Genetic Model Of Absence Epilepsy Research Articles

Sensory coding is impaired in rat absence epilepsy.

Absence epilepsy is characterized by the occurrence of spike-and-wave discharges concomitant with an alteration of consciousness and is associated with cognitive comorbidities. In a genetic model of absence epilepsy in the rat, the genetic absence epilepsy rat from Strasbourg (GAERS), spike-and-wave discharges are shown to be initiated in the barrel field primary somatosensory cortex that codes whisker-related information, therefore playing an essential role in the interactions of rodents with their environment. Sensory-information processing is impaired in the epileptic barrel field primary somatosensory cortex of GAERS, with a delayed sensory-evoked potential and a duplicated neuronal response to whisker stimulation in in vivo extracellular recordings. Yet, GAERS present no defaults of performance in a texture discrimination task, suggesting the existence of a compensatory mechanism within the epileptic neuronal network. The results of the present study indicate that physiological primary functions are processed differently in an epileptic cortical network. Several neurodevelopmental pathologies are associated with disorganized cortical circuits that may alter primary functions such as sensory processes. In the present study, we investigated whether the function of a cortical area is altered in the seizure onset zone of absence epilepsy, a prototypical form of childhood genetic epilepsy associated with cognitive impairments. We first combined in vivo multichannel electrophysiological recordings and histology to precisely localize the seizure onset zone in the genetic absence epilepsy rat from Strasbourg (GAERS). We then investigated the functionality of this epileptic zone using extracellular silicon probe recordings of sensory-evoked local field potentials and multi-unit activity, as well as a behavioural test of texture discrimination. We show that seizures in this model are initiated in the barrel field part of the primary somatosensory cortex and are associated with high-frequency oscillations. In this cortex, we found an increased density of parvalbumin-expressing interneurons in layer 5 in GAERS compared to non-epileptic Wistar rats. Its functional investigation revealed that sensory abilities of GAERS are not affected in a texture-discrimination task, whereas the intracortical processing of sensory-evoked information is delayed and duplicated. Altogether, these results suggest that absence seizures are associated with an increase of parvalbumin-inhibitory neurons, which may promote the functional relationship between epileptic oscillations and high-frequency activities. Our findings suggest that cortical circuits operate differently in the epileptic onset zone and may adapt to maintain their ability to process highly specialized information.

Cortical expression of AMPA receptors during postnatal development in a genetic model of absence epilepsy

Childhood absence epilepsy has been associated with poor academic performance, behavioural difficulties, as well as increased risk of physical injury in some affected children. The frequent episodes of ‘absence’ arise from corticothalamocortical network dysfunction, with multifactorial mechanisms potentially involved in genetically different patients. Aberrations in glutamatergic neurotransmission has been implicated in some seizure models, and we have recently reported that reduced cortical AMPA receptor (AMPAR) expression (predominantly GluA4- containing AMPARs) in parvalbumin-containing (PV+) inhibitory interneurons, could underlie seizure generation in the stargazer mutant mouse. In the present study, we investigate AMPA receptor subunit changes occurring during postnatal development in the stargazer mouse, to determine when these changes occur relative to seizure onset and thus could be contributory to seizure generation. Using quantitative western blotting, we analysed the expression of AMPAR GluA1-4 subunits in the somatosensory cortex at three critical time points; two before seizure onset (postnatal days (PN) 7–9 and 13–15), and one at seizure onset (PN17–18) in stargazers. We report that compared to their non-epileptic littermates, in the stargazer somatosensory cortex, there was a significant reduction in expression of AMPARs containing GluA1, 3 and 4 subunits prior to seizure onset, whereas reduction in expression of GluA2-AMPARs appears to be a post-seizure event. Thus, while loss of GluA4-containing AMPARs (likely GluA1/4 and GluA3/4) may be linked to seizure induction, the loss of GluA2-containing AMPARs is a secondary post-seizure mechanism, which is most likely involved in seizure maintenance.

Neuropeptide Y affects thalamic reticular nucleus neuronal firing and network synchronization associated with suppression of spike-wave discharges.

