Exposure to chronic stress downregulates corticosterone responses to acute stressors.

Abstract in brief

• Chronic stress in European starlings lowers both baseline and stress-induced corticosterone levels, meaning their overall hormonal stress response is reduced.
• The study shows that this reduction is linked to changes in how the hypothalamic-pituitary-adrenal (HPA) axis responds to stimuli like ACTH and AVT, with ACTH and AVT playing roles in regulating corticosterone during chronic stress.
• The researchers suggest that under normal conditions, ACTH from the pituitary controls maximum corticosterone levels, while during chronic stress, decreased AVT release helps keep corticosterone levels lower.]