Fig. 3.

Association (a) and dissociation (b) curves for [³H]XAC binding to rabbit striatal A₂-adenosine receptors. Total binding at A₂-receptors (□) and non-specific binding (○) are shown. Concentration of the radioligand was 0.7 nM, in the presence of 50 nM CPX. Dissociation was initiated after 75 min by the addition of 100 μM N⁶-cyclopentyladenosine. Data were fit to exponential curves by weighted non-linear least squares curvefitting. The experiments were carried out twice with essentially identical results. Association and dissociation constants of 0.13 min⁻¹ nM⁻¹ and 0.36 min⁻¹, respectively, were calculated from linear transformation of the data. The linear regression coefficients for association and dissociation plots were 0.09 and 0.824, respectively.