RADON HORMESIS IN EPILEPTIC PATHOGENESIS AND PREDICTORS OF OXIDATIVE STRESS.

Numerous experimental and clinical studies have shown that oxidative stress (OS) plays an important role in the development of epilepsy. The epileptic seizures themselves are caused by OS and, under conditions of a hypermetabolic state, cause an intensive production of reactive oxygen species (ROS) in the brain. The reason for this is called a change in the energy balance in the brain. According to the literature, ROS and other markers of oxidative stress were observed in the brain after seizures. Based on the above data, the aim of our study was to study a short-term 5-day (5 min) inhalation of radonized water from Tskhaltubo using an epileptic model of the Krushinsky-Molotkin line in rats and to identify changes in markers of oxidative stress in rats. Predictors of oxidative stress were studied, PAT, D-ROM (reactive oxygen metabolite index), OBRI (oxidative stress balance risk index) and OSI (oxidative stress index) were evaluated to assess the antioxidant capacity of plasma. Based on the data obtained, it can be concluded that: inhalation of Tskhaltubinsk water develops the effect of hormesis, which causes positive changes in all of the above markers of oxidative stress in the brain. Based on the data presented, inhalation of Tskhaltubo water can be considered as one of the methods for removing and treating convulsive phenomena, which is confirmed by experimental studies.

[THE INFLUENCE OF LOCUS COERULEUS ON DIFFERENT ACTIVITIES OF THE THALAMO-CORTICAL SYSTEMS].

As revealed from our experiments, in facilitation of passage of the thalamo-cortical visual signals a key role is attributed to variability of activity of visual neurons in reticular nucleus of the thalamus. It was demonstrated that a facilitatory action of locus coeruleus gets augmented following functional exclusion of the thalamic reticular nucleus. Nevertheless, stimulation of locus coeruleus stipulated facilitation of neuronal activity in the anterior part of thalamic reticular nucleus. Emerging from this data one may assume that in the inhibition of evoked responses from a sensorimotor area of the neocortex in response to stimulation of locus coeruleus a certain role is played by reticular nucleus of the thalamus. Namely, augmentation of neurons activity in the anterior part of the thalamic reticular nucleus must condition inhibition of neuronal activity in the ventral nuclei. In spite of the stated, it is not excluded locus coeruleus ha-ving an immediate, direct inhibitory action on the neuron activity within the sensorimotor cortex and thalamic ventral nucleus.

INTERACTION BETWEEN THE THALAMIC NUCLEUS AND PREOPTIC AREA NEURONS.

The thalamic reticular nucleus which is known to delineate the dorsal thalamus stipulates development of inhibitory processes in the thalamo-cortical neurons that is necessary for generating slow (8-12 Hz), high-amplitude electric activity in this system. It was demonstrated that majority of preoptic area neurons get activated during slow-wave sleep. Activation of neurons in the anterior hypothalamus and preoptic area during slow-wave sleep and synchronization of the brain electric activity was demonstrated. The study was aimed at clarifying the relationship between the thalamic reticular nucleus and the preoptic area neurons. Under acute conditions experiments were carried out on mature cats. It was shown that blockade of preoptic area neuron activity during mesencephalic reticular formation stimulation and the fact that on the background of mesencephalic reticular formation stimulation thalamic reticular nucleus stimulation elicited preoptic area neurons activation must be in part stipulated by the fact that thalamic reticular nucleus activation leads to suppression of mesencephalic reticular formation neuron activity.

NEOCORTICAL IMPACT ON THE AUDIOGENIC SEIZURE ACTIVITY DEVELOPMENT.

Out of genetically determined epilepsy models a special interest draws the model of audiogenic seizures, which does not require whatever additional intervention (e.g. pharmacological or/and electric stimulation), because epileptic responses are elicited by specific sensory stimulation only. Notwithstanding the fact that different formations of the central nervous system are recruited in audiogenic seizure reactions, critical importance for the manifestation of this type epilepsy is attributed to the inferior colliculus and brainstem reticular nuclei. Significance of the diencephalic structures and the thalamic reticular nucleus, in particular for development and/or modulation of audiogenic seizures is ambiguous. Total of eight Krushinsky- Molodkina (KM) strain rats, weighting 250-300 g, served as the subjects of chronic experiments. The neocortex was bilaterally activated by way of administration of 1 µl strychnine (0.1% solutipon) with a microsyringe through a metal capillary prefixed on the cortical surface. Metal electrodes for recording electrical activity were implanted into the neocortex and brainstem reticular formation. Experiments have shown that against strychnine discharges in the neocortex there occurred an increase in the latency of wild runs and the pause between the first and second wild runs in response to a sound stimulus. Proceeding from the above-said, it can be assumed that activation of the neocortex must stipulate intensification of the thalamic reticular nucleus neuronal activity that, in turn, should have a modulating effect on the audiogenically induced seizure reactions.

