Animal Model Of Absence Epilepsy Research Articles

Investigating the mechanism of action of ginkgolides and bilobalide on absence seizures in male WAG/Rij rats.

The effects of a single and multiple doses of ginkgolide A, B, C, and bilobalide, active components of Ginkgo biloba extract (EGb 761), on absence seizures were investigated in male WAG/Rij rats, a genetic animal model of absence epilepsy. Furthermore, the interactions of ginkgolide A together with NMDA receptor antagonist MK-801, AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), or L-type calcium channel blocker nicardipine were studied to figure out how ginkgolide A affects spike-wave discharges (SWDs) in the brain. The experiments were done using 6-8-month-old male WAG/Rij rats with infusion cannula and EEG electrode implanted. Ginkgolide A, B, C, and bilobalide were administered intraperitoneally for 7 days at a dose of 6mg/kg. In interaction groups, 6μg ginkgolide A was injected intracerebroventricularly in combination with MK-801 (10μg), CNQX (1μg), and nicardipine (50 μg) for 7 days. EEG was recorded from animals at the baseline, first dose, and seventh dose periods for 4 h. Ginkgolide A (p=.028), C (p=.046), and bilobalide (p=.043) significantly increased the frequency of SWDs in WAG/Rij rats. Ginkgolide A injected into the lateral ventricle with MK-801 (p=.046), CNQX (p=.043), and nicardipine (p=.046) significantly increased the number of SWDs after seventh dose. Finally, the EGb 761-related increase in absence epilepsy was determined to be caused by ginkgolide A, C, and bilobalide. All three receptor antagonists/channel blockers do not inhibit the pro-absence effect of ginkgolide A. The findings revealed that ginkgolide A's pro-absence effect is mediated by brain circuits other than ionotropic glutamate receptors or L-type calcium channels.

Electron microscopic GABA evaluation in hippocampal mossy terminals of genetic absence epilepsy rats receiving kindling stimulations

Objective: The hypotheses related to the fact of epileptic mechanisms are mainly based on excitation-inhibition imbalance in central nervous system. GAERS (Genetic Absence Epilepsy Rats from Strasbourg) is a well-known animal model of absence epilepsy, and frequently used in experimental studies. In the present study, we aimed to examine possible morphological and gamma-aminobutyric acid (GABA) density changes in GAERS hippocampus after electrical kindling stimulations.
 Methods: All control and test group rats received 6 kindling stimulations. Rats were decapitated 1 h after the last stimulation. Ultrastructural GABA immunocytochemistry was used to evaluate GABA density quantitatively in mossy terminals of hippocampal CA3 region.
 Results: GABA levels were less in kindling groups compared to their controls, and in GAERS groups compared to Wistar groups; mitochondrial and dendritic spine area ratios were greater in GAERS groups compared to Wistar groups, although all these evaluations were statistically nonsignificant. Depletion of synaptic vesicles was evident in the mossy terminals of kindling groups.
 Conclusion: The reason of decreased levels of GABA found in the present study might be that GABA has been released from the synaptic pool rapidly at an early time period after the last stimulation, for compansation mechanisms. Depletion of synaptic vesicles observed in kindling groups shows that even 6 kindling stimulations have an impact of changing hippocampal morphology in trisynaptic cycle. The increased mitochondrial area in GAERS might be related to the increased mitochondrial activity. The increased dendritic spine area might be related to the increased performance of learning in GAERS. Our findings indicating that absence epilepsy and temporal lobe epilepsy have different mechanisms of epileptogenesis might be a basis for further experimental studies

Alteration in Neuregulin 1/ERbB4 in Absence Epilepsy: Regulatory Effect on TRPV1 Expression.

