Modified limited bedding and nesting is a model of early-life stress that affects reproductive physiology and behavior in female and male Long-Evans rats

We used a modification of the limited bedding and nesting (LBN) model to evaluate the effects of early-life stress (ELS) on female and male reproductive physiology and behavior in Long-Evans rats. On postnatal day (PD) 2, dams and pups were transferred to a cage containing 100 mL of bedding (LBN condition) or to a cage containing 500 mL of bedding (control condition); bedding conditions remained until PD 10. In female rats, we measured vaginal opening, estrous cyclicity, female sexual behavior and motivation, and anxiety-like behavior. In male rats, we measured preputial separation, the development of male copulatory behavior, sexual motivation, and anxiety-like behavior. We found that relative to controls, female rats reared with LBN experienced precocious puberty and enhanced sexual motivation, but normal estrous cyclicity. Relative to controls, male rats reared with LBN experienced delayed puberty and enhanced sexual motivation, but normal development of copulatory behavior. Anxiety-like behavior was not affected by LBN in either female or male rats. In summary, the ELS of being reared with LBN affected the onset of puberty in the opposite direction in females and males, but enhanced sexual motivation in both. The current study is the first to examine the effects of ELS on sexual motivation using the LBN model. These findings further support the hypothesis that maternal care affects the development of sexual maturation and sexual motivation.