Animals

All animal experiments were in accordance with the French Guidelines for the Care and Use of Laboratory Animals following the EU-Directive on protection of animals used for scientific purposes, and were approved by the Animal Care Ethics Committee of the Nord-Pas-de-Calais region (approval ID: 01564.01). Eight-week-old females and males FVB/NRj mice (Janvier Labs, Le Genest-Saint-Isle, France) were maintained under standard conditions in a specific pathogen-free environment, with a standard chow diet appropriate for breeding (RM3, Special Diets Services, France) ad libitum. After eight days of acclimation, female mice were mated (2:1) during eight days with FVB/NRj male breeders. During the whole gestation and lactation period, pregnant dams were fed a standard chow diet ad libitum. In order to eliminate as much as possible the impact of the prenatal period on lactation of the mothers and nutritional status of the pups⁴⁵, litters were adjusted to eight pups per mother at PN1, and litters less than six or more than 11 pups were excluded to normalize lactation of each mother. At PN4, all pups were randomly distributed among mothers to generate large litters with 15 pups per mother to induce PNGR. Normal litters were maintained with eight pups per mother and served as CTRL group. Each pup from either normal or large litters was assigned to a new mother when litter size was manipulated to normalize social stress. After weaning at PN21, litters received a standard chow diet (RM3, Special Diets Services, France) ad libitum.