A protocol for investigating long-term social discrimination memory: Evidence in female and male Long Evans rats

Social discrimination, the investigation of a novel peer more so than a familiar peer, is used as a measure of social memory. There is much less research on long-term social memory than short-term social memory, and no long-term social memory research in female rats. The majority of long-term social discrimination research has relied on long familiarization session of an hour or more and involved juveniles as the stimulus peers. Here we show that a 30-minute familiarization session is sufficient to produce social discrimination 24 h later in both male and female rats and allows for measurement of social approach. Other methodological considerations are described, such as: that age- and sex-matched stimulus peers can be used across a wider range of ages than the use of juveniles; evidence that a familiar peer in a novel location attenuates social discrimination; that the first 10 minutes of the social approach reliably shows a preference for the social peer over an object whereas the 30-minute session does not; and that 10-minute discrimination sessions are preferable to 5-minute sessions. The research satisfies the goal of obtaining an efficient procedure to investigate both the possibility of enhancing or diminishing social approach and social memory with experimental manipulations in both sexes.