Cortical neuron number and thickness are decreased after exposure to hypoxia. A–D, Immunostaining for Tbr1 (red) in the cerebral cortex of wild-type (A, B) or Fgfr1 cKO mice (C, D) at P10 under normoxia (A, C) or after hypoxia from P3 to P10 (B, D). Inset shows DAPI low magnification. Each panel is the composite of four 20× images demonstrating the entire extent of the cerebral cortex. E–H, SMI-32 (green) and DAPI (blue) stained cortices of wild-type (E, F) or Fgfr1 cKO mice (G, H) at P10 under normoxia (E, G) or after hypoxia from P3 to P10 (F, H). Scale bars, 100 μm. I–K, Total number of NeuN (I), Tbr1 (J) and SMI-32 (K) immunoreactive neurons in the cerebral cortex by stereological analyses in wild-type (blue bars) and Fgfr1 cKO (red bars) mice. Values are expressed in 106 units. N = 3 for each group. *p < 0.05 by ANOVA with Sheffe post hoc test.