In the present study, we investigated the effect of immediate post-training bilateral infusion of spermidine, a polyamine agonist, into the amygdala on inhibitory avoidance learning of rats. Bilateral microinjection of spermidine (0.02--20 nmol) caused an increase in test step-down latencies at high concentrations. Administration of arcaine (0.002--0.2 nmol), an antagonist of the NMDA receptor polyamine binding site, decreased test step-down latencies. On the other hand, co-administration of arcaine and spermidine completely reversed the spermidine-induced increase of test step-down latencies. These results provide evidence that polyamines may be involved in learning and memory modulation in the amygdala.