Fig. 3. Time course of p38, Erk, JNK and Akt activation by MG132 in rat primary astrocytes. Rat primary astrocytes were incubated in serum-free DMEM/F12 with 1 μM MG132 for 3-24 h. Cells were harvested for Western blot analysis and the activation of p38, Erk, JNK and Akt at different time points was assessed by measuring the respective phosphorylated forms of signaling molecules. Total level of p38, Erk, JNK and Akt were measured as controls. The graph represents quantification data which is the mean ± S.E.M. of four independent experiments (**p<0.01 versus Control).