Effects of psychogenic stress on some peripheral and central inflammatory markers in rats with the different level of excitability of the nervous system.

Patients with post-stress pathologies display the signs of inflammation in the peripheral blood as well as in the brain. The mechanisms of such post-stress neuroimmune changes, their contribution to the behavior, the relationship of the intensity of inflammation with genetically determined features have not been clarified. The goal of this work was to evaluate the dynamics of post-stress inflammation in the blood and hippocampus of rats which differ in level of excitability of the nervous system. Rats of two strains (high/low excitability threshold) were subjected to stress according to the K. Hecht protocol and their behavior, neutrophil:lymphocyte ratio and the number of Iba+ cells in the hippocampus were analysed 24 hours, 7 and 24 days after stress exposure. Highly excitable animals show an increase in anxiety-like behavior, in the number of neutrophils compared to lymphocytes as well as in the number of Iba1+ cells in CA1, CA3 and DG areas of the hippocampus in response to stress. Thus, hereditary high excitability of the nervous system is a possible risk factor for the development of post-stress pathologies.

[Epigenetic mechanisms in post-stress states].

There is a continued interest in the research of epigenetic mechanisms of genes regulation in the brain, associated with the stress-induced adaptive and pathological consequences during the formation of post-stress states, in particular post-traumatic stress disorder (PTSD). Brief overview of epigenetic modifications was presented, while the process of DNA methylation was discussed comprehensively. Key stress-induced epigenetic changes in the human and animal brain in response to stress were summarized. Epigenetic modifications in certain genes (genes of stress responses, hormones and neurotransmitters genes, NGF gene) while post-stress states and PTSD formation were discussed in detail.

[Metabotropic receptor of the group I of the 5th subtype (ImGLuR5) in honeybee associative olfactory learning].

The work deals with study of character of localization in the honeybee head ganglion of metabotropic receptor ImGluR5 and its role in memory formation. With aid of pharmacological method (injections of antisense oligonucleotide and of selective receptor agonist and antagonist) and of behavioral criterion (formation and testing of preservation in memory of conditioned alimentary reflex for olfactory stimulus), there is first shown participation of the studied receptor in formation of the honeybee long-term memory. By using the immunohistochemical method, there is first revealed the predominant expression of the ImGluR5 receptor in the mushroom body Canyon cells responsible for the insect integrative activity. The present study, together with the previous ones, allows concluding about the presence in the honeybee head ganglion of the group I of metabotropic glutamate receptors with two subtypes 1 and 5 (ImGluR1,5) that have similar with mammalian pharmacological properties favoring preservation of the individually acquired experience in the long-term memory.

Effect of long-term stress on H3Ser10 histone phosphorylation in neuronal nuclei of the sensorimotor cortex and midbrain reticular formation in rats with different nervous system excitability.

The effects of long-term mental and pain stress on H3Ser10 histone phosphorylation in neurons of the the sensorimotor corex and midbrain reticular formation were studied 24 h, 2 weeks, and 2 months after exposure of rats differing by the nervous system excitability. Rats with high excitability threshold exhibited higher basal level of H3Ser10 histone phosphorylation in the midbrain reticular formation neurons than rats with low excitability threshold. The sensorimotor cortical neurons of the two strains did not differ by this parameter. Stress led to a significant increase in the counts of immunopositive neuronal nuclei in rats with low excitability threshold: the parameter increased significantly in the sensorimotor cortex 24 h after exposure and normalized in 2 weeks after neurotization. In the midbrain reticular formation of this rat strain stress stimulated H3Ser10 histone phosphorylation after 24 h and after 2 weeks; the parameter normalized after neurotization in 2 months. Hence, genetically determined level of the nervous system excitability was essential for the basal level of neuron phosphorylation and for the time course of this process after long-term exposure to mental and pain stress, depending on the brain structure. A probable relationship between H3Ser10 histone phosphorylation process and liability to obsessive compulsive mental disorders in humans was discussed.

[On epigenetic regulation of process of formation of long-term memory].

The review summarizes current concepts on role of several covalent posttranslation chromatin modifications in the process of memory formation in vertebrate and invertebrate animals. There is described a chain of intracellular events from activation of receptors and signal pathways to change of the functional state of genome.

[Effect of activity of NMDA-receptors on process of methylation of histone H3 and on its asymmetry in hippocampal pyramidal neurons of rats with different threshold of excitability of the nervous system 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-painful 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 state of channels of NMDA-receptors. On the background of active receptors the proportion of immunopositive cells predominantly increased. In the CA1 field those changes were not connected to excitability and lateralization, whereas in the CA3 field it had a complex character and depended on those 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 to lateralization, while its direction in different hippocampal fields was different. Action of the short-time emotional-painful stress did not lead to a change of shape of interhemisphere asymmetry 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.

