Publication Date

2022

Document Type

Dissertation/Thesis

First Advisor

Grippo, Angela J.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Psychology

Abstract

Background: A positive rearing environment is important for the health and well-being of growing offspring. Chronic parental stress can create a toxic rearing environment, which may impair developmental and sociobehavioral outcomes of the offspring. Specifically, parental stress is linked to unstable parental emotionality, tension between mother and father, and poor parenting quality, although the inter-relatedness of these factors and the mechanisms through which they contribute to the outcomes of the offspring need further investigation. The current study investigated developmental and sociobehavioral outcomes in prairie vole offspring exposed to chronic preconception stress, with parental emotionality, strength of mother-father bond, and parental care quality as potential mediators. The prairie vole (Microtus ochrogaster) is an ideal translational model for the current study, as these rodents are socially monogamous, exhibit biparental care, and display behavioral, neuroendocrine, and cardiovascular responses similar to humans when exposed to social and environmental stressors.

Methods: Adult male and female prairie voles were randomly selected to be in either the stress exposure group (n = 11 for each sex) or nonstress exposure control (n = 9 for each sex). Stress-exposed animals were separated from their sibling and housed individually for 4 weeks; during the last 2 weeks of this isolation period, these animals were also exposed to unpredictable environmental stressors. At the same time, nonstress controls were housed with a sibling partner and were undisturbed. At the end of the 4-week housing manipulations, all animals underwent the elevated-plus maze (EPM) and forced swim test (FST) to assess for anxiety- and depressive-like behaviors, respectively. Following the last behavioral assessment, male and female animals were paired according to their housing condition (i.e., a stressed male was paired with a stressed female). Pair bonding quality was assessed on postpairing days 1 and 5 via homecage observations. All couples were left undisturbed until the birth of their offspring. Parenting quality was assessed during a parental care test on postnatal day 3. All family units were left undisturbed until the pups were weaned.

All pups were weaned on postnatal day 21 (nonstress-exposed offspring n = 22; stress-exposed offspring n = 38), and pups were housed in same-sex sibling pairs (nonstress exposed offspring n = 9 pairs; stress-exposed offspring n = 14 pairs), opposite-sex sibling pairs (nonstress-exposed n = 2 pairs; stress-exposed offspring n = 1 pair), or same-sex stranger pairs (stress-exposed n = 2 pairs). Brains of parents were collected for immunohistochemical analyses following the weaning of pups. Social development of offspring was assessed during the juvenile and adulthood ages using a combination of homecage observations and social interaction tests. As adults, offspring underwent the EPM and FST to assess for anxiety- and depressive-like behaviors, respectively. Brains of offspring were collected following the last social interaction test for immunohistochemical analyses.

Results: Exposure to chronic social and environmental stressors did not affect parental anxiety- and depressive-like behaviors or related cFos and oxytocin immunoreactivity in the paraventricular nucleus. All couples appeared to be pair bonded by postpairing day 5. Stress-exposed couples groomed each other more frequently and were more aggressive to each other compared to nonstress-exposed couples. During the parental care test, all parents took care of their pups, but stress-exposed parents engaged in an alternative patenting style. Specifically, stress-exposed parents preferred to be physically next to each other while taking care of pups, and stress-exposed mothers groomed their pups less frequently than control mothers.

Offspring of stress-exposed parents exhibited impaired social development; they displayed less frequent social play behavior, and they also groomed themselves less frequently compared to offspring of nonstress-exposed parents. Preconception exposure to chronic stress was associated with elevated depressive-like behavior as adults, without affecting anxiety-like behavior or social interaction-related cFos and OT immunoreactivity. Mediation analyses revealed that preconception exposure to chronic stress predicted juvenile and adulthood social behaviors of the offspring when controlling for maternal and paternal factors. However, parental emotionality, strength of mother-father bond, and parental care quality were not significant mediators.

Conclusions: Findings from this study further elucidate the complexity of how parental stress can impact multiple aspects of rearing environments, which may contribute to long-term behavioral and neuroendocrine outcomes in the offspring. Future studies should consider examining biological mediators such as parental genetic and epigenetic factors. Importantly, these findings can be applied to humans and may facilitate potential interventions to improve behavioral, social, and neurobiological development.

Extent

351 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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