MULTIPLE DOPAMINE BINDING-SITES - SUBCELLULAR-LOCALIZATION AND BIOCHEMICAL CHARACTERIZATION

Abstract— The biochemical and pharmacological characteristics of dopamine agonist and antagonist binding to rat striatal subcellular fractions were studied and compared to the localization of dopamine–sensitive adenylate cyclase activity. The highest specific activity of adenylate cyclase sensitive to dopamine was associated almost exclusively with the crude synaptic membrane fraction (P2). Using [3H]‐haloperidol, [3H]apomorphine and [3H]spiroperidol as markers for the dopamine receptor, high affinity and stereoselective specific binding was observed for the crude synaptic fraction and the microsomal fraction (P3). Analysis of the binding of [3H]haloperidol to the striatal microsomal preparation revealed a homogeneous receptor site with a Kd value of 3.0 nm. The data for [3H]haloperidol binding to the crude synaptosomal fraction showed two saturable binding sites with Kd values of 2.5 nm and 12.5 nm. A similar heterogeneous binding profile was observed in the P2 fraction using [3H]apomorphine. The Kd values for [3H]apomorphine in this fraction were determined to be 1.2 nm and 7.2 nm. The effects of various biochemical parameters including ionic strength, salt concentration and pH on the binding of [3H]haloperidol to the P2 fraction were also studied. Overall, these data show that the subcellular localization of multiple binding sites in the crude synaptosomal fraction and the identification of specific binding to purified synaptosomes correlate with the subcellular distribution of striatal dopamine‐sensitive adenylate cyclase activity. Copyright © 1979, Wiley Blackwell. All rights reserved