Open-field behavior of rats with different levels of nervous system excitability

The dependence was studied of characteristics of organization of orienting-investigating behaviour in the open field test on the level of nervous system excitability in rats selected by the threshold of excitability of the peripheral nervous system. It is established that the studied rats lines can be divided into groups according to entropy level of their behaviour. Rats of highly excitable line build their behaviour in highly probable stereotypes as compared with the animals of low-excitable line, which organize their behaviour with more plasticity, diversity. Differences in the nervous system excitability influence first of all the organization of animals behaviour.     

The differential sensitivity to a neurotigenic exposure of rat strains differing by the threshold of nervous system excitability]

The influence was studied of 15-days stressing on the appearance of stable neurosis-like state of rats lines, selected by the excitability of the nervous system. Unconditioned and conditioned components of behaviour were tested: pain sensitivity, behaviour in the open field, level of "anxiety", passive and active defensive avoidance. Differential reactivity was shown of the rats lines to prolonged stressing, depending on the genetically determined level of the nervous system functional state. Interlinear differences in dynamics of the development of neurosis-like state were established.     

Structural-functional and metabolic changes in the nervous system in low- and high-excitable rats deprived of paradoxical sleep

Studying of the influence of 24-hour deprivation of paradoxical sleep phase (PSPh) on rats with different genetically determined levels of excitability of the nervous system allowed to establish: 1) significant changes in functional state of the central part of the nervous system responsible for elaboration and preservation of defensive conditioned reflexes; 2) considerable lowering of functional state of the peripheral nervous system expressed both in a decrease of tibial nerve excitability thresholds and in changing of morpho-tinctorial characteristics of the studied nerve receptor parameters. The degree of the observed effects of PSPh deprivation is dependent on animal line belonging.     

Changes in the Content of Glial Fibrillary Acidic Protein in the Frontal Cortex of Rats during Conditioned Active Avoidance Training

We studied the dynamics of expression of glial fibrillary acidic protein (GFAP) in the frontal neocortex of rats during training for conditioned active avoidance reaction (CAAR). The GFAP content in a cytoskeletal fraction of the frontal cortex tissue was quantitatively estimated with the use of solid-phase immunoenzyme analysis, 2 h and 1, 3, 7, 14, 21, and 30 days after the beginning of training of the animals. It was found that the changes in expression of the filamentous form of GFAP in the neocortex are clearly pronounced and possess a three-phase pattern: the level of GFAP significantly increased within the first hours after the beginning of CAAR training, within 7-14 days this index decreased and became smaller than that in the initial state, and then again rose (with a maximum after 21 days). The obtained data indicate that the neurospecific protein under study is involved in the processes of learning and formation of conditioned memory engrams.     

Morphologic differences in the cutaneous receptors of low- and high-excitability lines of rats

By means of methylene blue staining of the rat plantar skin, receptor terminals in lines with low- and high-excitability have been revealed with a subsequent morphometric and cytophotometric estimation of the dye sorption degree. Divergence of the signs at selection according to excitability of the nervous-muscular apparatus is spreading to the peripheral nervous system elements, affecting its structural and tinctorial indices. In rats with low threshold of excitability increasing size of the receptor plates and areas of the receptors division is observed in comparison to the animals with high threshold of excitability. The receptors in the former line are stained less intensively than the receptors in the latter line.     

Individual typologic characteristics of the open-field behavior of rats

By means of ethograms record and analysis, connection has been studied between the properties of rats behaviour organization in the open field, determining the level of behaviour entropy in this test, and the speed of conditioned reflexes formation in the Skinner chamber. According to behaviour entropy level the rats are significantly divided into four groups; the lowest speed of conditioned reflexes formation in the Skinner's chamber is observed in the animals of the first (low entropy) group, the highest--in the fourth (high entropy) group. The obtained data are discussed according to Pavlov's concepts on the characteristics of the basic nervous processes, determining individual-typological characteristics of the higher nervous activity of the animal. Conclusion is made that division according to the level of behaviour entropy in the open field test may serve as a safe method of express-estimation of the animals abilities to conditioned habits formation.     

