Male rats form short-term memory for the olfactory characteristics of juvenile conspecifics. Alaptide, a synthetic derivative of the hypothalamic MIF, given subcutaneously at doses of 0.5 and 1.0mg/kg immediately after the initial exposure to an adult male, reduced the time spent by adults in social investigation of the same juvenile upon re-exposure 4h, 24h and 72h after the initial exposure. Oxiracetam (30 and 60mg/kg) had a similar effect. Both drugs were ineffective in animals re-exposed to a novel juvenile. Thus, both alaptide and oxiracetam improved an animal's capacity to recognize the juvenile. The findings may be interpreted in terms of a prolonged retention of memory traces based on olfactory information received during a short social interaction.