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The genetic audiogenic seizure hamster from Salamanca: The GASH:Sal
... The hamster strain GASH/Sal is a natural model for audiogenic seizures, where altered GABA signaling plays a key role (19)(20)(21). The inferior colliculus is a major center for auditory processing, where GABA is the central inhibitory neurotransmitter; it is the generally accepted initiation site for all audiogenic models. ...
... The epileptic hamster groups consisted of three-month-old male seizure-prone hamster belonging to the GASH/Sal strain. This strain derives from one original epileptic hamster which appeared spontaneously at the University of Valladolid and gave rise to the first seizureprone hamster strain called GPG:Vall (19). The hamsters in this study were obtained from the inbred strain maintained at the animal facility of the University of Salamanca (USAL, Spain) and were housed during the experiments at facilities of the Research Department of the Albacete General Hospital, Spain. ...
... The findings of altered NKCC1 and GAD67 expression in response to seizures in the GASH/Sal strain support the use of this model to investigate the various factors that impact the GABAergic system in epilepsy. The GASH/Sal strain is a natural model of genetic audiogenic epilepsy (19), validated by ictal electroencephalogram recordings (Carballosa-Gonzalez) and the similarity of GASH/Sal seizures to other established models (20). The involvement of GABA neurotransmission in GASH/Sal epilepsy is supported by the dysregulation of GABA A R found in this model (23). ...
Background
The balance between the activity of the Na ⁺ /K ⁺ /Cl ⁻ cotransporter (NKCC1) that introduces Cl ⁻ into the cell and the K ⁺ /Cl ⁻ cotransporter (KCC2) that transports Cl ⁻ outside the cell is critical in determining the inhibitory or excitatory outcome of GABA release. Mounting evidence suggests that the impairment of GABAergic inhibitory neurotransmission plays a crucial role in the pathophysiology of epilepsy, both in patients and animal models. Previous studies indicate that decreased KCC2 expression is linked to audiogenic seizures in GASH/Sal hamsters, highlighting that Cl ⁻ imbalance can cause neuronal hyperexcitability. In this study, we aimed to investigate whether the Na ⁺ /K ⁺ /Cl ⁻ cotransporter NKCC1 is also affected by audiogenic seizures and could, therefore, play a role in neuronal hyperexcitability within the GASH/Sal epilepsy model.
Methods
NKCC1 protein expression in both the GASH/Sal strain and wild type hamsters was analyzed by immunohistochemistry and Western blotting techniques. Brain regions examined included cortex, hippocampus, hypothalamus, inferior colliculus and pons-medulla oblongata, which were evaluated both at rest and after sound-inducing seizures in GASH/Sal hamsters. A complementary analysis of NKCC1 gene slc12a2 expression was conducted by real-time PCR. Finally, protein and mRNA levels of glutamate decarboxylase GAD67 were measured as an indicator of GABA release.
Results
The induction of seizures caused significant changes in NKCC1 expression in epileptic GASH/Sal hamsters, despite the similar brain expression pattern of NKCC1 in GASH/Sal and wild type hamsters in the absence of seizures. Interestingly, the regulation of brain NKCC1 by seizures demonstrated regional specificity, as protein levels exclusively increased in the hippocampus and hypothalamus. Complementary real-time PCR analysis revealed that NKCC1 regulation was post-transcriptional only in the hypothalamus. In addition, seizures also modulated GAD67 mRNA levels in a brain region-specific manner. The increased GAD67 expression in the hippocampus and hypothalamus of the epileptic hamster brain suggests that NKCC1 upregulation overlaps with GABA release in these regions during seizures.
Conclusions
Our results indicate that seizure induction causes dysregulation of NKCC1 expression in GASH/Sal animals, which overlaps with changes in GABA release. These observations provide evidence for the critical role of NKCC1 in how seizures affect neuronal excitability, and support NKCC1 contribution to the development of secondary foci of epileptogenic activity.
... The genetic audiogenic seizure hamster from Salamanca (GASH/Sal) is a genetic model of audiogenic seizures derived from an autosomal recessive disorder. The GASH/Sal model exhibits generalized tonic-clonic audiogenic seizures induced by high-intensity acoustic stimulation, mimicking those sensory-evoked reflex seizures seen in humans [24]. This animal model of epilepsy has the potential to offer innate susceptibility to the development of convulsive seizures in response to acoustic stimuli, without genetic or chemical manipulation, in contrast to other models, which only enable epilepsy studies in the context of the effects of a knocked gene of interest. ...
... To identify gene variants possibly implicated in the development of audiogenic seizures in the GASH/Sal strain, additional selection criteria were defined and applied to focus our study on the variants that are most likely to be involved in the phenotype of our experimental model. These criteria include the presence of homozygous mutations in GASH/Sal animals, because susceptibility is inherited in an autosomal recessive inheritance pattern [24], the existence of similar mutations related to the development of seizures or different types of epilepsy, in both humans and animal models, and the lack of duplicates and adequate coverage. After applying these criteria, 22 qualifying variants were selected, namely 7 high-and 15 moderate-impact variants (Table 1). ...
... In all these models, different types of studies on seizures and pharmacological treatments have been conducted in the inferior colliculus as an epileptogenic nucleus and in auditory pathways [31,[74][75][76][77][78]. In the GASH/Sal model, previous studies have determined that susceptibility to developing the epileptic phenotype shows an autosomal recessive inheritance pattern [24]. A recent study, which analyzed the transcriptome of the WAR model, highlighted changes in the expression of 64 genes after audiogenic stimulation, thereby identifying new genes involved in the epileptic phenotype [79]. ...
Epilepsy is a complex neurological disorder characterized by sudden and recurrent seizures, which are caused by various factors, including genetic abnormalities. Several animal models of epilepsy mimic the different symptoms of this disorder. In particular, the genetic audiogenic seizure hamster from Salamanca (GASH/Sal) animals exhibit sound-induced seizures similar to the generalized tonic seizures observed in epileptic patients. However, the genetic alterations underlying the audiogenic seizure susceptibility of the GASH/Sal model remain unknown. In addition, gene variations in the GASH/Sal might have a close resemblance with those described in humans with epilepsy, which is a prerequisite for any new preclinical studies that target genetic abnormalities. Here, we performed whole exome sequencing (WES) in GASH/Sal animals and their corresponding controls to identify and characterize the mutational landscape of the GASH/Sal strain. After filtering the results, moderate- and high-impact variants were validated by Sanger sequencing, assessing the possible impact of the mutations by “in silico” reconstruction of the encoded proteins and analyzing their corresponding biological pathways. Lastly, we quantified gene expression levels by RT-qPCR. In the GASH/Sal model, WES showed the presence of 342 variations, in which 21 were classified as high-impact mutations. After a full bioinformatics analysis to highlight the high quality and reliable variants, the presence of 3 high-impact and 15 moderate-impact variants were identified. Gene expression analysis of the high-impact variants of Asb14 (ankyrin repeat and SOCS Box Containing 14), Msh3 (MutS Homolog 3) and Arhgef38 (Rho Guanine Nucleotide Exchange Factor 38) genes showed a higher expression in the GASH/Sal than in control hamsters. In silico analysis of the functional consequences indicated that those mutations in the three encoded proteins would have severe functional alterations. By functional analysis of the variants, we detected 44 significantly enriched pathways, including the glutamatergic synapse pathway. The data show three high-impact mutations with a major impact on the function of the proteins encoded by these genes, although no mutation in these three genes has been associated with some type of epilepsy until now. Furthermore, GASH/Sal animals also showed gene variants associated with different types of epilepsy that has been extensively documented, as well as mutations in other genes that encode proteins with functions related to neuronal excitability, which could be implied in the phenotype of the GASH/Sal. Our findings provide valuable genetic and biological pathway data associated to the genetic burden of the audiogenic seizure susceptibility and reinforce the need to validate the role of each key mutation in the phenotype of the GASH/Sal model.
... The Wistar Audiogenic Rat (WAR) and the Genetic Audiogenic Seizure Hamster from Salamanca (GASH/Sal) strains are the most recent audiogenic models in rodents (8,9). Although they originate from different species, the WAR and GASH/Sal strains present common aspects. ...
... Although they originate from different species, the WAR and GASH/Sal strains present common aspects. Both are genetic models sensitive to sound stimuli, the WAR strain developed by selective reproduction of Wistar animals and the GASH/Sal strain with DNA mutations arising in a colony of Syrian hamsters (8,9). During acoustic stimulation (sound intensity 110-120 dB), WAR and GASH/Sal animals exhibit a latency period that is interrupted by a wild running and subsequent generalized tonic-clonic seizures that may progress to more severe motor manifestations, such as dorsoventral flexion of the neck and hyperextension of the forelimbs and hindlimbs (8,9). ...
... Both are genetic models sensitive to sound stimuli, the WAR strain developed by selective reproduction of Wistar animals and the GASH/Sal strain with DNA mutations arising in a colony of Syrian hamsters (8,9). During acoustic stimulation (sound intensity 110-120 dB), WAR and GASH/Sal animals exhibit a latency period that is interrupted by a wild running and subsequent generalized tonic-clonic seizures that may progress to more severe motor manifestations, such as dorsoventral flexion of the neck and hyperextension of the forelimbs and hindlimbs (8,9). ...
The Wistar Audiogenic Rat (WAR) and the Genetic Audiogenic Seizure Hamster from Salamanca (GASH/Sal) strains are audiogenic epilepsy models, in which seizures are triggered by acoustic stimulation. These strains were developed by selective reproduction and have a genetic background with minimal or no variation. In the current study, we evaluated the transcriptome of the inferior colliculus, the epileptogenic nucleus, of both audiogenic models, in order to get insights into common molecular aspects associated to their epileptic phenotype. Based on GASH/Sal RNA-Seq and WAR microarray data, we performed a comparative analysis that includes selection and functional annotation of differentially regulated genes in each model, transcriptional evaluation by quantitative reverse transcription PCR of common genes identified in both transcriptomes and immunohistochemistry. The microarray data revealed 71 genes with differential expression in WAR, and the RNA-Seq data revealed 64 genes in GASH/Sal, showing common genes in both models. Analysis of transcripts showed that Egr3 was overexpressed in WAR and GASH/Sal after audiogenic seizures. The Npy, Rgs2, Ttr, and Abcb1a genes presented the same transcriptional profile in the WAR, being overexpressed in the naïve and stimulated WAR in relation to their controls. Npy appeared overexpressed only in the naïve GASH/Sal compared to its control, while Rgs2 and Ttr genes appeared overexpressed in naïve GASH/Sal and overexpressed after audiogenic seizure. No statistical difference was observed in the expression of Abcb1a in the GASH/Sal model. Compared to control animals, the immunohistochemical analysis of the inferior colliculus showed an increased immunoreactivity for NPY, RGS2, and TTR in both audiogenic models. Our data suggest that WAR and GASH/Sal strains have a difference in the timing of gene expression after seizure, in which GASH/Sal seems to respond more quickly. The transcriptional profile of the Npy, Rgs2, and Ttr genes under free-seizure conditions in both audiogenic models indicates an intrinsic expression Damasceno et al. Transcriptome GASH/Sal and WAR Models already established in the strains. Our findings suggest that these genes may be causing small changes in different biological processes involved in seizure occurrence and response, and indirectly contributing to the susceptibility of the WAR and GASH/Sal models to audiogenic seizures.
