Long-term behavioral consequences of brief, repeated neonatal isolation

Area of Science:

• Neuroscience
• Endocrinology
• Behavioral Science

Background:

• Early-life stress can cause long-term neuroendocrine and behavioral changes.
• The stress hyporesponsive period (SHRP) is a critical window for stress exposure effects.

Purpose of the Study:

• To investigate the effects of neonatal isolation stress on adult anxiety-related behavior and endocrine stress reactivity in rats.
• To determine if early-life stress during the SHRP alters hypothalamic-pituitary-adrenal (HPA) axis function.

Main Methods:

• Rats were isolated daily for 1 hour from postnatal day 4 to 9.
• Adult rats were assessed for anxiety-related behaviors using the elevated plus maze and open field tests.
• Endocrine stress reactivity was measured by assessing ACTH and corticosterone levels following restraint stress.

Main Results:

• Neonatal isolation significantly decreased exploration in the center of the open field and reduced entries into the open arms of the elevated plus maze, indicating enhanced anxiety-related behaviors.
• Neonatal isolation did not affect basal or restraint-induced levels of ACTH or corticosterone.
• Early-life stress enhanced anxiety-related behaviors without altering HPA axis function.

Conclusions:

• Neonatal isolation stress during the SHRP can lead to increased anxiety-like behaviors in adult rats.
• The observed behavioral changes occur independently of alterations in the HPA axis's endocrine response to stress.