Figure 2. Acute morphine-induced MAPK modulation. Mice were habituated and then injected with saline, 10 mg/kg morphine, or 100 mg/kg morphine (subcutaneous). Thirty minutes after injection, mice were perfused, and brains were processed for immunohistochemistry. Digital images were quantified using NIH Image. Results are presented from 5-12 mice per treatment group, and for each brain area, at least five consecutive sections were analyzed. One-way ANOVA revealed a main effect of morphine for the Acc (total pixels stained, F(2,26) = 11.72; p < 0.001), somatosensory cortex (total pixels stained, F(2,18) = 5.02; p < 0.05), association cortex (total pixels stained, F(2,9) = 6.42; p < 0.05), LC (average optical density, F(2,17) = 44.80; p < 0.0001), NAc (total pixels stained, F(2,26) = 11.07; p < 0.001), CeA (total pixels stained, F(2,26) = 54.39; p < 0.0001), and posterior BLA (total pixels stained, F(2,26) = 6.42; p < 0.01). There was no main effect of morphine in the hippocampus (total pixels stained, F(2,26) = 1.47; p > 0.05). Tukey's post hoc comparisons revealed a significant increase after 10 and 100 mg/kg morphine in the Acc (A), somatosensory cortex (B), association cortex (C), and LC (D). In the posterior BLA, a significant increase was observed only after 100 mg/kg (G). A significant decrease in MAPK activation after morphine treatment was observed in the NAc (E) and CeA (F). No significant difference was observed in CA3 of the hippocampus (H). *Significant difference from saline (p < 0.05). **Significant difference from 10 mg/kg morphine (p < 0.05). Results are presented as mean ± SEM.