medical need, the National Institute of Neurological Disorders and Stroke (NINDS) Epilepsy Therapy Screening Program (ETSP) revised its approach to the early evaluation of investigational agents for the treatment of epilepsy in 2015 to include a focus on preclinical approaches to model pharmacoresistant seizures. This present report highlights the in vivo and in vitro findings associated with the initial pharmacological validation of this testing approach using a number of mechanistically diverse, commercially available antiseizure drugs, as well as several probe compounds that are of potential mechanistic interest to the clinical management of epilepsy.


Assuntos
Anticonvulsivantes/uso terapêutico , Avaliação Pré-Clínica de Medicamentos/normas , Epilepsia Resistente a Medicamentos/tratamento farmacológico , Animais , Avaliação Pré-Clínica de Medicamentos/métodos , Epilepsia Resistente a Medicamentos/induzido quimicamente , Epilepsia Resistente a Medicamentos/etiologia , Eletrochoque/efeitos adversos , Ácido Caínico/toxicidade , Excitação Neurológica/efeitos dos fármacos , Excitação Neurológica/fisiologia , Masculino , Camundongos , Técnicas de Cultura de Órgãos , Ratos , Ratos Sprague-Dawley
13.
Epilepsia ; 57(12): 1958-1967, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27739576

RESUMO

OBJECTIVE: Infection with Theiler's murine encephalomyelitis virus (TMEV) in C57Bl/6J mice induces acute seizures and development of spontaneous recurrent seizures and behavioral comorbidities weeks later. The present studies sought to determine whether acute therapeutic intervention with an anti-inflammatory-based approach could prevent or modify development of TMEV-induced long-term behavioral comorbidities. Valproic acid (VPA), in addition to its prototypical anticonvulsant properties, inhibits histone deacetylase (HDAC) activity, which may alter expression of the inflammasome. Minocycline (MIN) has previously demonstrated an antiseizure effect in the TMEV model via direct anti-inflammatory mechanisms, but the long-term effect of MIN treatment on the development of chronic behavioral comorbidities is unknown. METHODS: Mice infected with TMEV were acutely administered MIN (50 mg/kg, b.i.d. and q.d.) or VPA (100 mg/kg, q.d.) during the 7-day viral infection period. Animals were evaluated for acute seizure severity and subsequent development of chronic behavioral comorbidities and seizure threshold. RESULTS: Administration of VPA reduced the proportion of mice with seizures, delayed onset of symptomatic seizures, and reduced seizure burden during the acute infection. This was in contrast to the effects of administration of once-daily MIN, which did not affect the proportion of mice with seizures or delay onset of acute symptomatic seizures. However, VPA-treated mice were no different from vehicle (VEH)-treated mice in long-term behavioral outcomes, including open field activity and seizure threshold. Once-daily MIN treatment, despite no effect on the maximum observed Racine stage seizure severity, was associated with improved long-term behavioral outcomes and normalized seizure threshold. SIGNIFICANCE: Acute seizure control alone is insufficient to modify chronic disease comorbidities in the TMEV model. This work further supports the role of an inflammatory response in the development of chronic behavioral comorbidities and further highlights the utility of this platform for the development of mechanistically novel pharmacotherapies for epilepsy.


Assuntos
Anticonvulsivantes/uso terapêutico , Comportamento Animal/efeitos dos fármacos , Epilepsia do Lobo Temporal , Minociclina/uso terapêutico , Theilovirus/patogenicidade , Ácido Valproico/uso terapêutico , Animais , Transtornos de Ansiedade/tratamento farmacológico , Transtornos de Ansiedade/etiologia , Peso Corporal/efeitos dos fármacos , Distribuição de Qui-Quadrado , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Epilepsia do Lobo Temporal/tratamento farmacológico , Epilepsia do Lobo Temporal/etiologia , Epilepsia do Lobo Temporal/virologia , Comportamento Exploratório/efeitos dos fármacos , Camundongos , Atividade Motora/efeitos dos fármacos , Desempenho Psicomotor/efeitos dos fármacos , Teste de Desempenho do Rota-Rod
14.
Exp Neurol ; 280: 89-96, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27072529

RESUMO

Seizures occur due to an imbalance between excitation and inhibition, with the balance tipping towards excitation, and glutamate is the predominant excitatory neurotransmitter in the central nervous system of mammals. Since upregulation of expression and/or function of glutamate receptors can contribute to seizures we determined the effects of three antagonists, NBQX, GYKI-52466 and MK 801, of the various ionotropic glutamate receptors, AMPA, NMDA and KA, on acute seizure development in the Theiler's murine encephalomyelitis virus (TMEV)-induced seizure model. We found that only NBQX had an effect on acute seizure development, resulting in a significantly higher number of mice experiencing seizures, an increase in the number of seizures per mouse, a greater cumulative seizure score per mouse and a significantly higher mortality rate among the mice. Although NBQX has previously been shown to be a potent anticonvulsant in animal seizure models, seizures induced by electrical stimulation, drug administration or as a result of genetic predisposition may differ greatly in terms of mechanism of seizure development from our virus-induced seizure model, which could explain the opposite, proconvulsant effect of NBQX observed in the TMEV-induced seizure model.


