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

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

The genetic audiogenic seizure hamster from Salamanca: The GASH:Sal

The hamster has been previously described as a paroxysmal dystonia model, but our strain is currently recognized as a model of audiogenic seizures (AGS). The original first epileptic hamster appeared spontaneously at the University of Valladolid, where it was known as the GPG:Vall line, and was transferred to the University of Salamanca where a new strain was developed, named GASH:Sal. By testing auditory brainstem responses, the GASH:Sal exhibits elevated auditory thresholds that indicate a hearing impairment. Moreover, amplified fragment length polymorphism analysis distinguished genetic differences between the susceptible GASH:Sal hamster strain and the control Syrian hamsters. The GASH:Sal constitutes an experimental model of reflex epilepsy of audiogenic origin derived from an autosomal recessive disorder. Thus, the GASH:Sal exhibits generalized tonic-clonic seizures, characterized by a short latency period after auditory stimulation, followed by wild running, a convulsive phase, and finally stupor, with origin in the brainstem. The seizure profile of the GASH:Sal is similar to those exhibited by other models of inherited AGS susceptibility, which decreases after six months of age, but the proneness across generations is maintained. The GASH:Sal can be considered a reliable model of audiogenic seizures, suitable to investigate current antiepileptic pharmaceutical treatments as well as novel therapeutic drugs. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".

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

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