[The impact of pregnancy and postnatal period on the development of generalized convulsive activity in experiment].

Interrelation between pregnancy and epilepsy is one of the pressing problems of current neurology. Those mechanisms, which suppress or amplify the seizure reactions in pregnancy, have not been yet determined experimentally. The goal of present work was investigation of impact of gestation and the postpartum period on initiation and development of convulsive reactions in the experimental animal model. Epileptic reactions were significantly suppressed during gestation (2 and 3 weeks). The data showed changes in behavioral reactions and EEG seizure activity. In the period of gestation the development of audiogenic kindling in response to repetitive acoustic stimulation is markedly reduced. This indicates the strengthening of inhibitory processes in the brain. It is supposed that in the period of gestation in rats with genetically determined audiogenic seizures excess of sexual hormones and enhancement of GABA-ergic transmission causes marked reduction of development of audiogenic kindling.

Noradrenergic modulation of seizure activity.

The mechanisms underlying pathogenesis of epileptic rections have been studied insufficiently as yet. Therefore, it is considered that determining the structures, transmitters, and receptors of the brain, which putatively produce development and intensity modulation of the convulsions, is highly important. The locus coeruleus is a norepinephrinic structure and an endogenous modulator of epilepsy, determining a role of which in a course of seizure reactions is an important problem of epileptology. The goal of the study was assessment of importance of the norepinephrine synapses in development of the local hippocampal seizure activity. The studies were carried out in adult rats, in conditions of chronic experiments. Influences of microinjections of agonist (clonidine) and antagonist (yohimbine) of the alpha-2 norepinephrine receptors on a course of local hippocampal seizure reactions (without behavioral manifestation), have been evaluated. It was found that microinjection of alpha-2 norepinephrine receptors' agonist determined a blockage of the local hippocampal seizures, while alpha-2 norepinephrine receptors' antagonist increased the seizures' power. It is suggested that the effects of locus coeruleus are determined by activation of the alpha-2 norepinephrine receptors.

[Influence of solitary tract nucleus stimulation on activity of thalamic reticular nucleus and mesencephalic reticular formation of the brain].

Elucidation of interrelations between the brainstem (BSN) and diencephalic structures of the brain is an important problem of neurophysiology, solution of which might allow revealing mechanisms of the workings of certain structures of the brain, on the one hand, and an overall activity of the central nervous system, on the other. The goal of present investigation was examination of the mechanism of interrelations between the mesencephalic reticular formation (MRF), solitary tract nucleus (STN), and the thalamic reticular nucleus (TRN). Activity of the TRN and MRF neurons was recorded with the tungsten microelectrodes, with tip diameter of 4-8 microm and a resistance of 4-15 MOhm. In some experiments a simultaneous (coupled) recording of the TRN and MRF neurons was made with an aid of two separate microelectrodes. Our experiments have shown that threshold stimulation of the MRF exerted an inhibitory influence on activity of the TRN neurons, while supra-threshold stimulation induced their activation. Stimulation of the STN induced inhibition of the MRF neurons and activation of the TRN. Meanwhile, during activation of the TRN neurons, in the MRF neurons inhibitory postsynaptic potentials did occur. Whatever mechanisms may underlie inhibition of the TRN neurons in response to the STN stimulation, it seems an important fact that synchronizing structure of the brainstem, which exerted a blocking impact on the MRF, facilitated activity of the TNR neurons. This is even more important because for revealing the neurophysiologic mechanisms of activity of the whole central nervous system in both norm and disorder.

[Mechanisms involved in anticonvulsive effect of pregnancy in an animal model of epilepsy].

Interrelation between pregnancy and epilepsy is one of the pressing problems of current neurology. Those mechanisms, which suppress or amplify the seizure reactions in pregnancy, have not been yet determined experimentally. Investigation of the interrelation between the epileptic fits and pregnancy in women is complicated by the bioethical considerations, as well as by the antiepileptic therapy. Therefore, in order to solve this problem, an implementing the animal models seems expedient; moreover that this problem is scarcely investigated so far. The goal of present work was investigation of impact of gestation and the postpartum period on initiation and development of convulsive reactions in the experimental animal model. Epileptic reactions were significantly suppressed during gestation (2 and 3 weeks). The data on the changes are concerned behavioral reactions and EEG seizure activity. Therefore, generalization of the seizure activity is blocked during pregnancy.

