Ilantide reduces social memory deficits induced by amyloid-β. Ilantide-t (10 mg/kg; n = 12) or vehicle (saline, 1 ml/kg; n = 13) was subcutaneously injected on days postimmunization (dpi) 7, 9, 11, 13, 15, 17 and 19 after intracerebroventricular administration of aggregated Aβ25–35 (15 μg). The control group consisted of 11 rats. The social recognition test was performed on dpi 20. Social memory was estimated as the recognition ratio (RR). RRfamiliar was calculated as T2/(T1 + T2). T1 and T2 are the times spent investigating the same juvenile animal during the first and second trials, respectively. RRnew was calculated as T3/(T1 + T3). T1 and T3 are the times spent investigating the different juvenile animals during the first and third trials, respectively. An RR value significantly less than the theoretical value of 0.5 obtained by one-sample t-test was taken as an indication of the presence of social memory. **P < 0.01 and ***P < 0.001 by one-sample t-test compared with theoretical value of 0.5. +
P < 0.05 and +++
P < 0.001 by one-way analysis of variance followed by the Newman-Keuls post hoc test.