DOPAMINE-D2 RECEPTOR-BINDING PROPERTIES OF [H-3] U-86170, A DOPAMINE RECEPTOR AGONIST

U-86170F, an imidazoguinolinone, is a potent dopamine D2 agonist, binding with high affinity to the dopamine D2 receptor. A K(d) of 0.99 nM was determined in membranes from Chinese hampster ovarian (CHO) cells transfected with the D2 receptor and a K(d) of 1.72 nM was obtained in rat striatal homogenates. GTP sensitivity was demonstrated when its addition (300-mu-M) reduced [H-3]U-86170 binding by 60%. This agonist ligand is especially effective in identifying agonists and partial agonists, as well as antagonists, and affords a more precise evaluation of their affinity for the dopamine D2 receptor, without the use of multiple site analysis, than does an antagonist [H-3]-ligand.