Lidia Demchyshyn

A primordial dopamine D1-like adenylyl cyclase-linked receptor from Drosophila melanogaster displaying poor affinity for benzazepines

We report here the isolation from Drosophila melanogaster of a 2.0 kb cDNA clone encoding a 385 amino acid protein (dDA1) displaying, within putative transmembrane domains, highest amino acid sequence homology (49–53%) to members of the vertebrate dopamine D1‐like receptor family. When expressed in either Sf9 or COS‐7 cells, dDA1 did not bind the specific D1‐like receptor antagonist [3H]SCH‐23390 or numerous other dopaminergic, adrenergic or serotoninergic ligands with high affinity. However, like vertebrate dopamine D1‐like receptors, dDA1 stimulated the accumulation of cAMP in response to DA (EC50 ∼300 nM) and 6,7‐ADTN (EC50∼500 nM). The dopaminergic rank order of potency (DA > NE⪢5‐HT) and the lack of stimulation by other possible neurotransmitters (octopamine, tyramine, tryptamine) or DA metabolites (e.g. N‐acetyl dopamine) found in Drosophila suggests that this receptor functionally belongs to the dopamine D1‐like subfamily. Benzazepines, which characteristically bind to vertebrate dopamine D1‐like receptors with high affinity, were relatively poor in stimulating (SKF‐38393, SKF‐82526; EC50 > 10 μM) dDA1‐mediated accumulation of cAMP. Of the numerous compounds tested, a few dopaminergic antagonists inhibited DA‐stimulated production of cAMP in a concentration‐dependent manner, albeit with considerably reduced affinity, and with the rank order of potency: (+)‐butaclamol(K b∼125nM) > SCH‐23390(K b∼230nM) > α‐flupenthixol (K b ∼ 400 nM) > chlorpromazine ≥ spiperone (K b ∼ 680 nM) ≥ clozapine In situ hybridization revealed that dDA1 receptor mRNA is expressed as a maternal transcript, and at later blastoderm stages is restricted to apical regions of the cortical peripheral cytoplasm. The generation of inter‐species D1 receptor chimeras may help to identify those particular sequence‐specific motifs or amino acid residues confering high affinity benzazepine receptor interactions.

N1-(Benzenesulfonyl)tryptamines as novel 5-HT6 antagonists

N-Benzenesulfonyl-5-methoxy-N,N-dimethyltryptamine (BS/5-OMe DMT; 5) was shown to bind at human 5-HT6 serotonin receptors with high affinity (Ki = 2.3 nM) relative to serotonin (Ki = 78 nM). Structural variation failed to result in significantly enhanced affinity. BS/5-OMe DMT acts as an antagonist of 5-HT-stimulated adenylate cyclase (pA2 = 8.88 nM) and may represent the first member of a novel class of 5-HT6 antagonists.

A human somatostatin receptor (SSTR3), located on chromosome 22, displays preferential affinity for somatostatin‐14 like peptides

We report here on the cloning of a human intronless gene encoding a member of the G‐protein linked somatostatin (SST) receptor subfamily, termed SSTR3. Based on the deduced amino acid sequence, this gene encodes a 418 amino acid protein displaying sequence similarity, particularly within putative transmembrane domains, with the recently cloned human SSTR1 (62%), SSTR2 (64%) and SSTR4 (58%) receptors. Membranes prepared from COS‐7 cells transiently expressing the human SSTR3 gene bound [125I]Leu8,d‐Trp22,‐Tyr22 SST‐28 in a saturable manner with high affinity (~200 pM) and with rank order of potency (d‐Trp8 SST‐14 > SST‐14 > SMS‐201‐995 > SST‐28) indicative of a somatostatin‐14 selective receptor. The pharmacological profile of the expressed human SSTR3 receptor is similar but not identical to that reported for the rat homolog [(1992) J. Biol. Chem. 267,20422] where the peptide selectivity is SST‐28 ≧ SST‐14 XXX SMS‐201‐995. Northern blot analysis reveals the presence of an SSTR3 mRNA species of ~5 kb in various regions of the monkey brain, including the frontal cortex, cerebellum, medulla, amygdala, with little or no SSTR3 mRNA detectable in brain regions such as the striatum, hippocampus, and olfactory tubercle. The SSTR3 receptor gene maps to human chromosome 22. The existence of at least four distinct human genes encoding somatostatin‐14 selective receptors with diverse pharmacological specificities may help to account for some of the multiple biological actions of somatostatin under normal and pathological conditions.

6-Bicyclopiperazinyl-1-arylsulfonylindoles and 6-bicyclopiperidinyl-1-arylsulfonylindoles derivatives as novel, potent, and selective 5-HT6 receptor antagonists

A novel series of 6-bicyclopiperazinyl-1-arylsulfonylindoles and 6-bicyclopiperidinyl-1-arylsulfonylindoles derivatives was synthesized and found to be potent and selective 5-HT6 receptor antagonists.

Pyrrolo[3,2,1-ij]quinoline derivatives, a 5-HT2c receptor agonist with selectivity over the 5-HT2a receptor: potential therapeutic applications for epilepsy and obesity.

A series of pyrrolo[3,2,1-ij]quinoline derivatives was synthesized, evaluated for their activity against the 5-HT2c and 5-HT2a, receptors and found to be agonists at 5-HT2c with selectivity over 5-HT2a.

Imidazoline-modified benzylimidazolines as h5-HT1D/1B serotonergic ligands

Sumatriptan, a h5-HT1D and h5-HT1B receptor agonist used clinically as a migraine-abortive, produces certain side effects thought to result from its affinity for h5-HT1B receptors. The present investigation extends our work with benzylimidazolines as novel non-tryptamine h5-HT(1D/1B) ligands. The effect of N-methylation, N-benzylation, ring-aromatization, and variation of the imidazoline ring on affinity both at h5-HT1D and h5-HT1B receptors was examined. Several compounds were identified with good affinity and enhanced (i.e., > 100-fold) h5-HT1D versus hS-HT1B selectivity.

1-(Bicyclopiperazinyl)ethylindoles and 1-(homopiperazinyl)ethyl-indoles as highly selective and potent 5-HT7 receptor ligands

A novel series of 1-(bicyclopiperazinyl)ethylindole and 1-(homopiperazinyl)ethyl-indole derivatives was synthesized and found to be potent and selective 5-HT(7) receptor ligands.

(R)-3-(N-Methylpyrrolidin-2-ylmethyl)-5-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole derivatives as high affinity h5-HT1B/1D ligands

A series of (R)-3-(N-methylpyrrolidin-2-ylmethyl)-5-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole derivatives (2) have been prepared using parallel synthesis, and their structure-activity relationship studied. High affinity human 5-HT(1B/1D) (h5-HT(1B/1D)) ligands have been identified.