Do social statuses affect the startle reflex in male mice?

Usual housing conditions lead to dominance hierarchy forming between male mice. The situation produces physiological and behavioural differences between dominants and subordinates. The goal of the present study was to assess stress responses, and possible changes in prepulse inhibition (PPI) of the startle reflex in dominant and subordinate male mice. Three weeks of daily social interactions led to stable aggressive dominance in 11 pairs of male NMRI mice. Stress levels were assessed by measuring faecal corticosterone metabolites (FCM), a non-invasive technique for monitoring hormonal changes in response to specific situations, with repeated sampling of each animal. The analysis of FCM levels showed greater stress in subordinate males at the beginning of the experiment, as the hierarchy was being established, but by the end of the experiment, FCM levels were reduced and similar in both dominants and subordinates. No significant differences were found in the startle response or PPI.