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Biomedical subjects

G D Kuznetsova

Publications and source records attributed to G D Kuznetsova.

At least 19 recordsLinked to original sources
PubMed2006

The brain 5HTergic response to an acute sound stress in rats with generalized (absence and audiogenic) epilepsy.

The brain serotoninergic (5HTergic) system of epileptic subjects can influence their vulnerability to stress. We studied the putative dependency of 5HT neurotransmission parameters on emotional stress, and the presence, types and severity of seizures using rats with genetic generalized (absence and/or audiogenic) epilepsy, of WAG/Rij and Wistar strains. The animals were stressed by exposure to a short aversive noise or left without sound stimulation. Tissue concentrations of 5HT, tryptophan (TRT) and 5-hydroxyindolacetic acid (5HIAA) were assessed by HPLC. The stressor activated the 5HTergic system within thalamus (5HIAA elevated), frontal cortex (5HT, TRT elevated), hypothalamus (increased TRT) in all rats. However, the normal (non-epileptic) rats displayed the highest response in the frontal cortex and the lowest one in the thalamus, as compared to the epileptic rats. Absence-epileptic rats exhibited higher thalamic 5HIAA increase than their controls. Significant correlations existed between propensity of absence epilepsy and 5HTergic parameters measured in the cortex and hypothalamus of absence-epileptic rats. No major difference was found between groups with and without audiogenic epilepsy. The results imply that the stress response depends on the presence of epileptic pathology and the seizure type and severity. The brain 5HT may be involved in the control of the paroxysms and behaviour in absence-epileptic subjects.

Analysis of Variance↗
PubMed2005

Audiogenic seizures associated with a cortical spreading depression wave suppress spike-wave discharges in rats.

To study the role of the cortex and sub-cortical structures in the generation of epileptic spike-wave discharges in more detail, cortical and striatal activity was eliminated by the induction of spreading depression in a non-invasive way. EEG and DC potentials were recorded from the cortex and striatum of WAG/Rij rats. Several of these rats show two forms of generalised epilepsy: spontaneously occurring non-convulsive absence seizures, together with convulsive audiogenic seizures. The latter can be evoked by a brief sound stimulation, provoking a fit of wild running, which is regarded as the first phase of an audiogenic seizure. In a majority of fits the cortical DC potential does not show main changes, while the spontaneously occurring spike-wave discharges are briefly suppressed for some minutes. In a minority of fits, however, audiogenic seizures are associated with a spreading depression wave, clearly expressed in the cortical DC potential. This wave is bilaterally initiated in the cortex and propagates to the caudate nucleus of the striatum. In these cases spontaneously occurring spike-wave discharges are fully suppressed for about 1 h. It is suggested that cortical spreading depression, triggered by a short audiogenic seizure, induces a long-lasting suppression of spike-wave discharges. These results are in line with the concept that spike-wave discharges are originally initiated in the cortex, as proposed by the 'cortical focus' theory. The precise role of the striatum remains less clear, although this structure seems not to play a pivotal role in spike-wave generation.

Acoustic Stimulation↗
PubMed2005

Convulsive and nonconvulsive epilepsy in rats: effects on behavioral response to novelty stress.

Behavioral response to a new environment of Wistar and WAG/Rij rats with absence and/or audiogenic seizures (AGSs) was investigated. Behavior was observed in open-field (OF) and light-dark choice (LD) tests. Correlations of test performance with seizure parameters were evaluated. AGS-susceptible Wistar rats exhibited reduced exploration (rearing) in both tests and a tendency toward hyperlocomotion in the OF test. Genetically absence-epileptic WAG/Rij rats demonstrated agitation (increased vertical/horizontal locomotion, enhanced defecation/urination) in the LD test, whereas they exhibited reduced exploration, increased grooming, and hyperlocomotion in the OF test. Anxiety level, as estimated by grooming time in the OF test and latency to first "risk assessment" in the LD test, correlated positively with the propensity for absence seizures in WAG/Rij rats not susceptible to AGSs. It can be concluded that the behavioral response to novelty stress in epileptic subjects depends on the type and severity of seizures.

Acoustic Stimulation↗
PubMed2004

The multiple effects of ketamine on electroencephalographic activity and behavior in WAG/Rij rats.

The effects of ketamine, a noncompetitive antagonist at the NMDA receptor, were studied on the EEG and in the open field in a genetic animal model of generalized absence epilepsy--the WAG/Rij rat strain. Animals of this strain display spontaneous occurring generalized spike-wave discharges (SWDs) in the EEG. Ketamine was systemically administered in a dose range from 3 to 30 mg/kg. Biphasic effects of ketamine were observed in the EEG. The first phase was a dose-dependent suppression of SWDs, followed by a second phase characterized by the facilitation of SWDs. This increase was expressed first as an increased number of SWDs, and later on as a significant prolongation of individual discharges and decrease in frequency of SWDs. An obvious amplitude modulation of the discharges was also found. During the period of suppression of SWDs, a new phenomenon was observed: quasi-periodic groups of spikes or wave spikes, with an internal frequency of 4-5 Hz and a periodicity of about 5 s. That quasi-periodic activity vanished a few minutes prior to the recovery of the classical SWDs. However, a specific 5-s amplitude modulation of SWDs remained present in the recovery period. The propensity of that specific ketamine-induced activity was found to be correlated with propensity of SWDs in background EEGs of drug-free animals. Ketamine also produced a dose-related initial behavioral excitation, a decrease of muscle tone in hind quarters, followed by front quarters and head, and an absence of locomotor activity. However, the time course of the behavioral changes cannot explain the effects on the EEG. It can be concluded that ketamine has more effects on the EEG than previously assumed which cannot be explained by a simple blockade of the NMDA receptor. It is proposed that the obtained specific dynamics of SWDs' frequency may be caused by changes in the activity of the thalamo-cortical pacemaker that is generating SWDs.

