Neurobiological and behavioral aspects of recognition in female mice

Female mice were tested for their capability to recognize female littermates in adulthood. Sibling females did not show any of the behavioral indices of recognition reported in the literature for sibling males during a 2-h social interaction. Conversely, adult females that experienced 7 days of separation from unrelated cagemates were able to recognize each other: during reunion, they showed reduced olfactory exploration, higher levels of affiliative behavior, and changes in nociception that were opioid dependent. Familiar females treated with naloxone (5.0 mg/kg, i.p.) did not show the increase in tail-flick latency that characterized saline-treated familiar pairs. Unfamiliar females did not show any behavioral modifications during social interaction. These data stress the role of familiarity in female-female social interaction and suggest that more recent experiences conceal earlier information gained before weaning. The importance of familiarity in females was found to be in contrast with the relevance of genetic recognition in male mice, but was well adapted to male and female roles within the social structure of mouse populations.