Effect of chronic emotional and pain stress on histone H3 phosphorylation in the hippocampus of rat strains with different excitability of the nervous system.

Long-term effects of chronic emotional and pain stress on histone H3 phosphorylation by serine 10 in hippocampal CA3 neurons were examined 24 h, 2 weeks, and 2 months after termination of the stress procedure in 2 rat strains differing by excitability of the nervous system. The low excitable rats with high threshold (HT) of excitability were characterized by a high baseline level of histone H3 phosphorylation in comparison with the high excitable rats with low threshold (LT) of excitability. The long-term emotional and pain stress significantly changed the number of positive immune cells in highly excitable rats: this parameter increased in 24 h and 2 weeks after the stress, but returned to the control level in 2 months. In contrast, stress did not affect histone H3 phosphorylation in low excitable rats. Thus, long-term (up to 2 weeks) changes in histone H3 phosphorylation were reveled in rat hippocampal CA3 neurons, which depended on genetically determined functional status of the nervous system.

Long-term effects of prenatal stress on the characteristics of hippocampal neurons in rats with different excitability of the nervous systems.

We studied the effects of prenatal emotional painful stress on numerical density of neurons and characteristics of heterochromatin in developing and mature hippocampus of rats with different excitability of the nervous systems. It was shown that prenatal stress reduces the numerical density of neurons in hippocampal CA3 field in 24-day-old and adult (3 months) low excitable animals and chromocenter area in cells of developing hippocampus in embryos of both strains. The difference in chromocenter areas in offspring of stressed females was retained on postnatal day 24.

[Kainate receptors in the hippocampus of rat strains with different levels of the nervous system excitability].

Glutamate receptors in the central nervous system play a significant role in the mechanisms of differential adaptation to the environmental conditions. However, structural and functional parameters of kainate receptors (KR) under normal conditions and during exposure to stress are not well characterized. Therefore, the aim of this research was to 1) study the distribution and the quantity of KR GluR 5/6/7 subunits; 2) examine their changes in the pyramidal cell layer of the hippocampus in rat strains with have genetically determined distinctions in the levels of nervous system excitability following the exposure to short-term emotional-painful stress; 3) estimate the sensitivity of hippocampal pyramidal neurons to the action of KR agonist -kainic acid. It was demonstrated that GluR 5/6/7 KR are localized mainly in the region of hippocampal CA2 area; in the animals with low excitability their quantity was greater than in those with high excitability. Short-term emotional-painful stress resulted in the increase of KR in hippocampal CA2 area only in highly excitable rats. Selective sensitivity of pyramidal neurons in different hippocampal fields to the action of kainic acid was demonstrated and it was found to depend on animal strain characteristics of of the nervous system excitability.

Neuron density in the hippocampus in rat strains with contrasting nervous system excitability after prolonged emotional-pain stress.

A model system consisting of two rat strains bred for nervous system excitability in response to electric shocks was used to study changes in the number density of neurons in hippocampal field CA3 at 24 h, two weeks, and two and six months after prolonged emotional-pain stress (PEPS). Neuron density in hippocampal field CA3 decreased after completion of PEPS. These changes arose at different time points in the different rat strains (one day for low-excitability rats, two months for high-excitability rats) and persisted to six months. Thus, this is the first demonstration that persistent differential effects of stress on the number density of neurons in hippocampal field CA3, which plays an important role in learning and memory processes, depend on genetically determined constitutive characteristics of the nervous system.

Comparative analysis of the locations of the NR1 and NR2 NMDA receptor subunits in honeybee (Apis mellifera) and fruit fly (Drosophila melanogaster, Canton-S wild-type) cerebral ganglia.

The locations of the NR1 and NR2 subunits of the GABA receptor were studied in brain structures in insects--honeybees and fruit flies--using an immunohistochemical method. The specificities of the antibodies to the NR1 and NR2 subunits were confirmed by the antisense knockdown method for the NR1 subunit and western blotting. The data obtained here lead to the conclusion that the distributions of the NR1 and NR2 subunits of the NMDA receptor complex in the cerebral ganglia of the honeybee and fruit fly are similar; areas with the highest concentrations of NR1 and NR2 subunits were identified, and these were found to be different in the different insects. This is associated with the behavioral characteristics of these two insect species.

[Heterochromatin characteristics in hippocampal neurons of rats with different excitability of the nervous system under conditions of posttraumatic stress disorder modeling].

