Time-dependent modulation of inhibitory avoidance memory by spermidine in rats

The polyamines, spermine, spermidine, and putrescine, are a group of aliphatic amines that may act as physiological modulators of N-methyl-D-aspartate (NMDA) receptors. Although the modulatory role of polyamines in NMDA receptor function has long been known, the effects of polyamines on learning and memory only recently began to be unraveled. In the present study, we investigated the effect of bilateral infusions of spermidine (0.02-2 nmol), a polyamine agonist, into the CA1 region of the rat dorsal hippocampus on inhibitory avoidance learning 30 min pre-training, immediately post-training, 6 h post-training, or 10 min pre-test. Bilateral microinjections of 0.2 nmol spermidine prolonged step-down latencies compared to the respective control group when administered 30 min pre-training or immediately post-training. These results provide evidence that the modulatory effects of spermidine on the acquisition and/or early consolidation of memory of inhibitory avoidance tasks in the hippocampus occur within a limited time window.