Characteristic Features of the Transcriptome in a Rat Strain with Audiogenic Epilepsy

Audiogenic epilepsy (AE), developing in rodent strains in response to sound, is widely used as the model of generalized convulsive epilepsy, while the molecular mechanisms determining AE are currently poorly understood. The brain region that is crucial for AE development isthe inferior and superior colliculi (IC, SC). We compared IC-SC gene expression profiles in rats with different AE susceptibility using transcriptome analysis.The transcriptomes were obtained from the IC-SC of Wistar rats (with no AE), Krushinsky-Molodkina (KM) strain rats (100% AE susceptible), and ”0” strain rats (with no AE) selected from F2 KM x Wistar hybrids for AE absence. KM gene expression displayed characteristic differences inboth of the strains that were not susceptible to AE. There was increased expression of a number of genes responsible for positive regulation of the MAPK signaling cascade, as well as of genes responsible for the production of interferon and several other cytokines. An increase in the expression levels of theTTR gene was found in KM rats, as well as significantly lower expression of the Msh3 gene (involved in post-replicative DNA repair systems). AE was also describedin the 101/HY mouse strain with a mutation in the locus controlling DNA repair. The DNA repair system defects could be the primary factor leading to the accumulation of mutations, which, in turn, promote AE. Keywords: udiogenic seizure, KM strain, transcriptome, TTR gene, Msh3 gene, DNA repair

Rodent Brain Pathology, Audiogenic Epilepsy

The review presents data which provides evidence for the internal relationship between the stages of rodent audiogenic seizures and post-ictal catalepsy with the general pattern of animal reaction to the dangerous stimuli and/or situation. The wild run stage of audiogenic seizure fit could be regarded as an intense panic reaction, and this view found support in numerous experimental data. The phenomenon of audiogenic epilepsy probably attracted the attention of physiologists as rodents are extremely sensitive to dangerous sound stimuli. The seizure proneness in this group shares common physiological characteristics and depends on animal genotype. This concept could be the new platform for the study of epileptogenesis mechanisms.

Glutamatergic Fate of Neural Progenitor Cells of Rats with Inherited Audiogenic Epilepsy

Epilepsy is associated with aberrant neurogenesis in the hippocampus and may underlie the development of hereditary epilepsy. In the present study, we analyzed the differentiation fate of neural progenitor cells (NPC), which were isolated from the hippocampus of embryos of Krushinsky-Molodkina (KM) rats genetically prone to audiogenic epilepsy. NPCs from embryos of Wistar rats were used as the control. We found principal differences between Wistar and KM NPC in unstimulated controls: Wistar NPC culture contained both gamma-aminobutyric acid (GABA) and glutamatergic neurons; KM NPC culture was mainly represented by glutamatergic cells. The stimulation of glutamatergic differentiation of Wistar NPC resulted in a significant increase in glutamatergic cell number that was accompanied by the activation of protein kinase A. The stimulation of KM NPC led to a decrease in immature glutamatergic cell number and was associated with the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and protein kinase B/ glycogen synthase kinase 3 beta (Akt/GSK3β), which indicates the activation of glutamatergic cell maturation. These results suggest genetically programmed abnormalities in KM rats that determine the glutamatergic fate of NPC and contribute to the development of audiogenic epilepsy.

Gender differences in the pool of free amino acid neurotransmitters in Krushinsky-Molodkina rats

