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Maternal regulation of the adrenocortical response in preweanling rats
P Rosenfeld1, Y A Gutierrez, A M Martin
1Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine Stanford University, CA 94305.
Insights
Maternal deprivation potentiates infant stress responses, increasing corticosterone (CORT) levels. Maternal presence can mitigate some stress reactions, highlighting the crucial role of maternal care in infant HPA axis regulation.
Area of Science:
- Neuroscience
- Endocrinology
- Developmental Biology
Background:
- The hypothalamic-pituitary-adrenal (HPA) system regulates stress responses.
- Maternal care is crucial for infant development and stress modulation.
Purpose of the Study:
- To investigate the impact of 24-hour maternal deprivation on the infant's HPA axis reactivity.
- To examine the ontogeny of deprivation-induced stress responses and maternal regulatory capacity.
Main Methods:
- Experiment 1: Assessed corticosterone (CORT) response to adrenocorticotropin hormone (ACTH) after deprivation.
- Experiment 2: Evaluated age-related stress responses and the effect of maternal reunion.
- Experiment 3: Investigated prolonged effects of deprivation on CORT levels post-reunion.
Main Results:
- Maternal deprivation potentiated ACTH-induced CORT responses across all ages studied.
- Deprived pups showed heightened CORT responses to saline, which were reduced by maternal reunion.
- ACTH-induced CORT elevations persisted for 2 hours post-reunion in deprived pups, returning to baseline by 6 hours.
Conclusions:
- Maternal deprivation significantly alters infant HPA axis responsiveness.
- Maternal factors play a critical role in regulating the infant's stress system.
- Early life stress and maternal care interact to shape HPA axis development.
Abstract:
In the following studies, we investigated the effects of 24-h maternal deprivation on the infant's hypothalamic-pituitary-adrenal system. Experiment 1 examined the effect of deprivation on the infant's corticosterone (CORT) response to adrenocorticotropin hormone (ACTH) injection. At all ages studied, deprivation resulted in a potentiation of the response. At some ages, deprived nontreated pups had higher CORT levels than nondeprived pups. Experiment 2 examined the ontogeny of the deprivation-induced stress response, and the capacity of the mother to inhibit it. From 8 days of age onwards, deprived animals showed a CORT response to saline injection that was either absent or far smaller in nondeprived pups. Saline-induced CORT secretion was diminished, or prevented, by returning the infant to its dam. Maternal reunion had no effect on ACTH-induced CORT elevations. Finally, Experiment 3 investigated the effects of deprivation over a more extended period of time. In maternally deprived pups, ACTH-induced CORT elevations persisted for at least 2 h following reunion, but by 6 h had returned to baseline. These data suggest that maternal factors are involved in the regulation of the responsiveness of the pup's hypothalamic-pituitary-adrenal system.