Susceptibility to audiogenic seizure and neurotransmitter amino acid levels in different brain areas of IL-6-deficient mice

Audiogenic epileptic DBA/2 mice strain as a model of genetic reflex seizures and SUDEP

Epilepsy is a chronic neurological disease characterized by abnormal brain activity, which results in repeated spontaneous seizures. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of seizure-related premature death, particularly in drug-resistant epilepsy patients. The etiology of SUDEP is a structural injury to the brain that is not fully understood, but it is frequently associated with poorly controlled and repeated generalized tonic-clonic seizures (GTCSs) that cause cardiorespiratory and autonomic dysfunctions, indicating the involvement of the brainstem. Both respiratory and cardiac abnormalities have been observed in SUDEP, but not much progress has been made in their prevention. Owing to the complexity of SUDEP, experimental animal models have been used to investigate cardiac and/or respiratory dysregulation due to or associated with epileptic seizures that may contribute to death in humans. Numerous rodent models, especially mouse models, have been developed to better understand epilepsy and SUDEP physiopathology. This review synthesizes the current knowledge about dilute brown agouti coat color (DBA/2) mice as a possible SUDEP model because respiratory arrest (RA) and sudden death induced by audiogenic generalized seizures (AGSs) have been observed in these animals. Respiratory/cardiac dysfunction, brainstem arousal system dysfunction, and alteration of the neurotransmitter systems, which are observed in human SUDEP, have also been observed in these mice. In particular, serotonin (5-HT) alteration and adenosine neurotransmission appear to contribute to not only the pathophysiological mechanisms of medication but also seizure-related respiratory dysfunctions in this animal model. These neurotransmitter systems could be the relevant targets for medication development for chronic epilepsy and SUDEP prevention. We reviewed data on AGSs in DBA/2 mice and the relevance of this model of generalized tonic-clonic epilepsy to human SUDEP. Furthermore, the advantages of using this strain prone to AGSs for the identification of possible new therapeutic targets and treatment options have also been assessed.

Neuroinflammation in Pathogenesis of Audiogenic Epilepsy: Altered Proinflammatory Cytokine Levels in the Rats of Krushinsky-Molodkina Seizure-Prone Strain

Neuroinflammation plays an important role in epileptogenesis, however, most studies are performed using pharmacological models of epilepsy, while there are only few data available for non-invasive, including genetic, models. The levels of a number of pro-inflammatory cytokines were examined in the Krushinsky-Molodkina (KM) rat strain with high audiogenic epilepsy (AE) proneness (intense tonic seizure fit in response to loud sound) and in the control strain "0" (not predisposed to AE) using multiplex immunofluorescence magnetic assay (MILLIPLEX map Kit). Cytokine levels were determined in the dorsal striatum tissue and in the brain stem. Background levels of IL-1β, IL-6, and TNF-α in the dorsal striatum of the KM rats were significantly lower than in the rats "0" (by 32.31, 27.84, and 38.87%, respectively, p < 0.05, 0.05, and 0.01), whereas no inter-strain differences in the levels of these metabolites were detected in the brain stem in the "background" state. Four hours after sound exposure, the TNF-α level in the dorsal striatum of the KM rats was significantly lower (by 38.34%, p < 0.01) than in the "0" rats. In the KM rats, the dorsal striatal levels of IL-1β and IL-6 were significantly higher after the sound exposure and subsequent seizure fit, compared to the background (35.29 and 50.21% increase, p < 0.05, 0.01, respectively). In the background state the IL-2 level in the KM rats was not detected, whereas after audiogenic seizures its level was 14.01 pg/ml (significant difference, p < 0.01). In the KM rats the brain stem levels of IL-1β and TNF-α after audiogenic seizures were significantly lower than in the background (13.23 and 23.44% decrease, respectively, p < 0.05). In the rats of the "0" strain, the levels of cytokines in the dorsal striatum after the action of sound (which did not induce AE seizures) were not different from those of the background, while in the brain stem of the "0" strain the levels of IL-1β were lower than in the background (40.28%, p < 0.01). Thus, the differences between the background levels of cytokines and those after the action of sound were different in the rats with different proneness to AE. These data suggest involvement of the analyzed cytokines in pathophysiology of the seizure state, namely in AE seizures.

Metabolic responses in the cortex and hippocampus induced by Il-15rα mutation

Metabolomics showed distinct metabolic phenotypes of the different brain regions related to the IL-15 system, enhancing our understanding of the IL-15 system and its interactions with neuropsychiatric disorders.

