Socrates: A Novel N-Ethyl-N-nitrosourea-Induced Mouse Mutant with Audiogenic Epilepsy.

Epilepsy is one of the common neurological diseases that affects not only adults but also infants and children. Because epilepsy has been studied for a long time, there are several pharmacologically effective anticonvulsants, which, however, are not suitable as therapy for all patients. The genesis of epilepsy has been extensively investigated in terms of its occurrence after injury and as a concomitant disease with various brain diseases, such as tumors, ischemic events, etc. However, in the last decades, there are multiple reports that both genetic and epigenetic factors play an important role in epileptogenesis. Therefore, there is a need for further identification of genes and loci that can be associated with higher susceptibility to epileptic seizures. Use of mouse knockout models of epileptogenesis is very informative, but it has its limitations. One of them is due to the fact that complete deletion of a gene is not, in many cases, similar to human epilepsy-associated syndromes. Another approach to generating mouse models of epilepsy is N-Ethyl-N-nitrosourea (ENU)-directed mutagenesis. Recently, using this approach, we generated a novel mouse strain, soc (socrates, formerly s8-3), with epileptiform activity. Using molecular biology methods, calcium neuroimaging, and immunocytochemistry, we were able to characterize the strain. Neurons isolated from soc mutant brains retain the ability to differentiate in vitro and form a network. However, soc mutant neurons are characterized by increased spontaneous excitation activity. They also demonstrate a high degree of Ca2+ activity compared to WT neurons. Additionally, they show increased expression of NMDA receptors, decreased expression of the Ca2+-conducting GluA2 subunit of AMPA receptors, suppressed expression of phosphoinositol 3-kinase, and BK channels of the cytoplasmic membrane involved in protection against epileptogenesis. During embryonic and postnatal development, the expression of several genes encoding ion channels is downregulated in vivo, as well. Our data indicate that soc mutation causes a disruption of the excitation-inhibition balance in the brain, and it can serve as a mouse model of epilepsy.

The highly efficient powerhouse in the Wistar audiogenic rat, an epileptic rat strain.

The Wistar audiogenic rat (WAR) is an animal model of tonic-clonic epileptic seizures, developed after genetic selection by sister × brother inbreeding of Wistar rats susceptible to sound stimuli. Although metabolic changes have been described in this strain, nothing is known about its mitochondrial metabolism. Here, we addressed mitochondrial aspects of oxidative phosphorylation, oxidative stress, biogenesis, and dynamics in liver, skeletal muscle, and heart of male WARs and correlating them with physiological aspects of body metabolism. The results showed higher mitochondrial content, respiration rates in phosphorylation and noncoupled states, and H2O2 production in WARs. Liver presented higher content of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α) and mammalian target of rapamycin, proteins related to mitochondrial biogenesis. In agreement, isolated liver mitochondria from WARs showed higher respiration rates in phosphorylation state and ADP-to-O ratio, as well as higher content of proteins related to electron transport chain ATP synthase, TCA cycle, and mitochondrial fusion and fission compared with their Wistar counterparts. Mitochondria with higher area and perimeter and more variable shapes were found in liver and soleus from WARs in addition to lower reduced-to-oxidized glutathione ratio. In vivo, WARs demonstrated lower body mass and energy expenditure but higher food and water intake and amino acid oxidation. When exposed to a running test, WARs reached higher speed and resisted for a longer time and distance than their Wistar controls. In conclusion, the WAR strain has mitochondrial changes in liver, skeletal muscle, and heart that improve its mitochondrial capacity of ATP production, making it an excellent rat model to study PGC1α overexpression and mitochondrial function in different physiological conditions or facing pathological challenges.

Energetic, oxidative and ionic exchange in rat brain and liver mitochondria at experimental audiogenic epilepsy (Krushinsky-Molodkina model).

