Fig. 3

Oxycodone induces integrative stress response in rat brain. a. Western blot analysis of hsp70, BiP and phosphorylated eIF2α in rat brain lysates from nucleus accumbens, cortex, and brain stem of rats treated with water (W) or oxycodone (O1, O2). Left, the representative images of western blots. Right, graphs of the densitometric analysis of western blots. The graphs represent the mean ratio of signal of hsp70 to GAPDH, BiP to actin, or phospho-eIF2α to total eIF2α with oxycodone data normalized to water samples in corresponding tissues (±SEM). Western blot analysis was performed for each set of proteins using lysates from three separate drug administration experiments and repeated at least twice for each set of lysates. Hsp70, NuAcc, p < 0.001; Cortex, p < 0.001; Stem, p < 0.01. BiP, NuAcc, p < 0.01; Cortex, p < 0.05; Stem, p = 0.38. Phospho-eIF2α, NuAcc, p < 0.01; Cortex, p < 0.01; Stem, p < 0.01. Open bars water samples; gray filled bars oxycodone samples. b Polysomal analyses of nucleus accumbens in sucrose density gradients. Upper panels the representative images of polysomal distribution of nucleus accumbens lysates from water and oxycodone-treated animals in sucrose density gradients. Top of the gradient is on left side of each image. Direction of sedimentation is shown. The polysomal analysis was repeated three times using lysates from different drug administration experiments. Lower panels the representative images of western blots of 60S ribosomal protein L7a (Rs-L7a), eIF4A, eIF4E, and hsp70 in corresponding fractions (Frs) along sucrose gradients. The western blot analysis of proteins was investigated in two sucrose density gradients using lysates from separate drug administration experiments