Properties of [3H]Haloperidol and [3H]Dopamine Binding Associated with Dopamine Receptors in Calf Brain Membranes

Abstract

[ 3 H]Haloperidol and [ 3 H]dopamine bind in saturable fashion to membranes from calf brain with high affinity and other characteristics indicating an association with post-synaptic dopamine receptors. Kinetic analysis of rates of association and dissociation yields K D values in agreement with equilibrium measurements. Regional variations in [ 3 H]dopamine and [ 3 H]haloperidol binding are parallel and correspond to regional differences in dopaminergic innervation. Drug specificity does not appear to differ between limbic and striatal areas. The relative potencies of various agonists and antagonists on the binding of the two ligands parallel their pharmacological actions at dopamine receptor sites. Dopamine agonists have 6-38 times more affinity for [ 3 H]dopamine than [ 3 H]haloperidol binding sites. By contrast, dopamine antagonists have 20-12,000 times more affinity for [ 3 H]haloperidol than [ 3 H]dopamine binding sites. Ergot derivatives, including d -lysergic acid diethylamide, and other serotonin antagonists have substantial affinity for both types of binding.