Assuntos
Antagonistas de Aminoácidos Excitatórios/toxicidade , Infecções por Picornaviridae/complicações , Quinoxalinas/toxicidade , Convulsões , Análise de Variância , Animais , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Lectinas de Plantas/metabolismo , Convulsões/etiologia , Convulsões/mortalidade , Convulsões/virologia
15.
J Neuropathol Exp Neurol ; 75(4): 366-78, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26945036

RESUMO

It is estimated that 30%-40% of epilepsy patients are refractory to therapy and animal models are useful for the identification of more efficacious therapeutic agents. Various well-characterized syndrome-specific models are needed to assess their relevance to human seizure disorders and their validity for testing potential therapies. The corneal kindled mouse model of temporal lobe epilepsy (TLE) allows for the rapid screening of investigational compounds, but there is a lack of information as to the specific inflammatory pathology in this model. Similarly, the Theiler murine encephalomyelitis virus (TMEV) model of TLE may prove to be useful for screening, but quantitative assessment of hippocampal pathology is also lacking. We used immunohistochemistry to characterize and quantitate acute neuronal injury and inflammatory features in dorsal CA1 and dentate gyrus regions and in the directly overlying posterior parietal cortex at 2 time points in each of these TLE models. Corneal kindled mice were observed to have astrogliosis, but not microgliosis or neuron cell death. In contrast, TMEV-injected mice had astrogliosis, microgliosis, neuron death, and astrocyte and microglial proliferation. Our results suggest that these 2 animal models might be appropriate for evaluation of distinct therapies for TLE.


Assuntos
Proliferação de Células/fisiologia , Modelos Animais de Doenças , Epilepsia do Lobo Temporal/complicações , Gliose/etiologia , Neuroglia/patologia , Neurônios/patologia , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Infecções por Cardiovirus/complicações , Epilepsia do Lobo Temporal/patologia , Epilepsia do Lobo Temporal/virologia , Fluoresceínas/metabolismo , Antígeno Ki-67/metabolismo , Excitação Neurológica/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Proteínas dos Microfilamentos/metabolismo , Microscopia Confocal , Proteínas do Tecido Nervoso/metabolismo , Theilovirus/patogenicidade
16.
Exp Neurol ; 279: 116-126, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26896834

RESUMO

More efficient or translationally relevant approaches are needed to model acquired temporal lobe epilepsy (TLE) in genetically tractable mice. The high costs associated with breeding and maintaining transgenic, knock-in, or knock-out lines place a high value on the efficiency of induction and animal survivability. Herein, we describe our approaches to model acquired epilepsy in C57BL/6J mice using repeated, low-dose kainate (KA) administration paradigms. Four paradigms (i.p.) were tested for their ability to induce status epilepticus (SE), temporal lobe pathology, and the development of epilepsy. All four paradigms reliably induce behavioral and/or electrographic SE without mortality over a 7d period. Two of the four paradigms investigated produce features indicative of TLE pathology, including hippocampal cell death, widespread astrogliosis, and astrocyte expression of mGluR5, a feature commonly reported in TLE models. Three of the investigated paradigms were able to produce aberrant electrographic features, such as interictal spiking in cortex. However, only one paradigm, previously published by others, produces spontaneous recurrent seizures over an eight week period. Presentation of spontaneous seizures is rare (N=2/14), with epilepsy preferentially developing in animals having a high number of seizures during SE. Overall, repeated, low-dose KA administration improves the efficiency and pathological relevance of a systemic KA insult, but does not produce a robust epilepsy phenotype under the experimental paradigms described herein.


