Stress-restress: effects on ACTH and fast feedback

Area of Science:

• Neuroscience
• Endocrinology
• Psychiatry

Background:

• Glucocorticoid secretion is regulated by negative feedback, which is altered in depression and post-traumatic stress disorder (PTSD).
• Depression is associated with hyposensitive glucocorticoid feedback, while PTSD exhibits hypersensitive or enhanced negative feedback.
• The stress-restress or time-dependent sensitization (TDS) model is proposed as an animal model for PTSD, potentially reflecting enhanced negative feedback.

Purpose of the Study:

• To investigate the effects of the stress-restress model on the hypothalamic-pituitary-adrenal (HPA) axis.
• To determine if this model induces increased sensitivity to negative feedback, mirroring findings in PTSD patients.

Main Methods:

• Adult male Sprague-Dawley rats were subjected to a single prolonged stress session followed by a brief restress 7 days later.
• Plasma ACTH and corticosterone levels were measured at 0, 5, and 30 minutes post-restress.
• Glucocorticoid fast feedback was assessed by comparing cortisol versus saline pretreatment effects.

Main Results:

• Animals exposed to single prolonged stress exhibited enhanced negative feedback compared to naive controls (p = .0107).
• No significant differences in ACTH or corticosterone responses were observed during the restress period.
• Cortisol pretreatment during the initial stress session did not prevent the development of enhanced fast feedback upon restressing.

Conclusions:

• The stress-restress paradigm leads to a sensitization of the inhibitory elements of the HPA axis.
• This model may effectively replicate the HPA axis abnormalities observed in patients with PTSD.
• The findings support the use of the stress-restress model for studying PTSD-related HPA axis dysregulation.