The role of brain and liver mitochondria at epileptic seizure was studied on Krushinsky-Molodkina (KM) rats which respond to sound with an intensive epileptic seizure (audiogenic epilepsy). We didn't find significant changes in respiration rats of brain and liver mitochondria of KM and control rats; however the efficiency of АТР synthesis in the KM rat mitochondria was 10% lower. In rats with audiogenic epilepsy the concentration of oxidative stress marker malondialdehyde in mitochondria of the brain (but not liver) was 2-fold higher than that in the control rats. The rate of H2O2 generation in brain mitochondria of КМ rats was twofold higher than in the control animals when using NAD-dependent substrates. This difference was less pronounced in liver mitochondria. In KM rats, the activity of mitochondrial ATP-dependent potassium channel was lower than in liver mitochondria of control rats. The comparative study of the mitochondria ability to retain calcium ions revealed that in the case of using the complex I and complex II substrates, permeability transition pore is easier to trigger in brain and liver mitochondria of KM and КМs rats than in the control ones. The role of the changes in the energetic, oxidative, and ionic exchange in the mechanism of audiogenic epilepsy generation in rats and the possible correction of the epilepsy seizures are discussed.

Overexpression of the immediate-early genes Egr1, Egr2, and Egr3 in two strains of rodents susceptible to audiogenic seizures.

Genetic animal models of epilepsy are an important tool for further understanding the basic cellular mechanisms underlying epileptogenesis and for developing novel antiepileptic drugs. We conducted a comparative study of gene expression in the inferior colliculus, a nucleus that triggers audiogenic seizures, using two animal models, the Wistar audiogenic rat (WAR) and the genetic audiogenic seizure hamster (GASH:Sal). For this purpose, both models were exposed to high intensity auditory stimulation, and 60min later, the inferior colliculi were collected. As controls, intact Wistar rats and Syrian hamsters were subjected to stimulation and tissue preparation protocols identical to those performed on the experimental animals. Ribonucleic acid was isolated, and microarray analysis comparing the stimulated Wistar and WAR rats showed that the genomic profile of these animals displayed significant (fold change, |FC|≥2.0 and p<0.05) upregulation of 38 genes and downregulation of 47 genes. Comparison of gene expression profiles between stimulated control hamsters and stimulated GASH:Sal revealed the upregulation of 10 genes and the downregulation of 5 genes. Among the common genes that were altered in both models, we identified the zinc finger immediate-early growth response gene Egr3. The Egr3 protein is a transcription factor that is induced by distinct stress-elicited factors. Based on immunohistochemistry, this protein was expressed in the cochlear nucleus complex, the inferior colliculus, and the hippocampus of both animal models as well as in lymphoma tumors of the GASH:Sal. Our results support that the overexpression of the Egr3 gene in both models might contribute to neuronal viability and development of lymphoma in response to stress associated with audiogenic seizures. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".

Maternal methyl-enriched diet in rat reduced the audiogenic seizure proneness in progeny.

Audiogenic epilepsy proneness was analyzed in the progeny of rats from two strains (audiogenic seizure prone-strain "4"-and audiogenic seizure non-prone, strain "0"). Females were fed by a diet which contained substances enriched with methyl-groups during 1week before mating (MED), during pregnancy period and 1week after the delivery. This MED treatment resulted in a decrease of audiogenic seizure fit intensity, which was more evident in rats of strain "0". Control rats of strain "4" displayed intense seizures (tonic seizure, 3.85 arbitrary units). Med "4" rats seizures were less intense (3.23, tonic seizure of lower intensity), control "0" strain rats demonstrated the seizure with mean 3.09 arbitrary units, "0" MED rats only 2.03 arbitrary unit intensity (only clonic seizures, significantly, p<0.05, different from controls). Methyl-enriched diet resulted in the significant changes in methylation status of several genes (Cpne6, Gtf2i, Sctr,1 Sfmbt, Phe2). These genes among others were chosen for analysis as their expression was analyzed in other methylation study. These genes were hypermethylated after "epileptic tolerance". Due to this procedure, the intensity of status epilepticus, produced by kainate in mice, decreased (Miller-Delaney et al., 2012). The modulation of audiogenic seizure intensity as the result of methyl-enriched diet during prenatal and early postnatal ontogeny was demonstrated for the first time.

[Selection for catatonic reaction in rats: a study of interstrain differences by magnetic resonance imaging].

