A putative new melatonin binding site in sheep brain, MTx: preliminary observations and characteristics.

In mammals, MT and MT melatonin receptors are high affinity G protein-coupled receptors and are thought to be involved in the integration of the melatonin signaling throughout the brain and periphery. In the present study, we describe a new melatonin binding site, named MTx, with a peculiar pharmacological profile. This site had a low affinity for 2-[I]-melatonin in saturation assays in hypothalamus and retina (pK = 9.

Mechanistic characterization of S 38093, a novel inverse agonist at histamine H3 receptors.

Histaminergic H3 inverse agonists, by stimulating central histamine release, represent attractive drug candidates to treat cognitive disorders. The present studies aimed to describe the mechanistic profile of S 38093 a novel H3 receptors inverse agonist. S 38093 displays a moderate affinity for rat, mouse and human H3 receptors (Ki=8.

Peripheral injections of melanin-concentrating hormone receptor 1 antagonist S38151 decrease food intake and body weight in rodent obesity models.

The compound S38151 is a nanomolar antagonist that acts at the melanin-concentrating hormone receptor 1 (MCH(1)). S38151 is more stable than its purely peptide counterpart, essentially because of the blockade of its N-terminus. Therefore, its action on various models of obesity was studied.

S32212, a novel serotonin type 2C receptor inverse agonist/α2-adrenoceptor antagonist and potential antidepressant: I. A mechanistic characterization.

Although most antidepressants suppress serotonin (5-HT) and/or noradrenaline reuptake, blockade of 5-HT(2C) receptors and α(2)-adrenoceptors likewise enhances monoaminergic transmission. These sites are targeted by the urea derivative N- [4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]-1,2-dihydro-3-H-benzo[e]indole-3-carboxamide (S32212). S32212 was devoid of affinity for monoamine reuptake sites, yet displayed pronounced affinity (pK(i), 8.

Synthesis of new 8(S)-HETE analogs and their biological evaluation as activators of the PPAR nuclear receptors.

Structural modifications around 8-HETE (8-hydroxyeicosatetraenoic acid), a natural agonist of the PPAR (peroxisome proliferator-activated receptor) nuclear receptors have led previously to the identification of a promising analog, the quinoline S 70655. Series of novel quinoline or benzoquinoline derivatives were designed through the modification of this lead. Variations of the nature of the aromatic core and of the side chains were carried out.

Design, synthesis and pharmacological evaluation of novel naphthalenic derivatives as selective MT(1) melatoninergic ligands.

Novel heterodimer analogues of melatonin were synthesized, when agomelatine (1) and various aryl units are linked via a linear alkyl chain through the methoxy group. The compounds were tested for their actions at melatonin receptors. Several of these ligands are MT(1)-selective with nanomolar or subnanomolar affinity.

S38151 [p-guanidinobenzoyl-[Des-Gly(10)]-MCH(7-17)] is a potent and selective antagonist at the MCH(1) receptor and has anti-feeding properties in vivo.

Structure-activity relationships studies have established the minimal sequence of melanin-concentrating hormone (MCH) that retains full agonist potency at the MCH(1), to be the dodecapeptide MCH(6-17). The alpha-amino function is not required for activity since arginine(6) can be replaced by p-guanidinobenzoyl, further improving activity. We report that the deletion of glycine in this short potent agonist (EC(50) 3.

Design and synthesis of 3-phenyltetrahydronaphthalenic derivatives as new selective MT2 melatoninergic ligands. Part II.

Following our studies of the melatoninergic receptors, we have developed new tetrahydronaphthalenic derivatives of melatonin that have been tested as selective melatonin receptors ligands. Regarding the role of the phenyl substituent to obtain selective ligands, modulation of selectivity and activity have been achieved by modifications of the acyl group and substitutions on the phenyl ring. Ten of the seventeen evaluated derivatives have MT(2) receptor affinity similar to that of melatonin.

Synthesis of 3-phenylnaphthalenic derivatives as new selective MT(2) melatoninergic ligands.

A series of naphthalenic analogues of melatonin were prepared and evaluated as melatonin receptor MT(2) selective ligands. Activity and MT(2) selectivity can be modulated with suitable variations of the C-3 phenyl and the acyl group on the C-1 side chain. Surprisingly, in contrast with what had been previously described in other series (2-benzylindoles, 2-benzylbenzofurans and 3-phenyltetralins), the presence of a C-3 phenyl with a functional group on the meta position seems to be primordial for MT(2) affinity and selectivity.

