Effect of Ethosuximide on Audiogenic Epilepsy in Krushinsky-Molodkina Rats.

The anticonvulsant effect of ethosuximide (T-type calcium channel blocker) was evaluated in Krushinsky-Molodkina rats predisposed to audiogenic epilepsy. Ethosuximide given with drinking water (300 mg/kg/day) over 45 days slightly reduced proneness to audiogenic epilepsy and increased locomotor activity of the animals at the periphery of the open field. Neonatal administration of ethosuximide (3-4 mg per animal, from 2 to 10 days of life) insignificantly modulated the parameters of audiogenic epilepsy in these animals at the age of 1.5 months and reduced manifestation of audiogenic myoclonic convulsion that developed after long daily sound presentation started at the age of 3 months. The findings attested to a weak anticonvulsant effect of ethosuximide on tonic convulsions with its predominant effect on convulsions with forebrain focus location.

Study of Uridine Effect on the Development of Audiogenic Tonic Seizures in Krushinsky-Molodkina Strain Rats.

The latency of tonic seizure in response to loud sound (in rats of the Krushinsky-Molodkina strain with audiogenic epilepsy) had been slightly (although statistically significantly) longer after chronic uridine injections (100 mg/kg, i.p., three times a day during 9 or 12 days). The recovery time from the tonic seizure was shorter after 12 days of injections in comparison to the 9-day injection period. At the same time, the intensity of tonic seizures provoked by loud sound did not change after chronic uridine injections. The lack of uridine anticonvulsive effect demonstrated in the audiogenic epilepsy model contradicts the anticonvulsant effects of uridine in experiments with other seizure models, in which the epileptic foci were localized in the forebrain structures.

Remote effects of short-term neonatal hyperthermia in Krushinsky-Molodkina rats prone to audiogenic seizures strain.

Using the audiogenic seizure prone Krushinsky-Molodkina rat strain, it was demonstrated that short-term (5 min) exposure of 14-day-old pups to an elevated temperature (42°C) resulted in a significant decrease in audiogenic seizure severity at the age of 1 month. Presumably, this effect is determined by the activation of the heat-shock protein system (stress proteins).

The Krushinsky-Molodkina rat strain: The study of audiogenic epilepsy for 65years.

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 and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".

Effect of chronic fluoxetine treatment on audiogenic epilepsy, symptoms of anxiety and depression in rats of four lines.

Anxiety (Anx) and depression (Dp) levels were evaluated in rats of 4 lines: 2 of them (KM and "4") exhibited audiogenic seizures (AS), and 2 (Wistar and "0") had no AS. In KM rats (with AS), Anx and Dp levels were higher than in Wistars (without AS), while in "4" and "0" rats with the related genetic background but contrasting in AS severity, Anx and Dp indices were not different. Fluoxetine treatment exerted antidepressant effect in all rat lines irrespective of its effect on AS. Thus, phenotypic expression of AS is not directly associated with the mechanisms of Anx and Dp development.

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

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

[Laboratory rat selection for the trait "the absence of audiogenic seizure proneness"].

The hybrids between Krushinsky-Molodkina (KM) inbred strain, selected for high predisposition to audiogenic epilepsy (AE), and Wistar rats non-prone to audiogenic seizure were the initial population for selection. Rats were selected for the trait "the absence of audiogenic seizure proneness". The creation of such strain in which the significant proportion of animals develop no AE in response to sound and share partly the genetic background of the KM strain is very important for the correct use of RV strain as the laboratory model of seizure states. As alleles which determine the AE proneness are recessive the selection for the "opposite" trait proceeds necessarily slow.

Binding of specific ligand by D2- and NMDA-receptors of striatum cells in two rat strains predisposed and resistant to audiogenic seizures.

We studied parameters of specific receptor binding of D2-dopamine receptor ligand [(3)H]-sulpiride and NMDA-receptor ligand [(3)H]-MK-801 on the membranes of striatum cells in Krushinsky-Molodkina rats (predisposed to audiogenic seizures) and strain "0" selected for the absence of audiogenic seizures. No interstrain differences were observed in affinity (K(d)) of both D2- and NMDA-receptors to ligands. At the same time, significant interstrain differences in receptor density (B(max)) were found for both D2-receptors and NMDA-receptors. The reduced number of dopamine and glutamate receptors in the striatum can be associated with neurological peculiarities of Krushinsky-Molodkina rat strain (audiogenic seizures and postictal catalepsy).

