ABSTRACT
Intrauterine position (IUP), the proximity of a fetus relative to same and opposite sex fetuses, is a reliable predictor of the direction and intensity of social and regulatory behaviors in adult male and female mice. In the present experiment, female Rockland-Swiss (R-S) mice who had resided in utero between two females (OM) and females who had resided between two males (2M) were compared with respect to five indices of maternal behavior: Spontaneous parental responses exhibited toward neonates; nestbuilding during pregnancy; aggression during pregnancy; aggression during lactation; and reproductive/lactation performance. There was no significant difference between 0M and 2M females in their spontaneous parental responses toward neonates or their level of nestbuilding behavior during pregnancy. However, when tested for aggression during pregnancy and lactation, 2M females exhibited aggression on a greater number of test days during pregnancy than did 0M females. Also, during pregnancy and lactation, 2M females displayed more lunges and attacks toward adult male intruders than 0M females. Although 0M females tended to have larger litters than 2M females, the animals did not differ with respect to any other measure of reproductive/lactation performance. Intrauterine position, therefore, modulates some aspects of maternal behavior but apparently not others.
Subject(s)
Fetus/physiology , Maternal Behavior , Aggression/physiology , Animals , Female , Fertility , Lactation , Male , Mice , Mice, Inbred C57BL , Nesting Behavior/physiology , Phenotype , Pregnancy , Sex Factors , Testosterone/pharmacologyABSTRACT
Rockland-Swiss (R-S) Albino female mice that receive suckling stimulation from young consume significantly more water and food and gain significantly more weight than dams without young. Excision of nipples (thelectomy) prevents postpartum increases in these consummatory behaviors and in body weight gain even in dams with extensive prior suckling exposure. Thus, both the initiation and maintenance of postpartum ingestive behaviors depend primarily upon suckling stimulation from young.
