Figure 6.

[³H]DPCPX (2 nM) versus R-PIA (a) or CHA (b) competition-binding assays (90 min, 25°C in 50 mM Tris(HCl) buffer) performed at human A₁ receptors stably expressed in CHO cell membranes. Membranes had undergone either 10 U ml⁻¹ ADA pretreatment during the preparation plus subsequent addition of 0.1 U ml⁻¹ ADA in the assay in the absence or presence of 100 μM Gpp(NH)p, or membranes have undergone 7 M urea pretreatment during preparation. Data points represent the mean+s.e.m. obtained from three or four separate experiments conducted in triplicate. Curves superimposed on the data represent the best of equation (5) estimated using simultaneous global nonlinear regression with Prism. All other details as for Figure 1.