WHEN MATERNAL SENSITIZATION FAILS: INSIGHTS FROM BEHAVIOURAL OUTCOME OF DAMS AND VIRGIN FEMALE RATS CO-HOUSED

Motherhood constitutes a period characterized by an increase in pup motivation ensuring their survival. Motivated maternal behaviour is shaped by pregnancy-related hormones and nonapeptides acting on the brain, although external factors, particularly sensory signals from pups, can also initiate maternal responses in rodents. Indeed, virgin female mice exhibit maternal care in the presence of the dam, likely acting as godmothers. By contrast, virgin rats avoid pups and become maternal after continuous pup exposure for several days. Then, we explore if the godmother model also works for sensitizing virgin rats, thus, aiming to assess the dynamics of maternal care in the absence of hormonal influence (maternal sensitization). In this study, we performed a detailed ethological analysis of the maternal, social and self-grooming behaviour of pairs of virgin and lactating Sprague-Dawley rats cohabitating, before (early and late-pregnancy) and after parturition. Our results reveal that maternal behaviour was exclusively displayed by dams, whereas virgin females were not maternally sensitized but exhibit pup exploratory behaviour in the absence of dams. Moreover, dams reduced social behaviour already during the pregnancy period. Self-grooming behaviour increased in the presence of pups similarly in virgins and dams. Thus, our results contribute to a better understanding of social and maternal caregiving behaviour in rats, underscoring the behavioural adaptation associated with motherhood and the adaptative strategies that arise when there is no key hormonal influence.
Funding sources: Universitat Jaume I (UJIA2019-14, GACUJIMC/2024/23 GACUJIMC/2025/14), Ministerio de Ciencia e Innovación (PID2019-107322GB), Generalitat Valenciana (GV/2020/173, ACIF/2021/330) and German Research Foundation (DFG BO 1958/8-2).