Neuropeptide Y (NPY) potently suppresses spike-wave discharges (SWDs) in a genetic rat model of absence epilepsy (GAERS), but the underlying neurophysiologic mechanisms are not clear. We therefore sought to determine the in vivo effects of NPY on neuronal firing in the cortico-thalamo-cortical network activity, known to play a critical role in the generation of SWDs in these rats. NPY was administered intracerebroventricularly (ICV) or in separate experiments locally on the neurons of caudal thalamic reticular nucleus (NRT) by use of juxtacellular iontophoresis in triple-barrel electrodes in male GAERS aged 12-15 weeks, in vivo under neuroleptic anesthesia. Drug infusions and electroencephalography (EEG) monitoring were performed simultaneously with juxtacellular single neuronal recordings. Effect of NPY on electrically induced SWD induction threshold were also measured. NPY administration ICV led to a decrease in the total length of SWDs in EEG recordings. Both ICV administration and iontophoresis of NPY on NRT neurons led to an increase in interictal neuronal firing of NRT neurons. During ictal periods, ICV NPY administration reduced the number of thalamic action potentials per SWDs, as well as reduced waveform correlations between field potentials within the NRT and the cortical EEG. NPY administration ICV did not significantly alter the firing patterns of relay thalamic neurons interictally and cortical neurons during ictal and interictal periods. In addition, SWD induction threshold in the S2 region of the cortex was significantly increased after NPY administration. Our results show alterations in cortico-thalamo-cortical local and network properties following ICV administration of NPY, suggesting mechanisms of SWD suppression in GAERS. Cellular and network alteration of NRT activity, resulting from a direct action of NPY, may be a contributor to this effect.

Alterations in hippocampal and cortical densities of functionally different interneurons in rat models of absence epilepsy

Recent data from absence epileptic patients and animal models provide evidence for significant impairments of attention, memory, and psychosocial functioning. Here, we outline aspects of the electrophysiological and structural background of these dysfunctions by investigating changes in hippocampal and cortical GABAergic inhibitory interneurons in two genetically absence epileptic rat strains: the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) and the Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. Using simultaneously recorded field potentials from the primary somatosensory cortex (S1 cortex, seizure focus) and the hippocampal hilus, we demonstrated that typical frequencies of spike-wave discharges (SWDs; 7–8 Hz, GAERS; 7–9 Hz, WAG/Rij) and their harmonics appeared and their EEG spectral power markedly increased on recordings not only from the S1 cortex, but also from the hilus in both GAERS and WAG/Rij rats during SWDs. Moreover, we observed an increased synchronization between S1 cortex and hilus at 7–8 Hz (GAERS) and 7–9 Hz (WAG/Rij) and at their harmonics when SWDs occurred in the S1 cortex in both rat strains. In addition, using immunohistochemistry we demonstrated changes in the densities of perisomatic (parvalbumin-immunopositive, PV+) and interneuron-selective (calretinin-immunopositive, CR+) GABAergic inhibitory interneuron somata. Specifically, GAERS and WAG/Rij rats displayed lower densities of PV-immunopositivity in the hippocampal hilus compared to non-epileptic control (NEC) and normal Wistar rats. GAERS and WAG/Rij rats also show a marked reduction in the density of CR + interneurons in the same region in comparison with NEC rats. Data from the S1 cortex reveals bidirectional differences in PV + density, with GAERS displaying a significant increase, whereas WAG/Rij a reduction compared to control rat strains. Our results suggest an enhanced synchronization and functional connections between the hippocampus and S1 cortex as well as thalamocortical activities during SWDs and a functional alteration of inhibitory mechanisms in the hippocampus and S1 cortex of two genetic models of absence epilepsy, presumably in relation with increased neuronal activity and seizure-induced neuronal injury.

Maternal care exerts disease-modifying effects on genetic absence epilepsy and comorbid depression.

