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Plasma corticosterone fluctuations in an infant-learning paradigm
M B Hennessy1, A C Collier, A C Griffin
1Department of Psychology, Wright State University, Dayton, Ohio 45435.
Insights
Maternal presence reduces stress hormone (corticosterone) levels in infant rats during learning tasks. This suggests mothers play a key role in modulating infant stress responses and learning.
Area of Science:
- Developmental Psychology
- Neuroendocrinology
- Animal Behavior
Background:
- Infant stress responses are critical for development and learning.
- Maternal care significantly influences the physiological and behavioral development of offspring.
- Understanding the neuroendocrine mechanisms underlying infant stress is essential.
Purpose of the Study:
- To investigate plasma corticosterone fluctuations in infant rats during a learning task.
- To examine the impact of maternal deprivation and presence on stress responses.
- To explore the role of the dam in moderating pup's corticosterone levels.
Main Methods:
- Collected blood samples from 10- and 15-day-old rat pups.
- Exposed pups to different conditions: no disturbance, maternal deprivation, or deprivation with a learning task.
- Assessed plasma corticosterone levels following varying durations of isolation or dam presence.
Main Results:
- Plasma corticosterone levels increased in pups after deprivation and training, and in 15-day-old pups after deprivation alone.
- The presence of the anesthetized dam significantly reduced corticosterone elevations.
- This moderating effect was more pronounced in 15-day-old pups and at longer exposure times (60 min).
Conclusions:
- Maternal presence effectively buffers the stress response in infant rats.
- The dam's capacity to moderate corticosterone suggests a significant role in reinforcement during learning.
- These findings highlight the importance of maternal care in shaping infant neuroendocrine and learning processes.
Abstract:
Plasma corticosterone fluctuations of infant rats were examined in a learning task. A blood sample for analysis of plasma corticosterone was collected from groups of 10- and 15-day-old pups following either no disturbance, standard maternal deprivation only, or deprivation and training in an established approach-mother, avoid-shock conflict task. In the latter condition, pups remained in the goalbox either alone or with an anesthetized dam for either 15 or 60 min before blood sample collection. Plasma corticosterone levels were elevated following deprivation plus training in pups of both ages and following deprivation only in the 15-day-old pups. Further, the presence of the dam in the goalbox reduced plasma corticosterone elevations, particularly among 15-day-old pups and at 60 min. These findings suggest that the mother's capacity to moderate the pup's plasma corticosterone response may contribute to her reinforcement value in infant-learning paradigms.