Are the consequences of neonatal hypoxia–ischemia dependent on animals' sex and brain lateralization?

Hypoxia–ischemia on 3-day-old rats (HIP3) allows the investigation of HI damage in the immature brain. HIP3 is characterized for neurological disabilities caused by white matter injury. This study investigates the relationship between animals' sex and injured hemisphere on HIP3 consequences. Male and female Wistar rats had their right or left common carotid artery occluded under halotane anesthesia and exposed to 8% O2 for 1.5 h. Control rats received sham surgery and exposure to 1.5 h of room air in isolation of their mothers. Sex and injured hemisphere influence in Na+/K+-ATPase activity 24 h after lesion: females and the right brain hemispheres showed decreased enzymatic activity after HIP3. Cognitive impairment was observed in step-down inhibitory avoidance, in which females HIP3 left injured were the most damaged. Histological analysis showed a trend to white matter damage in females left injured without hemispherical nor hippocampal volume decrease in HIP3 rats at postnatal day 21. However, at PND90, hemisphere and sex effects were noted in hemispherical volume and myelination: left brain hemisphere and the females evidenced higher histological damage. Our results points to an increased resistance of male rats and right brain hemisphere to support the impairment caused in Na+/K+-ATPase activity early after HIP3, and evidencing more discrete behavioral impairments and histological damage at adulthood. Present data adds new evidence of distinct effects of brain lateralization and sex vulnerability on biochemical, behavioral and histological parameters after hypoxia–ischemia.

► Hypoxia–ischemia (HI) is a major cause of neurological damage.
► Performed in rat postnatal day 3 (HIP3) mimics HI occurred in preterm infants.
► Outcomes were influenced by animals' sex and by hemisphere injured.
► The left hemisphere and the female sex were more vulnerable to HIP3.