The footprint of Neuregulin 1 (NRG1) / ERbB4 in the pathophysiology of some neurological disorders and TRPV1 regulation has been indicated. The alterations in NRG1 and ErbB4 as well as the TRPV1 signaling pathway were investigated during the development of absence epilepsy in the genetic animal model of absence epilepsy. Male WAG/Rij and Wistar rats were divided into four experimental groups of two and six months of age. The protein levels of NRG1, ERbB4, and TRPV1 were measured in the somatosensory cortex and hippocampus. The cortical protein levels of NRG1 and ErbB4 in the 6-month-old WAG/Rij rats were lower than in Wistar rats. Protein levels of TRPV1 were lower in two- and six-month-old WAG/Rij rats compared to age-matched Wistar rats.Hippocampal protein levels of NRG1 in 6-month-old WAG/Rij rats were lower than two-month-old WAG/Rij rats. Low levels of ErbB4 protein in two-month-old and high levels in six-month-old WAG/Rij rats were found compared to Wistar rats. Protein levels of TRPV1 were lower in the two-month-old and higher in the six-month-old WAG/Rij rats compared to age-matched Wistar rats.Furthermore, a high correlation between NRG1/ERbB4 and TRPV1 expressions in the cortex and hippocampus was indicated. The expression of NRG1/ERbB4 and TRPV1 followed a similar pattern during the life span of Wistar and WAG/Rij rats. Our findings indicated the potential role of the NRG1/ErbB4 pathway as well as TRPV1 in the pathogenesis of absence epilepsy. The regulatory effect of the ERbB4 receptor on the TRPV1 expression has been suggested following the similar pattern of expression.

The effect of chronic treatment with sodium channel blocker lacosamide on early development of absence seizures in genetic absence epilepsy rats

ObjectiveLacosamide (LCM) is a new generation antiepileptic drug that affects the slow inactivation of voltage-gated sodium channels. We studied whether chronic LCM treatment prior to onset of absence seizures was able to prevent/reduce the development of absence seizures in GAERS rats, a well-validated animal model of absence epilepsy and epileptogenesis. Drug effects on the duration, mean duration, number and spectral characteristics of spike-wave discharges (SWDs) were measured both 1 and 2 months after treatment withdrawal and compared with the ethosuximide (ETX) that has anti-epileptogenic activity in GAERS. Furthermore, the acute effects of LCM on SWDs in adult GAERS were evaluated. MethodsGAERS rats were administered either with LCM (10 mg/kg/day or 30 mg/kg/day, i.p) or ETX (25 mg/kg/day, i.p) or saline (%0.9 NaCl) until PN60 for 40 consecutive days starting from PN20. Animals were stereotaxically implanted with cortical screw electrodes under ketamine/xylazine anesthesia at PN53. Following recovery period, EEG were recorded at PN60 (last day of drug administration)− 61–62, PN90–91–92 and PN120–121–122 time periods for 3 consecutive days. ResultsThe chronic treatment with both LCM and ETX led to an ∼50% reduction in the development of spontaneous absence seizures in GAERS at PN90 and PN120 after the treatment withdrawal at PN60. The spectral analysis of EEG data revealed significant slowing of the peak frequency of SWDs in LCM treated animals at PN62. ConclusionThese results confirm that chronic LCM treatment modifies the development of absence seizures in GAERS and suggest that LCM exerts beneficial effects on absence seizure epileptogenesis.

A Novel Spike-Wave Discharge Detection Framework Based on the Morphological Characteristics of Brain Electrical Activity Phase Space in an Animal Model

Background: Animal models of absence epilepsy are widely used in childhood absence epilepsy studies. Absence seizures appear in the brain’s electrical activity as a specific spike wave discharge (SWD) pattern. Reviewing long-term brain electrical activity is time-consuming and automatic methods are necessary. On the other hand, nonlinear techniques such as phase space are effective in brain electrical activity analysis. In this study, we present a novel SWD-detection framework based on the geometrical characteristics of the phase space. Methods: The method consists of the following steps: (1) Rat stereotaxic surgery and cortical electrode implantation, (2) Long-term brain electrical activity recording, (3) Phase space reconstruction, (4) Extracting geometrical features such as volume, occupied space, and curvature of brain signal trajectories, and (5) Detecting SDWs based on the thresholding method. We evaluated the approach with the accuracy of the SWDs detection method. Results: It has been demonstrated that the features change significantly in transition from a normal state to epileptic seizures. The proposed approach detected SWDs with 98% accuracy. Conclusion: The result supports that nonlinear approaches can identify the dynamics of brain electrical activity signals.

