Betahistine (0-10 μM) inhibits [I]iodoproxyfan binding to membranes of CHO (rH3(445)R) and CHO (hH3(445)R) cells with IC50 values of 1.9 μM and 3.3 μM, respectively. Lead to Ki values of 1.4 μM and 2.5 μM, respectively.
Betahistine (0-10 μM) has a regulating function on cAMP formation in CHO (rH3(445)R), CHO (rH3(413)R), and CHO (hH3(445)R) cells. At low concentrations, betahistine behaves an apparent inverse agonist, and progressively enhances cAMP formation with EC50 values of 0.1 nM, 0.05 nM and 0.3 nM, respectively. In contrast, at concentrations higher than 10 nM, betahistine inhibits cAMP formation with an EC50 value of 0.1 μM in CHO (rH3(445)R) and full agonist activity.