WAG/Rij rats, a genetic animal model of absence epilepsy with comorbidity of depression, exhibit behavioral depression-like symptoms and spontaneous generalized spike-wave discharges (SWDs) in the EEG at the age of 6 to 8 months. The aim of the present study was to test the hypothesis that maternal care is an environmental factor which, along with genetic predisposition, may contribute to the expression of absence seizures and depression-like comorbidity later in life. To achieve this, a cross-fostering procedure was used. EEG and behavior in the forced swimming test were analyzed in WAG/Rij and Wistar offspring reared by their own mothers (non-cross-fostered), foster mothers of the same strain (in-fostered) or another strain (cross-fostered) at the age of 7 to 8 months. Maternal care and forced swimming test behavior were assessed in the dams. WAG/Rij mothers showed depression-like behavior and reduced maternal care irrespective of litter size and litter composition (own or foster pups) compared with Wistar dams. WAG/Rij offspring reared by Wistar dams with a high level of maternal care exhibited less and shorter SWDs and reduced depression-like comorbidity in adulthood compared with age-matched WAG/Rij offspring reared by their own or foster WAG/Rij mothers with a low level of maternal care. Moreover, rearing by Wistar mothers delayed the onset of absence epilepsy in WAG/Rij rats. Adoption by WAG/Rij dams did not change EEG and behavior in Wistar rats. Our study demonstrates that improvement of early care-giving environment can be used as a disease-modifying treatment to counteract epileptogenesis and behavioral comorbidities in genetic absence epilepsy.

Fingolimod Exerts only Temporary Antiepileptogenic Effects but Longer-Lasting Positive Effects on Behavior in the WAG/Rij Rat Absence Epilepsy Model.

One of the major challenges in the epilepsy field is identifying disease-modifying drugs in order to prevent or delay spontaneous recurrent seizure onset or to cure already established epilepsy. It has been recently reported that fingolimod, currently approved for the treatment of relapsing-remitting multiple sclerosis, has demonstrated antiepileptogenic effects in 2 different preclinical models of acquired epilepsy. However, to date, no data exist regarding the role of fingolimod against genetic epilepsy. Therefore, we have addressed this issue by studying the effects of fingolimod in Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats, a well-established genetic model of absence epilepsy, epileptogenesis, and neuropsychiatric comorbidity. Our results have demonstrated that an early long-term treatment with fingolimod (1mg/kg/day), started before absence seizure onset, has both antiepileptogenic and antidepressant-like effects in WAG/Rij rats. However, these effects were transitory, as 5months after treatment discontinuation, both absence seizure and depressive like-behavior returned to control levels. Furthermore, a temporary reduction of mTOR signaling pathway activity, indicated by reduced phosphorylated mammalian target of rapamycin and phosphorylated p70S6k levels, and by increased phosphorylated Akt in WAG/Rij rats of 6months of age accompanied the transitory antiepileptogenic effects of fingolimod. Surprisingly, fingolimod has demonstrated longer-lasting positive effects on cognitive decline in this strain. This effect was accompanied by an increased acetylation of lysine 8 of histone H4 (at both 6 and 10months of age). In conclusion, our results support the antiepileptogenic effects of fingolimod. However, the antiepileptogenic effects were transitory. Moreover, fingolimod might also have a positive impact on animal behavior and particularly in protecting the development of memory decline.

Developmental changes in Notch1 and NLE1 expression in a genetic model of absence epilepsy.

Childhood absence epilepsy (CAE) is an epilepsy syndrome with seizures occurring in the early childhood, highlighting that seizures susceptibility in CAE is dependent on brain development. The Notch 1 signalling pathway is important in brain development, yet the role of the Notch1 signalling pathway in CAE remains elusive. We here explored Notch1 and its modulator notchless homologue 1 (NLE1) expression in WAG/Rij and control rats using immunohistochemistry. Functional Notch 1 effects were assessed in WAG/Rij rats in vivo. WAG/Rij rats lack the developmental increase in cortical Notch1 and NLE 1 mRNA expression seen in controls, and Notch 1 and NLE1 mRNA and protein expression were lower in somatosensory cortices of WAG/Rij rats when compared to controls. This coincided with an overall decreased cortical GFAP expression in the early development in WAG/Rij rats. These effects were region-specific as they were not observed in thalamic tissues. Neuron-to-glia ratio as a marker of the impact of Notch signalling on differentiation was higher in layer 4 of somatosensory cortex of WAG/Rij rats. Acute application of Notch 1 agonist Jagged 1 suppressed, whereas DAPT, a Notch antagonist, facilitated spike and wave discharges (SWDs) in WAG/Rij rats. These findings point to Notch1 as an important signalling pathway in CAE which likely shapes architectural organization of the somatosensory cortex, a region critically involved in developmental epileptogenesis in CAE. More immediate effects of Notch 1 signalling are seen on in vivo SWDs in CAE, pointing to the Notch 1 pathway as a possible treatment target in CAE.