Assuntos
Epilepsia do Lobo Temporal/induzido quimicamente , Epilepsia do Lobo Temporal/patologia , Agonistas de Aminoácidos Excitatórios/toxicidade , Ácido Caínico/toxicidade , Animais , Astrócitos/patologia , Morte Celular/efeitos dos fármacos , Modelos Animais de Doenças , Eletroencefalografia , Proteína Glial Fibrilar Ácida/metabolismo , Gliose/induzido quimicamente , Gliose/patologia , Hipocampo/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Receptor de Glutamato Metabotrópico 5/biossíntese , Convulsões/induzido quimicamente , Estado Epiléptico/induzido quimicamente , Estado Epiléptico/patologia
17.
Epilepsy Behav ; 49: 17-9, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26219575

RESUMO

Temporal lobe epilepsy (TLE) is a devastating seizure disorder that is often caused by status epilepticus (SE). Temporal lobe epilepsy can be very difficult to control with currently available antiseizure drugs, and there are currently no disease-modifying therapies that can prevent the development of TLE in those patients who are at risk. While the functional changes that occur in neurons following SE and leading to TLE have been well studied, only recently has research attention turned to the role in epileptogenesis of astrocytes, the other major cell type of the brain. Given that epilepsy is a neural circuit disorder, innovative ways to evaluate the contributions that both neurons and astrocytes make to aberrant circuit activity will be critical for the understanding of the emergent network properties that result in seizures. Recently described approaches using genetically encoded calcium-indicating proteins can be used to image dynamic calcium transients, a marker of activity in both neurons and glial cells. It is anticipated that this work will lead to novel insights into the process of epileptogenesis at the network level and may identify disease-modifying therapeutic targets that have been missed because of a largely neurocentric view of seizure generation following SE. This article is part of a Special Issue entitled "Status Epilepticus".


Assuntos
Astrócitos/patologia , Encéfalo/patologia , Epilepsia do Lobo Temporal/patologia , Neurônios/patologia , Estado Epiléptico/patologia , Animais , Encéfalo/fisiopatologia , Forma Celular/fisiologia , Modelos Animais de Doenças , Epilepsia do Lobo Temporal/fisiopatologia , Humanos , Estado Epiléptico/fisiopatologia
18.
Exp Neurol ; 271: 329-34, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26079647

RESUMO

Temporal lobe epilepsy (TLE) is the most common form of acquired epilepsy that can be caused by several inciting events including viral infections. However, one-third of TLE patients are pharmacoresistant to current antiepileptic drugs and therefore, there is an urgent need to develop antiepileptogenic therapies that prevent the development of the disease. Oxidative stress and redox alterations have recently been recognized as important etiological factors contributing to seizure-induced neuronal damage. The goal of this study was to determine if oxidative stress occurs in the TMEV (Theiler's murine encephalomyelitis virus) model of temporal lobe epilepsy (TLE). C57Bl/6 mice were injected with TMEV or with PBS intracortically and observed for acute seizures. At various time points after TMEV injection, hippocampi were analyzed for levels of reduced glutathione (GSH), oxidized glutathione (GSSG) and 3-nitrotyrosine (3 NT). Mice infected with TMEV displayed behavioral seizures between days 3 and 7 days post-infection (dpi). The intensity of seizures increased over time with most of the seizures being a stage 4 or 5 on the Racine scale at 6 days p.i. Mice exhibiting at least one seizure during the observation period were utilized for the biochemical analyses. The levels of GSH were significantly depleted in TMEV infected mice at 3, 4 and 14 days p.i. with a concomitant increase in GSSH levels as well as an impairment of the redox status. Additionally, there was a substantial increase in 3 NT levels in TMEV infected mice at these time points. These redox changes correlated with the occurrence of acute seizures in this model. Interestingly, we did not see changes in any of the indices in the cerebellum of TMEV-infected mice at 3 dpi indicating that these alterations are localized to the hippocampus and perhaps other limbic regions. This is the first study to demonstrate the occurrence of oxidative stress in the TMEV model of infection-induced TLE. The redox alterations were observed at time points coinciding with the appearance of acute behavioral seizures suggesting that these changes might be a consequence of seizure activity. Our results support the hypothesis that redox changes correlate with seizure activity in acquired epilepsies, regardless of the inciting insults, and suggest oxidative stress as a potential therapeutic target for their treatment.