Brain studies by magnetic resonance imaging, angiography, and spectroscopy have been performed with rat strains Wistar, GC (genetic and catatonia), and PM+ (pendulum movements). Both GC and PM+ rats show similar deviations from the ancestral Wistar population in having smaller areas of the right striatum (coronal slice). The anterior horns of lateral ventricles in GC rats are smaller than in the control strain. The maximum blood flow velocity in the common carotid arteries of PM+ rats is greater. The GC and PM+ strains differ in myo-inositol level in the hippocampus. The PM+ strain is characterized by a lower taurine level in the hippocampus, which may be one of the participants regulated the predisposition to audiogenic seizures.

Very large G protein-coupled receptor 1 regulates myelin-associated glycoprotein via Gαs/Gαq-mediated protein kinases A/C.

VLGR1 (very large G protein-coupled receptor 1), also known as MASS1 (monogenic audiogenic seizure susceptible 1), is an orphan G protein-coupled receptor that contains a large extracellular N terminus with 35 calcium-binding domains. A truncating mutation in the Mass1 gene causes autosomal recessive, sound-induced seizures in the Frings mouse. However, the function of MASS1 and the mechanism underlying Frings mouse epilepsy are not known. Here, we found that MASS1 protein is enriched in the myelinated regions of the superior and inferior colliculi, critical areas for the initiation and propagation of audiogenic seizures. Using a panel of myelin antibodies, we discovered that myelin-associated glycoprotein (MAG) expression is dramatically decreased in Frings mice. MASS1 inhibits the ubiquitylation of MAG, thus enhancing the stability of this protein, and the calcium-binding domains of MASS1 are essential for this regulation. Furthermore, MASS1 interacts with Gαs/Gαq and activates PKA and PKC in response to extracellular calcium. Suppression of signaling by MASS1 RNAi or a specific inhibitor abrogates MAG up-regulation. We postulate that MASS1 senses extracellular calcium and activates cytosolic PKA/PKC pathways to regulate myelination by means of MAG protein stability in myelin-forming cells of the auditory pathway. Further work is required to determine whether MAG dysregulation is a cause or consequence of audiogenic epilepsy and whether there are other pathways regulated by MASS1.

Early age conductive hearing loss causes audiogenic seizure and hyperacusis behavior.

Recent clinical reports found a high incidence of recurrent otitis media in children suffering hyperacusis, a marked intolerance to an otherwise ordinary environmental sound. However, it is unclear whether the conductive hearing loss caused by otitis media in early age will affect sound tolerance later in life. Thus, we have tested the effects of tympanic membrane (TM) damage at an early age on sound perception development in rats. Two weeks after the TM perforation, more than 80% of the rats showed audiogenic seizure (AGS) when exposed to loud sound (120 dB SPL white noise, < 1 min). The susceptibility of AGS lasted at least sixteen weeks after the TM damage, even the hearing loss recovered. The TM damaged rats also showed significantly enhanced acoustic startle responses compared to the rats without TM damage. These results suggest that early age conductive hearing loss may cause an impaired sound tolerance during development. In addition, the AGS can be suppressed by the treatment of vigabatrin, acute injections (250 mg/kg) or oral intakes (60 mg/kg/day for 7 days), an antiepileptic drug that inhibits the catabolism of GABA. c-Fos staining showed a strong staining in the inferior colliculus (IC) in the TM damaged rats, not in the control rats, after exposed to loud sound, indicating a hyper-excitability in the IC during AGS. These results indicate that early age conductive hearing loss can impair sound tolerance by reducing GABA inhibition in the IC, which may be related to hyperacusis seen in children with otitis media.

cAMP-dependent phosphorylation of microtubule-associated protein-2 during treatment of sodium valproate and audiogenic kindling.

Administration of anticonvulsant sodium valproate alleviated audiogenic seizures in Krushinskii-Molodkina rats, which was accompanied by a decrease in cAMP-dependent phosphorylation of microtubule-associated protein MAP2 in the hippocampus ex vivo. In contrast, audiogenic kindling resulted in a marked increase in MAP2 phosphorylation at cAMP-dependent protein kinase-specific sites. These changes in the state of MAP2 phosphorylation providing restructuring of dendrites in response to specific influences modulate neuronal activity and are the important mechanisms of neuronal plasticity.

