Privileged structure based ligands for melanocortin receptors--4,4-disubstituted piperidine derivatives.

Homologation and cyclization back to the chiral methine of compound 3 yields achiral 4,4-disubstituted piperidine privileged structures (e.g., 8a) useful in the construction of melanocortin 4 receptor (MC4R) ligands.

Privileged structure based ligands for melanocortin-4 receptors--aliphatic piperazine derivatives.

Aliphatic carbocyclic replacement of the benzyl group of compound 1 yielded compounds with high affinity for the melanocortin-4 receptor (MC4R). Compounds with a cyclohexyl group showed a consistent high affinity, while different polar groups with less basicity were good replacements for the original diethyl amines. Substitution of the polar group found in these privileged structures with an aliphatic moiety produced compounds with high affinity for MC4R.

Synthesis and structure-activity relationships of novel dipeptides and reduced dipeptides as ligands for melanocortin subtype-4 receptor.

A series of benzylic piperazines (e.g., 4 and 5) attached to an 'address element', the dipeptide H-D-Tic-D-p-Cl-Phe-OH, 3 has been identified as ligands for the melanocortin subtype-4 receptor (MC4R).

Privileged structure based ligands for melanocortin receptors--substituted benzylic piperazine derivatives.

Replacement of the aryl piperazine moiety in compound 1 with a variety of substituted benzylic piperazines (6) yields compounds that afford melanocortin receptor 4 (MCR4) activity. Analogs with ortho substitution on the aromatic ring afforded the highest affinity. Resolution of the stereocenter of the benzylic piperazine based privileged structure revealed that the R-enantiomer was more active.

Privileged structure-based ligands for melanocortin receptors-tetrahydroquinolines, indoles, and aminotetralines.

Substitution of the aryl sulfonamide moiety contained in MC4 agonist 1 with bicyclic heterocycles and aminotetralines produced compounds with MC4 activity. The heterocycles represent alternative privileged structures to that contained in 1. Compounds in which the polar group of the privileged structure was displayed in an endocyclic fashion were not as active as the parent agonist 1, while those with an exocyclic polar group afforded activity competitive with 1.

[3H]LY334370, a novel radioligand for the 5-HT1F receptor. I. In vitro characterization of binding properties.

[(3)H]LY334370 was developed as a radioligand to study the characteristics of this compound's interaction with the 5-HT(1F) receptor. Monovalent or divalent cations did not enhance the binding of [(3)H]LY334370 to the cloned human 5-HT(1F) receptor. In the presence of MgCl(2), the time to reach equilibrium was approximately 2 h, while in its absence equilibrium was reached in less than 1 h.

Synthesis and structure-activity relationships of novel arylpiperazines as potent and selective agonists of the melanocortin subtype-4 receptor.

The melanocortin receptors have been implicated as potential targets for a number of important therapeutic indications, including inflammation, sexual dysfunction, and obesity. We identified compound 1, an arylpiperazine attached to the dipeptide H-d-Tic-d-p-Cl-Phe-OH, as a novel melanocortin subtype-4 receptor (MC4R) agonist through iterative directed screening of nonpeptidyl G-protein-coupled receptor biased libraries. Structure-activity relationship (SAR) studies demonstrated that substitutions at the ortho position of the aryl ring improved binding and functional potency.

Substituted furo[3,2-b]pyridines: novel bioisosteres of 5-HT 1F receptor agonists.

Synthesis and evaluation of a series of 2,3,5- and 3,5-substituted furo[3,2-b]pyridines were undertaken in order to investigate their utility as bioisosteres of 5-HT(1F) receptor agonist indole analogues, 1-3. The replacement proved to be effective, providing compounds with similar 5-HT(1F) receptor affinity and improved selectivity when compared with the indole analogues. Through these studies we identified 4-fluoro-N-[3-(1-methyl-piperidin-4-yl)-furo[3,2-b]pyridin-5-yl]-benzamide (5), a potent and selective 5-HT(1F) receptor agonist with the potential to treat acute migraine.

Novel potent 5-HT(1F) receptor agonists: structure-activity studies of a series of substituted N-[3-(1-methyl-4-piperidinyl)-1H-pyrrolo[3,2-b]pyridin-5-yl]amides.

Compound 1a (LY334370), a selective 5-HT(1F) receptor agonist (SSOFRA), inhibited dural inflammation in the neurogenic plasma protein extravasation model of migraine and demonstrated clinical efficacy for the acute treatment of migraine. Although 1a was greater than 100-fold selective over both the 5-HT(1B) and 5-HT(1D) receptors, it exhibited appreciable 5-HT(1A) receptor affinity. Described here is the synthesis and evaluation of a series of pyrrolo[2,3-c]pyridine and pyrrolo[3,2-b]pyridine (2a and 3a) as well as pyrrolo[3,2-d]pyrimidine (4a) analogues of 1a, compounds prepared in an effort to identify SSOFRAs with improved selectivity over other 5-HT(1) receptor subtypes.

