Memory deficits in adult rats following postnatal iron administration

Two experiments investigated the effects of Fe2+, administered postnatally to rat pups on days 10-12, upon tests of memory performance and motor behav iour. In experiment I, Wistar rat pups were administered Fe2+ at doses of e ither 2.5, 7.5, 15.0 or 30.0 mg/kg, or vehicle, postnatally, and tested in the open-field at 3 months of age, followed 6 weeks later by testing in the radial arm maze. In the open-field test, only the 30.0 mg/kg Fe2+ group sh owed a significantly decreased number of ambulations, but not rearings. In the radial arm maze, all four dose groups, demonstrated deficits in acquisi tion performance from test days 3 to 5. Retention quotients confirmed the c ognitive deficits over all four Fe2+ groups. In experiment II, rats were ad ministered either 2.5, 7.5 or 22.5 mg Fe2+ per kg, or vehicle, postnatally, and tested in the inhibitory avoidance (IA) conditioning and retention tes t at 3 months of age. In the IA conditioning test, groups were either given five 10-min preexposures to the test chamber (preexposed) or simply moved to another cage (non-preexposed). IA retention was blocked in non-preexpose d rats administered 7.5 and 22.5 mg Fe2+ per kg whereas in preexposed rats the 7.5 mg/kg group did not differ from the control (vehicle) group, althou gh the preexposed control group showed significantly better retention than the non-preexposed control group. Postnatal iron administration appears to induce long-lasting detrimental effects upon performance of both appetitive ly and negatively reinforced tests of memory. Analysis of iron content indi cated significant increases in the substantia nigra of the 7.5, 15.0 and 30 .0 mg/kg dose groups, but not in the 2.5 mg/kg dose group. Postnatal iron a dministration appears to induce far-reaching effects upon the performance o f certain learned behaviours, (C) 2001 Elsevier Science B.V. All rights res erved.