Elevated sulfatide levels in neurons cause lethal audiogenic seizures in mice.

Galactosylceramide (GalCer) and 3-O-sulfo-GalCer (sulfatide) are abundant sphingolipids in myelinating glial cells. However, low levels of GalCer and sulfatide have also been found in neurons, though their physiological role in these cells is unknown. Transgenic mice over-expressing UDP-galactose : ceramide galactosyltransferase (CGT) under control of the Thy1.2 promoter synthesize C18 : 0 fatty acid containing GalCer and sulfatide in neurons. Depending on the genetic background, these transgenic mice have a significantly reduced life span. Transgenic mice were extremely sensitive to sound stimuli and displayed lethal audiogenic seizures after relatively mild acoustic stimulation, i.e., key jangling. CGT-transgenic mice additionally over-expressing the adenosine 3'-phospho 5'-phosphosulfate : cerebroside sulfotransferase were more sensitive to audiogenic seizure induction than mice expressing only the CGT-transgene. This correlated with the higher sulfatide content in neuronal plasma membranes of the double-transgenic mice compared with CGT-transgenic mice, and strongly suggests that lethal audiogenic seizures are caused by elevated sulfatide levels in transgenic neurons. CGT-transgenic mice will be a useful model to further investigate how sulfatide affects functional properties of neurons.

A spontaneous mutation of the Wwox gene and audiogenic seizures in rats with lethal dwarfism and epilepsy.

The lde/lde rat is characterized by dwarfism, postnatal lethality, male hypogonadism, a high incidence of epilepsy and many vacuoles in the hippocampus and amygdala. We used a candidate approach to identify the gene responsible for the lde phenotype and assessed the susceptibility of lde/lde rats for audiogenic seizures. Following backcross breeding of lethal dwarfism with epilepsy (LDE) to Brown Norway rats, the lde/lde rats with an altered genetic background showed all pleiotropic phenotypes. The lde locus was mapped to a 1.5-Mbp region on rat chromosome 19 that included the latter half of the Wwox gene. Sequencing of the full-length Wwox transcript identified a 13-bp deletion in exon 9 in lde/lde rats. This mutation causes a frame shift, resulting in aberrant amino acid sequences at the C-terminal. Western blotting showed that both the full-length products of the Wwox gene and its isoform were present in normal testes and hippocampi, whereas both products were undetectable in the testes and hippocampi of lde/lde rats. Sound stimulation induced epileptic seizures in 95% of lde/lde rats, with starting as wild running (WR), sometimes progressing to tonic-clonic convulsions. Electroencephalogram (EEG) analysis showed interictal spikes, fast waves during WR and burst of spikes during clonic phases. The Wwox protein is expressed in the central nervous system (CNS), indicating that abnormal neuronal excitability in lde/lde rats may be because of a lack of Wwox function. The lde/lde rat is not only useful for understanding the multiple functions of Wwox but is also a unique model for studying the physiological function of Wwox in CNS.

The expression of glutamate transporters in chest compression-induced audiogenic epilepsy: a comparative study.

BACKGROUND: This study was conducted to compare the expression of three glutamate transporter subtypes (GLAST, GLT-1 and EAAC1) in rats undergoing chest compression-induced global cerebral ischemia in the presence and absence of cerebral ischemia-related epilepsy. MATERIAL AND METHODS: A reliable rat model of global cerebral ischemia-related epilepsy was established. The rats were divided into the following groups: sham surgery group (Group S), global cerebral ischemia without epilepsy (Group I) and global cerebral ischemia with epilepsy (Group E). The latter two groups were further divided into four subgroups based on time (24 hours, 72 hours, 5 days and 7 days) after 8 minutes of chest compression. Electroencephalographic recordings were obtained in all rats. Hippocampal tissue samples were prepared, and the expression of GLAST, GLT-1 and EAAC1 in the hippocampal CA1 region and the motor cortex area was studied using immunohistochemical methods. RESULTS: Seizure developed in 32 (64%) of 50 rats. Compared with that in group I, the expression of GLT-1 in the hippocampal CA1 region and the motor cortex area in group E was down-regulated, and EAAC1 was up-regulated in those regions. CONCLUSION: Altering the expression of GLT-1 and EAAC1 through some means might lead them to be potential targets for therapy in cerebral ischemia-related epilepsy.

c-Fos immunohistochemical mapping of the audiogenic seizure network and tonotopic neuronal hyperexcitability in the inferior colliculus of the Frings mouse.