Bidirectional Control of Generalized Epilepsy Networks via Rapid Real-Time Switching of Firing Mode

Thalamic relay neurons have well-characterized dual firing modes: bursting and tonic spiking. Studies in brain slices have led to a model in which rhythmic synchronized spiking (phasic firing) in a population ofrelay neurons leads to hyper-synchronous oscillatory cortico-thalamo-cortical rhythms that result in absence seizures. This model suggests that blocking thalamocortical phasic firing would treat absence seizures. However, recent invivo studies in anesthetized animals have questioned this simple model. Here we resolve this issue by developing a real-time, mode-switching approach to drive thalamocortical neurons into or out of a phasic firing mode in two freely behaving genetic rodent models of absence epilepsy. Toggling between phasic and tonic firing in thalamocortical neurons launched and aborted absence seizures, respectively. Thus, a synchronous thalamocortical phasic firing state is required for absence seizures, and switching to tonic firing rapidly halts absences. This approach should be useful for modulating other networks that have mode-dependent behaviors.

The Anticonvulsant Activity of a Flavonoid-Rich Extract from Orange Juice Involves both NMDA and GABA-Benzodiazepine Receptor Complexes.

The usage of dietary supplements and other natural products to treat neurological diseases has been growing over time, and accumulating evidence suggests that flavonoids possess anticonvulsant properties. The aim of this study was to examine the effects of a flavonoid-rich extract from orange juice (OJe) in some rodent models of epilepsy and to explore its possible mechanism of action. The genetically audiogenic seizures (AGS)-susceptible DBA/2 mouse, the pentylenetetrazole (PTZ)-induced seizures in ICR-CD1 mice and the WAG/Rij rat as a genetic model of absence epilepsy with comorbidity of depression were used. Our results demonstrate that OJe was able to exert anticonvulsant effects on AGS-sensible DBA/2 mice and to inhibit PTZ-induced tonic seizures, increasing their latency. Conversely, it did not have anti-absence effects on WAG/Rij rats. Our experimental findings suggest that the anti-convulsant effects of OJe are likely mediated by both an inhibition of NMDA receptors at the glycine-binding site and an agonistic activity on benzodiazepine-binding site at GABAA receptors. This study provides evidences for the antiepileptic activity of OJe, and its results could be used as scientific basis for further researches aimed to develop novel complementary therapy for the treatment of epilepsy in a context of a multitarget pharmacological strategy.

Integrative properties and transfer function of cortical neurons initiating absence seizures in a rat genetic model.

Absence seizures are accompanied by spike-and-wave discharges in cortical electroencephalograms. These complex paroxysmal activities, affecting the thalamocortical networks, profoundly alter cognitive performances and preclude conscious perception. Here, using a well-recognized genetic model of absence epilepsy, we investigated in vivo how information processing was impaired in the ictogenic neurons, i.e. the population of cortical neurons responsible for seizure initiation. In between seizures, ictogenic neurons were more prone to generate bursting activity and their firing response to weak depolarizing events was considerably facilitated compared to control neurons. In the course of seizures, information processing became unstable in ictogenic cells, alternating between an increased and a decreased responsiveness to excitatory inputs, depending on the spike and wave patterns. The state-dependent modulation in the excitability of ictogenic neurons affects their inter-seizure transfer function and their time-to-time responsiveness to incoming inputs during absences. Epileptic seizures result from aberrant cellular and/or synaptic properties that can alter the capacity of neurons to integrate and relay information. During absence seizures, spike-and-wave discharges (SWDs) interfere with incoming sensory inputs and preclude conscious experience. The Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well-established animal model of absence epilepsy, allows exploration of the cellular basis of this impaired information processing. Here, by combining in vivo electrocorticographic and intracellular recordings from GAERS and control animals, we investigated how the pro-ictogenic properties of seizure-initiating cortical neurons modify their integrative properties and input-output operation during inter-ictal periods and during the spike (S-) and wave (W-) cortical patterns alternating during seizures. In addition to a sustained depolarization and an excessive firing rate in between seizures, ictogenic neurons exhibited a pronounced hyperpolarization-activated depolarization compared to homotypic control neurons. Firing frequency versus injected current relations indicated an increased sensitivity of GAERS cells to weak excitatory inputs, without modifications in the trial-to-trial variability of current-induced firing. During SWDs, the W-component resulted in paradoxical effects in ictogenic neurons, associating an increased membrane input resistance with a reduction in the current-evoked firing responses. Conversely, the collapse of cell membrane resistance during the S-component was accompanied by an elevated current-evoked firing relative to W-sequences, which remained, however, lower compared to inter-ictal periods. These findings show a dynamic modulation of ictogenic neurons' intrinsic properties that may alter inter-seizure cortical function and participate in compromising information processing in cortical networks during absences.

