Early social enrichment affects responsiveness to different social cues in female mice.

Communal nesting (CN), an early social enrichment procedure in which multiple females rear the offspring in a single nest, increases maternal care levels received by offspring and interaction with peers. It has been shown that male mice reared under CN conditions show increased social competence and propensity to social interactions at adulthood. In the present study we investigated long-term behavioural effects of CN on female offspring. Mouse pups were reared under two different experimental conditions: standard nesting (SN, where single mother rears her pups) and CN (three females rearing their pups in a single nest). At adulthood CN and SN virgin females underwent three different behavioural tests: (i) maternal induction following presentation of foster pups; (ii) social recognition test in which ultrasound vocalizations (USVs) and social investigation behaviour emitted by a resident female in the presence of a female partner were recorded; (iii) zero-maze to analyze anxiety profiles. CN females showed (i) decreased licking response in the maternal induction test accompanied by an increased sniffing response; (ii) decreased of social interest towards a novel partner (during the Retest Different phase), and decreased USV emission rate in the social recognition test; CN and SN females did not differ in the emotional responses measured in the zero-maze apparatus. As a whole these data suggest that CN rearing render female mice less reactive to social novelty.