... The genetic audiogenic seizure hamster (GASH:Sal), in which exposure to intense acoustic stimulation induces generalized convulsive audiogenic seizures, is a strain of Syrian hamster inbred at the University of Salamanca [1]. Recent studies have supported the GASH:Sal as a promising animal model to study the development of epileptic seizures [2][3][4] and the characterization of antiepileptic drugs [5,6]. Functional, electrophysiological, and structural characterization of the auditory pathways in the GASH:Sal might be a further step towards understanding the pathophysiological mechanisms involved in different types of seizures including focal and generalized tonic-clonic seizures. ...
... Several audiogenic seizure-susceptible strains have been genetically selected worldwide [8,9]. The GASH:Sal was originated at the University of Salamanca [1] and exhibits epileptic seizures in response to sounds [3,4]. After acoustic stimulation, the seizure appears within seconds and lasts for approximately 5 min, following a sequence of behavioral phases: wild running, tonic-clonic seizures, and a comatose postictal phase with subsequent recovery. ...
... After acoustic stimulation, the seizure appears within seconds and lasts for approximately 5 min, following a sequence of behavioral phases: wild running, tonic-clonic seizures, and a comatose postictal phase with subsequent recovery. The GASH:Sal hamsters exhibit their maximum susceptibility to seizures from 1 to 4 months of age, but this condition gradually disappears around the age of 1 year, showing the running phase without the convulsive phase [4,5]. ...
... It was developed at the University of Salamanca, and it exhibits genetic audiogenic epilepsy similar to human tonic-clonic seizures. 37 Additionally, it shows an autosomal recessive inheritance for susceptibility to audiogenic seizures and has already been validated as a model of epilepsy from a behavioral, 38 electroencephalographic, 37 and pharmacological perspective. 39,40 The analysis of gene variants in the GASH/Sal model has been previously published by Diaz-Casado et al. 41 GASH/Sal hamsters undergo generalized tonicclonic seizures that originate in the brainstem, characterized by a short latency period after auditory stimulation, followed by wild running, a convulsive phase, and a stupor period. ...
... 39,40 The analysis of gene variants in the GASH/Sal model has been previously published by Diaz-Casado et al. 41 GASH/Sal hamsters undergo generalized tonicclonic seizures that originate in the brainstem, characterized by a short latency period after auditory stimulation, followed by wild running, a convulsive phase, and a stupor period. 38 In contrast to traditional models of epilepsy induced by chemical or electrical means, the GASH/Sal model of genetic origin offers several advantages, such as innate susceptibility to seizures and the relative simplicity of the procedure to elicit seizures. ...
... On the other hand, CB1 receptor knockout mice possess poorer hearing thresholds than wild-type mice (Toal et al., 2016). The GASH/Sal has been described to exhibit a significant loss of spiral ganglion neurons (Sánchez-Benito et al., 2017), which results in a reduction in the amount of CB1Rs in the spiral ganglion, consistent with the significant hearing deficit in this model (Muñoz et al., 2017). ...
... The inferior colliculus (IC) is critical in audiogenic seizures (AGS) initiation Muñoz et al., 2017). Given the involvement of CB1R in seizures, a higher density of this receptor would be expected to be observed in the GASH/Sal' IC. ...
The endocannabinoid system modulates epileptic seizures by regulating neuronal excitability. It has become clear that agonist activation of central type I cannabinoid receptors (CB1R) reduces epileptogenesis in pre-clinical animal models of epilepsy. The audiogenic seizure-prone hamster GASH/Sal is a reliable experimental model of generalized tonic-clonic seizures in response to intense sound stimulation. However, no studies hitherto had investigated CB1R in the GASH/Sal. Although the distribution of CB1R has been extensively studied in mammalian brains, their distribution in the Syrian golden hamster brain also remains unknown. The objective of this research is to determine by immunohistochemistry the differential distribution of CB1R in the brains of GASH/Sal animals under seizure-free conditions, by comparing the results with wild-type Syrian hamsters as controls. CB1R in the GASH/Sal showed a wide distribution in many nuclei of the central nervous system. These patterns of CB1R-immunolabeling are practically identical between the GASH/Sal model and control animals, varying in the intensity of immunostaining in certain regions, being slightly weaker in the GASH/Sal than in the control, mainly in brain regions associated with epileptic networks. The RT-qPCR analysis confirms these results. In summary, our study provides an anatomical basis for further investigating CB1R in acute and kindling audiogenic seizure protocols in the GASH/Sal model as well as exploring CB1R activation via exogenously administered cannabinoid compounds.
... Thus, by using a neuroethological approach (Garcia-Cairasco et al., 1996, we carried out a quantitative behavioral analysis of the AGS phases after the treatments with VPA, CBD, or the combination of both drugs. As occurred in other AGS rodent models, activation of the auditory pathway is required for seizure development in the GASH/Sal model (Garcia-Cairasco, 2002;Muñoz et al., 2017). In fact, the innate AGS susceptibility of the GASH/Sal model lies in an upward spread of abnormal glutamatergic transmission throughout the primary acoustic pathway to the inferior colliculus, a critical integration center in the auditory midbrain that is considered the epileptogenic region (Sánchez-Benito et al., 2020). ...
... During loud acoustic stimulation and prior to any of the drug treatments, all GASH/Sal animals displayed a complete AGS as described by Muñoz et al. (2017). Beginning between 1 and 3 s after the stimulus onset, the GASH/Sal animals showed five differenced and consecutive phases that included (1) a behavioral arrest; (2) a wild-running period of nearly 5 s; (3) tonic-clonic convulsions for approximately 33 s; (4) head ventral flexion, forelimb, and hindlimb extensions; and (5) postictal immobility (stupor). ...
Despite evidence that supports cannabidiol (CBD) as an anticonvulsant agent, there remains controversy over the antiseizure efficacy, possible adverse effects, and synergistic interactions with classic antiepileptics such as valproate (VPA). The genetic audiogenic seizure hamster from the University of Salamanca (GASH/Sal) is a reliable experimental model of generalized tonic–clonic seizures in response to intense sound stimulation. The present study examines the behavioral and molecular effects of acute and chronic intraperitoneal administrations of VPA (300 mg/kg) and CBD (100 mg/kg) on the GASH/Sal audiogenic seizures, as well as the coadministration of both drugs. The GASH/Sal animals were examined prior to and after the corresponding treatment at 45 min, 7 days, and 14 days for seizure severity and neuroethology, open-field behaviors, body weight variations, and various hematological and biochemical parameters. Furthermore, the brain tissue containing the inferior colliculus (so-called epileptogenic nucleus) was processed for reverse transcription–quantitative polymerase chain reaction analysis to determine the treatment effects on the gene expression of neuronal receptors associated with drug actions and ictogenesis. Our results indicated that single dose of VPA helps prevent the animals from getting convulsions, showing complete elimination of seizures, whereas 7 days of chronic VPA treatment had few effects in seizure behaviors. Acute CBD administration showed subtle attenuation of seizure behaviors, increasing seizure latency and decreasing the duration of the convulsion phase, but without entirely seizure abolition. Chronic CBD treatments had no significant effects on sound-induced seizures, although some animals slightly improved seizure severity. Acute and chronic CBD treatments have no significant adverse effects on body weight, hematological parameters, and liver function, although locomotor activity was reduced. The combination of VPA and CBD did not alter the therapeutic outcome of the VPA monotherapy, showing no apparent synergistic effects. As compared to sham animals, chronic treatments with CBD caused abnormal mRNA expression levels for Trpv1, Adora1, Slc29a1 , and Cnr1 genes, whereas no differences in gene expression were found for Htr1a and Sigmar1 . Our study shed light on the behavioral and molecular effects of CBD and VPA on the GASH/Sal model and constituted the basis to develop further studies on the pharmacological effects of CBD and its interactions with other anticonvulsants.
... The complexity of this neurological disorder requires models for exploring different aspects of epilepsy [6]. Among the most used and well-characterized in vivo genetic models of epilepsy are those genetically predisposed animal species, in which seizures occur in response to high intensity acoustic stimulation, the so-called genetic audiogenic seizure models [7,8]. Genetic and protein alterations have been described as possible contributors to the development of epilepsy phenotypes in the audiogenic seizure models [9][10][11]. ...
... Animal models of epilepsy arose from artificial selection of seizure-susceptible strains over many generations that resulted in high predisposition to epilepsy, as is the case of audiogenic epilepsy models. Examples of rodent audiogenic seizure models are the Genetic Absence Epilepsy Rat from Strasbourg (GAERS; [25]), the Wistar Albino Glaxo from Rijswijk (WAG/Rij; [26]), the Wistar Audiogenic Rat (WAR; [27]), and the genetic audiogenic seizure hamster from Salamanca (GASH/Sal; [7]). Activation of auditory pathways are required for the onset and progression of seizures in all audiogenic seizure models, and many studies pointed out the inferior colliculus (IC), a critical integration center in the auditory midbrain pathway, as the epileptogenic nucleus [6]. ...
Epilepsy is a chronic neurological disorder characterized by abnormal neuronal activity that arises from imbalances between excitatory and inhibitory synapses, which are highly correlated to functional and structural changes in specific brain regions. The difference between the normal and the epileptic brain may harbor genetic alterations, gene expression changes, and/or protein alterations in the epileptogenic nucleus. It is becoming increasingly clear that such differences contribute to the development of distinct epilepsy phenotypes. The current major challenges in epilepsy research include understanding the disease progression and clarifying epilepsy classifications by searching for novel molecular biomarkers. Thus, the application of molecular techniques to carry out comprehensive studies at deoxyribonucleic acid, messenger ribonucleic acid, and protein levels is of utmost importance to elucidate molecular dysregulations in the epileptic brain. The present review focused on the great diversity of technical approaches available and new research methodology, which are already being used to study molecular alterations underlying epilepsy. We have grouped the different techniques according to each step in the flow of information from DNA to RNA to proteins, and illustrated with specific examples in animal models of epilepsy, some of which are our own. Separately and collectively, the genomic and proteomic techniques, each with its own strengths and limitations, provide valuable information on molecular mechanisms underlying seizure susceptibility and regulation of neuronal excitability. Determining the molecular differences between genetic rodent models of epilepsy and their wild-type counterparts might be a key in determining mechanisms of seizure susceptibility and epileptogenesis as well as the discovery and development of novel antiepileptic agents. This article is part of the Special Issue "NEWroscience 2018".
... The WAR strain is a genetic rat model; these rats are prone to audiogenic reflex epilepsy, acutely mimicking brainstemdependent tonic-clonic seizures and chronically mimicking temporal lobe epilepsy [170]. GASH:Sal (genetic audiogenic seizure hamster from Salamanca) exhibits generalized tonicclonic seizures that are characterized by a short latency period after auditory stimulation, followed by wild running, a convulsive phase, and finally stupor, with its origin being in the brainstem [171]. Krushinsky-Molodkina rats demonstrate a stable response to an audiogenic stimulus with a short latency period, which ends with a tonic-clonic seizure [172]. ...
Research into genetic and physiological mechanisms of widespread disorders such as arterial hypertension as well as neuropsychiatric and other human diseases is urgently needed in academic and practical medicine and in the field of biology. Nevertheless, such studies have many limitations and pose difficulties that can be overcome by using animal models. To date, for the purposes of creating animal models of human pathologies, several approaches have been used: pharmacological/chemical intervention; surgical procedures; genetic technologies for creating transgenic animals, knockouts, or knockdowns; and breeding. Although some of these approaches are good for certain research aims, they have many drawbacks, the greatest being a strong perturbation (in a biological system) that, along with the expected effect, exerts side effects in the study. Therefore, for investigating the pathogenesis of a disease, models obtained using genetic selection for a target trait are of high value as this approach allows for the creation of a model with a “natural” manifestation of the pathology. In this review, three rat models are described: ISIAH rats (arterial hypertension), GC rats (catatonia), and PM rats (audiogenic epilepsy), which are developed by breeding in the Laboratory of Evolutionary Genetics at the Institute of Cytology and Genetics (the Siberian Branch of the Russian Academy of Sciences).