The study of the role of neurotransmitter systems in the pathogenesis of epilepsy is one of the priorities of epileptology. New data on the functions of free neurotransmitter-like amino acid in the central nervous system are of the greatest importance and determine the prospects for the development of novel effective anticonvulsants. It is widely believed in clinical medicine that epilepsy has distinct gender characteristics. The aim of this study was to investigate the gender peculiarities in the content of neurotransmitter amino acids in the brain of Krushinsky-Molodkina (KM) rats, which were used as model organisms for the study of genetically induced audiogenic epilepsy. The content of Asp, Glu, GABA, Gly, and Tau of the medulla oblongata, hippocampus and cerebral cortex were determined using high-performance liquid chromatography (HPLC) in intact KM rats, KM rats exposed to a series of epileptiform seizures, and Wistar rats (control group). Both the Wistar and KM rats had gender distinctions in the distribution of free amino acids among the investigated brain parts. The audiogenic epilepsy was characterized by smoothing gender differences as well as differences between the concentrations of free amino acids in the cortex and medulla oblongata, specific for Wistar rats. The changes observed in male rats after the set of seizures included the increase in GABA concentration and a decrease in the Gly level in all investigated brain parts, as well as the decrease of the Tau content in the cortex and hippocampus. At the same time, the Glu content in cortex increased, while the Asp level decreased. After 6 days of audiogenic stimulations the female KM rats demonstrated the increase in the Glu level in all investigated brain parts, the increase in Gly and Asp levels in hippocampus, and no changes in the GABA content. Thus, after the set of epileptiform seizures the KM rats achieved a new steady state of the studied amino acids pool, which differed in males and females. In this case, gender differences significantly changed after the seizures.

Blood corticosterone in rats with different susceptibility to audiogenic epilepsy

Актуальность. Селектированная на проявление судорог в ответ на сильный звук (аудиогенную эпилепсию, АЭ) линия крыс Крушинского-Молодкиной (КМ) - модель судорожных состояний человека, c быстрым развитием судорожного припадка в ответ на включение звука (100-120 дБ). Однако у крыс с АЭ изменений уровня кортикостерона (КС) в крови в связи с судорогами не определяли, хотя анализ связи АЭ и стресс-реакции - важная практическая задача. Методы. Уровень КС в образцах сыворотки крови определяли с помощью набора у крыс линии КМ, а также у крыс линии «0», селектированных из гибридной популяции КМ х Вистар на отсутствие АЭ, и у крыс популяции Вистар. Результаты. У всех крыс КМ был зарегистрирован аудиогенный припадок, тогда как у крыс линии «0» и Вистар судорог не было. Через 30 мин после действия звука (и судорог) у крыс КМ повышеается уровень КС, тогда как сразу после судорог (через 1-3 мин) данная реакция не обнаруживается. У крыс линии «0» обнаружен достоверно более высокий фоновый уровень КС, по сравнению с КМ и Вистар. Уровень КС у них, как и у крыс Вистар, после действия звука не изменялся. Заключение. Подъем уровня КС в крови после действия звука наблюдали только у крыс КМ через 30 мин после припадка АЭ. Крысы линии «0», у которых нет судорог в ответ на звук, обнаружили более высокий, чем у КМ и Вистар уровень КС в фоне. Aims. The Krushinsky-Molodkina (KM) rat strain, which was selected for a seizure response to a sound (audiogenic epilepsy, AE), is known as a model of human seizure states. Although the association of blood CS with stress reaction is an important practical issue, blood levels of corticosterone (CS) have never been analyzed in rats with AE in relation with seizures. Methods. Serum concentration of CS was measured using IBL International Corticosterone ELISA kits in KM rats, rats of the «0» strain, which was selected (based on F2 KM х Wistar hybrids) for the lack of seizures in response to a sound, and Wistar rats. Results. All KM rats developed AE seizures in response to a sound while no seizures were observed in rats of the «0» strain and Wistar rats. The increase in blood CS was observed only in KM rats at 30 min after AE seizure. At background, the level of CS was significantly higher in rats of the «0» strain, which did not develop seizures in response to a sound, than in KM and Wistar rats. CS levels remained unchanged in both «0» and Wistar rats after the sound exposure. Conclusions. The increase in blood CS occurred in KM rats at 30 min after the seizure episode. At background, the CS level was higher in rats of the «0» strain, which did not respond with seizures to a sound, than in Wistar and KM rats. Therefore, the blood level of CS depends in a complicated way on both AE and the selection history of the «0» rat strain.