Intrahippocampal spermidine administration improves inhibitory avoidance performance in rats

Polyamines are polycations present at high concentrations in the mammalian brain. We investigated the effect of an intrahippocampal infusion of spermi dine, a polyamine agonist, immediately post-training on the inhibitory avoi dance learning paradigm in rats, Bilateral intrahippocampal microinjection of spermidine (0.02-20 nmol) caused an increase in test step-down latencies at low concentrations. Administration of arcaine (0.002-0.2 nmol), an anta gonist of the N-methyl-D-aspartate (NMDA) receptor polyamine binding site, did not modify the test step-down latencies. In contrast, co-administration of arcaine and spermidine completely reversed the facilitatory effect of s permidine on the test step-down latencies. These results provide evidence t hat polyamines may be involved in learning and memory modulation. (C) 2000 Lippincott Williams & Wilkins.