N-[3-(2-Dimethylaminoethyl)-2-methyl-1H- indol-5-yl]-4-fluorobenzamide: a potent, selective, and orally active 5-HT(1F) receptor agonist potentially useful for migraine therapy.

Recent studies have demonstrated that selective 5-HT(1F) receptor agonists inhibit neurogenic dural inflammation, a model of migraine headache, indicating that these compounds may be effective therapies for the treatment of migraine pain. This communication describes the synthesis and discovery of a novel compound, N-[3-(2-(dimethylamino)ethyl)-2-methyl-1H-indol-5-yl]-4-fluorobenzamide (4), which possesses high binding affinity and selectivity at the 5-HT(1F) receptor relative to more than 40 other serotonergic and nonserotonergic receptors examined.

The novel 5-Hydroxytryptamine(1A) antagonist LY426965: effects on nicotine withdrawal and interactions with fluoxetine.

LY426965 [(2S)-(+)-1-cyclohexyl-4-[4-(2-methoxyphenyl)-1-piperazinyl]2-methyl- 2-phenyl-1-butanone monohydrochloride] is a novel compound with high affinity for the cloned human 5-hydroxytryptamine (HT)(1A) receptor (K(i) = 4.66 nM) and 20-fold or greater selectivity over other serotonin and nonserotonin receptor subtypes. Both in vitro and in vivo studies indicate that LY426965 is a full antagonist and has no partial agonist properties.

N-Methyl-5-tert-butyltryptamine: A novel, highly potent 5-HT1D receptor agonist.

It has been observed that reported 5-HT1D receptor agonists have at least one heteroatom (N, O, or S) on the 5-substituent of the indole. This has led to the hypothesis that a 5-substituent capable of participating in hydrogen bonding is critical for conveying high affinity. This article describes the synthesis and biological evaluation of a new series of 5-alkyltryptamine analogues, which does not have a heteroatom in the 5-substituent group.

Multiple subtypes of serotonin receptors are expressed in rat sensory neurons in culture.

[3H]5-HT revealed the presence of serotonin receptors in cultured rat sensory neurons. [3H]5-CT binding was inhibited by cyanopindolol with an IC50 of 0.87 +/- 0.

Native 5-HT1B receptors expressed in OK cells display dual coupling to elevation of intracellular calcium concentrations and inhibition of adenylate cyclase.

The opossum kidney (OK) cell line has been shown previously to express endogenous 5-HT1B receptors which negatively couple to adenylate cyclase. Since other Gi-linked receptors have been shown to inhibit adenylate cyclase and to elevate intracellular calcium concentrations ([Ca2+]i), studies were initiated to determine whether native opossum 5-HT1B receptors could also display dual coupling to these signal transduction mechanisms. Saturation studies using [125I](-)-iodocyanopindolol ([125I]CYP) to radiolabel the 5-HT1B receptor in OK cell membranes (in the presence of 3 microM (-)-isoproterenol to mask beta-adrenergic receptors) yielded an equilibrium dissociation constant (pKd) of 10.

Functional characterization of the recombinant human 5-hydroxytryptamine7(a) receptor isoform coupled to adenylate cyclase stimulation.

Functional characterization of the recombinant human 5-hydroxytryptamine7(a) (h5-HT7(a)) receptor isoform was performed using stably transfected LM(tk-) cells. Expression levels of the h5-HT7(a) receptor determined from saturation studies using either a labeled agonist ([3H]5-HT) or antagonist ([3H]LSD) were very similar (Bmax = 160-190 fmol/mg protein), suggesting that all receptors may exist in the high affinity (G protein-coupled) state. In intact cells, 5-HT produced a concentration-dependent elevation of intracellular cAMP levels ([cAMP]i) with an EC50 value of 80 nM and a maximal response of 5-fold increase above basal levels.

5-HT1F receptor agonists inhibit neurogenic dural inflammation in guinea pigs.

The serotonin (5-HT) receptor subtype mediating inhibition of neurogenic dural inflammation in guinea pigs was investigated using a series of serotonin agonists with differing affinities for the 5-HT1B, 5-HT1D and 5-HT1F receptors. When agonist potencies for inhibiting neurogenic inflammation were compared with affinities for these receptor subtypes, a significant positive correlation was seen only with the 5-HT1F receptor. The potency of agonists in inhibiting adenylate cyclase in cells transfected with human 5-HT1F receptor was also highly correlated with their potency in the animal model of migraine.

Cloning and characterization of the guinea pig 5-HT1F receptor subtype: a comparison of the pharmacological profile to the human species homolog.

The anti-migraine compound, sumatriptan, has been shown to have substantial affinity for the cloned human 5-HT1F receptor suggesting that, in addition to 5-HT1B/5-HT1D receptor subtypes, the 5-HT1F receptor may be a therapeutic target for the treatment of migraine. Several investigators have used the guinea pig plasma extravasation model to evaluate potential anti-migraine drugs. Since species differences in the pharmacology of serotonin receptors are well known, we compared the pharmacological profiles of the cloned human and guinea pig 5-HT1F receptors in order to validate the usefulness of the in vivo model in predicting anti-migraine activity of compounds targeted for humans.