Vasoactive intestinal peptide (VIP) conducts the neuronal activity during absence seizures: GABA seems to be the main mediator of VIP

Absence epilepsy is classified as a childhood generalized epilepsy syndrome with distinctive electroencephalographic patterns. The Wistar Albino Glaxo originating from Rijswijk (WAG/Rij) strain is a very well validated animal model of absence epilepsy that also shows behavioral deficits. In addition to the gastrointestinal system, VIP is highly expressed throughout numerous brain regions, and it plays crucial roles as a neurotransmitter and as a neuromodulatory, neurotrophic and neuroprotective factor in both the central and peripheral nervous systems.In this study, adult WAG/Rij rats were divided into two groups (n = 10): a group that was administered VIP (25 ng/kg i.p.) every 2 days for 15 days and an age-matched control group that was administered physiological saline. Electrical brain activity and behavior (depressive- like behavior, learning and memory and anxiety) were investigated in both groups. In addition, the extracellular concentrations of GABA and glutamate and the GABA/glutamate ratio were measured by high-performance liquid chromatography in microdialysate samples collected from the somatosensorial cortex of WAG/Rij rats.Our results demonstrated that VIP treatment significantly suppressed the total duration and number of spike wave discharges in WAG/Rij rats. However, VIP had no significant effect on behavior. VIP increased the extracellular concentration of GABA and the GABA/glutamate ratio in the somatosensory cortex. In conclusion, VIP has suppressive effects on absence seizures, possibly by increasing the GABA concentration and inducing the transformation of glutamate to GABA in the somatosensory cortex of WAG/Rij rats.

Electroencephalographic investigation of the effects of Ginkgo biloba on spike-wave discharges in rats with genetic absence epilepsy

ObjectiveEGb 761, a plant extract obtained from the leaves of the Ginkgo biloba tree, is widely used in modern medicine and traditional medicine applications in the treatment of many diseases. However, in some clinical case reports, it has been suggested that G. biloba causes epileptic seizures. A limited number of experimental animal studies related to the effects of G. biloba on epileptic seizures do not provide sufficient information on the solution of a serious clinical problem with contrasting findings. We aimed to investigate the effects of EGb 761 administered in different doses to adult male Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats which is the genetic animal model of absence epilepsy, on absence seizures using in vivo electrophysiological method. In addition, the effects of EGb 761 doses on locomotor behavior of WAG/Rij rats were evaluated with open-field and rotarod behavioral tests. Methods50, 100, 200, and 400 mg/kg doses of EGb 761 were administered to male WAG/Rij rats with implanted EEG electrodes by oral gavage for 28 days. Evaluation of absence seizures was performed on spike-wave discharges (SWDs) in EEG recorded for 4 h each week. The number of SWDs, the total duration of SWDs, and the mean duration of SWD were determined for the analysis. ResultsIn the group treated with 400 mg/kg EGb 761, the number of SWDs and the mean duration of SWD at the 1st and 7th doses and the total duration of SWDs at the 1st, 7th and 14th doses were significantly increased (p < 0.05). In all experimental groups treated with EGb 761 doses, there was no significant change in locomotor activity in the open-field and the rotarod tests. ConclusionGinkgo biloba extract EGb 761 increased the epileptic SWD parameters of WAG/Rij rats at high doses (400 mg/kg), causing a pro-epileptic effect on absence seizures. It should be noted that in patients with epilepsy and in high-dose applications, G. biloba extract EGb 761 may lead to an increase in neuronal excitability.

