Fostered offspring develop hyper-reactive endocrine stress responses in a plural-breeding rodent, Octodon degus
Qinyue Stacy Guan1, Kaja S Arusha1, Nicholas Caramihai2
1Department of Biology, Swarthmore College, Swarthmore, PA, USA.
Insights
Parental separation impacts degu stress hormones long-term. Cross-fostering degu (Octodon degus) litters altered cortisol levels and negative feedback, showing timing matters for endocrine stress response development.
Area of Science:
- Neuroscience
- Endocrinology
- Animal Behavior
Background:
- Long-term parental separation affects human child development.
- Rodent models often use solitary breeding species, unlike human multi-caregiver systems.
- Maternal separation in rodents causes chronic endocrine stress response changes.
Purpose of the Study:
- To investigate the impact of cross-fostering on degu (Octodon degus) offspring stress hormone levels.
- To determine if the age of fostering influences short- and long-term endocrine stress responses.
- To validate degus as a model for human parental separation studies due to their communal care.
Main Methods:
- Cross-fostering degu litters at post-natal day (PND) 2, 8, and 14.
- Measuring baseline and stress-induced cortisol levels.
- Assessing cortisol negative feedback mechanisms at weaning (PND28).
Main Results:
- Fostered degus exhibited higher stress-induced cortisol levels and weaker negative feedback at weaning compared to non-fostered.
- The timing of fostering influenced stress responses: PND8 fostering led to higher immediate baseline cortisol, while PND2 fostering resulted in higher stress-induced cortisol at weaning.
- Enduring impacts on the endocrine stress response were observed in long-term cross-fostered degus.
Conclusions:
- Long-term cross-fostering significantly impacts the endocrine stress response in degus.
- The age at which fostering occurs is a critical factor in shaping stress system development.
- Degus serve as a valuable model organism for studying the effects of parental separation on human development and stress physiology.
Abstract:
Long-term parental separation can lead to altered behavioral and physical development in human children. Rodent models are popular for studying parent-child separation, and several studies have found that maternal separation leads to chronic changes in the endocrine stress response. However, while human children are generally raised by multiple caregivers, most rodent studies utilize solitary breeding species. Therefore, we used degus (Octodon degus) as a model for studying human parental separation, as these rodents practice plural breeding and communal care. In this study, we cross-fostered degu litters at different ages (post-natal day [PND] 2, 8, and 14) to test the hypotheses that fostering affects offspring stress hormone levels in both the short- and long-term and that these impacts differ depending on the age at which offspring are fostered. We found that fostering had long-term effects, as fostered offspring had higher stress-induced cortisol levels and weaker cortisol negative feedback than non-fostered offspring at weaning age (PND28). We also found that the timing of fostering mattered, as degus fostered at PND8 had higher baseline cortisol levels the day after fostering, while degus fostered at PND2 had higher stress-induced cortisol levels at weaning. These data suggest that long-term cross-fostering has enduring impacts on the endocrine stress response in degus, therefore making them a useful model organism for investigating impacts of parental separation in humans.
