Effects of litter‐overlapping on emotionality, stress response, and reproductive functions in male and female rats

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.

Self-organised criticality in the evolution of a thermodynamic model of rodent thermoregulatory huddling

“…For rats and mice, a direct selection pressure acting on the runt of the litter may derive from the tendency of the dam to eat the runt, particularly in cold environments (e.g., [ 35 ]). Cohabitation of successive litters, which occurs commonly in the wild due to mating at postpartum estrus, may also introduce direct competition between generations via huddling interactions [ 45 ]. These considerations suggest that applying selection pressure directly to the weakest group member, which is the key to self-organised criticality in theoretical formulations [ 23 ], captures an important component of natural selection in groups of endotherms.…”

“…The modelling approach here is necessarily limited to consideration of only the immediate metabolic costs and benefits of huddling in terms of thermoregulation, but secondary benefits of social thermoregulation may exert a strong influence on natural selection too. For example, pups reared in groups develop improved motor co-ordination [ 46 ], and score higher as adults on indices of emotionality [ 45 , 47 ] and personality [ 48 , 49 ] compared to pups reared in isolation. Interestingly, lighter pups that tend to occupy the periphery of the huddle have been shown to develop increased pro-social behaviours as adults [ 50 ].…”

Social aversive stimuli presented to the mother produce the precocious expression of fear in rat pups

“…In altricial rodents, alterations in the early postnatal environment, such as natural variations in the maternal or the social milieu could lead to complex and long‐term effects on their behavioral and neuro‐endocrine responses during adulthood (Caldji et al, ; Cirulli, Berry, & Alleva, ; Uriarte, Breigeiron, Benetti, Rosa, & Lucion, ; Uriarte, Ferreira, Rosa, & Lucion, ). However, little is known regarding the effects of early life experiences on the development of affective behaviors in pups.…”

“…On postnatal Day 8, the fear responses of pups toward an anesthetized male as well as their distress behaviors in isolation were evaluated. Since early experiences can differentially affect male and female pups during adulthood (Benetti, de Araujo, Sanvitto, & Lucion, ; Kosten, Miserendino, Bombace, Lee, & Kim, ; Uriarte et al, ), their responses were assessed separately in male and female pups.…”

Social behaviour of endangered European mink ( Mustela lutreola ) litters in captivity

“…In particular, the development of behaviour throughout the early ontogeny has frequently been found to have long-lasting effects on the reproductive performance of adult individuals (Diez-Leon et al, 2013;Uriarte et al, 2009), thus being of key importance in this context. For litter-bearing mammals in particular, it has been shown that the environment during the individual's early development influences the formation of its personality type (Melo et al, 2009;Rödel and Meyer, 2011).…”