Influence of hypothalamic stimulation on the development of status epilepticus in rats.

The main objectives of the present study were to explore whether emotional behavior, elicited by stimulation of the dorso-medial hypothalamus, can influence seizure development during self-sustained status epilepticus (SSSE). The study was conducted on animal models. The results suggest that increased inhibition in the hippocampal neurons during dorsomedial hypothalamic stimulation may trigger the mechanisms preventing the epileptiform activity and that hippocampal theta rhythm is a physiological state, which opposes its involvement into seizures. It was concluded that activation of the dorsomedial hypothalamus, as well as emotional behavior (anxiety/fear) retard development of the seizures experimentally induced SSSE by limbic stimulation.

Interictal emotional state and epilepsy.

The main objectives of the present study were twofold: to explore whether emotional behavior, elicited by stimulation of the hypothalamus, can influence seizure development during kindling epileptogenesis; to determine whether such stimulation can alter the expression of generalized convulsions when the fully epileptic syndrome has been established beforehand.The kindling process has been used as an animal model for studies of epilepsy. The findings indicate that stimulation in the hypothalamus, which determines fear, anxiety, and escape responses, with concomitant hippocampal theta, can significantly dampen the course of epileptogenesis. The emotional behaviors elicited by stimulation of the dorsomedial hypothalamus can suppress the development of generalized motor limbic convulsions during epileptogenesis, as well as dampen seizure expression in already established limbic epilepsy. It is assumed that the emotional disturbances can be considered as the emergence of instinctive behavior with an adaptive significance of defense and as a by-product of the inhibitory processes that build up to protect the occurrence of future seizures.

Influence of water deprivation on morphological peculiarities of the neuronal organization in hypothalamic supraoptic and paraventricular nuclei of the rats.

In the present study a histochemical investigation of the SO and PV nuclei of the hypothalamic-pituitary neurosecretory system are presented at different periods of the water deprivation. The experiments were carried out on laboratory rats (n = 50), weighing 200-250 grams. The experimental and control animals days was maintained at different feeding ration. The control rats (I) were given food and water, the experimental animals (II, III, IV, V) for five days were given the dry food only. Following the 5-day water deprivation, the animals of the Groups III, IV, and V, had given free access to water for 15, 30, and 45 days. In order to investigate histological properties, the animals were rapidly beheaded. In order to reveal a neurosecrete, the 5-10 mm thick slices of the hypothalamus and pituitary gland were stained with the Nissle method. Evaluation of the morphological-functional state of the HPNSS a working scheme of the neurosecretory cycle has been utilized. Analysis of the above data allows concluding that following prolonged water deprivation, recovery level of the structural-metabolic components in the hypothalamic SO and PV nuclei is not uniform. Deeper morphological changes occur in the large-granular region than in the small-granular one, where no significant changes are found; respectively, these cells recover much earlier. Capacity for restoration of the structural-metabolic complex varies and depends on functional properties of the cellular content of these nuclei.

[Effects of ultracaine on the local blood flow of the gum and on the development of cerebral seizures in experiment].

We have studied the effect of ultracaine DS forte on local blood flow of the rat gum as well as on the development of the convulsion activity of the brain at systemic injection. Experiments were carried out on 12 mongrel albino mail rats of 200-250 g weight. In the I group of animals under the light chloral hydrate anesthesia we studied the changes of local blood flow in the rat gum of lower jaw after ultracaine DS forte injection (right side) and the similar quantity of phisiological solution (left side). According to our data, in the right gum, the rate of local blood flow decreases statistically significantly at 18%, while the injection of physiological solution did not result in any changes. In the II group, experiments were carried out on the animals with bipolar electrodes in neocortex, as well as in the right and the left dorsal hippocampus. On the fifth day after surgical intervention, on the background of registration of electric activity of the above stated structures 0,03-0,04 ml of ultracaine Ds forte was injected intraperitoneally, which did not result in any significant deviation on the encephalogram. 10-fold doze injection was followed by abortion of epileptic discharges (0,3 ml), but repeated injection of 0,3 ml of preparation resulted in generalized clone-tonus type seizure activity. Simultaneously, clone-tonus type behavioral manifestation was revealed.

[Development of audiogenic kindling during the gestation period].

Some peculiarities of audiogenic kindling were studied in rats with genetically determined epileptic seizures during gestation period. In the period of gestation the development of audiogenic kindling in response to repetitive acoustic stimulation is markedly reduced. This indicates the strengthening of inhibitory processes in the brain. It is supposed that in the period of gestation in rats with genetically determined audiogenic seizures excess of sexual hormones and enhancement of GABA-ergic transmission causes marked reduction of development of audiogenic kindling.