Increased inhibitory synaptic activity in the hippocampus (CA1) of genetic absence epilepsy rats: Relevance of kindling resistance

PurposeGenetic absence epilepsy rats from Strasbourg (GAERS), a well-validated genetic rat model for typical absence epilepsy, are known to manifest a resistance to secondary generalization of abnormal focal electrical activity evoked by kindling. The mechanism of this resistance is still unclear. In order to understand the possible mechanism of kindling resistance, we investigated for the first time, the differences of short-term synaptic plasticity by using a paired-pulse paradigm as an indicator of GABAergic activity in CA1 region of hippocampus in GAERS and non-epileptic Wistar rats in-vivo. MethodsRats were subjected to kindling process, basolateral amygdala was stimulated twice a day, with a supra-threshold current, until they displayed limbic or convulsive seizures. One hour after the last kindling stimulation, evoked field potentials from CA1 pyramidal layer of hippocampus were recorded in-vivo under urethane anesthesia. ResultsIn response to supra-threshold kindling stimulations GAERS showed a significantly delayed kindling progression and displayed a significant increase in hippocampal excitability at early stages of kindling that is the critical for the development of convulsive seizures. In control rats that were not received kindling stimulation, paired-pulse depression (PPD) was significantly pronounced in GAERS with respect to the Wistar group. During the kindling course, PPD was gradually reduced in the Wistar rats as kindling progression was advanced. However in GAERS, PPD ratios were not significantly changed at early stages of kindling. When GAERS reached convulsive stage, their PPD ratios became similar to that of Wistar rats. DiscussionThe increased inhibition in paired-pulse responses at early stages of kindling in GAERS suggests the role of augmented GABAergic activity as one of the underlying mechanisms of kindling resistance observed in genetic rat models of absence epilepsy.

Comparing glutamatergic neuron population in the mediodorsal thalamic nucleus of genetic absence epilepsy rats from strasbourg (GAERS) and normal control Wistar rats

An imbalance between GABAergic inhibition and glutamatergic excitation is suspected to play a role in the genesis of epileptic processes. In the present study we quantified the number of glutamate+ve neurons in the mediodorsal thalamic nucleus (MD) of genetic absence epilepsy rats from Strasbourg (GAERS) and compared these with values for normal Wistar rats.The MD thalamic nucleus was removed from each animal and the glutamatergic neurons were labelled using light-microscopy glutamate immunohistochemistry. The disector method was used to quantify the glutamate+ve neurons in the MD thalamic nucleus of GAERS and Wistar rats. The data were statistically analyzed.In the Wistar animals glutamate+ve neurons formed 89% and in GAERS 92.3% of the total neurons in 1000μm3 of MD thalamic nucleus. In GAERS glutamate+ve neurons showed statistically significant increase in the MD thalamic nucleus compared to Wistar animals. In Wistar animals the glutamate−ve neurons formed 11% and in GAERS 7.7% of the total neurons in 1000μm3 of MD thalamic. No significant difference was observed in glutamate−ve neurons between the two strains. The average diameter of glutamate+ve neurons showed no significance, while glutamate−ve neurons were significant between the two strains.The results of the present study, on genetic absence epilepsy model, GAERS, confirms the role of MD thalamic nucleus in chemically induced absence epilepsy.