... The strain of AE-prone rats (P77PMC) also was selected in China [144,145]. The AE-prone hamster strain GASH/Sal (genetic audiogenic seizure hamster, Salamanca) was obtained in the University of Salamanca [146]. There are also several AE-prone mouse strains that were obtained as a result of spontaneous mutations: Frings, DBA/2J, Black Swiss, 101/HY and BALB/c [137,138,147,148]. ...
Animal models of epilepsy are of great importance in epileptology. They are used to study the mechanisms of epileptogenesis, and search for new genes and regulatory pathways involved in the development of epilepsy as well as screening new antiepileptic drugs. Today, many methods of modeling epilepsy in animals are used, including electroconvulsive, pharmacological in intact animals, and genetic, with the predisposition for spontaneous or refractory epileptic seizures. Due to the simplicity of manipulation and universality, genetic models of audiogenic epilepsy in rodents stand out among this diversity. We tried to combine data on the genetics of audiogenic epilepsy in rodents, the relevance of various models of audiogenic epilepsy to certain epileptic syndromes in humans, and the advantages of using of rodent strains predisposed to audiogenic epilepsy in current epileptology.
... Тонико-клонические судороги -неконтролируемое напряжение или сокращение мышц, наблюдаемое у людей и других млекопитающих: серых крыс Rattus norvegicus (Полетаева и др., 2017), домовых мышей Mus musculus (Skradski et al., 1998), монгольских песчанок Meriones unguiculatus (Buchhalter, 1993), оленьих хомячков Pero myscus maniculatus (Jackson, 1997), сирийского хомячка Mesocricetus auratus (Muñoz et al., 2017), луговой полевки Microtus pennsylvanicus (Bronson, De La Rosa,1994), собак Canis familiaris (Catala et al., 2018), кошек Felis catus (Pakozdy et al., 2014), кроликов (Gülersoy et al., 2021). Наиболее распространенная причина припадков -нарушение баланса возбуждающих и тормозящих нейромедиаторных механизмов в мозге (Полетаева и др., 2017). ...
Finding out the hereditary predisposition to seizures in response to specific external stimuli is important for understanding the causes of epileptiform conditions, developing new methods for their prevention and therapies. In the water vole, individuals with convulsive seizures are found both in natural and laboratory conditions. The data of long-lasting maintenance and breeding of water voles in vivarium conditions were analyzed in order to establish a hereditary predisposition to convulsive seizures, and the influence of sex and age on their development. In the vivarium, seizures are provoked by handling and are observed in 2.4 % of voles caught in the natural population with cyclic fluctuations in abundance. Seizures are observed more often in individuals caught in the phases of decline and depression of abundance than in individuals caught in the phases of rise or peak. Convulsive states are probably an element of adaptive behavior formed in the predator-prey system. In natural conditions, individuals predisposed to convulsive seizures may have a selective advantage when under increasing pressure from predators. Convulsive seizures in response to handling were noted in 29.8 % of descendants of captive-bred water voles. The proportion of such individuals increased significantly if one or both parents had convulsive states, which indicates the presence of a hereditary predisposition to seizures. In parent–offspring pairs, a significant correlation was found between the average age of onset of the first seizures in parents and their offspring, r = 0.42, p < 0.01. The minimum age of registration of seizures in the water vole is 39 days, the maximum is 1105 days, and the median is 274 days. Predisposition to seizures is not related to sex. Genes that control the occurrence of seizures have a pleiotropic effect on life span, since individuals with seizures live longer in vivarium conditions than individuals with a normal phenotype. The water vole can serve as a suitable model object for studying the nature of convulsive states and the evolution of longevity.
... (c) In vivo testing VNS surgery protocol used in the clinic was adapted to the experimental model of epilepsy genetic audiogenic seizure hamster from the University of Salamanca (GASH/Sal) [23]. Traditional VNS in patients requires a surgical intervention, in which a bipolar electrode is placed around the left vagus nerve. ...
In this research, a vagus nerve stimulator has been developed and miniaturized for use in epilepsy research. The board contains all the components necessary for its operation during the standard duration of the experiments, being possible to control it once implanted and even being able to reuse it. The VNS system has been designed for rodents since the VNS devices available for human are not only too large for laboratory animals, but also too expensive. With this solution the expenditure on materials made by laboratories is greatly reduced and bioethical considerations were kept in mind. The system was validated in hamsters.
This article is part of the theme issue ‘Advanced neurotechnologies: translating innovation for health and well-being’.
... Hamsters have long been used in behavioral science, especially to study the effects of seasonal endocrinological changes and the circadian rhythm (De Lorme et al., 2013;Harris, 2017;Korf, 2018;Loudon et al., 2007). They are also useful for research in the fields of reproductive biology (Hirose and Ogura, 2019) and epilepsy (Munoz et al., 2017). Hamsters have been used to study infectious diseases: they are used to model certain cutaneous leishmaniasis (Mears et al., 2015), prion diseases (Eckland et al., 2018), and recently they have found increasing use as a model to study viral infections . ...
Model animals are indispensable for the study of human diseases, and in general, of complex biological processes. The Syrian hamster is an important model animal for infectious diseases, behavioral, and metabolic science for which more experimental tools are becoming available. Here, we describe the generation and characterization of an interleukin-2 receptor subunit gamma (IL2RG) knockout (KO) Syrian hamster strain. In humans, mutations in IL2RG can result in a total failure in T and natural killer (NK) lymphocyte development and nonfunctional B lymphocytes (X-linked severe combined immunodeficiency; XSCID). Therefore, we sought to develop a non-murine model to study XSCID and the infectious diseases associated with IL2RG deficiency. We demonstrated that the IL2RG KO hamsters have a lymphoid compartment that is greatly reduced in size and diversity and is impaired in function. As a result of the defective adaptive immune response, IL2RG KO hamsters developed a more severe human adenovirus infection and cleared virus less efficiently than immune competent wild-type (wt) hamsters. Due to this enhanced virus replication, IL2RG KO hamsters developed more severe adenovirus-induced liver pathology than wt hamsters. This novel hamster strain will provide researchers with a new tool to investigate human XSCID and its related infections.
... Coleman et al. (1999) demonstrated that Long Evans rats submitted to a single high-intensity sound stimulus during development (P14) show shorter inter wave intervals between waves I -V, and III -V evoked by pure tones, as well as cochlear lesions associated with audiogenic seizures. Like GEPRs, Genetic Audiogenic Seizure Hamster from Salamanca (GASH-Sal) have higher thresholds for clicks and pure tones as compared to control hamsters and latencies to wave peaks were also longer in audiogenic animals (Muñoz et al., 2017). Finally, mice and humans with mutations on the gene Gipc3, expressed in inner cells of the cochlea, exhibit progressive hearing loss and in mice, audiogenic seizures. ...
While acute audiogenic seizures in response to acoustic stimulus appear as an alteration in sensory-motor processing in the brainstem, the repetition of the stimulus leads to the spread of epileptic activity to limbic structures. Here, we investigated whether animals of the Wistar Audiogenic Rat (WAR) strain, genetically selected by inbreeding for seizure susceptibility, would have alterations in their auditory response, assessed by the auditory brainstem responses (ABR) and sensory-motor gating, measured as pre-pulse inhibition (PPI), which could be related to their audiogenic seizures susceptibility or severity. We did not find differences between the amplitudes and latencies of ABR waves in response to clicks for WARs when compared to Wistars. Auditory gain and symmetry between ears were also similar. However, hearing thresholds in response to some tones were lower and amplitudes of wave II were larger in WARs. WARs had smaller acoustic startle reflex amplitudes and the percentages of startle inhibited by an acoustic prepulse were higher for WARs than for Wistars. However, no correlation was found between these alterations and brainstem-dependent seizure severity or limbic seizure frequency during audiogenic kindling. Our data show that while WARs present moderate alterations in primary auditory processing, the sensory motor gating measured in startle/PPI tests appears to be more drastically altered. The observed changes might be correlated with audiogenic seizure susceptibility but not seizures severity.
... Hamsters find wide variety of usage in research areas which includeresearch on cancer, infectious disease and behavioural studies. They serve as genetic models forvarious human diseases such as epilepsy (Munoz et al., 2017), atrial thrombosis (Clifford and Simmons, 2017), and muscular dystrophy (Iwata et al., 2018). ...
Hamsters have unique physiological characteristics rendering them well-suited for biomedical research as experimental model. They match beneficial traits of both smaller rodents and larger mammals that make them suitable for laboratory use, such as availability, breeding ease, greater tissue proportions and the like. In experimental design, it is inevitable to select laboratory animals of accurate age that can mimic the target human age in a specific research. In this article, we have calculated that one human year equals 13.67 hamster days, considering their entire lifespan. This simplistic calculation may not find universal relevance in biomedical research, given the accelerated non-uniform life stages of hamsters when matched with human. To resolve this issue, this is the first ever article where we have provided a concise perception of hamster days in human years by correlating their age at every major life stage. This article will aid precision in biomedical research via selection of laboratory hamster of accurate age corresponding to human age, which is the most primary and essential criteria in animal based research.
... [29] Notably, studies of this colony have suggested that the seizure phenotype may be linked to a deficiency for the nonvoltage-gated KCC2 potassium channel in the brain. [30] Thus, there is the possibility that a potassium channel deficiency may cooperate with HaPV in cancer development. More specifically, deficiency for the voltage-gated KCNQ1 potassium channel could cause membrane depolarization in bone marrow-derived stem cells, contributing to their transformation. ...
Background:
The golden Syrian hamster is an emerging model organism. To optimize its use, our group has made the first genetically engineered hamsters. One of the first genes that we investigated is KCNQ1 which encodes for the KCNQ1 potassium channel and also has been implicated as a tumor suppressor gene.
Materials and methods:
We generated KCNQ1 knockout (KO) hamsters by CRISPR/Cas9-mediated gene targeting and investigated the effects of KCNQ1-deficiency on tumorigenesis.
Results:
By 70 days of age seven of the eight homozygous KCNQ1 KOs used in this study began showing signs of distress, and on necropsy six of the seven ill hamsters had visible cancers, including T-cell lymphomas, plasma cell tumors, hemangiosarcomas, and suspect myeloid leukemias.
Conclusions:
None of the hamsters in our colony that were wild-type or heterozygous for KCNQ1 mutations developed cancers indicating that the cancer phenotype is linked to KCNQ1-deficiency. This study is also the first evidence linking KCNQ1-deficiency to blood cancers.
... Nevertheless, it is important to highlight that the WAR seizure susceptibility is not restricted to acoustic stimulation and presents lower thresholds to many other pro-convulsive stimuli, such as transauricular electroshock, pilocarpine and pentylenetetrazol (Magalhães et al., 2004;Scarlatelli-Lima et al., 2003). Several audiogenic models have been reported throughout literature (Muñoz et al., 2017;Poletaeva et al., 2017;Ribak, 2017), accumulating evidence suggesting that the corpus quadrigeminum, comprised of inferior and superior colliculus (IC and SC), is a critical structure for AS development (Garcia-Cairasco et al., 1993;Garcia-Cairasco, 2002). The IC is crucial in the initiation and transmission of the paroxysmal activity (Faingold, 2004;Garcia-Cairasco et al., 1993;Ross and Coleman, 2000;Rossetti et al., 2006). ...
