Early adolescent stress alters behavior and the HPA axis response in male and female adult rats: the relevance of the nature and duration of the stressor.

Adolescence is a period of transition from childhood to adulthood that involves the maturation of social and cognitive behavior. The activation of the stress system during this phase can lead to long-lasting adverse effects. We aimed to verify whether the nature and duration of stressors applied in adolescent female and male rats would alter their exploratory behavior and stress responses as adults. Wistar rats on day P26 were divided into groups that were subjected to 1 (acute) or 7 (chronic) insulin or lipopolysaccharide (LPS) injections or restraint stress for 1 h. At P60, the rats were subjected to the elevated plus-maze, and at P61, they were subjected to 30 min of restraint stress after which plasma samples and brains were collected. LPS acute injection promoted anxiolytic effects in male adults. Acute LPS treatment and acute or chronic restraint induced anxiolytic behavior in female adults. The administration of adolescent chronic stimuli to males decreased the adult plasma corticosterone (CORT) and progesterone levels after restraint. Adolescent acute restraint or LPS injection decreased the CORT response in female adults. The adult neuronal activation of the corticotrophin-releasing hormone and vasopressin on the paraventricular nucleus did not vary according to the type of adolescent stress or sex. Our results indicate that both adult behavior and the glucocorticoid stress response are affected differently in males versus females by adolescent stress. The duration of stressors had a greater effect on the CORT and progesterone response in males, whereas the nature of the stressor had a greater effect on exploratory behavior in females.