Anxiety and predisposition to audiogenic epilepsy in rats of different genotypes.

We studied plus-maze behavior of inbred Krushinskii-Molodkina, Wistar, and black-hooded rats (originating from the Long-Evans outbred strain) differing by predisposition to audiogenic seizures. The severity of audiogenic seizures partially correlated with anxiety and negatively correlated with the total level of locomotor activity in the elevated plus-maze. The anxiety parameters in Krushinskii-Molodkina rats were evaluated after injection of anticonvulsant levetiracetam and anxiolytic afobazol. Levetiracetam and afobazol somewhat stimulated locomotor activity.

[Levetiracetam modifies the pattern of audiogenic locomotive response in Wistar and Krushinsky-Molodkina strain rats].

The novel antiepileptic drug levetiracetam (keppra, 80 mg/kg, i.p.) produces a pronounced anticonvulsant effect on all parameters of the audiogenic locomotion response in Wistar rats, leading to the prevention of acoustic seizures approximately in 50% animals. Keppra injection also led to a decrease in the intensity of single audiogenic convulsive episode, a twofold prolongation of the latency of motor reaction, and a change in the pattern of seizure reaction toward increasing number of rats with "one-wave" response. In contrast, a lack of sound resistant animals and the change from one- to two-wave audiogenic response were observed in Krushinsky-Molodkina strain rats.

[Pinch-induced catalepsy in rats of various genetic groups with different predisposition to audiogenic epilepsy].

Proportion of animals which developed pinch-induced catalepsy and the duration of this state were analyzed in rats of several genotypes which differed in audiogenic epilepsy proneness and compared with "audiogenic" catalepsy after a sound-induced seizure fit. The following genotypes were studied: Wistar, KM (Krushinsky-Molodkina) strain and substrains "4" and "0" (selected from KM and Wistar hybrid population for high "4" and low "0" audiogenic epilepsy proneness). Adult KM and substrain "4" rats developed the most intense pinch induced catalepsy, whereas Wistar and 2-month-old KM showed practically no catalepsy. After a single sound exposure pinch-induced catalepsy developed in all animals which demonstrated an audiogenic seizure fit--in KM, substrain "4", part of Wistar rats and several animals of substrain "0", latency of the fit onset in all rats being shorter than initially. After sound exposure pinch-induced catalepsy was revealed even in those substrain "0" rats, which demonstrated no audiogenic fits. It is suggested that despite the phenomenological similarity between cataleptic states of different origin (pinch-induced, "audiogenic") their neurophysiologic substrates overlap only partially. The findings are considered as presenting genetic model for further analysis of catalepsy.

[The investigation of cataleptic muscle tonus changes in rats after audiogenic seizures].

The duration and severity of cataleptic freezing after audiogenic seizures were investigated in rats of several genotypes with different predisposition to audiogenic epilepsy. These genotypes were the Krushinsky-Molodkina strain (KM--the audiogenic seizure prone strain), the Wistar and two new substrains selected from hybrids KM x Wistar for high ("4") and low ("0") audiogenic seizure susceptibility. The drug injections, which modulated the audiogenic fit severity, induced the changes in catalepsy too. It was found, that in intact animals cataleptic freezing developed after audiogenic seizures only and was more intense after severe seizures, the correlation coefficient being statistically significant. Levetiracetam (anticonvulsant drug) injections resulted in significant decrease of audiogenic fit severity and cataleptic state in Wistar and KM rats. Caffeine injections resulted in audiogenic seizures accompanied by cataleptic freezing in rats of the substrain "0", selected for audiogenic non-pronness.

[Anticonvulsant effects of levetiracetam on audiogenic epileptiform siezures in Krushinsky-Molodkina rats].