Environmental enrichment imparts disease-modifying and transgenerational effects on genetically-determined epilepsy and anxiety

IntroductionThe absence epilepsies are presumed to be caused by genetic factors, but the influence of environmental exposures on epilepsy development and severity, and whether this influence is transmitted to subsequent generations, is not well known. We assessed the effects of environmental enrichment on epilepsy and anxiety outcomes in multiple generations of GAERS – a genetic rat model of absence epilepsy that manifests comorbid elevated anxiety-like behaviour. MethodsGAERS were exposed to environmental enrichment or standard housing beginning either prior to, or after epilepsy onset, and underwent EEG recordings and anxiety testing. Then, we exposed male GAERS to early enrichment or standard housing and generated F1 progeny, which also underwent EEG recordings. Hippocampal CRH mRNA expression and DNA methylation were assessed using RT-PCR and pyrosequencing, respectively. ResultsEarly environmental enrichment delayed the onset of epilepsy in GAERS, and resulted in fewer seizures in adulthood, compared with standard housed GAERS. Enrichment also reduced the frequency of seizures when initiated in adulthood. Anxiety levels were reduced by enrichment, and these anti-epileptogenic and anxiolytic effects were heritable into the next generation. We also found reduced expression of CRH mRNA in GAERS exposed to enrichment, but this was not due to changes in DNA methylation. ConclusionsEnvironmental enrichment produces disease-modifying effects on genetically determined absence epilepsy and anxiety, and these beneficial effects are transferable to the subsequent generation. Reduced CRH expression was associated with these phenotypic improvements. Environmental stimulation holds promise as a naturalistic therapy for genetically determined epilepsy which may benefit subsequent generations.

The Modulatory Effect of Metabotropic Glutamate Receptor Type-1α on Spike-Wave Discharges in WAG/Rij Rats.

Modulatory function of metabotropic glutamate type 1 (mGlu1) receptors plays a crucial role in the pathophysiology of some neurological disorders, including schizophrenia and epilepsy. In this study, the expression of mGlu1α receptors in the thalamic nuclei was assessed during development of absence seizures in the WAG/Rij rats, a valid genetic animal model of absence epilepsy. In addition, the effect of pharmacological modulation of mGlu1α receptors in the laterodorsal (LD) nucleus of the thalamus on the characteristic features of bioelectrical brain activities in the WAG/Rij rats was assessed. The expression of mGlu1α receptors in the LD was assessed in four experimental groups of both WAG/Rij and Wistar rats with 2 and 6months of age. Agonist and antagonist of mGlu1α receptors were infused in LD in the six months old WAG/Rij (epileptic) rats. The protein level of mGlu1α receptors in the thalamus of the 6-month-old WAG/Rij rats was lower than non-epileptic animals. In addition, the distribution of mGlu1α receptors in different thalamic nuclei was lower in the 6-month-old WAG/Rij compared to age-matched Wistar rats. The gene expression of mGlu1α receptor was also significantly lower in 6-month-old WAG/Rij rats in the LD compared to other animal groups. The microinjection of mGlu1α receptors agonist and antagonist in the LD reduced the duration of spike-wave discharges (SWDs) and increased the amplitude and duration of SWDs, respectively, in 6-month-old WAG/Rij rats. The alterations of mGlu1α receptors expression in the thalamus of epileptic WAG/Rij rats as well as its modulatory effects in the generation of SWDs suggest the potential of mGlu1 receptors as a therapeutic target in absence epilepsy.

Oxidative Stress and Antioxidant Defense Status in CSF and Blood Content of the WAG/Rij Rat Models Suffering from Absence Epilepsy