Glia and extracellular matrix molecules: What are their importance for the electrographic and MRI changes in the epileptogenic zone?

Glial cells and extracellular matrix (ECM) molecules are crucial for the maintenance of brain homeostasis. Especially because of their actions regarding neurotransmitter and ionic control, and synaptic function, these cells can potentially contribute to the hyperexcitability seen in the epileptogenic, while ECM changes are linked to synaptic reorganization. The present review will explore glial and ECM homeostatic roles and their potential contribution to tissue plasticity. Finally, we will address how glial, and ECM changes in the epileptogenic zone can be seen in magnetic resonance imaging (MRI), pointing out their importance as markers for the extension of the epileptogenic area. This article is part of the Special Issue "NEWroscience 2018".

Behavioral and neurochemical characterization of the spontaneous mutation tremor, a new mouse model of audiogenic seizures

The tremor mutant phenotype results from an autosomal recessive spontaneous mutation arisen in a Swiss-Webster mouse colony. The mutant mice displayed normal development until three weeks of age when they began to present motor impairment comprised by whole body tremor, ataxia, and decreased exploratory behavior. These features increased in severity with aging suggesting a neurodegenerative profile. In parallel, they showed audiogenic generalized clonic seizures. Results from genetic mapping identified the mutation tremor on chromosome 14, in an interval of 5 cM between D14Mit37 (33.21 cM) and D14Mit115 (38.21 cM), making Early Growth Response 3 (Egr3) the main candidate gene. Comparing with wild type (WT) mice, the tremor mice showed higher hippocampal gene expression of Egr3 and Gabra1 and increased concentrations of noradrenalin (NOR; p = .0012), serotonin (5HT; p = .0083), 5-hydroxyindoleacetic acid (5-HIAA; p = .0032), γ-amino butyric acid (GABA; p = .0123), glutamate (p = .0217) and aspartate (p = .0124). In opposition, the content of glycine (p = .0168) and the vanillylmandelic acid (VMA)/NOR ratio (p = .032) were decreased. Regarding to dopaminergic system, neither dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) contents nor the turnover rate of DA showed statistically significant differences between WT and mutant mice. Data demonstrated that audiogenic seizures of tremor mice are associated with progressive motor impairment as well as to hippocampal alterations of the Egr3 and Gabra1 gene expression and amino acid and monoamine content. In addition, the tremor mice could be useful for study of neurotransmission pathways as modulators of epilepsy and the pathogenesis of epilepsies occurring with generalized clonic seizures.

IL-6 trans-signaling in the brain influences the behavioral and physio-pathological phenotype of the Tg2576 and 3xTgAD mouse models of Alzheimer's disease

Alzheimer's disease (AD) is the most commonly diagnosed dementia but its underlying pathological mechanisms still unclear. Neuroinflammation and secretion of cytokines such as interleukin-6 (IL-6) accompany the main hallmarks of the disease: amyloid plaques and neurofibrillary tangles. In this study, we analyzed the role of IL-6 trans-signaling in two mouse models of AD, Tg2576 and 3xTg-AD mice. The inhibition of IL-6 trans-signaling partially rescued the AD-induced mortality in females of both models. Before amyloid plaques deposition, it reversed AD-induced changes in exploration and anxiety (but did not affect locomotion) in Tg2576 female mice. However, after plaque deposition the only behavioral trait affected by the inhibition of IL-6 trans-signaling was locomotion. Results in the Morris water maze suggest that cognitive flexibility was reduced by the blocking of the IL-6 trans-signaling in young and old Tg2576 female mice. The inhibition of IL-6 trans-signaling also decreased amyloid plaque burden in cortex and hippocampus, and Aβ₄₀ and Aβ₄₂ levels in the cortex, of Tg2576 female mice. The aforementioned changes might be correlated with changes in blood vessels and matrix structure and organization rather than changes in neuroinflammation. 3xTgAD mice showed a very mild phenotype regarding amyloid cascade, but results were in accordance with those of Tg2576 mice. These results strongly suggest that the inhibition of the IL-6 trans-signaling could represent a powerful therapeutic target in AD.