Action potential conduction velocity along the caudal and tibial nerves in rat strains selected for excitability of the neuromuscular system

The study was performed on 2 lines of rat selected for high (H) and low (L) excitability threshold of the nervous-muscle apparatus. H-line rats have higher values of spike conduction velocity in caudal and tibial nerves, as compared to those obtained in L-line rats. It is suggested that behavioral differences between these two lines of rat may be connected with changes of neurological characters both of peripheral and central nervous system, as a result of selection.     

Radiation resistance of motor-defensive conditioned reflexes in rats at different stages of the formation and stabilization of a temporary connection

Disturbances were studied of the motor defensive conditioned reflexes in rats radiated in a dose of 100 Gy at different stages of formation and stabilization of temporary connection. In comparison with consolidated (automatized) conditioned reflexes of active avoidance, early stages of formation and stabilization of the temporary connection are characterized by a relatively low resistance against extreme factors and by deepest disturbances of reproduction in radiated animals. The most probable mechanisms of these disturbances are connected with pathological changes of the nervous processes balance towards an increase of excitability and weakening of internal inhibition. Yet a direct radiation influence on the mechanisms of temporary connection reproduction at the second stage of its consolidation cannot be excluded. The role is shown of the emotional reactivity in the above-described processes.     

Comparative aspects of a study of the self-regulation of higher nervous activity in experimental neuroses in dogs, cats and rats

The higher nervous activity has been studied by means of motor-alimentary conditioned reflexes and delayed reactions in dogs, cats and albino rats at early stages of development of experimental informational neurosis. It was shown that formation of stable pathological reactions is preceeded by self- regulational activity of the brain directed towards elimination of a pathological situation, as well as to the increase of the stability of the nervous system to pathogenic agents. Comparative studies on rodents and predatory animals indicate that in different species the same pathogenic effects on the brain may elicit different forms of self-regulation of the higher nervous activity.     

The open-field behavior of neuroticized rats]

A detailed study has been carried out of the behaviour in the open field of the lines of rats with different functional state of the nervous system after prolonged neurotization in dependence on the phase of circadian rhythm and terms after the end of the influence. Significant changes have been shown by the amplitude of circadian rhythms of emotionality and motor activity. It is established that the reaction of the rats lines to prolonged neuroticizing action depends on the phase of the circadian rhythm, the time after its termination and on genetically determined level of excitability of the nervous system.     

Dynamics of NCAM Content in Rat Hippocampus during Conditioned Active Avoidance Reaction Training

We studied the dynamics of expression of neuronal cell adhesion molecule (NCAM) in the hippocampus of rats trained to perform conditioned active avoidance reaction (CAAR). Using a hard-phase immunoenzyme analysis technique, we quantitatively measured the NCAM content in the membrane fraction of hippocampal tissue and observed a statistically significant increase in this index on the third day and a certain decrease within the second to fourth weeks of the training course. These results confirm the statement that changes in the level of NCAM expression in the hippocampus of experimental animals can be one of the mechanisms providing plastic synaptic modifications in the processes of learning and formation of memory engrams and are also indicative of the important role of the hippocampus in such a formation.     

Peculiarities of modifying influence of the factors forming the functional status of the central nervous system on dynamics of the rat higher nervous activity disturbances totally exposed to electron and gamma-radiation at a dose of 100 Gy

The dynamics of using a stabilized motor defensive conditioned reflex of active avoidance in "shuttle-box" in rats after the total influence of high energy electrons and gamma-rays at a dose of 100 Gy and a modifying influence of the two most important factors forming the functional status of the central nervous system: the stage of the conditioned reflex consolidation and typological peculiarities of the higher nervous activity have been investigated. The influence of both types of ionizing radiation has been shown to cause far more profound disturbances of non consolidated conditioned reflexes in comparison with the automatized conditioned reflexes and provoke an inverted picture of disturbances in the animals with opposed peculiarities of the higher nervous activity. The qualitative picture of the dynamics of disturbances that are caused by these types of radiation is identical. In summary, the studied conditions that form the functional status of the central nervous system determine the nature of neuroradiation syndrome to a greater extent than differences in the effectiveness of these types of radiation.     

