Excitotoxic glutamate inhibits IR/Akt/mTOR pathway
a Dynamics of [Ca2+]i and b ΔΨm in single rat cortical neurons, loaded simultaneously with Fura-FF and Rh123 dyes and exposed to 100 μM glutamate. Grey lines represent sixty single neurons. Blue and red lines represent the respective means of [Ca2+]i and ΔΨm, averaged across sixty individual neurons at every time point. c Fura-FF and Rh123 fluorescence 30 min after the onset of glutamate exposure, expressed as the fold increase over baseline (at − 5 min). Data are the mean ± SEM from sixty neurons. ****P < 0.0001 compared to respective baselines (one-way ANOVA with repeated measures, followed by Tukey’s post hoc test). d-g Levels of d IRβ pY1150/1151, e Akt pS473, f mTOR pS2448, and g GSK3β pS9 in rat cortical neurons exposed to 0 nM (C) or 100 nM insulin for 15 min (I), 100 μM glutamate for 30 min g, or sequentially to 100 μM glutamate for 30 min and 100 nM insulin for 15 min (G + I). Bar graphs represent the levels of the phosphoproteins, normalised against respective total protein levels, in cell lysates and expressed as a percentage of levels in insulin-treated cells (group I). Each value represents the mean ± SEM from six independent cultures (cell populations obtained from twelve separate rats, two per culture). ###P < 0.001, ####P < 0.0001 compared with untreated control c; **P < 0.01, ***P < 0.001, ****P < 0.0001 compared with insulin i (one-way ANOVA, followed by Tukey’s post hoc test for multiple comparisons). h Scheme illustrating the inhibitory effects of glutamate on the insulin-induced activation of the IR/Akt/mTOR pathway.