The role of UCH-L1, MMP-9, and GFAP as peripheral markers of different susceptibility to seizure development in a preclinical model of epilepsy

In our study, we assessed the potency of the brain-derived proteins ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), matrix metalloproteinase 9 (MMP-9), glial fibrillary acidic protein (GFAP) and the immune activation indicators interleukin 1β (IL-1β) and interleukin 6 (IL-6) as peripheral biomarkers of different susceptibilities to kindling in a preclinical model. We observed increased plasma UCH-L1 levels in kindled vs. control animals. Furthermore, MMP-9 and IL-1β concentrations were the lowest in rats resistant to kindling. In summary, UCH-L1 is an indicator of neuronal loss and BBB disruption after seizure. MMP-9 and IL-1β may indicate resistance to kindling. UCH-L1, MMP-9 and IL-1β may have utility as peripheral biomarkers with translational potency in the clinic.

IL-6 knockout mice are protected from cocaine-induced kindling behaviors; possible involvement of JAK2/STAT3 and PACAP signalings

IL-6 has been recognized as an anticonvulsant against certain neuroexcitotoxicities. We aimed to investigate on the interactive role between IL-6 and PACAP in cocaine-induced kindling behaviors. Although we found that cocaine (45 mg/kg, i.p./day x 5) significantly increased IL-6 and TNF-α expression, it resulted in a decrease in IFN-γ expression. We observed that the cocaine-induced increase in IL-6 expression was more pronounced than that in TNF-α expression. Genetic depletion of IL-6 significantly activated cocaine kindling behaviors. This phenomenon was also consistently observed in WT mice that received a neutralizing IL-6 receptor antibody. Cocaine-treated IL-6 knockout mice exhibited significantly decreased PACAP and PACAP receptor (PAC1R) mRNA levels and significantly increased TNF-α gene expression. TNF-α knockout mice were protected from cocaine kindling via an up-regulation of IL-6, phospho-JAK2/STAT3, PACAP, and PAC1R levels, which produced anti-apoptotic effects. Recombinant IL-6 protein (rIL-6, 2 μg, i.v./mouse/day x 5) also up-regulated phospho-JAK2/STAT3, PACAP, and PAC1R mRNA levels, leading to anti-apoptotic effects in IL-6 knockout mice. Consistently, AG490, a JAK2/STAT3 inhibitor, and PACAP 6-38, a PAC1 receptor antagonist, counteracted rIL-6-mediated protection. Combined, our results suggest that IL-6 gene requires up-regulation of phospho-JAK2/STAT3, PACAP, and PAC1R and down-regulation of the TNF-α gene to modulate its anticonvulsive/neuroprotective potential.

Anti-Inflammatory Small Molecules To Treat Seizures and Epilepsy: From Bench to Bedside

As a crucial component of brain innate immunity, neuroinflammation initially contributes to neuronal tissue repair and maintenance. However, chronic inflammatory processes within the brain and associated blood-brain barrier (BBB) impairment often cause neurotoxicity and hyperexcitability. Mounting evidence points to a mutual facilitation between inflammation and epilepsy, suggesting that blocking the undesired inflammatory signaling within the brain might provide novel strategies to treat seizures and epilepsy. Neuroinflammation is primarily characterized by the upregulation of proinflammatory mediators in epileptogenic foci, among which cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), interleukin-1β (IL-1β), transforming growth factor-β (TGF-β), toll-like receptor 4 (TLR4), high-mobility group box 1 (HMGB1), and tumor necrosis factor-α (TNF-α) have been extensively studied. Small molecules that specifically target these key proinflammatory perpetrators have been evaluated for antiepileptic and antiepileptogenic effects in animal models. These important preclinical studies provide new insights into the regulation of inflammation in epileptic brains and guide drug discovery efforts aimed at developing novel anti-inflammatory therapies for seizures and epilepsy.

Cytokine-dependent bidirectional connection between impaired social behavior and susceptibility to seizures associated with maternal immune activation in mice

Maternal immune activation (MIA) results in the development of autism in the offspring via hyperactivation of IL-6 signaling. Furthermore, experimental studies showed that the MIA-associated activation of interleukin-1β (IL-1β) concurrently with IL-6 increases the rate and the severity of hippocampal kindling in mice, thus, offering an explanation for autism-epilepsy comorbidity. We examined whether epileptic phenotype triggered by prenatal exposure to IL-6 and IL-1β combination is restricted to kindling or whether it is reproducible in another model of epilepsy, whereby spontaneous seizures develop following kainic acid (KA)-induced status epilepticus. We also examined whether in mice prenatally exposed to IL-6 and IL-6+IL-1β, the presence of spontaneous seizures would exacerbate autism-like features. Between days 12 and 16 of pregnancy, C57BL/6J mice received daily injections of IL-6, IL-1β, or IL-6+IL-1β combination. At postnatal day 40, male offspring were examined for the presence of social behavioral deficit, and status epilepticus was induced by intrahippocampal KA injection. After 6weeks of monitoring for spontaneous seizures, sociability was tested again. Both IL-6 and IL-6+IL-1β offspring presented with social behavioral deficit. Prenatal exposure to IL-6 alleviated, while such exposure to IL-6+IL-1β exacerbated, the severity of KA-induced epilepsy. Increased severity of epilepsy in the IL-6+IL-1β mice correlated with the improvement of autism-like behavior. We conclude that complex and not necessarily agonistic relationships exist between epileptic and autism-like phenotypes in an animal model of MIA coupled with KA-induced epilepsy and that the nature of these relationships depends on components of MIA involved.