The Frings mouse is a model of audiogenic seizure (AGS) susceptibility. The genetic locus responsible for the AGS phenotype in the Frings mouse has been named monogenic audiogenic seizure-susceptible (MASS1). MASS1 is unique in that it is one of only two identified seizure loci that are not associated with an ion channel mutation. Furthermore, Frings mice display a robust AGS phenotype demonstrating very high and prolonged susceptibility to sound-induced tonic extension seizures. The purpose of this investigation was to use c-Fos immunohistochemistry to map the brain structures involved in the Frings AGS and to examine neuronal hyperexcitability in the inferior colliculus, the brain structure that is recognized as the site of AGS initiation. AGS mapping revealed that intense seizure-induced neuronal activation was mostly limited to structures involved in a brainstem seizure network, including the external and dorsal nuclei of the inferior colliculus, as observed in other AGS rodents. Acoustically induced c-Fos expression in the central nucleus of the inferior colliculus to sub-AGS threshold tone stimulations displayed a greater level of neuronal activation in AGS-susceptible Frings, DBA/2J and noise-primed C57BL/6J mice compared to AGS-resistant C57BL/6J and CF1 mice. The AGS-susceptible mice also displayed c-Fos immunoreactivity that was more focused within the tonotopic response domain of the inferior colliculus compared to AGS-resistant mice. Furthermore, Frings mice displayed significantly greater tonotopic hyper-responsiveness compared to other AGS-susceptible mice.

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

Interleukin-6-deficient (IL-6(-/-)) mice and their normal littermate (WT) were studied to evaluate their susceptibility to seizures induced by electroshock and audiogenic stimuli at different ages. No significant changes in maximal electroshock susceptibility were evidenced between the two strains, while audiogenic seizures (AGS) can be induced only in IL-6(-/-) mice. The effects of age and genetic condition on AGSs were evaluated. The behavioural and electrocortical changes during audiogenic stimulus were observed. In addition, the levels of neurotransmitter amino acids in five brain areas (of both strains) were measured at 60 days of age. Aspartate level significantly increased in the brain stem (BS) and hippocampus (HI), while it decreased in the diencephalon (DE) of IL-6(-/-) mice. Glutamate content significantly decreased in the cerebellum (CB), DE and HI. GABA levels significantly decreased in all the areas studied. Glycine significantly decreased in the BS, CB and DE, while taurine decreased only in the DE. The levels of glutamine significantly decreased in all the areas examined, except in the cortex (CX). The changes of neuroactive amino acid levels, particularly in the BS, might explain the characteristic of high propensity to AGS of IL-6(-/-) mice. The present data support the validity of IL-6(-/-) mice as a novel epileptic model for the study of the pathophysiology and pharmacology of epilepsy.

Comparative fos immunoreactivity in the brain after forebrain, brainstem, or combined seizures induced by electroshock, pentylenetetrazol, focally induced and audiogenic seizures in rats.

