Abstract Spermidine (SPD) is an endogenous polyamine that modulates N-methyl-D-aspartate (NMDA) receptor function, and has been reported to facilitate memory formation. In the current study we determined whether or not the PKA/CREB signaling pathway is involved in SPD-induced facilitation of memory of inhibitory avoidance task in adult rats. The post-training administration of the cAMP-dependent protein kinase (PKA) inhibitor, N-[2-bromocinnamylamino)ethyl]-5-isoquinoline sulfonamide [H-89, 0.5ρmol intrahippocampal (ih)] or the antagonist of the NMDA receptor polyamine-binding site (arcaine, 0.02nmolih) with SPD (0.2nmolih) prevented memory improvement induced by SPD. Intrahippocampal administration of SPD (0.2nmol) facilitated PKA and cAMP response element-binding protein (CREB) phosphorylation in the hippocampus 180min, but not 30min, after administration, and increased translocation of the catalytic subunit of PKA into the nucleus. Arcaine (0.02nmol) and H-89 (0.5ρmol) prevented the stimulatory effect of SPD on PKA and CREB phosphorylation. These results suggest that memory enhancement induced by the ih administration of SPD involves the PKA/CREB pathways in rats.