Post-weaning maternal presence exerts a protective effect against social isolation-induced behavioural alterations in mice.

Parental "watchful presence" is considered an important factor influencing behavioural and emotional development in offspring across mammalian species, including humans. However, the effects of such parental presence remain insufficiently understood, even in human studies. In laboratory mice, offspring are typically weaned at approximately three weeks of age, leaving the impact of post-weaning maternal presence on behavioural development largely unexplored. This study aimed to investigate whether maternal presence in an adjacent cage after weaning can attenuate behavioural effects of social isolation stress in mice. Furthermore, we sought to assess whether this experimental paradigm could serve as a novel animal model for studying the effects of parental watchful presence, with potential relevance to human parent-child relationship research. Mouse pups were weaned at postnatal day 21 and housed either adjacent to their mother (maternal presence group) or without maternal presence (control group). The pups were subsequently housed either in groups with littermates or individually until eight weeks of age. After maturation, behavioural tests were conducted to assess locomotor activity, anxiety-like behaviour, social behaviour, and depression-like behaviour. In group-housed mice, maternal presence did not influence behavioural outcomes. However, in individually housed mice, maternal presence partially attenuated social isolation-induced behavioural alterations, suggesting a subtle protective effect, including hyperlocomotion, reduced anxiety-like behaviour, and abnormal social interactions. Our findings demonstrate that maternal presence during the post-weaning period can offer a protective effect against certain behavioural abnormalities induced by social isolation stress in mice.　This simple adjacent-cage paradigm provides a novel and practical model for elucidating the impact of parental watchful presence on behavioural and emotional development, offering insights relevant to the understanding of parent-child relationships in humans.