Age dependent effects of Retigabine on absence seizure in WAG/Rij rats; an experimental study.

Retigabine (RTG, Ezogabine, DC23129) is the first neuronal potassium channel opener in the treatment of epilepsy and exerts its effects through the activation of neuronal KCNQ2/3 potassium channels; in higher doses, it acts also on sodium and voltage-gated calcium channels. The aim of this study was to investigate possible age-dependent therapeutic effects of RTG on spike-and-wave discharges (SWD) in an animal model of absence epilepsy using WAG/Rij rats. In this study, 6- and 12-month-old WAG/Rij rats were used. For both age categories, three sub-groups that consisted of one control group (n=7) by the administration of 20% DMSO (control) and two study groups by the administration of 5mg/kg (n=7) and 15mg/kg RTG (n=7) were designed. EEG electrodes were placed onto the skull of anaesthetized animals; and baseline EEG was recorded for one hour after a recovery period from surgery. Then, the pre-determined two distinct doses of RTG and 20% DMSO were administered as a solvent via intraperitoneal injections, and EEG was recorded for 3hours. After injection, both doses of RTG increased the total SWD number and duration of SWD in the first and second hours in 12-month-old rats. These parameters were elevated compared to 6-month-old rats. Age-dependent effects of RTG were observed in SWD activity. Pro-epileptic effects in middle-aged WAG/Rij rats were demonstrated in both RTG doses. Differences in the distribution of KCNQ2/3 channels and switch of GABAergic system from inhibitory to excitatory with age might contribute to increased SWD activity in middle-aged rats.

First evidence of altered microbiota and intestinal damage and their link to absence epilepsy in a genetic animal model, the WAG/Rij rat.

A large number of studies have highlighted the important role of the gut microbiota in the pathophysiology of neurological disorders, suggesting that its manipulation might serve as a treatment strategy. We hypothesized that the gut microbiota participates in absence seizure development and maintenance in the WAG/Rij rat model and tested this hypothesis by evaluating potential gut microbiota and intestinal alterations in the model, as well as measuring the impact of microbiota manipulation using fecal microbiota transplantation (FMT). Initially, gut microbiota composition and intestinal histology of WAG/Rij rats (a well-recognized genetic model of absence epilepsy) were studied at 1, 4, and 8 months of age in comparison to nonepileptic Wistar rats. Subsequently, in a second set of experiments, at 6 months of age, untreated Wistar or WAG/Rij rats treated with ethosuximide (ETH) were used as gut microbiota donors for FMT in WAG/Rij rats, and electroencephalographic (EEG) recordings were obtained over 4weeks. At the end of FMT, stool and gut samples were collected, absence seizures were measured on EEG recordings, and microbiota analysis and histopathological examinations were performed. Gut microbiota analysis showed differences in beta diversity and specific phylotypes at all ages considered and significant variances in the Bacteroidetes/Firmicutes ratio between Wistar and WAG/Rij rats. FMT, from both Wistar and ETH-treated WAG/Rij donors to WAG/Rij rats, significantly decreased the number and duration of seizures. Histological results indicated that WAG/Rij rats were characterized by intestinal villi disruption and inflammatory infiltrates already at 1 month of age, before seizure occurrence; FMT partially restored intestinal morphology while also significantly modifying gut microbiota and concomitantly reducing absence seizures. Our results demonstrate for the first time that the gut microbiota is modified and contributes to seizure occurrence in a genetic animal model of absence epilepsy and that its manipulation may be a suitable therapeutic target for absence seizure management.