To help discern sites of focal activation during seizures of different phenotype, the numbers of Fos immunoreactive (FI) neurons in specific brain regions were analyzed following "brainstem-evoked," "forebrain-evoked" and forebrain/brainstem combination seizures induced by a variety of methods. First, pentylenetetrazol (PTZ, 50 mg/kg) induced forebrain-type seizures in some rats, or forebrain seizures that progressed to tonic/clonic brainstem-type seizures in other rats. Second, minimal electroshock induced forebrain seizures whereas maximal electroshock (MES) induced tonic brainstem-type seizures in rats. Third, forebrain seizures were induced in genetically epilepsy-prone rats (GEPRs) by microinfusion of bicuculline into the area tempestas (AT), while brainstem seizures in GEPRs were induced by audiogenic stimulation. A final set was included in which AT bicuculline-induced forebrain seizures in GEPRs were transiently interrupted by audiogenic seizures (AGS) in the same animals. These animals exhibited a sequence combination of forebrain clonic seizure, brainstem tonic seizure and back to forebrain clonic seizures. Irrespective of the methods of induction, clonic forebrain- and tonic/clonic brainstem-type seizures were associated with considerable Fos immunoreactivity in several forebrain structures. Tonic/clonic brainstem seizures, irrespective of the methods of induction, were also associated with FI in consistent brainstem regions. Thus, based on Fos numerical densities (FND, numbers of Fos-stained profiles), forebrain structures appear to be highly activated during both forebrain and brainstem seizures; however, facial and forelimb clonus characteristic of forebrain seizures are not observable during a brainstem seizure. This observation suggests that forebrain-seizure behaviors may be behaviorally masked during the more severe tonic brainstem seizures induced either by MES, PTZ or AGS in GEPRs. This suggestion was corroborated using the sequential seizure paradigm. Similar to findings using MES and PTZ, forebrain regions activated by AT bicuculline were similar to those activated by AGS in the GEPR. However, in the combination seizure group, those areas that showed increased FND in the forebrain showed even greater FND in the combination trial. Likewise, those areas of the brainstem showing FI in the AGS model, showed an even greater effect in the combination paradigm. Finally, the medial amygdala, ventral hypothalamus and cortices of the inferior colliculi showed markedly increased FND that appeared dependent upon activation of both forebrain and brainstem seizure activity in the same animal. These findings suggest these latter areas may be transitional areas between forebrain and brainstem seizure interactions. Collectively, these data illustrate a generally consistent pattern of forebrain Fos staining associated with forebrain-type seizures and a consistent pattern of brainstem Fos staining associated with brainstem-type seizures. Additionally, these data are consistent with a notion that separate seizure circuitries in the forebrain and brainstem mutually interact to facilitate one another, possibly through involvement of specific "transition mediating" nuclei.

Fos expression in GABAergic cells and cells immunopositive for NMDA receptors in the inferior and superior colliculi following audiogenic seizures in rats.

Given the evidence that the inferior colliculus (IC) and superior colliculus (SC) seem to play key roles in connecting auditory pathways and seizure output pathways in the neuronal network for audiogenic seizures (AS) in rats, we examined Fos activation in GABAergic cells and cells immunopositive for glutamate N-methyl-D-aspartate (NMDA) receptors in the IC and SC following AS using the double-labeling procedure. Generalized tonic-clonic seizures (GTCS), which developed as an advanced form of AS in some of the susceptible rats, induced an increase in Fos expression in three IC substructures-the dorsal cortex of IC (DCIC), central nucleus of IC (CIC), and external cortex of IC (ECIC)-and in one SC substructure, the deep gray layer of SC (DpG). Compared with the rats showing GTCS, rats exhibiting wild running (WR) without proceeding to GTCS showed a different pattern of AS-induced Fos expression. The DpG in the WR animals showed no significant increase in the levels of Fos-like immunoreactivity. The degrees of Fos activation that occurred in GABAergic cells and cells immunopositive for NMDA receptors were similar in the DCIC, CIC, ECIC, and DpG following AS. These results suggest that Fos activation in the DpG is involved in the development from WR to GTCS in AS-susceptible rats. They also provide some evidence that some GABAergic neurons in the IC and SC and glutamatergic afferents (via NMDA receptors) to these structures are activated by AS.

Involvement of cAMP- and Ca(2+)/calmodulin-dependent neuronal protein phosphorylation in mechanisms underlying genetic predisposition to audiogenic seizures in rats.