Objective: Absence seizure as one of several kinds of seizures has been characterized by short-term episodes of either conscious or unconscious abnormal excessive or synchronous neuronal activity in the brain. WAG/Rij rats, a genetic model of absence epilepsy, were originally developed as experimental tools to resemble human absence epilepsy. Factors like blood variation and CSF (Cerebrospinal fluid) oxidative stress and antioxidant balance, play a key role in the induction and development of absence epilepsy and its complications. In this study we tried to evaluate the effects of changes in oxidative and antioxidant levels in CSF and blood on absence seizures. Materials and Methods: 20 male WAG/Rij rats and 20 male Wistar rats (250-350g, 6-7 months old) were used in the study. At the end of the experiment animals were anesthetized, then blood and CSF samples were collected and used for the determination of Glutathione peroxidase (GPx), Superoxide dismutase (SOD), Malondialdehyde (MDA) levels and total antioxidant capacity (TAC). Results: This study showed that the level of MDA, as an index of oxidative stress, significantly increased in WAG/Rij rats when compared to control group (p=0.001 for WD and p=0.003 for CSF). It was also found that the levels of antioxidants such as GPx, SOD, and TAC in WAG/Rij rats decreased significantly: p= 0.03, p= 0.013, p= 0.001,p= 0.003, p= 0.009 and p= 0.003, respectively, for GPx WB, GPx CSF, SOD WB, SOD CSF, TAC serum and TAC CSF. Conclusion: In absence seizure, measurement of oxidative stress markers and antioxidant levels such as MDA, SOD, GPx, in serum and CSF cases can lead to a better diagnosis and treatment of this condition.

The expression of Fetuin-A in brain tissues of WAG/Rij Rats, genetic rat model of absence epilepsy

Objective: In the present study, we aimed to determine the Fetuin-A levels in different regions of the brain in absence epileptic Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats in order to contribute the identification of new potential biomarkers of the diagnosis, prognosis and follow up the epilepsy treatment. Methods: 1, 3 and 6 months old male WAG/Rij rats (n=21) with absence epilepsy were used in this study. All of the rats were decapitated under anesthesia and their cortex and thalamus tissues were isolated. Fetuin-A levels of the groups were determined by Western Blot method by using standard techniques and differences between densities of the groups were compared. Results: According to data obtained, there was no Fetuin-A expression in brain cortex and thalamus tissues of WAG/Rij rats with absence epilepsy. Conclusion: In this study, it was shown that Fetuin-A is not expressed in brain cortex and thalamus tissues of WAG/Rij rats with absence epilepsy throughout the age-related development. By evaluating the findings obtained, extensive researches that contain molecular and histological methods must be planned, Fetuin-A findings that are obtained experimentally must be confirmed. J Clin Exp Invest 2015; 6 (4): 387-390 Key words: Absence epilepsy, Fetuin-A, WAG/Rij rat

Behavioral and Neurochemical Characteristics of Two Months Old WAG/Rij Rats with Genetic Absence Epilepsy

WAG/Rij rats are genetic animal model of absence epilepsy with comorbidity of depression. The first spike-wave discharges (SWDs) in WAG/Rij rats begin to appear at the age of 2-3 months and are fully manifested by 5-6 months. Occurrence of SWDs in the EEG is the main index of absence epilepsy. Previously it has been shown that the extensive absence epilepsy in 5-6 months old WAG/Rij rats is accompanied by decrease of dopamine and its metabolites concentrations in the meso-cortico-limbic and nigro-striatal dopaminergic brain systems, resulting in the expression of depression-like behavioral symptoms, and impairments of the learning and memory processes. In 36 days old WAG/Rij rats, SWDs are not manifested, deficiency of the mesolimbic dopamine is not revealed, and symptoms of depression-like behavior are not expressed. In this study, behavior in the open field, light-dark choice, forced swimming tests, monoamines and their metabolites concentrations in 5 brain structures (prefrontal cortex, nucleus accumbens, hypothalamus, striatum, hippocampus) were investigated in two months old WAG/Rij rats in comparison with age-matched Wistar rats. Reduced concentration of the dopamine and its metabolites, and increased concentration of the serotonin was found in WAG/Rij rats compared with Wistar rats only in the prefrontal cortex, indicating that the prefrontal cortex is the brain structure where neurochemical abnormalities appear first. No substantial changes in the monoamine and their metabolites concentrations have been revealed in other brain structures. Two months old WAG/Rij rats didn’t exhibit depression-like behavior in the forced swimming test, and learning/memory deficits in the passive avoidance test, but they showed behavioral changes, indicating increase anxiety/stress-reactivity, and alterations in learning/memory in the active avoidance test. Results suggest that two month-old WAG/Rij rats are at the stage of so called “pre-pathology” (increased anxiety and stress reactivity) preceding the development of depression-like behavior and substantial cognitive impairments which are co-morbid to fully expressed absence epilepsy in 5-6 months old rats of this strain.

