Fig. 2

Impact of postnatal age on serum and CSF levels of IGF-1, and activation of IGF-1R in the ChP of the immature brain. A-D. Levels of IGF-1 in serum (A) and CSF (B) in preterm rabbit pups, evaluated 5 h after s.c. injections of rhIGF-1/rhIGFBP-3 (8 mg/kg) or the corresponding vehicle solution at 0 (5), 24 (29) or 72 (77) hours postnatal age (corresponding time-point for termination within parentheses). The ratio of CSF IGF-1/serum IGF-1 was calculated (C). Linear model displaying the relation between the IGF-1 levels in serum and CSF in 0 (5) hours postnatal age pups (corresponding time-point for termination within parentheses) (D). Dark grey area represents the 95% confidence level. Data are presented as means ± SD (N = 6–9). Differences in IGF-1 concentrations were analyzed using one-way ANOVA with post hoc Tukey test for multiple comparisons of means. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001. E-F. Western blot analysis of pERK1/2 and pPKB in ChP from preterm rabbit pups 5 h after s.c. administration of rhIGF-1/rhIGFBP-3 (8 mg/kg) at 0 (5, upper), 24 (29, middle) or 72 h (77, lower) postnatal age (corresponding time-point for termination within parentheses). Data from 3 different experiments are presented as means ± SD (N = 3–4). A representative blot is shown. Differences between groups were analyzed using Student’s t-test. *P ≤ 0.05; NS, not significant