The Wistar Audiogenic Rat (WAR) is a model whose rats are predisposed to develop seizures following acoustic stimulation. We aimed to establish the transcriptional profile of the WAR model, searching for genes that help in understanding the molecular mechanisms involved in the predisposition and seizures expression of this strain. RNA-Seq of the corpora quadrigemina of WAR and Wistar rats subjected to acoustic stimulation revealed 64 genes differentially regulated in WAR. We validated twelve of these genes by qPCR in stimulated and naive (non-stimulated) WAR and Wistar rats. Among these, Acsm3 was upregulated in WAR in comparison with both control groups. In contrast, Gpr126 and Rtel1 were downregulated in naive and stimulated WAR rats in comparison with the Wistar controls. Qdpr was upregulated only in stimulated WAR rats that exhibited audiogenic seizures. Our data show that there are genes with differential intrinsic regulation in the WAR model and that seizures can alter gene regulation. We identified new genes that might be involved in the epileptic phenotype and comorbidities of the WAR model.
... Acoustically evoked seizures (e.g., audiogenic seizures or AGS) are common in models of inherited epilepsy and have been reported in a variety of species including rat, mouse, and hamster (Faingold, 1988;Garcia-Cairasco et al., 2017;Muñoz et al., 2017;Poletaeva et al., 2017; https://doi.org/10.1016/j.nbd.2017.12.014 Ross and Coleman, 2000). ...
Acoustically evoked seizures (e.g., audiogenic seizures or AGS) are common in models of inherited epilepsy and occur in a variety of species including rat, mouse, and hamster. Two models that have been particularly well studied are the genetically epilepsy prone rat (GEPR-3) and the Wistar Audiogenic Rat (WAR) strains. Acute and repeated AGS, as well as comorbid conditions, displays a close phenotypic overlap in these models. Whether these similarities arise from convergent or divergent structural changes in the brain remains unknown. Here, we examined the brain structure of Sprague Dawley (SD) and Wistar (WIS) rats, and quantified changes in the GEPR-3 and WAR, respectively. Brains from adult, male rats of each strain (n=8-10 per group) were collected, fixed, and embedded in agar and imaged using a 7-T Bruker MRI. Post-acquisition analysis included voxel-based morphometry (VBM), diffusion tensor imaging (DTI), and manual volumetric tracing. In the VBM analysis, GEPR-3 displayed volumetric changes in brainstem structures known to be engaged by AGS (e.g., superior and inferior colliculus, periaqueductal grey) and in forebrain structures (e.g., striatum, septum, nucleus accumbens). WAR displayed volumetric changes in superior colliculus, and a broader set of limbic regions (e.g., hippocampus, amygdala/piriform cortex). The only area of significant overlap in the two strains was the midline cerebellum: both GEPR-3 and WAR showed decreased volume compared to their control strains. In the DTI analysis, GEPR-3 displayed decreased fractional anisotropy (FA) in the corpus callosum, posterior commissure and commissure of the inferior colliculus (IC). WAR displayed increased FA only in the commissure of IC. These data provide a biological basis for further comparative and mechanistic studies in the GEPR-3 and WAR models, as well as provide additional insight into commonalities in the pathways underlying AGS susceptibility and behavioral comorbidity.
Epilepsy is a neurological disorder characterized by abnormal neuronal excitability, with glutamate playing a key role as the predominant excitatory neurotransmitter involved in seizures. Animal models of epilepsy are crucial in advancing epilepsy research by faithfully replicating the diverse symptoms of this disorder. In particular, the GASH/Sal (genetically audiogenic seizure-prone hamster from Salamanca) model exhibits seizures resembling human generalized tonic-clonic convulsions. A single nucleotide polymorphism (SNP; C9586732T, p.His289Tyr) in the Grik1 gene (which encodes the kainate receptor GluK1) has been previously identified in this strain. The H289Y mutation affects the amino-terminal domain of GluK1, which is related to the subunit assembly and trafficking. We used confocal microscopy in Xenopus oocytes to investigate how the H289Y mutation, compared to the wild type (WT), affects the expression and cell-surface trafficking of GluK1 receptors. Additionally, we employed the two-electrode voltage-clamp technique to examine the functional effects of the H289Y mutation. Our results indicate that this mutation increases the expression and incorporation of GluK1 receptors into an oocyte's membrane, enhancing kainate-evoked currents, without affecting their functional properties. Although further research is needed to fully understand the molecular mechanisms responsible for this epilepsy, the H289Y mutation in GluK1 may be part of the molecular basis underlying the seizure-prone circuitry in the GASH/Sal model.
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.
The Genetic Audiogenic Seizure Hamster from Salamanca (GASH/Sal), an animal model of reflex epilepsy, exhibits generalized tonic-clonic seizures in response to loud sound with the epileptogenic focus localized in the inferior colliculus (IC). Ictal events in seizure-prone strains cause gene deregulation in the epileptogenic focus, which can provide insights into the epileptogenic mechanisms. Thus, the present study aimed to determine the expression profile of key genes in the IC of the GASH/Sal after the status epilepticus. For such purpose, we used RNA-Seq to perform a comparative study between the IC transcriptome of GASH/Sal and that of control hamsters both subjected to loud sound stimulation. After filtering for normalization and gene selection, a total of 36 genes were declared differentially expressed from the RNA-seq analysis in the IC. A set of differentially expressed genes were validated by RT-qPCR showing significant differentially expression between GASH/Sal hamsters and Syrian control hamsters. The confirmed differentially expressed genes were classified on ontological categories associated with epileptogenic events similar to those produced by generalized tonic seizures in humans. Subsequently, based on the result of metabolomics, we found the interleukin-4 and 13-signaling, and nucleoside transport as presumably altered routes in the GASH/Sal model. This research suggests that seizures in GASH/Sal hamsters are generated by multiple molecular substrates, which activate biological processes, molecular processes, cellular components and metabolic pathways associated with epileptogenic events similar to those produced by tonic seizures in humans. Therefore, our study supports the use of the GASH/Sal as a valuable animal model for epilepsy research, toward establishing correlations with human epilepsy and searching new biomarkers of epileptogenesis.
Rodent models of audiogenic seizures, in which seizures are precipitated by an abnormal response of the brain to auditory stimuli, are crucial to investigate the neural bases underlying ictogenesis. Despite significant advances in understanding seizure generation in the inferior colliculus, namely the epileptogenic nucleus, little is known about the contribution of lower auditory stations to the seizure-prone network. Here, we examined the cochlea and cochlear nucleus of the genetic audiogenic seizure hamster from Salamanca (GASH/Sal), a model of reflex epilepsy that exhibits generalized tonic–clonic seizures in response to loud sound. GASH/Sal animals under seizure-free conditions were compared with matched control hamsters in a multi-technical approach that includes auditory brainstem responses (ABR) testing, histology, scanning electron microscopy analysis, immunohistochemistry, quantitative morphometry and gene expression analysis (RT-qPCR). The cochlear histopathology of the GASH/Sal showed preservation of the sensory hair cells, but a significant loss of spiral ganglion neurons and mild atrophy of the stria vascularis. At the electron microscopy level, the reticular lamina exhibited disarray of stereociliary tufts with blebs, loss or elongated stereocilia as well as non-parallel rows of outer hair cells due to protrusions of Deiters’ cells. At the molecular level, the abnormal gene expression patterns of prestin, cadherin 23, protocadherin 15, vesicular glutamate transporters 1 (Vglut1) and -2 (Vglut2) indicated that the hair-cell mechanotransduction and cochlear amplification were markedly altered. These were manifestations of a cochlear neuropathy that correlated to ABR waveform I alterations and elevated auditory thresholds. In the cochlear nucleus, the distribution of VGLUT2-immunolabeled puncta was differently affected in each subdivision, showing significant increases in magnocellular regions of the ventral cochlear nucleus and drastic reductions in the granule cell domain. This modified inputs lead to disruption of Vglut1 and Vglut2 gene expression in the cochlear nucleus. In sum, our study provides insight into the morphological and molecular traits associated with audiogenic seizure susceptibility in the GASH/Sal, suggesting an upward spread of abnormal glutamatergic transmission throughout the primary acoustic pathway to the epileptogenic region.
Considering the suitability of laboratory rats in epilepsy research, we and other groups have been developing genetic models of epilepsy in this species. After epileptic rats or seizure-susceptible rats were sporadically found in outbred stocks, the epileptic traits were usually genetically-fixed by selective breeding. So far, the absence seizure models GAERS and WAG/Rij, audiogenic seizure models GEPR-3 and GEPR-9, generalized tonic-clonic seizure models IER, NER and WER, and Canavan-disease related epileptic models TRM and SER have been established. Dissection of the genetic bases including causative genes in these epileptic rat models would be a significant step toward understanding epileptogenesis. N-ethyl N-nitrosourea (ENU) mutagenesis provides a systematic approach which allowed us to develop two novel epileptic rat models: heat-induced seizure susceptible (Hiss) rats with an Scn1a missense mutation and autosomal dominant lateral temporal epilepsy (ADLTE) model rats with an Lgi1 missense mutation. In addition, we have established episodic ataxia type 1 (EA1) model rats with a Kcna1 missense mutation derived from the ENU-induced rat mutant stock, and identified a Cacna1a missense mutation in a N-Methyl-N-nitrosourea (MNU)-induced mutant rat strain GRY, resulting in the discovery of episodic ataxia type 2 (EA2) model rats. Thus, epileptic rat models have been established on the two paths: 'phenotype to gene' and 'gene to phenotype'. In the near future, development of novel epileptic rat models will be extensively promoted by the use of sophisticated genome editing technologies.
Abstract: Epilepsy is a chronic neurological condition characterized by recurrent seizures that affects millions of people worldwide. Comprehension of the complex mechanisms underlying epileptogenesis and seizure generation in temporal lobe epilepsy and other forms of epilepsy cannot be fully acquired in clinical studies with humans. As a result, the use of appropriate animal models is essential. Some of these models replicate the natural history of symptomatic focal epilepsy with an initial epileptogenic insult, which is followed by an apparent latent period and by a subsequent period of chronic spontaneous seizures. Seizures are a combination of electrical and behavioral events that are able to induce chemical, molecular, and anatomic alterations. In this review, we summarize the most frequently used models of chronic epilepsy and models of acute seizures induced by chemoconvulsants, traumatic brain injury, and electrical or sound stimuli. Genetic models of absence seizures and models of seizures and status epilepticus in the immature brain were also examined. Major uses and limitations were highlighted, and neuropathological, behavioral, and neurophysiological similarities and differences between the model and the human equivalent were considered. The quest for seizure mechanisms can provide insights into overall brain functions and consciousness, and animal models of epilepsy will continue to promote the progress of both epilepsy and neurophysiology research.
The study was performed to characterize GASH:SAL audiogenic seizures as true epileptic activity based on electroencephalographic markers acquired with a wireless implanted radiotelemetry system. We analyzed cortical EEG patterns synchronized with video recordings of convulsive behavior of the GASH:Sal hamster following an acoustic stimulus. All GASH:Sal presented archetypal motor symptoms comparable to current animal models of generalized tonic-clonic epilepsy. Seizures consisted of an initial bout of wild running, followed by opisthotonus, tonic-clonic convulsions, tonic limb extension, and terminated in postictal depression. EEG patterns correlated with behavior and displayed phase appropriate spike-wave complexes, low-amplitude desynchronized activity, and high frequency large-amplitude peaks. Our results confirm that electroencephalographic profiles of the audiogenic seizures of the hamster GASH:Sal are parallel to EEG patterns of other animal models of generalized tonic-clonic seizures. Therefore, this animal may serve as an appropriate model for epilepsy research.
