Corticotropin responsiveness in the neonatal rat

Area of Science:

• Endocrinology
• Neuroscience
• Developmental Biology

Background:

• The hypothalamic-pituitary-adrenal (HPA) axis regulates the stress response.
• Understanding the developmental maturation of the HPA axis is crucial for neonatal health.

Purpose of the Study:

• To investigate the age-related maturation of the HPA axis in neonatal rats.
• To determine the responsiveness of the pituitary gland to corticotropin-releasing factor (CRF) and the development of stress response mediators.

Main Methods:

• Plasma adrenocorticotropic hormone (ACTH) levels were measured in neonatal rats (1, 7, 14, 21 days old).
• Rats were treated with either a median eminence extract containing CRF or exposed to ether stress.

Main Results:

• CRF administration consistently elevated plasma ACTH levels across all tested ages.
• Ether exposure significantly increased ACTH levels only in 14- and 21-day-old rats, not in younger ones.
• Pituitary responsiveness to CRF did not change with age, but higher-level stress mediators matured around day 14.

Conclusions:

• The neonatal pituitary gland is capable of responding to CRF from birth.
• The central neural pathways mediating the stress response mature approximately by postnatal day 14.
• Adrenal responsiveness recovery is delayed relative to the maturation of central stress mediators.