Molecular cloning and pharmacological characterization of rat melatonin MT1 and MT2 receptors.

In order to interpret the effects of melatonin ligands in rats, we need to determine their activity at the receptor subtype level in the corresponding species. Thus, the rat melatonin rMT(1) receptor was cloned using DNA fragments for exon 1 and 2 amplified from rat genomic DNA followed by screening of a rat genomic library for the full length exon sequences. The rat rMT(2) receptor subtype was cloned in a similar manner with the exception of exon 1 which was identified by screening a rat genomic library with exon 1 of the human hMT(2) receptor.

S33138 [N-[4-[2-[(3aS,9bR)-8-cyano-1,3a,4,9b-tetrahydro[1]-benzopyrano[3,4-c]pyrrol-2(3H)-yl)-ethyl]phenylacetamide], a preferential dopamine D3 versus D2 receptor antagonist and potential antipsychotic agent: I. Receptor-binding profile and functional actions at G-protein-coupled receptors.

The novel, potential antipsychotic, S33138 (N-[4-[2-[(3aS,9bR)-8-cyano-1,3a,4,9b-tetrahydro[1]benzopyrano[3,4-c]pyrrol-2(3H)-yl)-ethyl]phenylacetamide), displayed approximately 25-fold higher affinity at human (h) dopamine D(3) versus hD(2L) (long isoform) and hD(2S) (short isoform) receptors (pK(i) values, 8.7, 7.1, and 7.

New ligands at the melatonin binding site MT(3).

The third melatonin binding site, MT3 is a non-classical one since it is not a seven transmembrane domains receptor, but an enzyme, quinone reductase 2. A major concern for the study of the physiological role of this site is the lack of specific ligands, permitting to more accurately dissect the pathways linked to the activation of MT3. Indeed, in the course of finding new ligands, we identified a new series of compounds with affinity to the binding site in the nM range, particularly 2,3-dimethoxy 7-hydroxy 10-methyl 5H 10H indeno(1,2-b)indol-10-one (DMHMIO), with a Ki of 190 pM.

Molecular tools to study melatonin pathways and actions.

Melatonin, an indoleamine neurohormone that is synthesized mainly in the pineal gland and derived from 5-HT, has many effects on a wide range of physio-pathological functions. Some of these effects are mediated by the interactions of melatonin with the two melatonin MT1 and MT2 receptors. Other effects are often suggested to be due to the chemical antioxidant nature of this indoleamine, and are observed at high, non-physiological concentrations.

Functional characterization of human neuropeptide Y receptor subtype five specific antagonists using a luciferase reporter gene assay.

Neuropeptide Y (NPY) has several receptors; one of them, the neuropeptide Y5 receptor (NPY5) seems involved in feeding behavior in mammals. Although this particular receptor has been extensively studied in the literature, the difficulties encountered to obtain a stable cell line expressing this recombinant receptor have impaired the development of tools necessary to establish its molecular pharmacology. We thus established a method for the functional study of new ligands.

Preparation of 4-azaindole and 7-azaindole dimers with a bisalkoxyalkyl spacer in order to preferentially target melatonin MT1 receptors over melatonin MT2 receptors.

Several 4-azaindole and 7-azaindole dimer analogues of melatonin with a bisalkoxyalkyl spacer between the position 5 of each heterocycle were synthetized. Our aim was to investigate the influence of the spacers length on the selectivity of such compounds for the MT(1) receptors over the MT(2) receptors. Our results suggest the distance between indole ring seems to be an important parameter in determining the potency of binding with melatonin receptor site.

Molecular pharmacology of the ovine melatonin receptor: comparison with recombinant human MT1 and MT2 receptors.

The variations of the pharmacological properties of melatonin receptors between different mammalian species in transfected cell lines have been poorly investigated. In the present study, melatonin analogues have been used to characterize the pharmacology of the recombinant ovine melatonin receptor (oMT1) expressed in CHO cell lines and the native oMT1 from the pars tuberalis (PT). Studies with selective ligands on native and transfected oMT1 showed similar properties for binding affinities [r2(PT/CHO) = 0.

Synthesis of 5-substituted-2,3-dihydro-1,4-benzoxathiins: biological evaluation as melatonin receptors ligands.