It was shown that increased excitability in neurons underlying epilepsies would be maintained by abnormalities in protein phosphorylation systems. This study was initiated to compare the functioning of Ca(2+)/calmodulin- and cAMP-dependent systems of protein phosphorylation in homogenates of neocortex and hippocampus in three animal groups: genetically prone to audiogenic seizures (GPAS) rats, GPAS rats exposed to daily repeated audiogenic seizures (AGPAS rats) and nonepileptic Wistar ones. We found significant differences in phosphorylation of 270, 58, 54 and 42 kDa proteins in neocortex and hippocampus of GPAS rats in comparison with Wistar ones. Daily repeated seizures induced further modifications of phosphorylation of these proteins in only hippocampus of AGPAS rats as compared with GPAS ones. Ca(2+)-independent, functional CAMKII activity was considerably increased in hippocampus but decreased in neocortex of GPAS rats in comparison with Wistar ones. The activity of PKA was increased both in neocortex and hippocampus of GPAS rats. Daily repeated audiogenic seizures induced the decrease of Ca(2+)-independent CAMKII activity in hippocampus and the increase of PKA activity in neocortex of AGPAS rats in comparison with GPAS ones. The present results indicate that modification of 270, 58, 54, and 42 kDa proteins phosphorylation as well as altered CAMKII and PKA activities might be involved in mechanisms of genetic predisposition to audiogenic seizures.

Influence of D-cycloserine on the anticonvulsant activity of some antiepileptic drugs against audiogenic seizures in DBA/2 mice.

D-Cycloserine (DCS; 1-100 mg/kg, intraperitoneally (i.p.)) was able to antagonise the audiogenic seizures in DBA/2 mice in a dose-dependent manner. DCS, 2.5 mg/kg i.p. did not significantly affect the occurrence of audiogenic seizures in DBA/2 mice, but potentiated the anticonvulsant activity of carbamazepine, diazepam, felbamate, lamotrigine, phenytoin, phenobarbital and valproate against sound-induced seizures in DBA/2 mice. The degree of potentiation induced by DCS was greatest for diazepam, phenobarbital, phenytoin and valproate, less for carbamazepine and least for lamotrigine and felbamate. The increase in anticonvulsant activity was usually associated with a comparable increase in motor impairment. However, the therapeutic index of the combined treatment of the above drugs+DCS, was more favourable than the same drugs+saline with the exception of DCS+carbamazepine and DCS+lamotrigine. Since DCS did not significantly influence the total and free plasma levels of the anticonvulsant drugs studied, pharmacokinetic interactions, in terms of plasma levels, are not probable. The possibility that DCS can modify the clearance from the brain of the anticonvulsant drugs studied cannot be excluded. DCS did not significantly affect the hypothermic effects of the anticonvulsants tested. In conclusion, DCS potentiates the anticonvulsant action of some classical antiepileptic drugs, most notably diazepam, phenobarbital, phenytoin and valproate.

Modulation of audiogenic seizures by histamine and adenosine receptors in the inferior colliculus.

Susceptibility to behaviorally similar audiogenic seizures (AGS) occurs genetically and is inducible during ethanol withdrawal (ETX). Comparisons between AGS mechanisms of genetically epilepsy-prone rats (GEPR-9s) and ethanol-withdrawn rats (ETX-Rs) are yielding information about general pathophysiological mechanisms of epileptogenesis. The inferior colliculus (IC) is the AGS initiation site. Excitatory amino acid (EAA) abnormalities in the IC are implicated in AGS, and histamine and adenosine receptor activation each reduce EAA release and inhibit several seizure types. Previous studies indicate that focal infusion of an adenosine receptor agonist into the IC blocked AGS in GEPR-9s, but the effects of adenosine receptor activation in the IC on AGS in ETX-Rs are unknown. The effects of histamine receptor activation on either form of AGS are also unexamined. The present study evaluated effects of histamine or a nonselective adenosine A(1) agonist, 2-chloroadenosine, on AGS by focal microinjection into the IC. Ethanol dependence and AGS susceptibility were induced in normal rats by intragastric ethanol. Histamine (40 or 60 nmol/side) significantly reduced AGS in GEPR-9s, but histamine in doses up to 120 nmol/side did not affect AGS in ETX-Rs. 2-Chloroadenosine (5 or 10 nmol/side) did not affect AGS in ETX-Rs, despite the effectiveness of lower doses of this agent in GEPR-9s reported previously. Thus, histamine and adenosine receptors in the IC modulate AGS of GEPR-9s, but do not modulate ETX-induced AGS. The reasons for this difference may involve the chronicity of AGS susceptibility in GEPR-9s, which may lead to more extensive neuromodulation as compensatory mechanisms to limit the seizures compared to the acute AGS of ETX-Rs.