Wistar Audiogenic Rats (WAR) exhibit altered levels of cytokines and brain-derived neurotrophic factor following audiogenic seizures

Increasing body of evidence suggests that inflammatory and neurotrophic factors might be important for epileptogenesis. Most animal studies demonstrated altered levels of these mediators in drug-induced models of seizures and epilepsy. In the present study, we investigated the production of cytokines and a neurotrophin in the brain of Wistar Audiogenic Rats (WAR), a genetic model of epilepsy, stimulated with high-intensity sound. Four hours after stimulation, animals were decapitated and the hippocampus, inferior colliculus, striatum and cortex were removed for evaluation of the levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and brain derived neurotrophic factor (BDNF). All the cytokines and BDNF levels were increased in the cortex. Increased levels of TNF-α and IL-6 were also observed in the striatum. Finally, TNF-α also increased in the inferior colliculus after the seizures induced by high-intensity sound. Although different studies have demonstrated that the levels of cytokines and BDNF increase in animal models of epilepsy induced by chemical stimuli, we provided here evidence that these mediators are also increased in WAR, a genetic model of epilepsy. Thus, the observed increase in these mediators might be involved in the pathophysiology of epilepsy.

Interactions between levetiracetam and cardiovascular drugs against electroconvulsions in mice

BACKGROUND

Hypertension and heart failure belong to common comorbid conditions with epilepsy so drug interactions between antiepileptics and cardiovascular drugs are possible in clinical practice. The aim of this study was to evaluate the effects of angiotensin AT1 receptor antagonists (losartan potassium and candesartan cilexetil), angiotensin-converting enzyme (ACE) inhibitors (captopril and perindopril arginine) and diuretics (hydrochlorothiazide and ethacrynic acid) on the anticonvulsant activity of levetiracetam (LEV) in mice.

METHODS

The protective action of LEV was examined in the maximal electroshock seizure threshold test. Drugs were administered intraperitoneally (ip). Additionally, combinations of cardiovascular drugs with LEV were tested for adverse effects in the passive avoidance task and the chimney test.

RESULTS

Losartan potassium (50mg/kg), candesartan cilexetil (8mg/kg), captopril (50mg/kg), hydrochlorothiazide (100mg/kg) and ethacrynic acid (100mg/kg) did not affect the anticonvulsant activity of LEV. Perindopril arginine (10mg/kg) raised the convulsive threshold for LEV administered at doses of 100, 300 and 500mg/kg. This interaction could be pharmacodynamic in nature because the brain concentration of LEV remained unchanged by perindopril. The adverse effects of the combined treatment with LEV and cardiovascular drugs were not observed in the passive avoidance task or the chimney test.

CONCLUSIONS

Although experimental data can be hardly extrapolated to clinical practice, it is suggested that perindopril arginine may positively influence the anticonvulsant action of LEV in epileptic patients. The use of losartan potassium, candesartan cilexetil, captopril, hydrochlorothiazide or ethacrynic acid in patients treated with LEV seems neutral regarding its anticonvulsant activity.

Interleukin-6, a major cytokine in the central nervous system

Interleukin-6 (IL-6) is a cytokine originally identified almost 30 years ago as a B-cell differentiation factor, capable of inducing the maturation of B cells into antibody-producing cells. As with many other cytokines, it was soon realized that IL-6 was not a factor only involved in the immune response, but with many critical roles in major physiological systems including the nervous system. IL-6 is now known to participate in neurogenesis (influencing both neurons and glial cells), and in the response of mature neurons and glial cells in normal conditions and following a wide arrange of injury models. In many respects, IL-6 behaves in a neurotrophin-like fashion, and seemingly makes understandable why the cytokine family that it belongs to is known as neuropoietins. Its expression is affected in several of the main brain diseases, and animal models strongly suggest that IL-6 could have a role in the observed neuropathology and that therefore it is a clear target of strategic therapies.

