Neonatal Hypoxia Induces Behavioral Deficit Associated with Impaired Glucocorticoid and Serotoninergic Systems in Adult Rats

We investigated plasma concentrations of adrenocorticotropichormone (ACTH), corticosterone and serotonin in juvenile and adultrats, as well as raphe serotonin levels and behavioral responsesin the open field and elevated plus maze tests in adult rats, exposedto three sessions of neonatal hypobaric hypoxia (360 mm Hg, 2 heach, once a day) within days 8–10 postpartum. This noninvasiverat model of neonatal hypoxia (NH) simulates mild perinatal hypoxicinjury in human fetuses and premature infants. At 3 months of age,NH-exposed rats exhibited reduced exploratory behavior and increasedanxiety in both behavioral tests, accompanied by decreased serotoninlevels in the raphe nuclei. In adult NH-exposed rats, plasma corticosteroneand serotonin levels remained unaltered, while ACTH levels showed asignificant decrease. Our findings suggest that early postnatalhypoxic stress disrupts the serotoninergic system and modifies thehypothalamic–pituitary–adrenocortical axis, leading to long-lastingbehavioral deficits in adult rats.