[Damaging impacts at the critical time periods of prenatal ontogenesis as a factor modifying the cerebral structural development and postnatal behavior reactions].

Results of a study of the nature of changes in the rat neocortex, which were observed during an early postnatal period (postnatal days 1 to 10) and which were induced by a single prenatal hypoxia on the 16th or 19th embrionic day (E16, E19), are presented in the paper. Acute hypoxia, administered on E16, was shown to result in an underdevelopment of cortical layers as well in damage to cell orientation and differentiation, i.e. it disturbed the histogenic processes (proliferation, migration and differentiation), which are most active at this time period. An immunohistochemical examination of the brain made during the postnatal period after an intrauterine hypoxia suggests that damage to proliferation and differentiation occurred in glial cells. Hypoxia administered on E19, when the level of proliferation in the brain was lower, had a less pronounced damaging effect. Deviations in the neocortical structure and in the animal's behavior found during the postnatal period could be caused by the heterochromic and heteromorphous development of brain regions in the fetus.