The inferior colliculus (IC) and the locus coeruleus (LC) are two midbrain nuclei that integrate multimodal information and play a major role in novelty detection to elicit an orienting response. Despite the reciprocal connections between these two structures, the projection pattern and target areas of the LC within the subdivisions of the rat IC are still unknown. Here, we used tract-tracing approaches combined with immunohistochemistry, densitometry and confocal microscopy analysis to describe a projection from the LC to the IC. Biotinylated dextran amine (BDA) injections into the LC showed that the LC-IC projection is mainly ipsilateral (90%) and reaches, to a major extent, the dorsal and lateral part of the IC and the intercollicular commissure. Additionally, some LC fibers extend into the central nucleus of the IC. The neurochemical nature of this projection is noradrenergic, given that tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DBH) colocalize with the BDA-labeled fibers from the LC. To determine the total field of the LC innervations in the IC, we destroyed the LC neurons and fibers using a highly selective neurotoxin, DSP-4, and then studied the distribution and density of TH- and DBH-immunolabeled axons in the IC. In the DSP-4 treated animals, the number of axonal fibers immunolabeled for TH and DBH were deeply decreased throughout the entire rostrocaudal extent of the IC and its subdivisions compared to controls. Our densitometry results showed that the IC receives up to 97% of its noradrenergic innervations from the LC neurons and only 3% from non-coeruleus neurons. Our results also indicate that TH immunoreactivity in the IC was less impaired than the immunoreactivity for DBH after DSP-4 administration. This is consistent with the existence of an important dopaminergic projection from the substantia nigra to the IC. In conclusion, our study demonstrates and quantifies the noradrenergic projection from the LC to the IC and its subdivisions.
The ventrolateral periaqueductal gray is implicated as a component of the neuronal network for audiogenic seizure. This implication is based on immunocytochemical labeling of the proto-oncogene, c-fos, and microinjection studies in the severe substrain of genetically epilepsy-prone rats that exhibits tonic seizures. The present study examines changes in acoustically evoked neuronal responses within the periaqueductal gray in the awake and behaving genetically epilepsy-prone rat as compared to normal Sprague–Dawley rats. Two populations of neuronal response were observed in the periaqueductal gray of both genetically epilepsy-prone and normal rats. Most of the neurons exhibited long latencies (>10 ms) and lower thresholds, and were more responsive to the acoustic stimulus. The remainder of the periaqueductal gray neurons exhibited short latencies (<10 ms) and higher thresholds, and exhibited minimal responsiveness to the acoustic stimulus. The mean threshold of periaqueductal gray acoustically evoked neuronal firing of short-latency neurons was significantly higher than normal in the genetically epilepsy-prone rat. The number of acoustically evoked action potentials was significantly elevated in the genetically epilepsy-prone rat, particularly at the highest acoustic intensity and at a repetition rate of 1/2 s. In the genetically epilepsy-prone rat, the number of action potentials exhibited adaptation (habituation) at 1/s as compared to 1/2 s across stimulus intensities. Habituation in normal rats was observed primarily at high intensities (95 dB sound pressure level or above). During wild running and tonic seizures in the genetically epilepsy-prone rat, periaqueductal gray neurons, which had diminished firing rates due to habituation, exhibited a tonic firing pattern. Just (1–5 s) prior to the onset of tonic convulsive behaviors, an increase in the rate of periaqueductal gray tonic firing was observed.
A new method called the neighbor-joining method is proposed for reconstructing phylogenetic trees from evolutionary distance data. The principle of this method is to find pairs of operational taxonomic units (OTUs [= neighbors]) that minimize the total branch length at each stage of clustering of OTUs starting with a starlike tree. The branch lengths as well as the topology of a parsimonious tree can quickly be obtained by using this method. Using computer simulation, we studied the efficiency of this method in obtaining the correct unrooted tree in comparison with that of five other tree-making methods: the unweighted pair group method of analysis, Farris's method, Sattath and Tversky's method, Li's method, and Tateno et al.'s modified Farris method. The new, neighbor-joining method and Sattath and Tversky's method are shown to be generally better than the other methods.
Audiogenic epilepsy of rodents is a striking example of the pathogenic action of strong sounds on a living organism. The ascertainment of the physiological mechanisms of this reaction, and above all of the protective brain mechanisms which prevent or weaken it, is of great significance for the elaboration of measures aimed at struggling against the noxious influence of noises on the human organism.
The more recent history and main experimental data for the Krushinsky-Molodkina (KM) audiogenic rat strain are presented. The strain selection started in late 1940. Now this strain is inbred, and two new strains are maintained in a laboratory in parallel. These strains originated from KM×Wistar hybrids and were bred (starting from 2000) for no-seizure and intense audiogenic seizure phenotypes, respectively. The experimental evidences of audiogenic seizure physiology were accumulated in parallel with (and usually ahead of) data on other audiogenic-prone strains. The peculiar feature of the KM strain is its vulnerability to brain hemorrhages. Thus, the KM strain is used not only as a genetic model of seizure states, but also as a model of blood flow disturbances in the brain. This article is part of a Special Issue entitled: "Genetic Models-Epilepsy".
Copyright © 2015 Elsevier Inc. All rights reserved.
In this review of neuroanatomical studies of the genetically epilepsy-prone rat (GEPR), three main topics will be covered. First, the number of GABAergic neurons and total neurons in the inferior colliculus of GEPRs will be compared to those of the nonepileptic Sprague-Dawley rat. Next, the number of small neurons in the inferior colliculus will be described in both developmental and genetic analyses of GEPRs and their backcrosses. Last, results from two types of studies on the propagation pathways for audiogenic seizures in GEPRs will be shown. Together, these studies demonstrate a unique GABAergic, small neuron defect in the inferior colliculus of GEPRs that may play a vital role in the initiation and spread of seizure activity during audiogenic seizures. This article is part of a Special Issue entitled "Genetic Models-Epilepsy".
Copyright © 2015 Elsevier Inc. All rights reserved.
Epilepsy modeling is essential for understanding the basic mechanisms of the epileptic process. The Genetic Audiogenic Seizure Hamster (GASH:Sal) exhibits generalized tonic-clonic seizures of genetic origin in response to sound stimulation and is currently being validated as a reliable model of epilepsy. Here, we performed a pharmacological and neuroethological study using well-known and widely used antiepileptic drugs (AEDs), including phenobarbital (PB), valproic acid (VPA), and levetiracetam (LEV). The intraperitoneal administration of PB (5-20mg/kg) and VPA (100-300mg/kg) produced a dose-dependent decrease in GASH:Sal audiogenic seizure severity scores. The administration of LEV (30-100mg/kg) did not produce a clear effect. Phenobarbital showed a short plasmatic life and had a high antiepileptic effect starting at 10mg/kg that was accompanied by ataxia. Valproic acid acted only at high concentrations and was the AED with the most ataxic effects. Levetiracetam at all doses also produced sedation and ataxia side effects. We conclude that the GASH:Sal is a reliable genetic model of epilepsy suitable to evaluate AEDs.
This work reports on use of the recently described amplified fragment length polymorphism (AFLP) technology for DNA fingerprinting in cattle. The AFLP technology produces molecular markers through the high-stringency polymerase chain reaction (PCR)-amplification of restriction fragments that are ligated to synthetic adapters and amplified using primers, complementary to the adapters, which carry selective nucleotides at their 3' ends. While, for plants, the double digestion of genomic DNA with EcoRI and MseI is suggested, in mammals the enzyme combination EcoRI/TaqI produces clearer and more polymorphic AFLP patterns. In a sample of 47 Italian Holstein genotypes, 16 EcoRI/TaqI primer combinations identified 248 polymorphic bands in a species known for its low level of restriction polymorphism. In spite of the low information content carried by each AFLP polymorphism (average polymorphism information content = 0·31), the number of fragments revealed by each primer combination increased significantly the level of genetic information gained in each experiment. AFLP patterns are reproducible in independent experiments and polymorphic fragments segregate in cattle families according to Mendelian rules.
Despite numerous studies, the age-related risk of genetic defects in the offspring remains poorly understood. It is clear that the frequency at birth of some mendelian disorders is related to advanced paternal age, but this relationship is heterogeneous and varies from one disorder to another. Similarly, it has been proposed that among commonly observed birth defects, a subgroup of cases may be due to new unrecognized dominant mutations of paternal origin. Finally, despite many years of enquiry, increasing maternal age remains the only incontrovertible factor associated with human aneuploidy.
Purpose:
To describe the clinical and electroencephalographic (EEG) features of reflex myoclonic epilepsy in infancy (RMEI) and long-term cognitive outcome.
Methods:
We enrolled 31 children from 16 neuropediatric centres in Italy, who underwent clinical and video-EEG evaluation. Cognitive assessment was performed in all patients using standardized psychometric tests.
Results:
The age at onset ranged from 3 to 24 months of age. Seizures were characterised in all patients by symmetric myoclonic seizures (MS), triggered by sudden unexpected acoustic (38.7%) or tactile stimuli (29%) or both (29%). Spontaneous attacks were reported in 32.2% of the cases. Ictal EEG showed generalized high-amplitude 3 Hz polyspike and wave discharges, synchronous with brief rhythmic bursts of electromyographic activity. Patients were re-evaluated after a period of 7.2 ± 5.6 years. The prognosis for seizure control was excellent in all cases and reflex MS disappeared spontaneously or after valproate treatment. The cognitive outcome was excellent in 90.3% of children.
Conclusions:
RMEI appears to be a variety of idiopathic generalized epilepsy with specific features that occurs in developmentally normal children.
Most electrically induced seizures involve forebrain structures, such as the amygdala or frontal cortex, but the following studies characterized a specific anatomic site in the inferior colliculus which generated seizure-like behavior after a single, low current electrical stimulation. When a bipolar electrode was implanted into the dorsomedial aspect of the inferior colliculus, low stimulation currents (120 to 200 μA, 30 Hz) produced wild running behavior which outlasted the stimulation by 4 to 10 s. This wild running behavior was directly correlated with local afterdischarge in the inferior colliculus, while no changes were found in the EEG activity in the cortex or hippocampus. Though the threshold current necessary to invoke the wild running seizures remained stable for long periods of time, the presentation of two stimulations a day for 2 weeks caused a progressive increase in the duration of poststimulus wild running. In the last days of the chronic stimulations, some forelimb tonus or myoclonic jerks followed the wild running seizures. These latter behaviors were correlated with local afterdischarges at the electrode tips in the inferior colliculus and spiking EEG activity in the frontal cortex. Pharmacologically, haloperidol, phenobarbital, carbamazepine, and ethosuximide proved ineffective in attenuating the seizures, whereas phenytoin, sodium valproate, and chlordiazepoxide attenuated the seizures. These findings are discussed in relation to the genesis of epilepsy in humans.
In naive Wistar rats susceptible to sound, a single audiogenic seizure induced the expression of c-fos in the subcortical auditory nuclei whereas the forebrain was almost completely devoid of any labelling. After kindling of audiogenic seizures by 40 daily exposures to sound, the seizure induced a strong c-fos expression in the amygdala, the piriform cortex, the hippocampus and the neocortex. These results confirm: (i) that audiogenic seizures are brain-stem seizures related to dysfunction of auditory pathways, and (ii) that kindling of audiogenic seizures recruits forebrain and limbic structures into the seizure network.