Anesthetics, Dissociative↗
PubMed2001

Electrophysiological and pharmacological characteristics of two types of spike-wave discharges in WAG/Rij rats.

Rats of the WAG/Rij strain are commonly seen as a genetic model for generalised absence epilepsy in man. Interestingly, generalised absence epilepsy shows, in addition to the fully generalised spike-wave discharges, a second type of spike-wave discharge, which lasts for a shorter time, has a lower frequency, and a lower incidence. The originally described distinction between the two types of spike-wave discharges was mainly based on the shape, polarity and duration of the discharges. In the present study other characteristics such as the spatial and temporal distribution of the spike and wave components of the two discharges and frequency spectra were found to differ between the two types. In addition, a reciprocal regulation of the two types of spike-wave discharges by drugs affecting the dopaminergic system (haloperidol and apomorphine) was observed. The results convincingly demonstrate the difference between the two phenomena and warrant the search for neurobiological mechanisms underlying both types of spike-wave discharges.

Action Potentials↗
PubMed2000

The use of neural transplantation for suppression of seizure activity in genetically epilepsy-prone rats.

The possibility of correcting seizure activity with neural transplantation was studied in Wistar rats with audiogenic seizures and in Krushinskii-Molodkina rats with high level of audiogenic seizures. In Wistar rats seizures were absent during 24 weeks after combined bilateral transplantation of striatal and cerebellar tissue from newborn rats into the parietal cortex. The same transplantation performed in Krushinskii--Molodkina rats increased the latency of audiogenic seizures. In some rats the intensity of seizures decreased, but they did not completely disappeared. Suppression of seizure activity in Krushinskii-Molodkina rats was observed after transplantation of striatal and cerebellar tissue simultaneously into the parietal cortex and inferior colliculi.

Animals↗
PubMed1996

Generalized absence epilepsy and catalepsy in rats.

Adult WAG/Rij rats are considered adequate genetic models for human generalized absence epilepsy. Rats of this strain of 8, 12, and 18 weeks old and age-matched control Wistar rats were exposed to sound stimulation. After offset of stimulation, all WAG/Rij rats showed cataleptic or even cataplexic reactions, which could persist for up to 20 min. Age effects could be demonstrated. None of the Wistar rats showed cataleptic reactions. Electroencephalographic studies in WAG/Rij rats of 21 weeks showed that spike-wave discharges were abundantly present in the background electroencephalogram prior to sound stimulation. Age-matched Wistar rats had almost no spike-wave discharges. Spike-wave discharges in WAG/Rij rats disappeared during sound stimulation and were then increased compared to the prestimulation and stimulation periods. The electroencephalogram during the cataleptic state was also characterized by the presence of large amplitude 2 Hz waves, interspersed with spike-wave discharges. The data suggest that the cataleptic state can be elicited in genetically epilepsy-prone rats. The youngest WAG/Rij rats showed no spike-wave discharges during the cataleptic state. In all, the data suggest that epilepsy-prone animals are sensitive for catalepsy at an age at which the EEG signs of generalized absence epilepsy are not yet manifest.

Animals↗
PubMed1996

[The late sequelae of radiation exposure on the nervous system].

Clinical, neuropsychologic, neurophysiologic as well as neuromorphologic (in legal cases) examinations of Chernobyl liquidators were performed. In addition, the study was made of the monkeys exposed to 1,5 Gy radiation. The results obtained testified to the organic character of cerebral damages. They may be characterised as chronic progressive discirculatory-hypoxic syndrome in which disorders of vascular permeability were expressed and dystrophic destructive irreversible alterations of nervous cells occurred.

Adult↗
PubMed1989

[Changes in the spreading depression wave in rats in the postresuscitation period].

Functional state of the rat brain cortex after a 10-minute arrest of blood circulation was studied by means of the spreading depression wave, the latter leading to significant energy expenditures and being accompanied by a transmitter output and changes in extra- and intracellular ion concentration. The changes in the spreading depression wave took place at different stages of the postresuscitation period (2 hours to 2 1/2 months), suggesting various pathological changes in functional state of the brain cortex induced by disturbances in neurological interrelationships.

Animals↗
PubMed1987

[Temperature distribution on the surface of the rat brain during direct electric stimulation].

Dynamics of spatial temperature distribution over the dorsal surface of the cerebral cortex was studied through the skull with the thermovision technique on immobilized white rats. Direct cortical stimulation revealed local thermoresponses (up to +0.2 degrees C) under electrodes, in the symmetrical point in the opposite hemisphere as well as in some other cortical zones. The response latency was within the limit of 160 ms, peak latency--2-5 s and relaxation time 2-3 min. Nembutal caused depression of thermoresponses, increase in their thresholds, limitation in size as well as slowing down of the development and prolongation in time.

Animals↗
PubMed1986

[Dynamic thermomapping of the brain of the rat during sensory stimulation and spreading depression].

Dynamics of spatial distribution of temperature over the dorsal surface of white rat cerebral cortex was studied through the skull with the thermovision technics. Visual, somatosensory and acoustic stimulation revealed both diffuse and regionally specific thermoreactions of the brain as well as multiple local termoresponses. After injection of KCl into the cortex temperature waves spreading over the cortex were obtained. Mechanisms of brain patterned thermoreactions dealing with blood flow and neuronal metabolic thermoproduction are discussed.

Animals↗