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Neonatal anoxia induces long‐term brain injury that may underlie neurobehavioral deficits at adolescence. Neonatal anoxia, induced by exposure of 30‐hour old pups to 100% nitrogen, represents a non‐invasive and global stimulus, which simulates clinical conditions of human pre‐term babies (around 6 gestational months). Previous studies showed that neonatal anoxia induced impairments of spatial memory and altered anxiety‐like behaviors in male rats tested at adult age. This study evaluated if neonatal anoxia induces similar behavioral effects in female rats, as compared to males, by testing the animals at adolescence, and also searched for possible cell losses in hippocampal subfields. Results in the Elevated Plus Maze test showed that anoxic females spent proportionally more time within the open arms as compared to anoxic males, suggesting a less anxious‐like behavior. In the Morris Water Maze Test, latencies and path lengths of the anoxic subjects were longer as compared to control subjects, thus indicating that anoxia disrupted the cognitive functions required for spatial mapping. In addition, results showed that anoxia‐induced disruption was greater in male rats as compared to female rats. Stereological analysis revealed that anoxic male rats exhibited significant cell losses in the dorsal hippocampus dentate gyrus and CA1 subfields, but not in CA3‐2 subfield. Similar results were observed in the ventral hippocampus, but now with cell loss in the male CA3‐2 subfield. There were also significant cell loss differences of anoxic male rats as compared to anoxic female rats. In conclusion, neonatal anoxia induces deleterious and long lasting behavioral and cognitive disruptions, and these effects were stronger in male rats as compared to female rats. These changes are congruent with the pattern of cell losses observed in hippocampal subfields. Together, these results emphasize the relevance of scientific research, aiming at clinical strategies and treatments, consider the sex differential patterns of response to neonatal injury.

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Neonatal hypoxic‐ischemic encephalopathy (HIE) is one of the most important reasons for morbidity and mortality in term‐born infants. HIE impacts early somatic, neurological, and motor development including social. To illustrate the damages in the sensorimotor system, an adapted and validated model of neonatal anoxia is used. This study evaluated the sex differences in Wistar rats, neurological reflex, and motor development at the suckling period. Short‐ and long‐term impairments associated with sex differences were observed. In general, anoxic males were more affected in comparison to their control group and to anoxic females. Long‐lasting effects of the injury in adolescent rats predominately affected males. Similar to previous studies, we also found a decrease in the number of the substantia nigra cells in both sexes, compared to their control. So far, the results indicate that HIE caused neurobehavioral alterations and asymmetrical motor behavior with brain damage, possibly related to cognitive impairments previously observed at adolescence. These alterations may represent a useful endpoint for studying the efficacy of potential strategies that may improve the developmental consequences of a perinatal asphyxia insult in humans.

Difícil reduzir meus agradecimentos a apenas uma folha, pois todos que fizeram parte da minha vida, nesse período, contribuíram de alguma forma para o resultado final. Sinto-me honrada de ter sido aluna da Prof.ª Dra. Maria Inês Nogueira a qual agradeço pela oportunidade de trabalho, paciência e dedicação constantes. Agradeço também à Dr.ª Sílvia Honda Takada, por sempre se dispor a me ensinar e auxiliar quando necessário dispondo de seu valioso tempo e conhecimentos e pela amizade. Agradeço, também, à Aline Vilar Machado pela indispensável e significativa contribuição nos experimentos de comportamento animal. Agradeço à Lívia Clemente Teixeira, pela atenção carinhosa em vários momentos e pela companhia.

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