[(3)H]-F13640, a novel, selective and high-efficacy serotonin 5-HT(1A) receptor agonist radioligand.

F13640 is a selective and high-efficacy serotonin 5-HT(1A) receptor agonist that demonstrates outstanding analgesic potential in different animal models. Here, we use the radiolabelled compound to further characterise its binding properties at 5-HT(1A) receptors. F13640 was tritium-labelled to 47 and 64 Ci/mmol specific activity and used as radioligand at membrane preparations of CHO cells expressing human (h) 5-HT(1A) receptors.

Mutant 5-hydroxytryptamine 1A receptor D116A is a receptor activated solely by synthetic ligands with a rich pharmacology.

Like other biogenic amine G protein-coupled receptors, mutation of the conserved aspartatic residue into alanine at position 116 (D116A(3.32)) in the 5-hydroxytryptamine (5-HT)(1A) receptor greatly affects 5-HT binding and signal transduction. [(3)H]8-Hydroxy-2-dipropylaminotetralin (8-OH-DPAT) and [(3)H]-N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY100,635) are capable to bind the 5-HT(1A)-D116A mutant and, using these radioligands, we show here that this mutation dramatically reduces the affinities of the selective 5-HT(1A) agonists N-(3-chloro-4-fluorobenzoyl)-4-fluoro-4-[(5-methylpyridin-2-yl)-methylamino methyl]piperidine (F13640), 3-chloro-4-fluorophenyl-(4-fluorophenyl-4-{[(5-methyl-6 methylamino-pyridin-2-ylmethyl)-amino]-methyl}-piperidin-1-yl-methanone (F13714), and 2-[5-[3-(4-methylsulfonylamino)benzyl-1,4-oxadiazol-5-yl]-1H-indole-3-yl]ethylamine (L694247) and that of 5-carboxamidotryptamine.

Activation of G proteins and extracellular signal-regulated kinase 1/2 phosphorylation via human dopamine D4.4 receptors: differential pathway-dependent potencies of receptor agonists.

Agonist activity at recombinant human dopamine D4.4 receptors was compared in stably transfected CHO cells using two functional readouts: G protein activation by [35S]GTPgammaS binding and phosphorylation of extracellular signal-regulated kinase 1/2 (pERK1/2). Results with a large series of agonists reveal markedly higher relative agonist efficacy in the pERK1/2 assay compared with [35S]GTPgammaS binding, while potencies were generally higher in the latter readout.

Action of novel antipsychotics at human dopamine D3 receptors coupled to G protein and ERK1/2 activation.

The effects of new generation antipsychotic drugs (APDs) targeting dopamine D(2) and serotonin 5-HT(1A) receptors were compared with typical and atypical APDs on phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2) and measures of G protein activation in CHO cell lines stably expressing the human dopamine D(3) receptor. The preferential dopamine D(3) agonists (+)-7-OH-DPAT and PD128907, like dopamine and quinelorane, efficaciously stimulated ERK 1/2 phosphorylation at dopamine D(3) receptors. In contrast, in [(35)S]GTPgammaS binding experiments, (+)-7-OH-DPAT exhibited partial agonist properties, while PD128907 and quinelorane maintained full agonist properties.

Pharmacological characterization of protease activated receptor-1 by a serum responsive element-dependent reporter gene assay: major role of calmodulin.

We studied the protease activated receptor-1 coupling to a serum response element (SRE)-dependent luciferase activity readout in transfected COS-7 cells. Thrombin, with a pEC50 of 10.5, was 3000-fold more potent than the peptide agonists SFLLR and its derived compound C721-40 in stimulating luciferase activity, although the three agonists exhibited similar efficacy at the maximal concentration tested.

Constitutive coupling of a chimeric dopamine D2/alpha 1B receptor to the phospholipase C pathway: inverse agonism to silent antagonism by neuroleptic drugs.

Neuroleptic drugs have been suggested to act as inverse agonists at the dopamine D2 receptor, but no link between therapeutic efficacy and ligand's intrinsic activity could be determined. Since the resolving capacity to monitor inverse agonism at dopamine D2 receptors is limited, we speculated that receptor constitutive activation could be enhanced by constructing chimeric D2/alpha 1B receptors. Marked inverse agonist responses with a series of dopamine antagonists were obtained by: 1) exchange of the D 2short receptor's 3ICL by that of the alpha 1B-adrenoceptor, 2) incorporation of an activating mutation (Ala 279 Glu) in the distal portion of its 3ICL, and 3) coexpression with a G alpha11 protein.