Previous studies have implicated a decreased efficacy of GABA as an important defect subserving the audiogenic seizures of the genetically epilepsy-prone rat (GEPR-9). The inferior colliculus (IC) is a critical site for audiogenic seizure (AGS) initiation, and the pontine reticular formation (PRF) is implicated in the propagation fo AGS and in other generalized seizure models. The present study observed that microinjection of baclofen, a GABA-B receptor agonist, into Ic protects against AGS, and blockade of the breakdown of endogenous GABA by gabaculine, a GABA transaminase inhibitor, increased GABA levels and blocked AGS susceptibility in the GEPR-9. Microinjection of baclofen or gabaculine into the PRF reduced AGS severity, but the doses required were considerably greater and the degree of anticonvulsant effect was less. Uptake of [3H]GABA into GEPR-9 synaptosomes from the IC is significantly increased as compared to normal, which could contribute to the diminished effectiveness of GABA in the GEPR-9. Previous studies indicate that GABA-A receptor agonists block AGS with IC microinjection, and recent data indicate that blockade of GABA uptake in this nucleus significantly reduced AGS severity. These data taken together strongly support the critical importance of the defect in GABA function in the IC in modulating susceptibility to audiogenic seizure intiation in the GEPR-9.
The effects on audiogenic seizures of bilateral electrolytic lesions at levels of the inferior colliculus (IC), superior colliculus (SC), or medial geniculate body were determined for inbred mice. Of 88 control mice (surgical and nonsurgical), 82% displayed the full seizure syndrome when exposed to intense sound: wildrunning attacks progressed to clonic convulsions and then tonic convulsions. All remaining control animals displayed at least wild-running attacks. In 27 of 49 mice with IC-level lesions, either no seizure activity was observed or the syndrome terminated at the wild-running stage. In these mice, lesions consistently damaged the central IC nucleus (ICC) and sometimes adjacent midbrain tegmentum. In the 12 IC-lesion mice that displayed the full seizure syndrome, IC damage was generally lateral, primarily involving the external IC nucleus (ICX). In SC-lesion mice, absence of wild-running was observed in only 3 of 23 mice, but termination of seizures at wild-running or clonic stages was often seen (14 of 23 mice). Attenuation of seizure activity was correlated with damage to the deep SC and tegmentum, including the central gray. Little or no effect on audiogenic seizures was found with lesions of the dorsal SC or medial geniculate body. Analysis of the time course of components of the seizure syndrome revealed that IC-lesion mice attaining only the wild-running stage had increased latencies to onset of this behavior. In SC-lesion mice, time to onset of wild-running did not differ significantly from controls. Progression from wild-running attacks to onset of clonic convulsions was slowed by lesions at both IC and SC levels. The data indicate that the primary pathway of audiogenic seizure activity includes the ICC, deep SC, and adjacent tegmentum. Wild-running attacks appear to be mediated at the IC level, whereas progression to clonic and tonic convulsions may require more rostral levels.
Generalized epilepsy with febrile seizures plus (GEFS+) is a childhood genetic epilepsy syndrome. GEFS+ includes a wide spectrum of clinical manifestations, and SCN1A mutations have frequently been reported among the GEFS+-related gene abnormalities. In this study, to clarify the distributions of the clinical subtypes, we analyzed 34 families with GEFS+ in Indonesia using the hospital records of the patients and questionnaires for the family members. The number of patients with febrile seizures plus (FS+), FS+ and afebrile generalized/partial seizures, borderline severe myoclonic epilepsy in infancy (SMEB) and severe myoclonic epilepsy in infancy (SMEI) were 9, 11, 7, and 7, respectively. Most patients had a family history of febrile seizures. Next, we performed molecular analyses to clarify the contributions of SCN1A mutations to the development of the GEFS+ subtypes. Only 3 of 34 probands showed SCN1A mutations. These mutations were two missense mutations, p.V1612I and p.C1756G, in two patients with SMEI and SMEB, and one silent mutation, p.G1762G, in a patient with FS+ and afebrile partial seizures. In conclusion, the majority of GEFS+ patients in Indonesia were not associated with SCN1A mutations. To detect the GEFS+-causing mutations, we must search and analyze other genes in these patients.
Currently, approximately 20 genetic variants are known to cause Mendelian forms of human epilepsy, leaving a vast heritability undefined. Rodent models for genetically complex epilepsy have been studied for many years, but only recently have strong candidate genes emerged, including Cacna1 g in the GAERS rat model of absence epilepsy and Kcnj10 in the low seizure threshold of DBA/2 mice. In parallel, a growing number of mouse mutations studied on multiple strain backgrounds reveal the impact of genetic modifiers on seizure severity, incidence or form--perhaps mimicking the complexity seen in humans. The field of experimental genetics in rodents is poised to study discrete epilepsy mutations on a diverse choice of strain backgrounds to develop better models and identify modifiers. But, it must find the right balance between embracing the strain diversity available, with the ability to detect and characterize genetic effects. Using alternative strain backgrounds when studying epilepsy mutations will enhance the modeling of epilepsy as a complex genetic disease.
Severe myoclonic epilepsy (SMEI) or Dravet syndrome is caused by mutations of the SCN1A gene that encodes voltage-gated sodium channel alpha-1 subunit. Recently, we generated and characterized a knock-in (KI) mice with an SCN1A nonsense mutation that appeared in three independent SMEI patients. The SCN1A-KI mice well reproduced the SMEI disease phenotypes. Both homozygous and heterozygous knock-in mice developed epileptic seizures within the first postnatal month. In heterozygous knock-in mice, trains of evoked action potentials in inhibitory neurons exhibited pronounced spike amplitude decrement late in the burst but not in pyramidal neurons. We further showed that in wild-type mice the Nav1.1 protein is expressed dominantly in axons and moderately in somata of parbalbumin (PV) - positive inhibitory interneurons. Our immunohistochemical observations of the Nav1.1 are clearly distinct to the previous studies, and our findings has corrected the view of the Nav1.1 protein distribution. The data indicate that Nav1.1 plays critical roles in the spike output from PV interneurons and further, that the specifically altered function of these inhibitory circuits may contribute to epileptic seizures in the mice. These information should contribute to the understanding of molecular pathomechanism of SMEI and to develop its effective therapies.
A 36-year-old right-handed man, who had experienced partial seizures since the age of 24 every time he played or listened to music with a strong emotional charge, underwent videopolygraphic recording, including autonomic variables, and brain fMRI study during which he listened to both "neutral" and "emotionally charged" music. Three right temporal seizures recorded during videopolygraphic monitoring were elicited by listening to the triggering song. The fMRI study disclosed activation in right acoustic areas during "neutral music," whereas an "emotionally charged melody" provoked widespread activation over the right fronto-temporo-occipital area before seizure onset. The literature review disclosed 110 published cases of musicogenic epilepsy that seemed to suggest a right-sided predominance of the epileptogenic zone. Our results support the role of the right temporal lobe in musicogenic epilepsy and demonstrate that the cerebral areas activated during the period of strong emotion leading to the seizures encompass the auditory cortex activated by neutral music.
When certain strains of mice are exposed to loud high-frequency sounds, they experience violent generalized seizures that can often be fatal. Audiogenic seizures (AS) susceptibility in mice can occur spontaneously as an inherited trait or can be induced in AS resistant strains by prior auditory exposure or audiogenic priming. Priming-induced AS susceptibility is most influenced by the age at which the mice are primed and the interval between priming and testing. Although genetic factors significantly influence both spontaneous and priming-induced AS susceptibility, the mode of inheritance of either form of AS is still controversial. Furthermore, both forms of AS susceptibility appear to be influenced by different genes. Neurophysiological studies have revealed that the primary neuronal pathways involved with the manifestation of AS are located in subcortical structures. The biochemical mechanism responsible for AS susceptibility has not been conclusively established. Susceptibility to AS has been attributed to deficiencies in ATPase activities, alterations in neurotransmitter metabolism, and differences in endocrine function. The pharmacological manifestation of AS susceptibility has been the subject of numerous studies. However, differences in dosage, age of mice, and genotype may significantly modify the influence of drugs on AS susceptibility. Because AS in mice provide additional dimensions to the more commonly employed electrically or chemically induced seizures, they may help to evaluate the usefulness of potential anticonvulsant drugs for the treatment of human epilepsy. Therefore, this paper reviews the current literature and presents new developments in the study of this animal model of epilepsy.
A mathematical model for the evolutionary change of restriction sites in mitochondrial DNA is developed. Formulas based on this model are presented for estimating the number of nucleotide substitutions between two populations or species. To express the degree of polymorphism in a population at the nucleotide level, a measure called "nucleotide diversity" is proposed.
A prolonged anticonvulsant action of taurine has been shown in a strain of seizure susceptible rats. The audiogenic rat (AS) has lower intracerebral electroshock thresholds in three auditory nuclei; the ventral cochlear, the inferior colliculi and the medial geniculate, and in one nonauditory structure; the reticular formation, than a strain of nonaudiogenic rats (NAS). Furthermore, the AS animals routinely display maximal (tonic-clonic) convulsion, regardless of brain structure stimulated, whereas NAS subjects respond with minimal (clonic) convulsions. Within three minutes of intraventricular injection of 8 μ moles, taurine reduces the susceptibility of AS rats to intracerebral electroshock seizures along with attenuation of the severity of the convulsion. The initial elevation in intracerebral electroshock threshold returns to pretreatment value at 24 hours, only to rise again at 48 hours and to remain elevated through day six after injection. In contrast, the severity of convulsions remains attenuated through 24 hours, after which it returns to pre-injection level. By comparison, NAS animals injected intracerebroventricularly in an identical fashion to the AS rats showed no changes in either seizure threshold or severity of convulsion. The direct injection of 200n-moles of taurine in the inferior colliculi of AS rats produced a slow developing, but prolonged, elevation of intracerebral electroshock threshold of this auditory nuclei. However, at no time after the intracerebral injection of taurine was convulsive severity changed. Injection of taurine into the inferior colliculi of NAS subjects did not change either susceptibility or severity of intracerebral electroshock seizures. The data indicate that taurine produces an anticonvulsant effect which is slow in onset, potent, selective and prolonged.
In 13 healthy adult cats chronically implanted with parasagittal electrodes applied to the dural surface, curarization was performed and baseline recordings of the visual evoked response (VER), auditory evoked response (AER).and brainstem auditory evoked response (BAER) were made. Following the procedure of Prince and Farrell (1969), the animals were then given intramuscular doses of 300,000 to 500,000 U/kg of penicillin with the subsequent development of diffuse, bilaterally symmetrical,‐photosensitive spike‐and‐wave discharges in the EEG
These data and the similarity of this model to human petit mal epilepsy argue against increased inhibitory impulses to the visual system during the ictal discharge being responsible for the subjective loss of visual information during petit mal absence. If the amplitude of the evoked response is directly related to the functional integrity of a sensory system, this suggests that the impairment of sensory input, or absence, during spike‐and‐wave paroxysm is due to interference with sensory processing rostral to the brainstem ascending auditory pathway, and probably does not occur in primary sensory cortex but rather in cortical or subcortical association tracts.
RÉSUMÉ
Chez 13 chats adultes et sains, curarisés, porteurs d'électrodes épidurales chroniques implantées dans la région parasagittale, on a enregistré comme contrôle, les potentiels évoqués visuels (PEV), auditifs (PEA) et les réponses évoquées acoustiques au niveau du brainstem (BAER).
Suivant la méthode de Prince et Farrel(1969)les animaux recevaient ensuite des doses de 300.000 à 500.000 unités/kg de pénicilline. Ceci produisait une heure à une heure et demi après des décharges EEG de pointes ondes diffuses bilatérales et symétriques évoquées par la SLI et s'accompagnant de myoclonies faciales, arrêt du mouvement et des épisodes de comportement à type “d'absence” chez les animaux non curarisés.
