In this study, we used the second generation of both mouse strains born in our facility. At seven weeks of age, SM/J and LG/J females were randomly mated with males of their own strain in a paired mating system. Males were removed from the breeding cage at least one week before females gave birth, at the point when the female was determined to be pregnant. Animals were fed ad libitum with TWS119 nmr Nuvilab CR1/Nuvital Inhibitors,research,lifescience,medical (Colombo, PR,

Brazil) and maintained at a constant temperature of 21 ± 1°C with 12-h light/dark cycles (lights on at 6 a.m.). For the purposes of the association study of Peg3 gene variation and maternal performance, we collected DNA from F2 progeny of the LG/J and SM/J intercross (Peripato et al. 2002). It is worth noting that in addition Inhibitors,research,lifescience,medical to the affected maternal care and prepulse inhibition (Samocha et al. 2010), other traits known to be affected by genetic variation in populations of LG/J and SM/J intercrosses include growth (Cheverud et al. 1996; Kramer et al. 1998; Vaughn et al. 1999), bone length (Norgard et al. 2008), obesity Inhibitors,research,lifescience,medical (Cheverud et al. 2001; Ehrich et al. 2005), and litter size (Peripato et al. 2004). Experiments were carried out in accordance with the Guidelines

for the Care and Use of Mammals in Neuroscience and Behavioral Research (ILAR, Washington, D.C.), and the protocol was approved by the Ethics Committee of the Federal University of Sao Carlos (Brazil). Maternal performance Maternal performance was scored as previously

described (Peripato et al. 2002). A total Inhibitors,research,lifescience,medical of 30 SM/J and 23 LG/J primi-parous females were monitored daily from pregnancy detection to seven days following delivery. All procedures were conducted between 8 a.m. and 12 p.m. Litter size was scored on the day of birth, and survival was monitored daily for the first week. The maternal features investigated included nest Inhibitors,research,lifescience,medical building before and after delivery, milk provision, and pup retrieval. Two observers using the same criteria analyzed each of these features. Nest building was determined by the presence of a nest and its quality. On the first day of pregnancy, a pressed cotton square was added to the cage. Pre- Thiamine-diphosphate kinase and postpartum nest building was analyzed daily by measuring nest height and scoring it as good (heights above 2.5 cm and shredded cotton in a structured way) or poor (shallow nests without cotton). Milk provision was indirectly evaluated by the presence or absence of milk in the stomach of each pup and was monitored once daily for seven days. Females usually perform protective behavior in response to external stimuli and bring the pups back to their nest if they are removed. Thus, we scored pup retrieval on the first day postpartum by removing offspring from the nest and relocating them randomly in the cage. We monitored pup retrieval for 6 min.