Effects of stress of postnatal development on corticosterone, serotonin and behavioral changes

Stressful events early in life are associated with later psychiatric disorders. We focused on developmental stage and evaluated changes in the corticosterone and serotonergic systems as well as in later anxiety-related behavioral tests. Stressed male Wistar rats were divided into two groups: stressed from postnatal day 11 (PND 11) to 15 and stressed from PND 16 to 20. The rats were exposed to an elevated open platform. Stress increased corticosterone in both experimental groups. In the hypothalamus, amygdala and hippocampus, 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) increased in the rats stressed from PND 11 to 15, and decreased in the rats stressed from PND 16 to 20. In a later behavioral test, rats stressed from PND 11 to 15 traveled shorter distances and tended to spend less time in the center than control rats following restraint stress. There were no significant changes in 5-HT and 5-HIAA in hypothalamus, amygdala and hippocampus after restraint stress in adults. These findings indicate that stress reactions and later effects are different depending on the developmental stage during which the rats were stressed. Stress during the PND 11–15 period may enhance later anxiety-related behaviors without altering 5-HT and 5-HIAA content.