Two lines of rats, selected according to the excitability of nervous system to the action of an electric current, served as the model objects to study the changes of heterochromatin characteristics in neurons of hippocampus (area CA3) 24 hours, 2 weeks, 2 and 6 months after exposure to prolonged emotional painful stress. It was shown that exposure to stress caused changes in the area, occupied by heterochromatin, only in rats with low-excitability: it was decreased 24 hours, 2 weeks and 2 months following the stress, while it was increased after 6 months as compared to control values. Thus, it was demonstrated for the first time that long-term modifications of heterochromatin structural characteristics of neurons in hippocampus (area CA3) could depend on genetically determined functional state of the nervous system.

[Numerical density of neurons in the hippocampus of rat lines contrasting in excitability of the nervous system exposed to prolonged emotional painful stress].

Two lines of rats, selected according to the excitability of nervous system to the action of an electric current, served as the model objects to study the changes of numerical density of neurons in hippocampus area CA3 24 hours, 2 weeks, 2 and 6 months after prolonged exposure to emotional painful stress. Reduction of neuron density in hippocampus area CA3 was demonstrated after exposure to stress that persisted as long as 6 months. These changes developed following time intervals that were different for each line of rats (24 hours for rats with low excitability and 2 month--for rats with high excitability). Thus, it was demonstrated for the first time, that prolonged differential effect of stress on numerical density of neurons in hippocampus area CA3, that plays an important role in the processes of learning and memory, depends on genetically determined constitutional peculiarities of the nervous system.

[Comparative analisys of localization NR1 and NR2 subunits of NMDA-receptor in the brain structures in honeybee (Apis mellifera L.) and Drosophila (Drosophila melanogaster, wild type canton-S)].

Localization NR1 and NR2 subunits of NMDA-receptor was studied in brain structures of the honeybee and Drosophila by immunohistochemistry. The Western-blotting and NR1 subunit antisense-knockdown confirmed specificity of antibodies to NR1 and NR2 subunits. The data obtained demonstrated similar distribution of NR1 and NR2 subunits of NMDA-receptor in the insect brain (cranial ganglion). The brain regions with the highest expression NR1 and NR2 were different in the honeybee and Drosophila. This can be associated with behavioral repertoire peculiarities in these insects.

Effect of prolonged emotional and pain stress on the content of methylcytosine-binding protein MeCP2 in nuclei of hippocampal neurons in rats with different excitability of the nervous system.

In rats with low excitability threshold of the nervous system demonstrating significant and persistent behavioral disorders under stress conditions, the content of methylcytosine-binding protein MeCP2 in neuronal nuclei of hippocampal field CA3 decreased over 2 weeks after long-term emotional and pain stress. It was hypothesized that protein MeCP2 triggers epigenetic changes in DNA that underlie "stress memory".

Effect of long-term mental and pain stress on the dynamics of H4 histone acetylation in hippocampal neurons of rats with different levels of nervous system excitability.

Priority data on specific effect of long-term mental and pain stress on the dynamics of H4 histone acetylation in the pyramidal neuron nuclei of the hippocampal CA3 field in rats selected by the nervous system excitability were obtained using a comparative genetic method. The congruency of long-term post-stress modification of H4 histone acetylation in neurons of rats with high threshold excitability and behavioral changes intrinsic of these rats suggest that increased acetylation of H4 histone together with changes in heterochromatin conformation play a triggering role in long-term modifications of genome expression underlying the pathogenesis of posttraumatic stress disorders and other psychogenias.

Vagal stimulation modifies parameters of heterochromatin in the nuclei of vagosolitary complex neurons of medulla oblongata in rats.

New data were obtained on modification of heterochromatin parameters in the nuclei of medulla oblongata neurons in Wistar rats after stimulation of the vagus nerve: decrease in the area of heterochromatin regions and redistribution of chromocenters within the neuronal nuclear system. It was concluded that realization of the viscero-visceral reflex is associated with rearrangement of chromatin in neurons involved in transmission of the corresponding information.

Characteristics of interphase chromatin in hippocampal neurons in rats with different excitability of the nervous system exposed to stress at different time of the day.

The structural (number and area of chromocenters) and optical (relative optical density of chromocenters) characteristics of condensed chromatin in hippocampal CA3 neurons in rats differing by excitability of the nervous system (intact and exposed to short-term emotional painful stress) depended on the time of the day and genotypical characteristics of the experimental animals. The detected changes were independent, which attests to specificity of mechanisms determining these features and/or can be attributed to structural and functional heterogeneity of condensed chromatin (heterochromatin, euchromatin, etc.).

Differences in protein peroxidation in pregnant rats selected by nervous system excitability threshold.

Differences in the intensity of serum protein peroxidation were detected in pregnant rats with high and low peripheral nervous system excitability threshold in stress. Stress induced shifts in serum protein peroxidation, but these changes were opposite in rats of the two studied strains.