Figure 1.

Quantitative analysis of phosphorylated cAMP-response element binding protein (pCREB) (in A,B) and total CREB (in C) in the hypothalamic paraventricular nucleus tissue isolated from placebo (p) or morphine (m)-dependent rats after s.c. administration of saline (s) or naloxone (n), at the times indicated. Levels of pCREB and total CREB were detected by Western blot analysis. Each bar represents the mean optical density ± SEM; values are expressed as the ratio pCREB/α-tubulin and total CREB/α-tubulin (% of controls). Newman–Keuls' post hoc comparison test revealed a significant increase in pCREB in morphine-withdrawn rats at 60 min after naloxone injection. **P < 0.01 versus placebo + naloxone; ⁺⁺P < 0.01 versus morphine + saline.