The synthesis of benzoxathiins bearing a retroamide function is described from 8-hydroxythiochroman, the key step involving the synthesis of the benzoxathiin ring through a sulfonium salt. These new melatonin analogues were evaluated on human receptors MT1 and MT2 and have a similar affinity to that of melatonin itself.

New selective ligands of human cloned melatonin MT1 and MT2 receptors.

Melatonin has a key role in the circadian rhythm relay to periphery organs. Melatonin exerts its multiple roles mainly through two seven transmembrane domain, G-coupled receptors, namely MT1 or MT2 receptors. A pharmacological characterization of these human cloned melatonin hMT1 and hMT2 receptors stably expressed in HEK-293 or CHO cells is presented using a 2-[125I]-iodo-melatonin binding assay and a [35S]-GTPgammaS functional assay.

Design and synthesis of naphthalenic dimers as selective MT1 melatoninergic ligands.

We report the synthesis and binding properties at MT(1) and MT(2) receptors of the first example of agomelatine (N-[2-(7-methoxynaphth-1-yl)ethyl]acetamide) dimers in which two agomelatine moieties are linked together through their methoxy substituent by a polymethylene side chain according to the "bivalent ligand" approach. Some of these compounds behave as MT(1)-selective ligands. The most selective one (5) behaves as an antagonist.

Design and synthesis of 3-phenyl tetrahydronaphthalenic derivatives as new selective MT2 melatoninergic ligands.

Tetrahydronaphthalenic analogues of melatonin have been synthesized and evaluated as melatonin receptor ligands. Introduction of a phenyl substituent in the 3-position of the tetraline ring allows to obtain MT(2) selective ligands. Activity and MT(2) selectivity can be modulated with suitable modifications of the N-acyl substituent.

Peroxisome proliferator-activated receptor gamma (PPARgamma ) as a molecular target for the soy phytoestrogen genistein.

The principal soy phytoestrogen genistein has an array of biological actions. It binds to estrogen receptor (ER) alpha and beta and has ER-mediated estrogenic effects. In addition, it has antiestrogenic effects as well as non-ER-mediated effects such as inhibition of tyrosine kinase.

Molecular identification of the long isoform of the human neuropeptide Y Y5 receptor and pharmacological comparison with the short Y5 receptor isoform.

The neuropeptide Y Y5 receptor gene generates two splice variants, referred to here as Y5(L) (long isoform) and Y5(S) (short isoform). Y5(L) mRNA differs from Y5(S) mRNA in its 5' end, generating a putative open reading frame with 30 additional nucleotides upstream of the initiator AUG compared with the Y5(S) mRNA. The purpose of the present work was to investigate the existence of the Y5(L) mRNA.

Differential actions of antiparkinson agents at multiple classes of monoaminergic receptor. II. Agonist and antagonist properties at subtypes of dopamine D(2)-like receptor and alpha(1)/alpha(2)-adrenoceptor.

The accompanying multivariate analysis of the binding profiles of antiparkinson agents revealed contrasting patterns of affinities at diverse classes of monoaminergic receptor. Herein, we characterized efficacies at human (h)D(2SHORT(S)), hD(2LONG(L)), hD(3), and hD(4.4) receptors and at halpha(2A)-, halpha(2B)-, halpha(2C)-, and halpha(1A)-adrenoceptors (ARs).

Differential actions of antiparkinson agents at multiple classes of monoaminergic receptor. I. A multivariate analysis of the binding profiles of 14 drugs at 21 native and cloned human receptor subtypes.

Because little comparative information is available concerning receptor profiles of antiparkinson drugs, affinities of 14 agents were determined at diverse receptors implicated in the etiology and/or treatment of Parkinson's disease: human (h)D(1), hD(2S), hD(2L), hD(3), hD(4), and hD(5) receptors; human 5-hydroxytryptamine (5-HT)(1A), h5-HT(1B), h5-HT(1D), h5-HT(2A), h5-HT(2B), and h5-HT(2C) receptors; halpha(1A)-, halpha(1B)-, halpha(1D)-, halpha(2A)-, halpha(2B)-, halpha(2C)-, rat alpha(2D)-, hbeta(1)-, and hbeta(2)-adrenoceptors (ARs); and native histamine(1) receptors. A correlation matrix (294 pK(i) values) demonstrated substantial "covariance". Correspondingly, principal components analysis revealed that axis 1, which accounted for 76% variance, was associated with the majority of receptor types: drugs displaying overall high versus modest affinities migrated at opposite extremities.