Alterations of the IGF-IR signaling pathways in arcuate explants from underfed pups.

<p>Activation of key elements of IGF-1R signaling pathways were measured by Western blot analysis as illustrated with representative blots in basal condition (-) or 15 min after IGF-I stimulation (IGF-I) (<b>A</b>). Quantification indicates activation of the IGF-1R (fold induction of the p-IGF-1R/ IGF-1R ratio) by IGF-I stimulation relative to basal levels (left panel), and total IGF-1R protein levels (right panel) in arcuate explants harvested from normally fed and underfed pups of both sexes (<b>B</b>). Similarly, activation of AKT (fold induction of the pAKT/AKT ratio) (<b>C</b>), ERK1 (<b>D</b>), ERK2 (<b>E</b>) and MEK-1 (<b>F</b>) are presented (left panels) with their respective total protein levels (right panels) (n = 4–6 per group). <i>In vitro</i> explant cultures indicate that specific inhibition of PI3K by LY294002 (LY) and of MEK by PD0325901 (PD) impaired axon growth of GHRH neurons in normally fed (n = 4 per group) (<b>G</b>) and underfed GHRH-eGFP⁺ pups (n = 6 per group) (<b>H</b>). All data are presented as the mean ± SEM with Mann Whitney analysis for Western blot analysis with *: <i>p</i> < 0.05 (<b>V-F</b>); and one way-ANOVA analysis with the Newman Keuls post-test (<b>G</b>, <b>H</b>) with *: <i>p</i> < 0.05 and ***: <i>p</i> < 0.001 for each treatment <i>vs</i>. Control; δδ: <i>p</i> < 0.01 and δδδ: <i>p</i> < 0.001 for each treatment <i>vs</i>. IGF-I; Δ Δ Δ: <i>p</i> < 0.001 IGF-I/PD <i>vs</i>. IGF-I/LY.