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Sub‐population of cultured hippocampal astrocytes expresses neuropeptide Y Y1 receptors

The expression and pharmacological characterization of neuropeptide Y (NPY) receptors of the Y1 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 Y1 receptors on cultured hippocampal astrocytes using similar strategies. Immunocytochemical experiments were carried out using three antisera directed against distinct domains (amino acids sequence 185–203, 198–213 and 355–382) of the Y1 receptor. Double‐labeling experiments and confocal microscopy with these Y1 receptor antisera demonstrated their recognition of the same sub‐population (20%) of GFAP‐positive astrocytes in culture. The immunostaining seen with all three Y1 receptor antisera took the form of large irregular clusters distributed throughout cell bodies and processes. Further experiments using radioactive ligands confirmed the presence of NPY receptors on cultured hippocampal astrocytes. Emulsion receptor autoradiography using a newly developed ligand, [125I]GR231118 in the presence of PYY, hPP or BIBP3226 (1 μM), pharmacologically established the Y1 nature of these receptors. Specific [125I]GR231118 binding was competed by PYY and the selective Y1 antagonist BIBP3226 but not by hPP (a Y4/Y5 agonist). Similar autoradiographic labeling patterns were obtained using [125I][Leu31.Pro34]PYY (a Y1/Y4/Y5 agonist) whereas [125I]PYY3–36 (a Y2/Y5 agonist) failed to generate any specific signal. Hence, rat cultured hippocampal astrocytes express a typical Y1 receptor without evidence for the presence of Y2, Y4 or Y5 subtypes. These data suggest a preferential regulation by NPY, acting via the Y1 receptors, of astrocytic function. GLIA 30:82–91, 2000. © 2000 Wiley‐Liss, Inc.