Fetal iron deficiency disrupts the maturation of synaptic function and efficacy in area CA1 of the developing rat hippocampus

Abstract

Late fetal and early postnatal iron deficiency (ID) is a common condition that causes learning and memory impairments in humans while they are iron deficient and following iron repletion. Rodent models of fetal ID demonstrate significant short- and long-term hippocampal structural and biochemical abnormalities that may predispose hippocampal area CA1 to abnormal electrophysiology. Rat pups made iron deficient during the fetal and early postnatal period were assessed for basal synaptic transmission, paired-pulse facilitation (PPF), and long-term potentiation (LTP) in CA1 at postnatal days (P)15 and P30 while iron deficient and at P65 following iron repletion. Our results showed no differences in basal synaptic transmission between iron sufficient and iron deficient pups at P15 or P30, but the ID group did fail to demonstrate the expected developmental increase in synaptic strength by P65 (P < 0.05). Similarly, PPF ratios from iron deficient slices also failed to demonstrate the characteristic developmental changes seen in the iron sufficient group (P < 0.001). Iron deficient slices retained a developmentally immature P15 pattern of LTP expression at P30 and after iron repletion, and LTP expression was lower (P < 0.05) in the iron deficient group at P65. Thus, ID in the fetal and early postnatal period delays or abolishes the developmental maturation of electrophysiological components of synaptic efficacy and plasticity, resulting in abnormalities beyond the period of deficiency. These findings provide a functional corroboration to previous structural and biochemical abnormalities found in the iron deficient rat hippocampus and provide a potential model for learning and memory deficits seen in humans exposed to fetal and early postnatal ID.