Unilateral and Bilateral Cortical Resection: Effects on Spike-Wave Discharges in a Genetic Absence Epilepsy Model

Research QuestionRecent discoveries have challenged the traditional view that the thalamus is the primary source driving spike-and-wave discharges (SWDs). At odds, SWDs in genetic absence models have a cortical focal origin in the deep layers of the perioral region of the somatosensory cortex. The present study examines the effect of unilateral and bilateral surgical resection of the assumed focal cortical region on the occurrence of SWDs in anesthetized WAG/Rij rats, a well described and validated genetic absence model.MethodsMale WAG/Rij rats were used: 9 in the resected and 6 in the control group. EEG recordings were made before and after craniectomy, after unilateral and after bilateral removal of the focal region.ResultsSWDs decreased after unilateral cortical resection, while SWDs were no longer noticed after bilateral resection. This was also the case when the resected areas were restricted to layers I-IV with layers V and VI intact.ConclusionsThese results suggest that SWDs are completely abolished after bilateral removal of the focal region, most likely by interference with an intracortical columnar circuit. The evidence suggests that absence epilepsy is a network type of epilepsy since interference with only the local cortical network abolishes all seizures.

The Effects of Verapamil and Ethosuximide on the Brain Bioelectrical Activity of WAG/Rij Rats

Introduction: Synchronization of bioelectrical activities of neurons contributes to the initiation of epileptiform activities occurred during a seizure attack. Absence seizures are characterized by synchronous and symmetric 2.5-4 Hz spike-wave discharges in children under 15 years old. More than half of children with absence epilepsy suffer from cognitive, education, and learning difficulties. The amplitude ratio of the theta and alpha waves is a reliable indicator for measuring of learning difficulties in children. The aim of this study was to evaluate the effect of L- and T-type voltage-dependent calcium channel blockers, verapamil and ethosuximide, on the amplitude of electroencephalogram (EEG) waves in WAG/Rij rats, a genetic animal model of absence epilepsy. Materials and Methods: 18 adult WAG/Rij rats in the age between 4 and 6 months were divided randomly into 3 groups. Using stereotaxic method, cannula was implanted in the peri-oral region of the primary somatosensory cortex for injection of drugs and recording electrodes were placed in the frontal and the occipital cortices. Electroencephalography was recorded 30 minutes before and one hour after drug injection. Results: The power of EEG sub-bands significantly decreased in the first 30 minutes after injection of verapamil and ethosuximide compared to the control group. Conclusion: Our data show that verapamil and ethosuximide can decrease the power of EEG sub-bands. However, they have not noticeable effect on theta to alpha ratio.

Synchrotron X-ray microbeams: A promising tool for drug-resistant epilepsy treatment

Epilepsy is one of the most important neurological diseases. It concerns about 1% of the population worldwide. Despite the discovery of new molecules, one third of epileptic patients are resistant to anti-epileptic drugs and among them only a few can benefit from resective surgery. In this context, radiotherapy is an interesting alternative to the other treatments and several clinical devices exist (e.g., Gamma Knife®). The European Synchrotron Radiation Facility offers the possibility to develop new methods of radiosurgery and to study their antiepileptic effects. Here, we discuss several studies that we performed recently to test and try to understand the antiepileptic effects of X-ray synchrotron microbeams in different animal models of epilepsy. We showed a decrease of seizures after Interlaced Microbeam Radiotherapy (IntMRT) of the somatosensory cortex, known as the seizure generator, in a genetic model of absence epilepsy. These antiepileptic effects were stable over 4 months and with low tissular and functional side-effects. The irradiated pyramidal neurons still displayed their physiological activity but did not synchronize anymore. We also obtained a lasting suppression of seizures after IntMRT of the dorsal hippocampus in a mouse model of mesiotemporal lobe epilepsy. However, an important variability of antiepileptic efficiency was observed probably due to the small size of the targeted structure. Despite these encouraging proofs-of-concepts, there is now a need to adapt IntMRT to other models of epilepsy in rodents which are close to refractory forms of epilepsy in human patients and to implement this approach to non-human primates, before moving to clinical trials.