Ultrastructural GABA immunogold labeling in the substantia nigra pars reticulata of kindled genetic absence epilepsy rats

ABSTRACT Genetic Absence Epilepsy Rats from Strasbourg (GAERS) is a well-known animal model of absence epilepsy and they are resistant to electrical kindling stimulations. The present study aimed to examine possible differences in gamma-aminobutyric acid (GABA) levels and synapse counts in the substantia nigra pars reticulata anterior (SNRa) and posterior (SNRp) regions between GAERS and Wistar rats receiving kindling stimulations. Animals in the kindling group either received six stimulations in the amygdala and had grade 2 seizures or they were kindled, having grade five seizures. Rats were decapitated one hour after the last stimulation. SNR regions were obtained after vibratome sectioning of the brain tissue. GABA immunoreactivity was detected by immunogold method and synapses were counted. Sections were observed by transmission electron microscope and analyzed by Image J program. GABA density in the SNRa region of fully kindled GAERS and Wistar groups increased significantly compared to that of their corresponding grade 2 groups. The number of synapses increased significantly in kindled and grade 2 GAERS groups, compared to kindled and grade 2 Wistar groups, respectively, in the SNRa region. GABA density in the SNRp region of kindled GAERS group increased significantly compared to that of GAERS grade 2 group. In the SNRp region, both kindled and grade 2 GAERS groups were found to have increased number of synapses compared to that of GAERS control group. We concluded that both SNRa and SNRp regions may be important in modulating resistance of GAERS to kindling stimulations.

Glutamate Signaling Pathway in Absence Epilepsy: Possible Role of Ionotropic AMPA Glutamate Receptor Type 1 Subunit.

AMPA receptors, consisting of glutamate receptor type1 (GluR1) subunit are involved in the pathophysiology of some neurological disorders. In this study, the role of the GluR1 subunit in the development, as well as features of absence seizures were assessed. Both Wistar and WAG/Rij (a genetic animal model of absence epilepsy) rats with 2 and 6-month ages were included in the study. The expression of GluR1 was measured in the somatosensory cortex. Moreover, the effects of pharmacological activation and inhibition of AMPA receptors on the characteristic of absence epileptic activities were evaluated by microinjection of agonist or antagonist of AMPA receptors on the somatosensory cortex in the epileptic WAG/Rij rats. Distribution of the GluR1 subunit of AMPA receptors in the both IV (p < 0.001) and VI (p < 0.01) layers of the somatosensory cortex in the epileptic WAG/Rij rats was higher than non-epileptic animals. In addition, the microinjection of AMPA receptors agonist on the somatosensory cortex of the WAG/Rij rats increased both amplitude (p < 0.01) and duration (p < 0.001) of spike-wave discharges (SWDs), while injection of antagonist reduced amplitude (p < 0.001) and duration (p < 0.01) of SWDs in the somatosensory cortex of epileptic rats. The high expression of GluR1 in the somatosensory cortex of epileptic rats suggests the role of AMPA receptors consisting of the GluR1 subunit in the development of absence seizures. The modulatory effects AMPA receptors on the feature of SWDs suggest the potential of AMPA receptors antagonists as a therapeutic target for absence epilepsy.

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.

Postnatal expression of thalamic GABAA receptor subunits in the stargazer mouse model of absence epilepsy.

Absence seizures are known to originate from disruptions within the corticothalamocortical network; however, the precise underlying cellular and molecular mechanisms that induce hypersynchronicity and hyperexcitability are debated and likely to be complex and multifactorial. Recent studies implicate impaired thalamic GABAergic inhibition as a common feature in multiple animal models of absence epilepsy, including the well-established stargazer mouse model. Recently, we demonstrated region-specific increases in the whole tissue and synaptic levels of GABAA receptor (GABAAR) subunits α1 and β2, within the ventral posterior region of the thalamus in adult epileptic stargazer mice compared with nonepileptic control littermates. The objective of this study was to investigate whether such changes in GABAAR subunits α1 and β2 can be observed before the initiation of seizures, which occur around postnatal (PN) days 16-18 in stargazers. Semiquantitative western blotting was used to analyze the relative tissue level expression of GABAAR α1 and β2 subunits in the thalamus of juvenile stargazer mice compared with their nonepileptic control littermates at three different time points before the initiation of seizures. We show that there is a statistically significant increase in the expression of α1 and β2 subunits in the thalamus of stargazer mice, at the PN7-9 stage, compared with the control littermates, but not at PN10-12 and PN13-15 stages. These results suggest that an aberrant expression of GABAAR subunits α1 and β2 in the stargazers does not occur immediately before seizure onset and therefore is unlikely to directly contribute to the initiation of absence seizures.

