Female pups receive more maltreatment from stressed dams

Abstract

The effects of exposure to developmental stress often diverge for males and females. Using the scarcity-adversity model of low nesting resources outside the home cage, our lab has discovered sex differences in both behavioral and epigenetic consequences of repeated exposure to caregiver maltreatment. For the measures we have performed to date, we have found more consequences for females. The reasons underlying this sex disparity are unknown. In the current experiment, we aimed to discern the quality of maternal care received by male and female pups in our model. As we have previously found more behavioral and epigenetic consequences in females, we hypothesized that females receive more adverse care compared to their male littermates. Our hypothesis was supported; in our maltreatment condition, we found that female pups received more adverse care than males. This sex difference in adverse care was not present in our two control conditions (cross-foster and normal maternal care). These data lend support to the notion that one reason females in our model incur more behavioral and epigenetic consequences is a result of greater mistreatment by the dam.

Keywords: early-life stress; maltreatment; maternal care; sex differences.

Figure 1

Utilizing a within-litter design, rat pups were exposed for 30 minutes daily to either dams with copious amounts of nesting material for the foster care condition or dams with insufficient nesting material for the maltreatment condition. Additional littermates were left inside the home cage (enriched with nesting material) with their own mother, providing normal care controls. PN=postnatal day.

Figure 2

Similar to our previous reports where adverse behaviors directed at both sexes were combined, pups in the maltreatment condition experienced more adversity and less nurturance. n=10 litters; *** denotes p < .001; NMC = normal maternal care; CFC = cross-foster care; MAL = maltreatment

Figure 3

In the maltreatment condition, female pups received more adverse care from the dam relative to their male littermates (A). No sex differences in adverse care were detected in the cross-foster (B) or normal maternal (C) care conditions. n=10 litters; *** denotes p < .001.