The Time of Prenatal Immune Challenge Determines the Specificity of Inflammation-Mediated Brain and Behavioral Pathology

Enhanced sensitivity to inflammation-mediated disturbances in postnatal Reelin expression in the brains of offspring after mid-pregnancy immune challenge. a–c, Distribution of Reelin-immunoreactive cells in the hippocampal formation and dentate gyrus of representative control animals (a) and animals subjected to prenatal PolyI:C exposure on GD9 (b) or GD17 (c). As evident in the images at a higher magnification (indicated by the square in a), prenatal PolyI:C exposure affected Reelin expression particularly in the stratum oriens (sto) of the CA1 subfield. The arrows in b indicate the lack of Reelin-positive cells in the entire stratum oriens of GD9-Polyl:C offspring. e, g, This effect was particularly pronounced GD9-PolyI:C-exposed animals (e) relative to controls (d), leading to a significant reduction in Reelin-positive cells in the brains of GD9-PolyI:C offspring compared with controls (g). f, Prenatal PolyI:C exposure on GD17 only resulted in a marginal reduction in postnatal Reelin immunoreactivity. n = 4 in each treatment group. The values in g are mean ± SEM. ∗p < 0.05, statistical significance based on Fisher's LSD post hoc analysis. Scale bars: a–c, 500 μm; d, e, 50 μm. Cntr, Control; sto, stratum oriens; str, stratum radiatum; pcl, pyramidal cell layer.