Guanosine 5′-(γ-[35S]thio)triphosphate (GTPγ[35S]) autoradiography was performed as described earlier [21] with minor modifications. GluA1+/+ and GluA1−/− mice were decapitated, their brains removed, and frozen on dry ice and stored at −80°C. Coronal sections of 14 µm were cut using a cryostat (Leica CM 3050 S, Leica Microsystems, Nussloch, Germany), thaw-mounted on Superfrost slides (Mentzel-Glaeser, Brauschweig, Germany) and stored at −80°C. Air-dried sections were surrounded by hydrophobic pen (Daido Sangyo Co., Tokyo, Japan). Sections were preincubated at 20°C for 20 min in 50 mM Tris-HCl (pH 7.4), 1 mM EDTA, 100 mM NaCl and 5 mM MgCl2 in a volume of 0.95 ml per slide. Thereafter, in the second preincubation, the sections were loaded with 2 mM guanosine diphosphate (GDP) in the same buffer for 60 min at 20°C in the presence of 1 µM adenosine A1 receptor blocker 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, Tocris). DPCPX was added to reduce the extensive basal activity of adenosine receptors [22]. The final 90-min incubation with GTPγ[35S] (54–68 pM; Perkin Elmer, Boston, USA) took place in the buffer supplemented with 2 mM GDP, 1 mM dithiothreitol, 1