Effect of NMDA receptor activity on histone H3 methylation and its asymmetry in the hippocampal pyramidal neurons of rats with different excitability thresholds under normal and stress conditions

Process of methylation of histone H3 for lysine 4 (H3K4) was studied in hippocampal pyramidal neurons of rats—intact and submitted to emotional-pain stress with active and inactivated channels of NMDA-receptors with taking into account the interhemisphere lateralization and in connection with the genetically determined level of excitability of the animals’ nervous system. There were revealed interstrain differences in the basal level of the H3K4 methylation whose direction depends on structural-functional peculiarities of hippocampal fields and lateralization. Under action of stress the direction of the observed changes in the degree of the H3K4 methylation depended on the functional states of channels of NMDA-receptors. On the background of active receptors the proportion of immunopositive cells predominantly increased. In the CA1 field this change was not connected with excitability and lateralization, whereas in the CA3 field it had a complex character and depended on these two factors. At inactivation of channels of NMDA-receptors the portion of immunopositive nuclei as a result of the stress action, on the contrary, predominantly decreased; interstrain specificity of these changes was connected with lateralization, while its direction in different hippocampal fields was different. Action of the short-time emotional-pain stress did not lead to a change of shape of interhemisphere at active state of receptors, whereas at inactivation of receptors it changes depending on the structural-functional organization of hippocampus and on excitability of the nervous system.     

Single-strand DNA breaks in brain cells of different rat strains under normal condition and during exposure to stress

This study was aimed to characterize pattern of occurrence of spontaneous single-strand breaks in situ in glial and neuronal nuclei of the cortex, middle brain and hyppocapmi (CA3 field) of rats selected for a threshold of nervous system excitability, and to study the influence of stress of various modality on such breaks. The results obtained evidence that: 1) intact animals possess a subpopulation of glial and neuronal cells revealed following gap filling in situ in opposite to other types of terminally differentiated non-proliferating cells; 2) the size of such a subpopulation differs depending on the lines of examined rats, parts of brain, and the type of stress.     

Spontaneous and orienting-exploratory motor activity in rats with hereditary arterial hypertension

In rats of spontaneously hypertensive line (SHR) in comparison with normotensive animals of WKY line an increased activity was revealed in new surroundings in conditions of open illuminated space, and reduced activity in limited darkened space with weakened extinction of activity. Male SHR rats had a higher daily motor activity and SHR females--a lower level of defecation. The revealed behavioural changes testify to an enhancement of investigatory motivation and weakening of "fear" in SHR rats as well as to increased excitatory and decreased inhibitory processes in these animals. Behavioural characteristics of SHR rats reflect an increased reactivity of their nervous system which may be connected with the mechanisms of the increase of arterial pressure.     

Characteristics of memory and the functional organization of the hippocampo-reticulo-neocortical complex of the brain in the acute postoperative period

In tests on dogs, rabbits and rats, it has been established that in acute postoperative period, the time of memorizing of conditioned signals (light, tone and metronome) is reduced, the time of realization of conditioned reactions increases, the excitability and the bloodflow of the midbrain reticular formation and Mg-AtPhase activity of pons Varolii raise. In the hippocampus the excitability and local bloodflow lower and the activity of Ca-Mg-ATPhase is enhanced. In the frontal cortex these processes do not change. Functional interrelations of the brain structures in the acute postoperative period are characterized by the weakening of the activating influence of the reticular formation on the frontal cortex and an increase of its suppressive action on the dorsal hippocampus. It is suggested, that the discovered damages in the higher nervous activity are stipulated by the changes in neurochemical organization of the brain.     

