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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-1ß, 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-1ß 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-1ß 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-1ß 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.

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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.

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BACKGROUND: Anxiety and depression are the most frequent comorbidities of different types of convulsive and non-convulsive epilepsies. Increased anxiety and depression-like phenotype have been described in the genetic absence epilepsy models as well as in models of limbic epilepsy and acquired seizure models, suggesting a neurobiological connection. However, whether anxiety and/or depression are comorbid to audiogenic epilepsy remains unclear. The aim of this study was to investigate whether anxiety or depression-like behavior can be found in rat strains with different susceptibility to audiogenic seizures (AS) and whether chronic fluoxetine treatment affects this co-morbidity. METHODS: Behavior in the elevated plus-maze and the forced swimming test was studied in four strains: Wistar rats non-susceptible to AS; Krushinsky-Molodkina (KM) strain, selectively bred for AS propensity from outbred Wistar rats; and a selection lines bred for maximal AS expression (strain "4") and for a lack of AS (strain "0") from KM×Wistar F2 hybrids. Effects of chronic antidepressant treatment on AS and behavior were also evaluated. RESULTS: Anxiety and depression levels were higher in KM rats (with AS) compared with Wistar rats (without AS), indicating the comorbidity with AS. However, in strains "4" and "0" with contrasting AS expression, but with a genetic background close to KM rats, anxiety and depression were not as divergent as in KMs versus Wistars. Fluoxetine treatment exerted an antidepressant effect in all rat strains irrespective of its effect on AS. CONCLUSIONS: Genetic background contributes substantively to the co-morbidity of anxiety and depression with AS propensity.

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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.

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