Assuntos
Epilepsia do Lobo Temporal/etiologia , Epilepsia do Lobo Temporal/virologia , Estresse Oxidativo/fisiologia , Theilovirus/patogenicidade , Análise de Variância , Animais , Cromatografia Líquida de Alta Pressão , Modelos Animais de Doenças , Eletroencefalografia , Glutationa/metabolismo , Dissulfeto de Glutationa/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Tirosina/análogos & derivados , Tirosina/metabolismo
19.
Front Mol Neurosci ; 8: 10, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25926768

RESUMO

Complex interactions between networks of astrocytes and neurons are beginning to be appreciated, but remain poorly understood. Transgenic mice expressing fluorescent protein reporters of cellular activity, such as the GCaMP family of genetically encoded calcium indicators (GECIs), have been used to explore network behavior. However, in some cases, it may be desirable to use long-established rat models that closely mimic particular aspects of human conditions such as Parkinson's disease and the development of epilepsy following status epilepticus. Methods for expressing reporter proteins in the rat brain are relatively limited. Transgenic rat technologies exist but are fairly immature. Viral-mediated expression is robust but unstable, requires invasive injections, and only works well for fairly small genes (<5 kb). In utero electroporation (IUE) offers a valuable alternative. IUE is a proven method for transfecting populations of astrocytes and neurons in the rat brain without the strict limitations on transgene size. We built a toolset of IUE plasmids carrying GCaMP variants 3, 6s, or 6f driven by CAG and targeted to the cytosol or the plasma membrane. Because low baseline fluorescence of GCaMP can hinder identification of transfected cells, we included the option of co-expressing a cytosolic tdTomato protein. A binary system consisting of a plasmid carrying a piggyBac inverted terminal repeat (ITR)-flanked CAG-GCaMP-IRES-tdTomato cassette and a separate plasmid encoding for expression of piggyBac transposase was employed to stably express GCaMP and tdTomato. The plasmids were co-electroporated on embryonic days 13.5-14.5 and astrocytic and neuronal activity was subsequently imaged in acute or cultured brain slices prepared from the cortex or hippocampus. Large spontaneous transients were detected in slices obtained from rats of varying ages up to 127 days. In this report, we demonstrate the utility of this toolset for interrogating astrocytic and neuronal activity in the rat brain.

20.
J Pharmacol Exp Ther ; 353(2): 318-29, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25755209

RESUMO

Central nervous system infections can underlie the development of epilepsy, and Theiler's murine encephalomyelitis virus (TMEV) infection in C57BL/6J mice provides a novel model of infection-induced epilepsy. Approximately 50-65% of infected mice develop acute, handling-induced seizures during the infection. Brains display acute neuropathology, and a high number of mice develop spontaneous, recurrent seizures and behavioral comorbidities weeks later. This study characterized the utility of this model for drug testing by assessing whether antiseizure drug treatment during the acute infection period attenuates handling-induced seizures, and whether such treatment modifies associated comorbidities. Male C57BL/6J mice infected with TMEV received twice-daily valproic acid (VPA; 200 mg/kg), carbamazepine (CBZ; 20 mg/kg), or vehicle during the infection (days 0-7). Mice were assessed twice daily during the infection period for handling-induced seizures. Relative to vehicle-treated mice, more CBZ-treated mice presented with acute seizures; VPA conferred no change. In mice displaying seizures, VPA, but not CBZ, reduced seizure burden. Animals were then randomly assigned to acute and long-term follow-up. VPA was associated with significant elevations in acute (day 8) glial fibrillary acidic protein (astrocytes) immunoreactivity, but did not affect NeuN (neurons) immunoreactivity. Additionally, VPA-treated mice showed improved motor performance 15 days postinfection (DPI). At 36 DPI, CBZ-treated mice traveled significantly less distance through the center of an open field, indicative of anxiety-like behavior. CBZ-treated mice also presented with significant astrogliosis 36 DPI. Neither CBZ nor VPA prevented long-term reductions in NeuN immunoreactivity. The TMEV model thus provides an etiologically relevant platform to evaluate potential treatments for acute seizures and disease modification.


Assuntos
Anticonvulsivantes/farmacologia , Comportamento Animal/efeitos dos fármacos , Carbamazepina/farmacologia , Epilepsia do Lobo Temporal/tratamento farmacológico , Epilepsia do Lobo Temporal/etiologia , Theilovirus/fisiologia , Ácido Valproico/farmacologia , Animais , Anticonvulsivantes/efeitos adversos , Anticonvulsivantes/uso terapêutico , Ansiedade/induzido quimicamente , Carbamazepina/efeitos adversos , Carbamazepina/uso terapêutico , Infecções por Cardiovirus/complicações , Comorbidade , Modelos Animais de Doenças , Epilepsia do Lobo Temporal/complicações , Epilepsia do Lobo Temporal/virologia , Proteína Glial Fibrilar Ácida , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Teste de Desempenho do Rota-Rod , Theilovirus/efeitos dos fármacos , Fatores de Tempo , Ácido Valproico/efeitos adversos , Ácido Valproico/uso terapêutico
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