Characteristics of heterochromatin of heterophase nuclei from interphase neurons of various brain structures selected for the nervous system excitability

Quantitative characteristics (the area and number of chromocenters) of the interphase C-heterochromatin in the nuclei of pyramidal neurons of the midbrain reticular formation, sensorimotor cortex, and hippocampus (CA3) of rat strains with different genetically determined excitability were studied in the normal state of the animals and after exposure to a short-term emotional pain stress. The results indicate a relationship between the excitability of the nervous system and structural-functional state of the neuronal interphase heterochromatin. The role of cytogenetic features of different brain structures in the CNS functioning and behavior and their relation with genetically determined excitability of the nervous system are discussed.     

Heart rate variability in domestic chicken lines genetically selected on feather pecking behavior

Domestic chicken lines of the White Leghorn type differing in their level of feather pecking were developed by divergent genetic selection specifically on feather pecking behavior. We determined parameters of heart rate variability to elucidate the relative activation of the sympathetic and parasympathetic nervous systems during rest and stressful situations. A total of 48 hens were tested in 8 batches. Segments of 2 min were extracted from electrocardiograms recorded by radio-transmitter implants, before (basal undisturbed conditions) and during physical restraint and a social test. Under basal conditions mean distance between R-waves were shorter in the low and high lines compared to the control. During physical restraint, stress reactions [reduced root of the mean squares of successive differences (RMSSD), reduced high frequency (HF), high low frequency (LF/HF) and low vagal-sympathetic effect (VSE) compared to basal levels] were significant in all lines. During the physical restraint the high feather pecking (HFP) line reacted significantly stronger than control (CON) and low feather pecking (LFP) line. During social test the LFP line reacted different than the other two lines. Seemingly birds from LFP conceived the social test as less stressful than birds from the CON and HFP lines. From this it follows that (1) physical restraint generally induced higher stress reactions than the social test and (2) genetic selection for higher levels of feather pecking increased the autonomic nervous system reaction to physical restraint whereas selection against feather pecking has reduced the response to increased social contact.     

Stability of the cardiovascular functions of different genetic strains of rats subjected to emotional stress

The level of catecholamines was measured in various brain parts in rats of August and Wistar lines, characterized by different stability of cardio-vascular functions in emotional stress. In norm, the August line has a higher content of dopamine (DA), in the mid-brain in particular; the Wistar line has a higher content of noradrenaline (NA) in the hypothalamus. In susceptible animals, which showed different cardio-vascular disorders during 30 hours of immobilization (48% of the Wistar line and 90% of the August), and in animals resistent against emotional stress, the changes in the initial level of catecholamines were observed, both common and specific for two lines. An assumption is made that the stability of cardio-vascular functions in the emotional stress is provided for by an intensive metabolism of the NA-synthesizing neurones in the brain isthmus, and by a moderate activity of the DA-synthesizing neurones of the mid-brain; the susceptibility to cardio-vascular disorders in the emotional stress is due to increase in the activity of the DA-synthesizing mid-brain neurones, the decrease in the activity of the DA-hydroxilase and the exhaustion of NA in the hypothalamus.     

Sodium oxybutyrate and piracetam acceleration of the compensatory-reparative processes after damage to the cerebral cortex in rats

The effects of sodium hydroxybutyrate and piracetam on compensatory-reparative processes in the central nervous system have been investigated in rats after extirpation of the frontal cortex. The animals were pretrained to conditioned reflex of active avoidance. Extirpation of the frontal cortex has been shown to disturb the conditioned reflex. Sodium hydroxybutyrate (50 mg/kg) and piracetam (200 mg/kg) were found to precipitate the recovery of the damaged reflexes.