Chemosignaling is widespread among animals as tool for regulation of synecological interactions. Evolutional conservatism of such signaling allows us to suggest that same chemosignals play an important role in different animal species including human beings. Aversion/attraction of mouse pheromone 2,5- dimethylpyrazine (2,5-DMP) and 2,3-dimethylpyrazine (2,3-DMP) for CBA and C57BL/6 mice was studied in T-maze. It is shown that intact males and females of both strains under choice condition prefer 2,3-DMP to water and 2,5-DMP. They also prefer water to 2,5-DMP Stress after swimming modifies behavior in T-maze: all preferences disappear in C57BL/6 males and remain without changes in CBA males. Importance of behavioral changes obtained here under stress condition is discussed. Detailed studies of the preference modulation with recently shown other effects of 2,5-DMP could connect specific sensitivity to chemosignals with the pheromone, stress and genotype.

We studied changes in the stability of the genome in cells of two brain regions (prefrontal cortex and hippocampus), as well as in the bone marrow of rats with a hereditary high and low thresholds of excitability of the nervous system (strains HT and LT, respectively) after prolonged exposure with emotional-pain stressor. To study the reactivity of the brain cells genome, phosphorylated histone -H2AX (-H2AX phospho Ser139) was used. The level of mitotic disturbances in bone marrow cells was also assessed. Between the animals of the control groups, there were no interstrain differences in the studied parameters. Stress exposure increases the immunoreactivity to -H2AX phospho Ser139 of the prefrontal cortex cells and the level of chromosomal aberrations in bone marrow cells in animals of both strains. In cells of the dentate gyrus of the hippocampus, a specific increase in immunoreactivity to -H2AX phospho Ser139 was revealed in rats of the low-excitable HT strain. The relationship between the reaction of cells of this zone of hippocampus to the stressor exposure with the hereditary level of excitability of the nervous system of animals is discussed.

Current data on the effects of stress at the level of the cell genomes of the central nervous system and peripheral organs in animals are discussed. Regulatory and structural genomic changes in the cells of the central nervous system under stress are considered as a mechanism for regulating the functions of the brain and peripheral organs that form the organism manifestations of stress. Based on the Yu.Ya. Kerkis and M.E. Lobashev point of view, we consider stress as a special physiological state of the nervous system, affecting the work and integrity of the genome in target cells in animals, and thus playing a major role in microevolutionary transformations.

Too broad understanding of the term stress, which Selye himself and his followers used in their popular science works, reduces its scientific value. Based on a brief analysis of examples of the ambiguity of the term stress, it is proposed to restore its research significance. For that, the concept of stress should be used more strictly and unequivocally and it would not be allowed to use a commonly broad understanding the term in scientific papers. In the frame of earlier Selyes stress definition, it suggests a more detailed structuring of the term based on levels of studying of living objects, including genetic.