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Effects of litter-overlapping on emotionality, stress response, and reproductive functions in male and female rats
Natalia Uriarte1, Annabel Ferreira, Ximena F Rosa
1Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde (ICBS), Universidade Federal do Rio, Grande do Sul (UFRGS), Sarmento Leite 500, Porto Alegre, 90050-170, RS, Brazil. natiuria@gmail.com
Insights
Overlapping litters in rats alters early life experiences, leading to long-term changes in adult behavior and stress responses. These effects, including reduced emotional inhibition and altered reproductive functions, manifest in a sex-specific manner.
Area of Science:
- Neuroscience
- Behavioral Endocrinology
- Developmental Psychology
Background:
- Early-life experiences significantly influence brain development, behavior, and reproductive capabilities in rodents.
- In natural rat populations, overlapping litters can occur due to postpartum mating and delayed pup dispersal, creating a mixed-age rearing environment.
- This altered early environment exposes newborns to interactions with both mothers and older siblings, potentially impacting their development.
Purpose of the Study:
- To investigate the long-term effects of overlapping litters on emotionality, stress response, and reproductive functions in adult male and female rats.
- To determine if these effects are sex-specific.
Main Methods:
- Rats were reared in either standard litters or overlapped litters.
- Adult rats underwent behavioral testing, including the open field test for emotionality.
- Corticosterone levels were measured in response to acute stress.
- Sexual behavior was assessed in adult females.
Main Results:
- Both male and female rats reared in overlapped litters showed reduced behavioral inhibition in the open field test.
- Adult females from overlapped litters exhibited a blunted corticosterone response to stress during diestrus.
- Overlapped-reared adult females also displayed reduced sexual behavior, while males did not show significant changes in these measures.
Conclusions:
- Natural alterations in early-life experience, such as litter overlapping, can lead to lasting sex-dimorphic changes in affective behaviors, stress reactivity, and reproductive functions.
- These findings highlight the critical role of early social environment composition in shaping adult neurobehavioral and endocrine outcomes.
Abstract:
In rats, mating at postpartum estrus and delayed dispersal of the young would result in the overlapping of two different-age litters. As a consequence, newborn pups' early experience will include not only that acquired during the interaction with the mother and age-matched littermates, but also with older siblings. As early-life experience modulates rodents' brain function, behavior and reproduction, we aimed to assess how changes in the early environment provoked by the overlapping of litters would affect emotionality, stress response and reproductive functions of male and female pups during adulthood. Results showed that both male and female overlapped reared pups exhibited a reduced behavioral inhibition in the open field test during adulthood. In addition, overlapped reared adult females, but not males, showed a blunted corticosterone response to an acute stressor during diestrus and a reduction in sexual behavior. In summary, natural changes in early experience provoked by the overlapping of litters, long-term modulate affective and reproductive behaviors, and the endocrine stress response in a sex dimorphic manner.
