MOR is increased in binding affinity and number in retinal endothelial cells of sickle mice. Saturation binding curves (A) and Scatchard plots (B) for binding of [³H]diprenorphine to membranes from RECs isolated from WT and NY1DD mice. (C-D) Competitive binding of opioid receptor ligands with [³H]diprenorphine in membranes derived from RECs of WT (C) and NY1DD mice (D). MOR-specific agonists morphine, D-Ala(2), N-Me-Phe(4), Gly(5)-ol-enkephalin (DAMGO), and etorphine effectively competed for [³H]diprenorphine binding, reaching 0% of the specific binding, whereas {[D-Pen (2, 5)]-Enkephalin} (DPDPE; δ opioid receptor agonist) and U50488H (κ opioid receptor agonist) could not effectively compete for the specifically bound [³H]diprenorphine. In all cases, 10 μM of naloxone was used to determine nonspecific binding. Results represent mean ± SEM of 3 independent experiments performed in triplicate. (E) MOR expression is increased in retinae and RECs of sickle mice. Reverse transcription polymerase chain reaction was performed for MOR on total RNA on retinae or RECs isolated from naïve WT and NY1DD mice. Representative image for total RNA from retinae or RECs from 3 mice per group. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.