Altered synaptic transmission in the hippocampus of transgenic mice with enhanced central nervous systems expression of interleukin-6

Elevated levels of the inflammatory cytokine interleukin-6 (IL-6) occur in a number of CNS disorders. However, little is known about how this condition affects CNS neuronal function. Transgenic mice that express elevated levels of IL-6 in the CNS show cognitive changes, increased propensity for hippocampal seizures and reduced number of inhibitory interneurons, suggesting that elevated levels of IL-6 can cause neuroadaptive changes that alter hippocampal function. To identify these neuroadaptive changes, we measured the levels of protein expression using Western blot analysis and synaptic function using field potential recordings in hippocampus from IL-6 transgenic mice (IL-6 tg) and their non-transgenic (non-tg) littermates. Western blot analysis showed enhanced levels of the GFAP and STAT3 in the IL-6 tg hippocampus compared with the non-tg hippocampus, but no difference for several other proteins. Field potential recordings of synaptic transmission at the Schaffer collateral to CA1 synapse showed enhanced dendritic excitatory postsynaptic potentials and somatic population spikes in the CA1 region of hippocampal slices from IL-6 tg mice compared with slices from non-tg littermate controls. No differences were observed for several forms of short-term and long-term synaptic plasticity between hippocampal slices from IL-6 tg and non-tg mice. These results demonstrate that elevated levels of IL-6 can alter mechanisms involved in the excitability of hippocampal neurons and synapses, an effect consistent with recent evidence indicating that elevated production of IL-6 plays an important role in conditions associated with seizure activity and in other impairments observed in CNS disorders with a neuroinflammatory component.

Cytokines and epilepsy

Epilepsy is a common chronic neurological disorder affecting approximately 8 out of 1000 people. Its pathophysiology, however, has remained elusive in many regards. Consequently, adequate seizure control is still lacking in about one third of patients. Cytokines are soluble mediators of cell communication that are critical in immune regulation. In recent years, studies have shown that epileptic seizures can induce the production of cytokines, which in turn influence the pathogenesis and course of epilepsies. At the time of this review, the focus is mostly on interleukin-1beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNFα). In this review, we summarize the current knowledge regarding these cytokines and their potential roles in epilepsy. The focus concentrates on their expression and influence on induced seizures in animal models of epilepsy, as well as findings in human studies. Both proconvulsive and anticonvulsive effects have been reported for each of these molecules. One possible explanation for this phenomenon is that cytokines play dichotomous roles through multiple pathways, each of which is dependent on free concentration and available receptors. Furthermore, the immune-mediated leakage in the blood-brain-barrier also plays an important role in epileptogenesis. Nonetheless, these observations demonstrate the multifarious nature of cytokine networks and the complex relationship between the immune system and epilepsy. Future studies are warranted to further clarify the influence of the immune system on epilepsy and vice versa.

The role of cytokines in the pathophysiology of epilepsy

Recent findings in experimental models and in the clinical setting highlight the possibility that inflammatory processes in the brain contribute to the etiopathogenesis of seizures and to the establishment of a chronic epileptic focus. Prototypical inflammatory cytokines such as IL-1 beta, TNF-alpha and IL-6 have been shown to be overexpressed in experimental models of seizures in brain areas of seizure generation and propagation, prominently by glia and to a lesser extent by neurons. Cytokines receptors are also upregulated, and the related intracellular signalling is activated, in both cell populations highlighting autocrine and paracrine actions of cytokines in the brain. Cytokines have been shown to profoundly affect seizures in rodents; in particular, IL-1 beta is endowed of proconvulsant activity in a large variety of seizure models. The recent demonstration of functional interactions between cytokines and classical neurotransmitters such as glutamate and GABA, suggest the possibility that these interactions underlie the cytokine-mediated changes in neuronal excitability, thus promoting seizure phenomena and the associated neuropathology. These findings point out at novel glio-neuronal communications in diseased conditions and highlight potential new targets for therapeutic intervention.

Interleukin-6 upregulates neuronal adenosine A1 receptors: implications for neuromodulation and neuroprotection

The immunological response in the brain is crucial to overcome neuropathological events. Some inflammatory mediators, such as the immunoregulatory cytokine interleukin-6 (IL-6) affect neuromodulation and may also play protective roles against various noxious conditions. However, the fundamental mechanisms underlying the long-term effects of IL-6 in the brain remain unclear. We now report that IL-6 increases the expression and function of the neuronal adenosine A1 receptor, with relevant consequences to synaptic transmission and neuroprotection. IL-6-induced amplification of A1 receptor function enhances the responses to readily released adenosine during hypoxia, enables neuronal rescue from glutamate-induced death, and protects animals from chemically induced convulsing seizures. Taken together, these results suggest that IL-6 minimizes the consequences of excitotoxic episodes on brain function through the enhancement of endogenous adenosinergic signaling.

