Sub-population of cultured hippocampal astrocytes expresses neuropeptide YY1 receptors

The expression and pharmacological characterization of neuropeptide Y (NPY) receptors of the Y-1 subtype on cultured hippocampal neurons was reported using radioreceptor assays and immunohistochemical approaches (St-Pierre et al., 1998). The present study aimed to establish the presence of NPY Y-1 r eceptors on cultured hippocampal astrocytes using similar strategies. Immun ocytochemical experiments were carried out using three antisera directed ag ainst distinct domains (amino adds sequence 185-203, 198-213 and 355-382) o f the Y-1 receptor. Double-labeling experiments and confocal microscopy wit h these Y-1 receptor antisera demonstrated their recognition of the same su b-population (20%) of GFAP-positive astrocytes in culture. The immunostaini ng seen with all three Y-1 receptor antisera took the form of large irregul ar clusters distributed throughout cell bodies and processes. Further exper iments using radioactive ligands confirmed the, presence of NPY receptors o n cultured hippocampal astrocytes. Emulsion receptor autoradiography using a newly developed ligand, [I-125]GR231118 in the presence of PYY, hPP or BI BP3226 (1 mu M), pharmacologically established the Y-1 nature of these rece ptors. Specific [I-125]GR231118 binding was competed by PYY and the selecti ve Y-1 antagonist BIBP3226 but not by hPP (a Y-4/Y-5 agonist) . Similar aut oradiographic labeling patterns were obtained using [I-125][Leu(31).Pro(34) ]PYY (a Y-1/Y-4/Y-5 agonist)whereas [I-112]PYY3-36 (a Y-2/Y-5 agonist) fail ed to generate any specific signal. Hence, rat cultured hippocampal astrocy tes express a typical Y-1 receptor without evidence for the presence of Y-2 , Y-4 or Y-5 subtypes. These data suggest a preferential regulation by NPY, acting via the Y-1 receptors, of astrocytic function. GLIA 30.82-91, 2000. (C) 2000 Wiley-Liss, Inc.