Effect of hypoxia in early perinatal ontogenesis on behavior and structural characteristics of the rat brain.

The study has shown that acute hypoxia in newborn rat pups can lead to disturbances in processes of formation of brain structures, behavior reactions, and learning in the subsequent ontogenesis. The single normobaric hypoxia at the 2nd day of life causes retardation of such integrative parameter or general development and growth as body mass at the period of feeding. In such animals, essential disturbances of the sensorimotor development were revealed in forms of delay of reflex reactions of turning on a plane, negative geotaxis, and avoidance of edge. Also detected was action of hypoxia on hanging on a rope by using front legs (a symptom of muscle weakness). Morphological study has shown all studied functional zones of neocortex (motor, sensomotor, auditory, visual) to response stereotypically to the early postnatal action of hypoxia. The death of nerve cells is predominant in the II-III associative layers, the sizes and number of pyramidal neurons are sharply decreased. Different hippocampus fields maturing after death in mammals show a characteristic response to hypoxia. In individual hippocampus fields there was detected a different degree of death of neurons, with predominance in the CA3 and CA4 fields. A possibility of modeling the perinatal encephalopathy with minimal brain dysfunctions in children is discussed. [ABSTRACT FROM AUTHOR]