Social discrimination procedure: an alternative method to investigate juvenile recognition abilities in rats

Experiments were performed to establish the social discrimination procedure as an alternative method to the widely used social recognition test for investigating short-term olfactory memory processes in rats. The time that 4-mo old male animals spent investigating conspecific juveniles was taken as an index of their juvenile recognition/discrimination abilities. When the same juvenile was reexposed to the adult 30 min after its initial exposure, it was investigated at a significantly lower intensity compared to a simultaneously presented novel juvenile. If the second exposure to the previously exposed juvenile occurred 2 h later, however, both juveniles were investigated equally, indicating an extinction of olfactory memory. The simultaneous presentation of the previously exposed juvenile and novel juvenile provides not only an internal control under identical experimental conditions (thus reducing the number of sessions for a given experimental series), but also the opportunity to separate specific (i.e., memory-related) from nonspecific (i.e., investigatory behavior-suppression) effects in pharmacological studies. Furthermore, the social discrimination procedure enables even in sexually naive adult male rats the detection of juvenile recognition abilities which seem to be masked in the social recognition test by sexual/aggressive behavior-motivated investigation. The method described here might be an attractive alternative to the conventional social recognition procedure.