P. Butkevich - Dr. Sc. (Biol.), Leading Research Scientist, I.P. Pavlov Institute of Physiology, RAS, St.-Petersburg; Associate Professor, Saint Petersburg State Pediatric Medical University. E-mail: irinabutkevich@yandex.ru
V. A. Mikhailenko - Ph.D. (Biol.), Senior Research Scientist, I.P. Pavlov Institute of Physiology, RAS, St.-Petersburg. E-mail: viktormikhailenko@yandex.ru
T. N. Shimaraeva - Ph.D. (Biol.), Associate Professor, Saint Petersburg State Pediatric Medical University. E-mail: 3706381@mail.ru

Early life adversities modify the central nervous system development that induces later impairments in somatosensory, nociceptive systems and mental abnormalities [1]. The study of mechanisms of formation of pathological and adaptive alterations in the central nervous system following adverse impairments contribute to diagnostics, treatment and prevention of a number of psychoemotional pathologies. In basic investigations the maternal separation (maternal deprivation) model is used in these purposes. Available data in literature are obtained in animals exposed to long-term, days-long maternal separation. The phenotypic and epigenetic mechanisms of this phenomenon are under intensive study [2]. Newborns particularly premature babies are exposed to medical treatments and general care with stress and pain impairments and to maternal separation also. Therefore, this factor can effect pain behavior in the following ontogeny. The aim of the study was to investigate effects of short-term (60 min) repeated (the first and the second days of rat pups life) maternal separation on the time of immobility, which is the index of depression, in the test of forced swimming (Porsolt test) in rats reached the age of adolescent period (25 days). One-day-old Wister rat pups, females and males, born to six dams were separated from the dams and placed singly in a thermostat (27 °С) at 60 min. Next day the manipulation was repeated. Control animals were stayed with the dams. Experimental animals were marked and returned to the dams. At the age of 25 days of life each rat was placed singly in a standard cylinder with the warm water (27 °С) to register the time of immobility, of active swimming and of movement up to the wall. Sexual dimorphism was revealed in intact rats: the time of immobility was more in males (p = 0.04), the time of moving up to the wall was more in females (р = 0.03). Experimental rats displayed an increase in the time of immobility in both males (р < 0.01) and females (р < 0.001), a decrease in swimming in males and females (р < 0.001) and an increase in moving up to the wall in males (р < 0.001) as compared with appropriate controls. Sex differences were cancelled in experimental rats. Thus, the data obtained indicate that it is necessary to take into account the factor of short-term maternal separation in newborns in studies of early pain impairment effects on psychoemotional behavior and indices of inflammatory pain in the following ontogeny. The study was supported by RFBR project N 14-04-00106a.