9.A.14.13.33
Neuropeptide Y receptor type 2, NPYR2, of 381 aas and 7 TMSs. It is a receptor for neuropeptide Y and peptide YY. The rank order of affinity of this receptor for pancreatic polypeptides is PYY > NPY > PYY (3-36) > NPY (2-36) > [Ile-31, Gln-34] PP > [Leu-31, Pro-34] NPY > PP, [Pro-34] PYY and NPY free acid. Neuropeptide Y (NPY) and NPY receptors are widely expressed in the central nervous system, including the retina. Retinal cells express this peptide and its receptors (Y1, Y2, Y4 and/or Y5), and NPY is expressed in the retina of various mammalian and non-mammalian species. Its early expression strongly suggests that NPY may be involved in the development of retinal circuitry. NPY inhibits the increase in [Ca²⁺]_i, triggered by elevated KCl in retinal neurons, due to inhibition of Ca²⁺ channels, and  it protects retinal neural cells against toxic insults while inducing the proliferation of retinal progenitor cells. Santos-Carvalho et al. 2014 reviewed the roles of NPY in the retina, specifically proliferation, neuromodulation and neuroprotection. Alterations in the NPY system in the retina might contribute to the pathogenesis of retinal degenerative diseases, such as diabetic retinopathy and glaucoma.