The effects of itasetron (endo-N-8-methyl-8-azabicyclo-[3.2.1.]-octo-3-yl) -2,3-dihydro-2-oxo-1 H-benzimidazole-1-carboxamide hydrochloride), a 5-HT3 receptor antagonist, on discrete memory abilities of the aged rat were assessed by using the multiple choice avoidance behavioral task. Chronic treatment with itasetron (i.p., 10 micrograms/kg, b.i.d., for three consecutive weeks), but not with vehicle, significantly improved retention abilities of the aged rats in this memory test. These results further support the important role of this 5-HT3 receptor antagonist in counteracting age-related memory degeneration in rodents.