Effect of administration of spermine or ifenprodil on memory. Immediately after training, the animals were injected with saline, spermine (0.1 to 10 mg/kg, intraperitoneally) or ifenprodil (0.3 to 10 mg/kg, intraperitoneally). Twenty-four hours after training, the animals were subjected to the novel object recognition test session. (A) Spermine increased and (B) ifenprodil decreased the recognition index on novel object recognition task. Date are expressed as mean ± standard error of the mean for 6 to 9 animals in each group. *P < 0.01 compared with saline group (one-way ANOVA followed by the Bonferroni’s post-hoc test). SAL, saline; SPM, spermine.