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Serotonin in the development of pituitary-adrenocortical response to stress
Insights
Young rats develop stress responses early, with the pituitary-adrenocortical system responding to stress by day 4. Brain serotonin (5-HT) metabolism changes are crucial for this stress response later in development.
Area of Science:
- Neuroendocrinology
- Developmental Biology
- Stress Physiology
Background:
- The adrenocortical system's response to stress develops postnatally.
- Serotonin (5-HT) plays a role in stress regulation.
Purpose of the Study:
- To investigate the ontogeny of the adrenocortical response to stress and 5-HT administration in developing rats.
- To determine the role of central and peripheral 5-HT in the developing stress response.
Main Methods:
- Administration of 5-HT and immobilization stress to rats at different postnatal ages (day 4 and days 12-16).
- Measurement of plasma corticosteroid (11-OHCS) levels.
- Analysis of brain 5-hydroxyindoleacetic acid (5-HIAA) levels.
- Pretreatment with dexamethasone.
Main Results:
- Rats showed an adrenocortical response to intraperitoneal 5-HT and immobilization stress by day 4, but not to intraventricular administration.
- Dexamethasone did not affect the stress response in 4-day-old rats.
- Plasma 11-OHCS response significantly increased by days 12-16, coinciding with observed changes in brain 5-HIAA.
- Central 5-HT, rather than peripheral, became essential for the pituitary-adrenocortical system response to stress from days 12-16.
Conclusions:
- The rat's pituitary-adrenocortical system exhibits early responsiveness to peripheral stress stimuli.
- Brain serotonin metabolism undergoes developmental changes that are critical for mediating the stress response in later postnatal life.
Abstract:
Adrenocortical response to intraperitoneal 5-HT administration and immobilization stress is observed in rats as early as the 4th day of life when response to intraventricular administration is still absent. Dexamethasone pretreatment influences plasma corticosteroid response to stimulation of peripheral 5-HT receptors in adult rats but does not alter such response to intraperitoneal 5-HT administration and immobilization in 4-day-old rats. Plasma 11-OHCS response to this stress increases considerably by days 12-16, when stress-induced changes in brain 5-HIAA are also observed. The increase of adrenocortical response to stress coincides with the appearance of brain 5-HT metabolic stress-induced changes as well as pituitary-adrenocortical response to centrally administrators, rather than to brain 5-HT, the latter appearing to become essential for the pituitary-adrenocortical system response to this stress from days 12-16 of life.