Molecular cloning and pharmacological characterization of guinea pig 5-HT1B and 5-HT1D receptors.

Human 5-HT1B and 5-HT1D receptors have been implicated as molecular targets for the treatment of acute migraine based upon the pharmacological actions and clinical efficacy of sumatriptan, an agonist for human 5-HT1B/1D receptors. The guinea pig has served as an animal model to assess 5-HT1B/1D receptor function, most recently in evaluating 5-HT1B/1D receptor agonists as potential anti-migraine agents. Since two distinct, but closely-related receptors displaying "5-HT1D receptor pharmacology" have been cloned previously from most mammalian species, the genes encoding these receptors were isolated from a guinea pig liver genomic DNA library using oligonucleotide probes targeted to nonconserved regions of recombinant human 5-HT1B and 5-HT1D receptors.

Characterization of LY344864 as a pharmacological tool to study 5-HT1F receptors: binding affinities, brain penetration and activity in the neurogenic dural inflammation model of migraine.

LY344864 is a selective receptor agonist with an affinity of 6 nM (Ki) at the recently cloned 5-HT1F receptor. It possesses little affinity for the 56 other serotonergic and non-serotonergic neuronal binding sites examined. When examined for its ability to inhibit forskolin-induced cyclic AMP accumulation in cells stably transfected with human 5-HT1F receptors, LY344864 was shown to be a full agonist producing an effect similar in magnitude to serotonin itself.

Differences in ligand binding profiles between cloned rabbit and human 5-HT1D alpha and 5-HT1D beta receptors: ketanserin and methiothepin distinguish rabbit 5-HT1D receptor subtypes.

The study of serotonin receptor function has been complicated by the extreme molecular diversity of serotonin receptor subtypes, the lack of selective agonists and antagonists for many of the subtypes, and divergence in the pharmacological properties of a single receptor subtype across different animal species. An example of this pharmacological diversity between species homologues is provided by the 5-HT1D receptor subfamily. To further advance the ability to characterize and pharmacologically compare functional responses mediated by native 5-HT1D receptors, we have cloned the 5-HT1D alpha and 5-HT1D beta receptor subtypes from the rabbit and evaluated their pharmacological profiles using radioligand binding assays.

Pharmacological characterizations of recombinant human 5-HT1D alpha and 5-HT1D beta receptor subtypes coupled to adenylate cyclase inhibition in clonal cell lines: apparent differences in drug intrinsic efficacies between human 5-HT1D subtypes.

Recombinant human 5-HT1D alpha and 5-HT1D beta receptor subtypes were stably expressed in NIH-3T3 fibroblasts (1D alpha cell line) and Y-1 adrenocortical tumor cells (1D beta cell line), respectively, for pharmacological evaluations of serotonergic compounds to inhibit forskolin-stimulated cAMP accumulation (FSCA). [3H]LSD saturation studies indicated that 5-HT1D receptor expression levels were slightly higher in the 1D beta cell line (Bmax = 1334 +/- 134 fmol/mg protein) than in the 1D alpha cell line (Bmax = 900 +/- 218 fmol/mg protein). 5-HT inhibited FSCA with similar potencies (EC50 approximately 2 nM) in both assay systems.

LY215840, a high-affinity 5-HT7 receptor ligand, blocks serotonin-induced relaxation in canine coronary artery.

The canine coronary artery possesses a smooth muscle relaxant serotonin (5-HT) receptor distinct from previously characterized 5-HT receptors. On the basis of the ability of LY53857 to block weakly coronary smooth muscle relaxation to 5-HT, we examined several structurally related ergolines in endothelium denuded rings of canine coronary artery precontracted with PGF2 alpha (10 microM). 5-HT (10 nM-100 microM)-induced relaxation was antagonized competitively by the ergoline esters LY53857 (-log KB = 6.

A receptor autoradiographic and in situ hybridization analysis of the distribution of the 5-ht7 receptor in rat brain.

1. Receptor autoradiography and in situ hybridization histochemistry have been used to delineate the distribution of the 5-ht7 receptor and its mRNA in rat brain. Receptor autoradiographic studies were performed using [3H]-5-carboxamidotryptamine (5-CT) as the radioligand.

Ketanserin and ritanserin discriminate between recombinant human 5-HT1D alpha and 5-HT1D beta receptor subtypes.

Compounds able to discriminate functionally between the closely related cloned human 5-HT1D alpha and 5-HT1D beta receptor subtypes have not been reported previously. In [3H]5-HT competition assays, the classical 5-HT2A receptor antagonists, ritanserin and ketanserin, displayed moderate affinity (pKi = 7.30 and 7.

Cloning of a novel human serotonin receptor (5-HT7) positively linked to adenylate cyclase.

An intron-containing gene encoding a novel human serotonin (5-HT) receptor was isolated from human genomic and cDNA libraries with probes directed to transmembrane regions of the adenylate cyclase stimulatory Drosophila serotonin receptor gene, 5-HTdrol. Membranes harvested from transiently transfected Cos-7 cells displayed high affinity (Kd = 8.5 nM), saturable (Bmax = 6.