Fig. 3

Neonatal inflammatory pain affected axonal development in the juvenile brain. Immunohistochemical staining was performed to determine whether peripheral inflammatory pain in neonates could affect axonal growth and myelination at P21. a Double-labeled images of NeuN (red) and neurofilament (NF; green) in the cortex of the control or formalin group. Nuclei were stained with Hoechst 33342 (blue). Scale bars = 20 μm. b–f Axon diameter was estimated by measuring the distance perpendicular to the center of the maximum diameter of the axon profile. Measured axons were categorized as small (<0.35 μm), medium (0.35–0.69 μm), large (0.7–1.4 μm), and extra-large (>1.4 μm) groups. *P < 0.05 vs. control; **P < 0.01 vs. control; ***P < 0.001 vs. control; n = 6 per group. g Images of MBP (red) in the cortex. Nuclei were stained with Hoechst 33342 (blue). Scale bars = 20 μm. h Juvenile rats subjected to neonatal inflammatory pain showed a significant decrease of MBP expression compared to control rats. *P < 0.05 vs. control; n = 6 per group