G protein-coupled receptors (GPCRs) represent attractive drug targets because they participate in a wide range of physiological processes and are believed to play a role in a variety of disease states. At least a third of all prescription drugs on the market today are molecules acting as agonists or antagonists of the GPCR. Receptor-ligand interaction studies are pivotal in the successful ident...

Here we describe a fully automated, hands-free radioligand filtration binding assay for dopamine D3 receptors. Three separate instruments were linked in tandem to perform the following operations: The Genmate and Genesis were linked to perform liquid handling, incubation, and the scheduling operations, while an automated harvester was used to perform rapid filtration. To minimize carryover of c...

To determine the exact potency of inhibitors acting at the glycine site of the NMDA receptor complex using [3H]glycine as a radioligand, the true equilibrium constant (KD) of the radioligand has to be known. To achieve this goal, (1) the contamination of water by glycine was studied, (2) the true affinity of glycine for the NMDA receptor was estimated by different methods, and (3) the inhibitio...

In view of the therapeutic importance of dopamine D3 and D2 receptors, there remains considerable interest in novel ligands. Herein, we show that the tetrahydroisoquinoline 1H-indole-2carboxylic acid {4-[2-(cyano-3,4-dihydro-1H-isoquinolin-2-yl)ethyl]-cyclohexyl}-amide (SB269,652) behaves as an atypical, allosteric antagonist at D3 and D2 receptors. Accordingly, SB269,652 potently (low nanomola...

G-protein-coupled receptors (GPCRs) represent the largest family of receptors involved in transmembrane signaling. Although these receptors were generally believed to be monomeric entities, accumulating evidence supports the presence of GPCRs in multimeric forms. Here, using immunoprecipitation as well as time-resolved fluorescence resonance energy transfer to assess protein-protein interaction...

Although equilibrium competitive radioligand binding studies are often used to characterize hormone and neurotransmitter receptors, the kinetics of such experiments have not been extensively explored. The interactions of the radioligand and competitor with the receptors can be described by two differential equations which can be solved to yield a single equation describing the binding of the ra...

We have developed a radioligand receptor assay (RRA) with sufficient sensitivity and specificity for quantifying follitropin (FSH) in unextracted serum samples. Standard curves prepared by adding pituitary FSH to either buffer or gonadotropin-free serum were parallel and statistically indistinguishable in this assay, whereas gonadotropin-free serum alone had no activity. Cross-reactivity with r...

The characteristics of a high-affinity antagonist radioligand are compared with those a high-affinity agonist in binding to the cloned corticotropin-releasing factor receptor type 1 (CRF-R1) and type 2 (CRF-R2) and to the native receptors that exist in rat cerebellum and brain stem. The relative potencies of CRF antagonists and agonists to the two types of cloned CRF receptors overexpressed sta...

The interaction of human growth hormone with human lymphocytes from an established culture (IM-9) was studied using lz51-human growth hormone. The binding of l*51human growth hormone was rapid; with human growth hormone at 0.1 no a steady state was observed in 90 min at 30”. Bound labeled human growth hormone was dissociated rapidly by addition of excess unlabeled human growth hormone. Binding ...