Figure 4.
Effect of suramin on the association and dissociation of [35S]GTPγS binding to CHO cell membranes expressing the dopamine D2 receptor. Dopamine-stimulated [35S]GTPγS association and dissociation assays were carried out as described in the Materials and methods section. (a) Association assays were performed for 60 min in the presence of a range of concentrations of suramin. (b) Dissociation assays were performed as described in the Materials and methods section. Association was carried out for 60 min and suramin was added to the assay after this association phase with or without 10 μM non-radioactive GTPγS, and dissociation allowed to proceed for a further 30 min. Suramin added without the 10 μM non-radiolabelled GTPγS had no effect on dissociation, but did prevent any further association of the [35S]GTPγS. The graphs show data from representative experiments carried out three times with similar results.