The new antiepileptic drug levetiracetam (LVT) at doses of 40 and 80 mg/kg exhibits a pronounced anticonvulsant effect, influencing all the parameters of audiogenic epileptiform seizures (AES) in Krushinsky-Molodkina (KM) rats. The latent period of the motor reaction was increased 3-15 times compared to control, and the intensity of single convulsive episodes was significantly decreased. Changes were also detected in the profile of the first stage of motor activity, and the "two-wave" reaction was observed in 50-80% of animals. The mechanism of LVT anticonvulsant action in KM rats is probably associated with an increase in the inhibitory and a decrease in the excitatory processes in the CNS.

[Neonatal buspirone modulates the intermale aggression in adult mice].

Mice of two strains with different levels of male aggression (RSB and RLB) were subjected to daily injections of 5-HT1A receptor agonist buspirone (25 microg) on the 2nd - 6th postnatal days. This neonatal treatment augmented the aggressive behavior (tested in the dyadic contests with non-aggressive A/Sn males) in aggressive RSB mice and reduced aggression in less aggressive RLB. Correlations with different signs were found between the 5-HT and 5-HIAA levels in the neocortex, hippocampus, and hypothalamus and behavioral indices of aggression in RSB and RLB males. The remote effects of neonatal buspirone in these two mice strains presumably depend on genotype-related features of ontogeny of the 5-HT system.

[Rats of Krushinsky-Molodkina strain: studies of audiogenic epilepsy, vascular pathology, and behavior].

Physiological, biochemical and genetic studies of audiogenic epilepsy in Krushinsky-Molodkina (KM) rat strain are analyzed. In brief, the history of KM strain selection and its current state are reviewed. Physiological mechanisms of the typical audiogenic seizure development and the audiogenic myoclonus (audiogenic kindling phenomena) are considered. The EEG correlates of these phenomena are presented. Biochemical features of the strain (neurotransmitter and neuronal membrane biochemistry) are described.

[Genetic analysis of the predisposition to audiogenic seizure fits in Krushinsky-Molodkina rat strain].

The expression of audiogenic seizure fits has been studied in F1 hybrids between audiogenic seizure-prone Krushinsky-Molodkina rat strain and Wistar rats not prone to audiogenic seizures, as well as in two backcross generations. Only 10% of F1 hybrids exhibit audiogenic seizure fits, whereas the frequency of this character in two generations of their backcrosses with Krushinsky-Molodkina rats is about 50%. A digenic model with incomplete penetrance has been put forward to explain the control of audiogenic seizure fits. This model fits the data obtained: the theoretically expected distributions of the character in offsprings of different crosses do not differ significantly from those observed in experiments. The model explains why the distribution of the character is the same in the first and second backcross offsprings.

[Remote effects of early postnatal pituitary hormone melatonin injection on audiogenic seizures in Krushinsky-Molodkina rats].

Rats Krushinsky-Molodkina inbred strain (KM) genetically prone to audiogenic seizures were injected with pineal hormone melatonin (50 mg/kg, s.c.) within the period 7th to the 14th posnatal days (PND). The remote effects of this injection adult KM rats consisted in a decrease in the latency and increase in severity of myoclonic seizures produced by audiogenic kindling (20 sound stimuli, 100 dB and 12-15 kHz). As compared to the control, in the cortex and hippocampus of rats of melatonin group, we also found a significant reduction of both total and functional activity of Ca2+/calmodulin-dependent protein kinase II (CAMK II) after audiogenic kindling. On the contrary, melatonin administration within the 1st to 7th PND and the 14th to the 21st PND resulted in a decrease in seizure activity. In the first case, both the total (cortical) and functional (hippocampal) CAMK II activities in melatonin-injected rats were increased as compared to control, whereas in the second case, only a slight increase in Ca2+-independent CAMK II activity in the hippocampus of melatonin-injected rats was observed. Probably, the melatonin administration in the period of early postnatal development changes the features of expression and/or regulation of CAMK II activity, and this could be one of the mechanisms of audiogenic seizure modulation in KM rats.

Nociceptive thresholds in adult rats of three strains after pain stimulation in the neonatal period.

Nociceptive thresholds in the tail-flick test decreased in adult 2.5-month-old KM, Wag/Rij, and Wistar rats receiving injections of placebo in the neonatal period (days 3-9 of life).