[Peculiarities of development of rat's audiogenic convulsive responses in the period of gestation].

In rats, with genetically determined audiogenic epileptic seizure some peculiarities of convulsive responses before and during gestation as well as after the delivery were studied. Depending on responses to audio stimuli the rats of Krushinsky-Molodkina line might be divided on two groups. The responses of first group are: fear and facial muscles clonus; the responses of other group--fear, wild running and then development of clonic and tonic seizures. The rats of this (second) group were used in our experiments. In the period of gestation: (a) extended latency of development of convulsive activity; (b) significant prolongation of the intervals between wild running and (c) marked reduction of behavioral manifestation of clonic and tonic seizures have been observed. These indicate the strengthening of inhibitory processes in the brain. It is supposed that in the period of gestation in rats with genetically determined to development of audiogenic seizures excess of sexual hormones causes the gaining of anticonvulsive processes in the brain. Evidently, this should be connected with GABA-ergic inhibitory mechanisms of the brain.

[Effect of lidocaine and lidocaine with adrenaline on development of cerebral seizures].

Experiments were carried out on male albino rats of 200-250 g weight with bipolar electrodes implanted in neocortex, as well as in the right and the left dorsal hippocampus for the study of the effect of lidocaine and its combination with adrenaline on the electric activity of brain. On the fifth day from the implantation in the first group of animals 0,3 ml 2% lidocaine was injected intra-peritoneally and the electric activity from the above mentioned structures was registered. In the second group 0,3 ml 2% lidocaine with adrenaline was injected intra-peritoneally (1:100000). In 8-12 sec after injection in the first group of animals the encephalogram showed sharply defined clone type seizure activity, which soon obtained tonus character. Simultaneously clone-tonus type behavioural manifestation was revealed, which lasted for 20-25 minutes. In the second group of animals in 30-40 sec after injection the encephalogram revealed convulsion activity with high amplitude synchronous oscillations, which lasted for 20-25 minutes, although in this group, in distinct from the first group, no clone-tonus behavioural manifestation was detected.

[Effect of stimulation of the thalamic reticular nucleus on spino-bulbo-spinal reflex activity]. / Vliianie stimuliatsii retikuliarnogo iadra talamusa na spino-bul'bo-spinal'nuiu reflektornuiu aktivnost'.

The effect of the thalamic reticular nucleus (RN) stimulation on the spino-bulbo-spinal reflex was studied in chloralose-anesthetized cats. RN stimulation was found to exert an inhibitory influence on this reflex. The same stimulation has also exerted an inhibitory influence on the spinal units activated during the spino-bulbo-spinal reflexes.

Locus ceruleus and neuronal activity of the reticular nucleus of the thalamus.

Reactions of neurons of the reticular nucleus of the thalamus and lateral geniculate body to stimulation of the locus ceruleus were studied on their unanesthetized, immobilized cats. It was found that preliminary brief rhythmic stimulation of the locus ceruleus causes inhibition of the activity of the majority of neurons of the reticular nucleus and facilitation of relay neurons of the lateral geniculate body. Such reactions are clearly exhibited during simultaneous recording (by means of two microelectrodes) of the neuronal activity of these brain structures.

[The locus coeruleus and neuronal activity of the thalamic reticular nucleus]. / Sinee piatno i neironnaia aktivnost' retikuliarnogo iadra talamusa.

The influence of LC stimulation on the unit activity (spontaneous and evoked by light flashes) of the thalamic reticular nucleus and the LGB was studied in adult cats. The LC stimulation was shown to result in the inhibition of the reticular units and facilitation of relay neurons of the LGB.

[Rhythmic afterdischarge in the cortical and subcortical structures of the cat in response to stimulation of the claustrum]. / Ritmicheskii razriad posledeistviia v kore i podkorkovykh strukturakh golovnogo mozga koshki pri razdrazhenii ogrady.

Effects of the claustrum and caudate nucleus stimulation in the neocortex and different subcortical structures were studied in unanesthetized tubarine-immobilized cats. Rhythmic afterdischarges were evoked in the neocortical regions 4-7 and 18 (according to the Reinoso-Suarez atlas) as well as in the caudate nucleus and in different regions of the thalamus. A similar rhythmic afterdischarge was observed in the claustrum itself. Diencephalic section of the brain at the level of the ventral anterior nucleus weakened but did not entirely eliminate rhythmic afterdischarge induced by stimulation of the claustrum in the anterior parts of the neocortex. Rhythmic afterdischarge was completely blocked after a sagittal section of the brain between the claustrum and the rest of the thalamus.