Figure 4.

μOR agonists inhibit CXCL12-induced phosphorylation of CXCR4. Glia-free neuronal cultures were treated with 1 μm morphine (or vehicle) or DAMGO for 24 h, followed by 20 nm CXCL12 for indicated amounts of time. Both agonists markedly reduce levels of pCXCR4 in total cellular extracts, and CTAP (1 μm) reversed this effect (A–C). The bar graphs (D) represent the mean ± SEM of pCXCR4 band densities represented with respect to control levels from three independent identical experiments [all CXCL12 treatments are significantly higher than control, i.e., p < 0.05 or less; DAMGO or μOR (MOR)-treated groups are all significantly lower than corresponding CXCL12 alone, p < 0.05 or less].