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 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.

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.

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.

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.

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".

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.

Proliferative activity and characteristics of the structural-functional organization of the chromosomes in cells of the developing brain, related to the genetically determined excitability of the nervous system in rats

This report describes the results of a comparative genetic analysis of the proliferation activity, level of chromosomal aberrations, and the state of interphase chromatin in nerve cells from the developing brains of rat embryos from lines with nervous systems of different excitation thresholds. A relationship between the basal level of nervous system excitability and these cytogenetic characteristics was found. Higher values were seen in embryos of the high-threshold line VP1, as compared with the low-threshold line NP1. The role of the cytogenetic characteristics of the embryo brain in the processes of CNS development and function are discussed in relation to the genetically determined level of nervous system excitability.

Effect of prenatal stress on proliferative activity and chromosome aberrations in embryo brain in rats with different excitability of the nervous system

Stress during pregnancy affects the morphogenesis of embryonal brain, its structural and functional characteristics, and behavior of the progeny. Genetic mechanisms of this process remain unclear. Cytogenetic characteristics of neuroblasts were analyzed in 17-18-day embryos of rats selected by threshold excitability of the nervous system in health and after emotional painful stress during the third trimester of pregnancy. The strains differed by the effect of stress on proliferative activity and chromosome aberrations in cells of the future hippocampus depending on the strain-specific characteristics of the nervous system excitability. This effect is regarded as an important component of epigenetic regulation of neurogenesis and behavior.