Variations of behavioral phenotype, parenting style and their influences on pups

The disposition to approach or avoid particular classes of salient stimuli constitutes the basis of motivated behavior of organisms. Such a critical feature of behavior seems to be biologically rooted and normally distributed, representing the primary reaction to rewarding or aversive stimuli. The purpose of this study is to investigate if a particular advancing or withdrawing phenotype in response to salient stimuli could affect parental relationship, parental care and finally offspring behavior. An animal model engaging C57BL/6J inbred mice is a particularly suitable tool to identify different approaching/avoidance (A/A) tendencies. By using behavioral test such as A/A Y-Maze it was possible to characterize male and female mice, classifying them into three main categories. Animals were defined Balancing (BA) when they reacted with balanced responses to a conflicting stimuli, Approaching (AP) or Avoiding (AV) when they reacted, respectively, with advancing or withdrawing responses to the stimulus. In order to assess the influence of parental phenotype on pups behavior, AV/BA/AP animals of both sexes were selected. AV/BA/AP males and females were tested in the Open Field Test with novel object (OF) and Elevated Plus Maze (EPM) and then mated, to assemble parenting couples of double (both AV or AP parents), single (one AV or AP parent and the other BA) and control (both BA parents) composition. The different couples obtained were kept in exclusive relationship throughout pregnancy, delivery and even up to the offspring weaning. To investigate the influence of phenotype on parenting style, an undisturbed parental care 30-min observation was performed at pup post-natal day (pnd) 3. Male and female offspring was likewise tested in the A/A Y-Maze (pnd 35-38), OF and EPM (pnd 55-60) for assessing offspring behavior. Results indicate that offspring varied according to maternal/paternal phenotype as well as to parental care, with significant differences between males and females.