A novel radioiodinated ligand of the butyrophenone type has been synthesized for the quantification and characterization of dopamine D2 receptors. This haloperidol-derived ligand, haloperidol-succinylglycyl-[125I]iodotyrosine ([125I]HSGTI), binds rapidly (equilibrium is reached within 30 min, at 10 pM and 37°C) and with high affinity (K d=0.3 nM) to bovine striatal membranes. Its pharmacology, determined by competitive displacement with dopaminergic and non-dopaminergic drugs, is characteristic of binding to dopamine D2 receptors.