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.

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.

The Role of Blood Electrolytes and Lipid Profile in Seizures Occurrence in WAG/Rij Rats

Introduction: Epilepsy is one of the most common neurological disorders associated with uncontrolled electrical activities in the brain. Electrolyte homeostasis is important for brain normal function. Imbalance in electrolytes can cause a seizure. The aim of this study is to evaluate the changes in lipids and electrolytes in absence seizure. Materials and Methods: In this study, 10 WAG/Rij and 10 Wistar rats (6-month old) were used. Blood samples were collected from heart under deep anesthesia. Biochemical parameters such as the amounts of cholesterol, triglycerides, high density lipoprotein (HDL), low density lipoprotein (LDL), sodium, potassium, calcium, and chloride were analyzed in the blood serum. Results: The amount of sodium, potassium, and chloride in WAG/Rij rat’s blood plasma were significantly higher compared to Wistar rats and the amount of calcium in WAG/Rij was significantly lower than Wistar rats. In addition, the values of blood plasma lipids, including cholesterol, triglycerides, HDL, and LDL in WAG/Rij was lower than Wistar rats. Conclusion: The results showed the differences in electrolytes and lipids of plasma between WAG/Rij and Wistar rats. Further studies are needed if changes of electrolytes and lipids of plasma may be associated with seizure occurrence in this animal model of absence epilepsy.

The expression of NMDA receptor NR2B subunit in animal model of absence epilepsy

The expression of NMDA receptor NR2B subunit in animal model of absence epilepsy

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.

Synaptic changes in GABAA receptor expression in the thalamus of the stargazer mouse model of absence epilepsy

Absence seizures are known to result from disturbances within the cortico-thalamocortical network, which remains partially synchronous under normal conditions but switches to a state of hypersynchronicity and hyperexcitability during absence seizures. There is evidence to suggest that impaired GABAergic inhibitory function within the thalamus could contribute to the generation of hypersynchronous oscillations in some animal models of absence epilepsy. Recently, we demonstrated region-specific alterations in the tissue expression level of GABAA receptors (GABAARs) α1 and β2 subunits within the thalamus of the stargazer mouse model of absence epilepsy. In the present study we investigated whether changes in these subunits also occur at synapses in the ventral posterior (VP) complex where they are components of phasic GABAAR receptors. Postembedding immunogold cytochemistry and electron microscopy were used to analyze the relative synaptic expression of α1 and β2 subunits in the VP thalamic region in epileptic stargazer mice compared to their non-epileptic littermates. We show that there is a significant increase in expression of α1 and β2 subunits (53.6% and 45.8%, respectively) at synapses in the VP region of stargazers, indicative of an increase in phasic GABAARs at thalamocortical (TC) relay neurons. Furthermore, we investigated whether tissue expression of GABAAR subunits α4 and δ, which constitute part of tonic GABAARs in the VP region, is altered in the stargazer mouse. Semi-quantitative Western blotting showed a significant increase in GABAAR α4 and δ subunits in the VP region of stargazer thalamus, which would indicate an increase in tonic GABAAR expression. Our findings show that there are changes in the levels of both phasic and tonic GABAARs in the VP thalamus; altered GABAergic inhibition within the VP could be one of many mechanisms contributing to the generation of absence seizures in this model.

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.