L es différents potentiels évoqués VER, AER, et BAER étaient enregistrés à des intervalles de 15 minutes pendant plusieurs heures durant lesquelles le VER diminuait significativement d'amplitude jusqu'au moment de l'apparition des premières pointes ondes évoquées par la stimulation photique environ une heure après 1'injection après laquelle toutes les composantes précoces (0 à 200 milli‐secondes) du VER augmentaient progressivement de 150 à 300 pour cent jusqu'à l'apparition constante de bouffées spontanées de pointes ondes (entre une heure et demi et deux heures).
En coincidence avec cette modification, on a aussi observé des modifications des composantes tardives (200 à 500 millisecondes). Les deux phénomènes de la diminution précoce et de l'augmentation tardive du PEV étaient également évidents dans le cortex visuel et non visuel.
Avec ce modèle on a observé aussi des modifications du PEA semblables mais de moindre importance par rapport à celle du PEV. L'amplitude des ondes de 1 jusqu'à 5 augmentait de 28 à 88% avec un maximum une heure et demi après l'injection de penicilline.
Ces données et les analogies du modèle expérimental utilisé et de l'épilepsie avec absences typiques de type Petit Mal chez 1'homme, sont contre l'hypothèse de l'existence au cours d'une décharge critique de type Petit Mal, d'une inhibition du système visuel qui serait responsable de la perte subjective d'informations visuelles pendant une absence Petit Mai.
Si l'amplitude de la réponse évoquée a une relation directe avec l'intégrité fonctionnelle d'un système sensoriel, ceci suggère que le déficit ou l'absence de l'afférence sensorielle pendant les décharges de pointes ondes sont la conséquence d'une interférence dans Intégration du message sensoriel qui se situe rostralement aux voies auditives ascendantes et qui n'a pas lieu dans le cortex sensoriel primaire, mais plutôt dans les voies associatives corticales ou souscorticales.
RESUMEN
Se implantaron electrodos parasagitales en contacto con la superficie de la dura en 13 gatos adultos y sanos. Tras la curarización se registraron los trazados basales de las Respuestas Visuales Evocadas (VER), de las Respuestas Auditivas Evocadas (AER) y de las Respuestas Auditivas Troncoencefalicas Evocadas (BAER). Siguiendo el procedimiento de Prince y Farell (1.969) los animales fueron inyectados con 300,000 o 500,000 Unidades/kg, de penicilina consiguiéndose el desarrollo subsiquiente, en el E.E.G., de descargas punta‐onda fotosensibles de presentación difusa, bilateral y simétrica. Aparecieron entre los 60 y 90 minutos y, en los animales no curarizados, coincidieron con mioclonias faciales, interrupción de las actividades motoras y “ausencias” con mirada fija en el espacio; Las VER, AER y BAER fueron monitorizadas, durante varias horas, con 15 minutos de intervalo, observándose que las amplitudes de los VER disminuían consistentemente hasta el momento en que la fotoestimulacíon provocaba los primeros brotes de complejos punta‐onda. Esto ocurrfa, aproximadamente, a los 60 minutos de la inyección y, a partir de este momento, todos los componentes precoces de las VER (0 a 200 milisegundos) aumentaban progresivamente del 150 a 300% hasta que los brotes de punta‐onda se registraban de forma consistente (de 90 a 120 minutos). Coincidiendo co este cambio tambien se observó un marcado incremento de los componenetes taríos (200 a 500 milisegundos). Ambos hallazgos, la disminución precoz y el incremento tardio de las VER, se observaron igualmente en las cortezas visuales y no visuales. Tambien se registraron cambios en las AER con el desarrollo de este modelo y fueron semejantes a los observados en las VER aunque en menor grado. Las amplitudes de las ondas I a V de las BAER aumentaron del 28 al 88%, siendo este aumento máximo a los 90 minutos de la inyección de penicilina.
Todos estos datos y la semejanza de este modelo con la epilepsía petit‐mal en humanos, ofrecen argumentos en contra de un aumento de los impulsos inhibidores de la corteza visual durante la descarga ictal, considerados como responsables de la pérdida de información visual durante la ausencia de petit‐mal. Si la amplitude de las respuestas evocadas está relacionada directamente con la integridad funcional del sistema sensorial, hay que suponer que la alteración del in‐put sensorial, o su ausencia, durante los paroxismos punta‐onda puede ser debida a una interferencia en el proceso de la información sensorial en zonas más rostrales que las vías auditivas ascendentes del tronco cerebral. Probablemente no tiene lugar en la corteza sensorial primaria sino, más bien, en vias asociativas corticales o subcorticales.
ZUSAMMENFASSUNG
13 Gesunden, ausgewachsenen Katzen wurden auf die durale Oberfläche parasagittal Elektroden chronisch implantiert. Die Tiere wurden curarisiert und Basisableitungen der visuellen evozierten Potentiale (VEP), der akustisch evozierten Potentiale (AEP) und der akustisch evozierten Potentiale des Hirnstamms (BAEP) durchgeführt. Entsprechend dem Vorgehen von Prince und Farell (1969) erhielten die Tiere intramuskuläre Dosen von 300.000 bis 500.000 E/kg Penicillin und entwickelten darauf diffuse bilateral symmetrische fotosensible spike‐ und wave‐Entladungen im EEG, die 1 bis 1 1/2 Std. später auftraten und bei nicht curarisierten Tieren einhergingen mit facialem Myoklonus, Bewegungsruhe und “absenceähnlichem” Starren. Die VEP, AEP, BAEP wurden in 15 Min. Intervallen für mehrere Stunden vom Monitor aufgezeichnet. Während dieser Zeit nahm die Amplitude der VEP deutlich ab bis zu dem Zeitpunkt an dem die ersten spike‐ und wave‐Ausbrüche durch Fotostimulation ausgelöst werden konnten; das geschah etwa 1 Std. nach der Injektion. Nach diesem Zeitpunkt traten alle frühen Komponenten (0–200 Millisekunden) der VEP zunehmend vermehrt von 150 auf 300% auf, bis spontane spike‐und wave‐Ausbrüche ständig abzuleiten waren (nach 1 1/2 bis 2 Std.) Mit diesen Veränderungen einhergehend konnte auch eine deutliche Zunahme der späten Komponenten (200–500 Millisekunden) beobachtet werden. Sowohl die frühe Verminderung und spätere Vermehrung der VEP waren gleichermassen im visuellen und nicht visuellen Cortex zu beobachten. Veränderungen der AEP wurden auch in der Entwicklung dieses Modells abgeleitet sie entsprachen den Veränderungen der VEP, waren aber geringer ausgeprägt. Die Amplituden der Wellen I bis V der BAEP waren 1 1/2 Std. nach der Penicillininjektion von 28 auf maximal 88% angestiegen.
Diese Ergebnisse und die Ännlichkeit der Versuchsanordnung mit der Petit‐Mal‐Epilepsie des Menschen sprechen gegen die Annahme, dass während der Krampfentladungen vermehrte inhibitorische Einflüsse auf das visuelle System ursächlich verantwortlich sind für den subjektiven Verlust visueller Information während einer Petit‐Mai‐Absence. Wenn die Amplitude der evozierten Potentiale in direkter Beziehung zu der funktionellen Integrität eines sensorischen Systems steht, lässt dies vermuten, dass die Störung der sensorischen Einflüsse oder ihr Fehlen während der spike‐und wave‐Entladungen die Folge einer Interferenz mit der sensorischen Verarbeitung darstellt. Sie ist rostral der zum Hirnstamm aszendierenden Hörbahn‐wahrscheinlich nicht in den primären sensorischen Cortex‐zu lokalisieren sondern viel eher in corticale oder subcortical Assoziations‐bahnen.
The cortical EEG of 5 inbred strains of mice susceptible to audiogenic seizures and of 3 inbred strains resistant to them as well as 3 accoustically primed inbred strains was recorded before, during, and after exposure to intense noise once a day for 4 consecutive days beginning at 29 or 30 days of age. None of the resistant mice had a convulsion and all of the susceptible mice had at least one convulsion. Before, during, and after the audiogenic seizure, there was no evidence of spike waves or paroxysmal activity in the trace from the bipolar cortical electrodes. Rather, there might be a slight amplification and acceleration of the trace at the stimulus onset with no further changes during wild circling activity, but with a diminution of the trace during clonic or clonic-tonic convulsions. This pattern was observed for all 5 genetically susceptible strains and for all 3 acoustically primed groups. However, during chemoconvulsive seizures with picrotoxin or thiosemicarbazide, these same mice as well as resistant mice show spike waves and paroxysmal activity of the cortex. It is suggested on the basis of these data that the neural mechanism for the expression of audiogenic seizures and chemoconvulsive seizures is different, that all audiogenic seizures have a common mechanism for expression but not for development of this phenotype, and that the audiogenic seizure is a type of brain stem epilepsy.
Hereditary spontaneous seizures in the Syrian hamsters are described. The seizures occur in 30 to 60-day-old animals from about 2 to 5 hours. The condition is a simple recessive trait, and the gene symbol sz is proposed.
In rats made susceptible to audiogenic seizures by exposing them to an intense noise at a critical time during development, subsequent noise exposure elicited seizures and induced the proto-oncogene c-fos in auditory regions of the brain. Cells showing Fos-like immunoreactivity were especially dense in dorsal and external cortices of the inferior colliculus, and were nearly absent after pretreatment with the N-methyl-D-aspartate (NMDA) antagonist MK-801. Noise exposure alone (i.e. no seizure) produced a localized zone of c-fos induction within the inferior colliculus, but only when presented during the time period when susceptibility to audiogenic seizures can be most effectively induced.
C-fos is a proto-oncogene that is expressed within some neurons following depolarization. The protein product, c-fos protein, can be identified by immunohistochemical techniques. Therefore, c-fos expression might be used as a marker for neuronal activity throughout the neuraxis following peripheral stimulation. This study has analyzed patterns of c-fos expression in both control and anesthetized animals and in anesthetized rats subjected to various forms of peripheral stimulation. Labeled cells were counted in the spinal cord, brainstem, hypothalamus, and thalamus. Little c-fos immunoreactivity was found in control animals. Prolonged inhalational anesthesia increased the number of labeled cells at several brainstem sites. Noxious stimulation of anesthetized rats induced c-fos within the neuraxis in patterns consistent with data obtained from electrophysiological studies and in additional locations for which few direct electrophysiological data are available, such as the ventrolateral medulla, the posterior hypothalamic nucleus, and the reuniens and paraventricular thalamic nuclei. Gentle mechanical stimulation was ineffective in inducing c-fos-like protein. The data suggest that c-fos can be used as a transynaptic marker for neuronal activity following noxious stimulation. However, c-fos is expressed only in some kinds of neurons following peripheral stimulation, and it therefore may be an incomplete marker for nociresponsive activity. In addition, at least a few neurons express c-fos protein in the absence of noxious stimulation. Experiments analyzing c-fos expression must be designed with care, as both extraneous stimuli and anesthetic depth influence the results.
Recently the nuclear proto-oncogene c-fos has been shown to be rapidly and transiently expressed following seizures in many types of epilepsies. Until now, immunohistochemical as well as in situ hybridization studies have reported that the dentate gyrus of the hippocampus and most of the cortical areas were invariably heavily labeled. In order to see whether this distribution was reproduced or not in a model of epilepsy which has been proved to not involve these structures, a study was performed on genetically epilepsy-prone DBA/2 mice. Here we show that following audiogenic seizures, c-fos oncoprotein is not expressed in cortical and limbic structures but rather mapped the subcortical auditory nuclei.
MHC class I glycoproteins are highly diverse in most species. The Syrian hamster has long been thought to express monomorphic MHC class I molecules and thus be an exception to this rule. Here we show that Syrian hamsters express diverse MHC class I gene products. The nucleotide sequences of the alpha 1 and alpha-2 domains of classical Syrian hamster MHC class I molecules are highly variable and show evidence of having been under selective pressures at their Ag recognition sites. Interestingly, none of the Syrian hamster class I genes was closely related to their counterparts in the mouse. These observations suggest that Syrian hamsters in the wild may express diverse MHC class I molecules.
