Morphine (MS) stimulates MOR and Flk1 gene expression by a STAT3-mediated mechanism. Reverse transcription polymerase chain reaction was performed for MOR and FLK-1/KDR (VEGFR2) on total RNA from RECs from WT and NY1DD sickle mice incubated with phosphate-buffered saline (PBS), 1 μM of MS, or 1 ng/mL of IL-6 in the absence or presence of 0.5 mM of STAT3 inhibitor peptide (STAT3-I) for 48 hours. Representative density images are shown. All graph values are mean ± SEM for 3 independent experiments with RECs performed in triplicate. Significance was determined by 1-way analysis of variance, Dunnet’s multiple comparisons. *P < .0001 vs PBS of matching mouse/messenger RNA, **P < .01, ***P < .05, and ****P < .001 for matching treatment vs treatment + STAT3-I.