Decreased levels of GABA in the inferior colliculus of the epilepsy-prone hamster (GPG/Vall)

Abnormalities in GABA levels in the central nucleus of the inferior colliculus (CNIC) of the epilepsy-prone hamster (GPG/Vall) were evaluated by using immunohistochemistry, densitometry and high performance liquid chromatography (HPLC). These findings demonstrate a decrease both in GABA immunostaining (neuropil and neurons) and in GABA concentration (HPLC) in the CNIC of the epileptic hamster compared to control animals. These decreases may reflect a reduced availability of this neurotransmitter that may act as an audiogenic seizure-initiating factor.

Interleukin-6 attenuates hyperthermia-induced seizures in developing rats

Previous studies indicated that several cytokines influenced the seizure propensity in convulsive disorders and were the cause of encephalopathies in childhood. We studied the role of one inflammatory cytokine, interleukin-6 (IL-6), in hyperthermia-induced seizures in developing rats. Twenty-four male Lewis rats (23-28 days old) were divided into three groups (n=8/IL-6 (500 ng), IL-6 (50 ng), and saline control groups). We applied human recombinant IL-6 intra-nasally to developing rats 1h before seizures induced by moist heated air (50 degrees C). The seizure latency was defined as the time from hyperthermia onset until the appearance of continuous seizure discharges on electroencephalography (EEG), and the seizure duration as the duration of continuous spike and wave discharges on EEG. Five of the eight rats in the IL-6 (500 ng) group, two in the IL-6 (50 ng) group, and one in the control group exhibited no seizure discharges during the 360 s heating period. In these cases, the seizure latency time was regarded as 360 s and the seizure duration time as 0 s. The median seizure latency for the IL-6 (500 ng) group, 360 s (range: 256-360), was significantly longer than that for the control one, 249 (121-360) (P<0.05). The seizure duration for the IL-6 (500 ng) group, 0 s (0-20), was significantly shorter than that for the control one, 33 (0-76) (P<0.025). Also, the adenosine receptor antagonist, aminophylline, prevented these effects of IL-6 on hyperthermia-induced seizures. These results indicate that IL-6 plays an anti-convulsive role through the adenosine system in hyperthermia-induced seizures, which might be relevant as to human febrile seizures.

Morphologic and neurochemical alterations in the superior colliculus of the genetically epilepsy-prone hamster (GPG/Vall)

The GPG/Vall hamster is an animal model that exhibits seizures in response to sound stimulation. Since the superior colliculus (SC) is implicated in the neuronal network of audiogenic seizures (AGS) in other forms of AGS, this study evaluated seizure-related anatomical or neurochemical abnormalities in the SC of the GPG/Vall hamster. This involved calbindin (CB) and parvalbumin (PV) immunohistochemistry, densitometric analysis and high performance liquid chromatography in the superficial and deep layers of the SC in control and epileptic animals. Compared to control animals, a reduction in SC volume and a hypertrophy of neurons located in the deep layers of the SC were observed in the epileptic hamster. Although, analysis of CB-immunohistochemistry in the superficial layers did not show differences between groups, analysis of PV-immunostaining in the deep SC revealed an increase in the mean gray level within immunostained neurons as well as a decreased immunostained neuropil in the GPG/Vall hamster as compared to control animals. These alterations were accompanied by a decrease in the levels of GABA and increased levels of taurine in the epileptic animal. These data indicate that the deep SC of the GPG/Vall hamster is structurally abnormal; suggesting its involvement in the neuronal network for AGS.

Ameliorative effect of pioglitazone on seizure responses in genetically epilepsy-susceptible EL mice

Pioglitazone, a peroxisome proliferator-activated receptor-gamma agonist, delayed the development of seizure responses and mildly shortened the duration of convulsion of genetically epileptic EL mice. mRNA levels of IL-1beta, IL-6 and TNF-alpha before seizure and mRNA levels of IL-6 and TNF-alpha after seizure were decreased in the brains of the mice with pioglitazone. These results suggest that pioglitazone may have ameliorative effects on epileptic seizure responses partly through the reduction of inflammatory responses in the brain.