Fig. 1.
In GP synaptosomal membranes, H3R activation decreases A2AR affinity for the agonist CGS-21680, whereas A2AR activation increases H3R affinity for the agonist immepip. a Saturation binding of [3H]-CGS-21680 to A2ARs. Specific receptor binding was determined by subtracting the binding in the presence of the A2AR antagonist ZM-241385 (10 μM) from total binding. Points are means ± range from duplicates from a single experiment, which was repeated a further four times. The line drawn is the best fit to a hyperbola. Best-fit values for the equilibrium dissociation constant (Kd) and maximum binding (Bmax) are given in the text. b The H3R agonist immepip (30 nM) decreases the potency of CGS-21680 to inhibit the specific binding of [3H]-CGS-21680 to A2ARs. c The A2AR agonist CGS-21680 (6 nM) increases the potency of immepip to inhibit [3H]-NMHA binding to H3Rs. For panels b and c, values are expressed as the percentage of control binding and correspond to means ± SEM from three replicates from representative experiments. The line drawn is the best fit to a logistic equation for a one-site model. The analysis of the Ki and pKi values calculated from the best-fit IC50 estimates is presented in the text