['Neuropeptide Y is a sympathetic neurotransmitter, a potent endothelium-derived angiogenic factor and a vascular mitogen. We have studied the role of the functional leucine7 to proline7 polymorphism of the signal peptide region of preproneuropeptide Y (prepro-NPY) as a genetic susceptibility factor for diabetic retinopathy. In addition, we investigated the role of the NPY Y2-receptor as a putative mediator of angiogenic NPY signaling in the retina.', 'Frequencies of proline7 (Pro7) carriers in the prepro-NPY were determined in type 1 and type 2 diabetes patients having retinopathy, in type 2 diabetes patients without retinopathy and in healthy control subjects. The role of Y2-receptor in hyperoxemia-induced retinal neovascularization was investigated in Y2-receptor knockout mice (Y2-/-) and in rats administered Y2-receptor mRNA antisense oligonucleotide.', 'The carriers having Pro7 in the preproNPY are markedly over-represented among type 2 diabetes patients with retinopathy compared to type 2 diabetes patients without retinopathy and to the population control. Neonatal exposure to hyperoxia resulted in development of retinal neovascularization that was prevented in Y2(-1-) -mice, and significantly inhibited in rats treated with the Y2-receptor antisense oligonucleotide.'] Are neuropeptide Y and Y2-receptor involved in development of diabetic retinopathy and retinal neovascularization?