Hearing deficits have been observed in rodents that are susceptible to audiogenic seizures (AGS), including the genetically epilepsy-prone rat (GEPR). AGS susceptibility can be induced in normal animals by treatments that damage the cochlea. In this study, we measured the relative degree of hearing loss in animals from the GEPR substrains that exhibit different degrees of AGS severity and examined the relationship between the deficit and the AGS severity. Auditory brain stem response (ABR) thresholds to clicks in the GEPR substrain that exhibits exclusively maximal AGS severity (GEPR-9) were significantly elevated, and latencies for ABR peaks I, III, and IV were significantly increased as compared to normal Sprague-Dawley rats. ABR thresholds for the substrain of GEPRs were even higher than those in the GEPR-9, and ABR waveforms were distorted. ABR peak IV was significantly longer than normal in the GEPR-3 substrain, as were mean interpeak intervals and central conduction times. These data indicate that significant hearing deficits occur in the GEPR-3 substrain. In non-AGS-susceptible progeny of the GEPR-9 [GEPR-0(9)], ABR thresholds were not significantly different from normal. These data along with studies of ABR thresholds in thyroid-deficient rats suggest that an inverted U-shaped relationship exists between hearing deficit and AGS severity. That is, moderate threshold elevations are associated with increasing AGS severity, but when the hearing deficit exceeds a certain level, a decrement in AGS severity occurs.
The regional distribution of c-fos mRNA in the mouse brain has been investigated by in situ hybridization autoradiography after seizures induced by an acute electroconvulsive shock (ECS). ECS led to a widespread induction of the proto-oncogene c-fos in the brain, with highest concentrations in discrete areas within the limbic system and also in the hypothalamus and cerebellum. The mild stress of sham treatment in earclipped animals induced a weaker and qualitatively different pattern of c-fos mRNA expression involving the cortex, hippocampus, and cerebellum. These data suggest the usefulness of c-fos in situ hybridization as a marker of neuronal stimulation and in mapping a range of effects from a mild stress to the robust changes of an electroconvulsive seizure.
Attacks of sustained dystonic postures of limbs and trunk can be initiated by mild environmental stimuli in an inbred line of Syrian hamsters. The trait is determined by an autosomal simple recessive genetic mutation, originally designated by the gene symbol sz, because the abnormal movements were thought to represent epileptic seizures. The attacks, which can be reproducibly initiated by placing the sz mutant hamsters in a new environment, begin with rapid twitches of the vibrissae, flattened ears, and flattened posture of the trunk while walking, followed by facial contortions, rearing, and sustained posturing of trunk and limbs, often resulting in falling over to the side or backwards. In the final stage, the hamsters became immobile, which can last for hours. An increased tone of limbs and trunk muscles can be palpated during the attack. Electromyographical recordings in awake, unrestrained mutant hamsters showed that the onset of the attack coincided with continuous tonic muscle activity and phasic bursts, which were present even when the animals did not move. During the attack, the animals continue to react to external stimuli. Bilateral electroencephalographic (EEG) recordings before and during motor disturbances in sz mutant hamsters showed no abnormalities. The severity of the dystonic syndrome in hamsters is age dependent with a peak at about 30-40 days of age. A score system for grading type and severity of dystonic attack was developed for use in drug activity studies. The severity of the attack was reduced or attacks were completely prevented by diazepam (1-2.5 mg/kg i.p.) and valproic acid (100-400 mg/kg i.p.) in a dose-dependent fashion. The latency to dystonic movements was significantly increased by diazepam but markedly reduced by subconvulsive doses of pentylenetetrazol (40 mg/kg s.c.). Diazepam antagonized the latency-reducing action of pentylenetetrazol in the hamsters. The pathophysiology and pharmacological sensitivity of the dystonic attacks in these animals remain to be further clarified, but the data indicate that the sz mutant hamsters might represent an interesting genetic model for paroxysmal dystonia. In view of these data, we propose that the hamster mutation should be re-named dystonic and that the new gene symbol should be designated dtsz.
Previous studies have shown an increase in the number of GABAergic and total neurons in the inferior colliculus (IC) of the genetically epilepsy-prone rat (GEPR). Amino acid analysis of the central nucleus of the IC, as well as cerebellum, sensorimotor, temporal, and occipital cerebral cortices of GEPRs with high pressure liquid chromatography showed significant increases in the levels of GABA, taurine and glutamate. The IC of GEPR displayed a 2.3-fold increase in GABA as compared to that of non-epileptic rats, a 2.4-fold increase of taurine, and a 1.9-fold increase of glutamate. In addition, taurine and glutamate were increased in the sensorimotor and temporal cortex, respectively. These results are consistent with previous anatomical data on the GABAergic system in the IC and provide additional information. The increase in taurine and glutamate in the IC indicates that other neurotransmitters could be involved in the mechanism of seizure activity.
The class I gene products of the Syrian hamster major histocompatibility complex are unique in that they lack functionally detectable polymorphism. Mouse cDNA and hamster genomic probes were used to analyze the hamster class I gene family using genomic Southern hybridization. These studies revealed that the hamster possesses a complex class I multigene family and that it shares extensive sequence homology with the corresponding mouse sequences. Unlike the mouse, however, the Syrian hamster demonstrates only limited restriction endonuclease polymorphism in these genes. These results suggest that the lack of detectable polymorphism in this species is directly related to limited DNA polymorphism. The data presented here support the hypothesis that this species has undergone an evolutionary bottleneck, i.e., that all surviving members of the species arose from a limited number of progenitors.
Competence genes, such as c-fos, may play key roles in information storage in the nervous system by linking relatively brief extracellular signals to long-term changes in the neuron. In support of this idea we, and others, have shown that the c-fos protein occurs in adult mammalian neurons and that higher levels of the protein are induced in certain brain regions after kindled or metrazol-induced seizures in mice and rats, sensory stimulation and mechanical damage in spinal cord neurons, and after depolarization in PC12 cells. Here we report that a massive induction of c-fos protein is observed in dentate granule cells in four conditions that result in repetitive firing: localized seizure discharges; high frequency antidromic activation; orthodromic activation in the presence of iontophoresed bicuculline; and frequency potentiation. However, stimulation of the perforant path with high frequency trains that produced long-term potentiation at the perforant path-granule cell synapse did not reliably induce c-fos in the dentate gyrus. These findings suggest that c-fos induction can follow repetitive neuronal discharge but is not involved in long-term potentiation.
The paroxysmal (px) chick is a mutant White Leghorn (Gallus domesticus) which appears normal at hatching and during the subsequent week. By ca. 8 days posthatching, various symptoms develop, of which the most obvious are depressed food intake (anorexia) and audiogenic seizures. Histological evidence suggests that central auditory and vestibular nuclei and fiber tracts begin to degenerate prior to seizure onset. This degeneration, which affects central and peripheral components of both systems, becomes increasingly severe over time although auditory stimulation continues to elicit seizures. Characterization and analysis of peripheral and brainstem auditory response to auditory stimuli indicated that major response differences between px and normal chicks exist in peaks reflecting brainstem activity (P3A, P3B, P4A, P5A). In 5 of 8 px chicks, these later response peaks were either grossly abnormal in terms of amplitude and latency (including amplitude input/output functions) or often entirely absent. Early peaks (P1A and P2A), however, in px waveforms were normal in morphology and amplitude, indicating normal function of peripheral auditory structures. Although lower body temperature of px chicks may account for some of the longer latencies observed, other abnormalities (e.g. absence of peaks) could not be produced in normal birds by induced hypothermia.
The Genetically Epilepsy-Prone Rat (GEPR) is rapidly gaining support as a model of epilepsy. In addition to a marked sensitivity to both sound-induced and hyperthermic seizures, GEPRs exhibit unusual sensitivity to a number of seizure-provoking modalities, including various forms of electrical and chemical stimulation. The existence of a moderate seizure colony (GEPR-3) and a severe seizure colony (GEPR-9) allows pathophysiological studies of seizure susceptibility and severity. The consistency of seizures within each colony allows for comparisons in seizure naive GEPRs and seizure experienced GEPRs. The consistent seizure responses of the GEPR are also ideal for the testing of anticonvulsant drugs. Further, the relative potencies of anticonvulsant drugs between the two colonies of GEPRs predict the clinical efficacies of traditional antiepileptic drugs and may be able to predict novel anticonvulsants.
The genetically epilepsy-prone rat (GEPR) is abnormally susceptible to induction of seizures by acoustic stimulation. The inferior colliculus (IC) is critically important to audiogenic seizure susceptibility. The GEPR is more susceptible to induction of audiogenic seizures at 12 kHz than at other pure tone frequencies. IC neurons in the GEPR exhibit significantly elevated response thresholds and broader tuning characteristics than normal. These findings along with previous neurophysiological and anatomical data suggest that a hearing deficit occurs in the GEPR. IC neurons in the GEPR exhibit a significantly elevated incidence of a response pattern with a peak of activity at the beginning and end of the stimulus, the onset-offset response. This response pattern occurs at 12 kHz and at characteristic frequency with high stimulus intensities and may represent an afterdischarge phenomenon. The onset-offset pattern may be a manifestation of central mechanisms developed to compensate for reduced peripheral auditory input that appears to be involved in the hearing deficit of the GEPR. Such compensatory mechanisms may involve alterations of the actions of neurotransmitters of the brain-stem auditory nuclei. GABA is implicated as an inhibitory transmitter in the IC. Iontophoretic application of GABA or a benzodiazepine produces significantly less inhibition of IC neurons of the GEPR than of the normal rat. Endogenous sound-induced (binaural) inhibition which is suggested to be GABA-mediated is also significantly reduced in IC neurons of the GEPR. Iontophoresis of the GABAA antagonist, bicuculline, often converts normal response patterns in the IC to onset-offset responses seen with high incidence in GEPR IC neurons, suggesting that the decreased effectiveness of GABA may lead to the onset-offset prevalence. This reduced effectiveness of inhibition may be unable to compensate for the rise in the putative excitatory transmitter, aspartate, in IC during high intensity acoustic stimulation in the GEPR. These altered transmitter actions may be important mechanisms subserving initiation of audiogenic seizures in the genetically epilepsy-prone rat.
Identification of the neural substrates subserving audiogenic convulsions in the GEPR is an important task and while it is not yet complete, many laboratories employing various techniques have contributed importantly to our current understanding. The present review focuses on the use of lesions to identify the neural substrates of audiogenic convulsions. Lesions in brain stem nuclei appear to have a much greater ability to attenuate audiogenic convulsions than do forebrain lesions. In fact, some forebrain lesions (dorsal hippocampus, caudate, intralaminar thalamic nuclei) appear to enhance the severity of audiogenic seizures. On the other hand, bilateral lesions in the inferior colliculus (IC) have been shown to completely abolish audiogenic convulsions, while lesions in the pontine reticular formation (PRF nucleus) abolish all aspects except the running episode suggesting that these two brain stem structures are important neural substrates involved in the expression of audiogenic convulsions. Large bilateral lesions of the substantia nigra also appear to attenuate audiogenic convulsions. The effect of lesions on audiogenic convulsions is basically similar to their effect on other generalized seizure models and the data appear to support the hypothesis that there are two anatomical systems involved in the expression of all generalized convulsions: a forebrain system responsible for the expression of face and forelimb clonus; and a brain stem system responsible in the expression of running-bouncing clonus and tonus.