Synthesis and Neuropeptide Y Y1 Receptor Antagonistic Activity of N,N-Disubstituted ω-Guanidino- and ω-Aminoalkanoic Acid Amides

Potent arpromidine-type histamine H₂ receptor agonists such as BU-E-76 (He 90481) were among the first non-peptides reported to display weak neuropeptide Y (NPY) Y₁ receptor antagonist activity. In search of new chemical leads for the development of more potent NPY antagonists, a series of N,N-disubstituted ω-guanidino and ω-aminoalkanoic acid amides were synthesized on the basis of structure-activity relationships and molecular modeling studies of arpromidine and related imidazolylpropylguanidines. In one group of compounds the imidazole ring was retained whereas in the second group it was replaced with a phenol group representing a putative mimic of Tyr³⁶ in NPY. Although the substitution patterns have not yet been optimized, the title compounds are NPY Y₁ antagonists in human erythroleukemia (HEL) cells (Ca²⁺ assay) achieving pKB values in the range of 6.3–6.6. For representative new substances tested in the isolated guinea pig right atrium histamine H₂ receptor agonism could not be found. In the N-(diphenylalkyl)amide series, compounds with a trimethylene chain were more active Y₁ antagonists than the ethylene homologs. Concerning the spacer in the ω-amino or ω-guanidinoalkanoyl portion, the best activity was found in compounds with a four- or five-membered alkyl chain or a 1,4-cyclohexylene group. Surprisingly, in contrast to the phenol series, in the imidazole series the compounds with a side chain amino group turned out to be considerably more potent than the corresponding strongly basic guanidines. Thus, the structure-activity relationships appear to be different for the diphenylalkylamide NPY antagonists with one or two basic groups.     

Studies on the binding of [3H]flumazenil and [3H]sarmazenil in post-mortem human brain

Two benzodiazepine analogues, [³H]flumazenil and [³H]sarmazenil, were used to study the GABA_A/benzodiazepine receptor complex in human post-mortem brain using in vitro receptor assays on homogenates and whole hemisphere autoradiography. Both radioligands bound in a saturable manner to single binding sites in the tissue preparations from any brain region. The highest levels of binding were found in the cortical regions and in cortex cerebelli. Both [³H]flumazenil and [³H]sarmazenil were excellent radioligands for autoradiography with high binding in cerebral and cerebellar cortex with no or very low binding in areas with white matter. The addition of a high concentration of flumazenil or clonazepam did not inhibit the binding of [³H]sarmazenil to granule cells in the cerebellum while the binding of [³H]flumazenil was abolished completely in all regions. The results show that with the two different radioligands, one an antagonist and one a partial inverse agonist, the binding pattern to GABA_A/benzodiazepine receptor complex is approximately similar in most brain regions. The additional binding seen in the cerebellum with [³H]sarmazenil is suggested to be due to binding to an α₆-containing complex.     

Identification of novel selective Mtb-DHFR inhibitors as antitubercular agents through structure-based computational techniques

Inhibition of dihydrofolate reductase from Mycobacterium tuberculosis-dihydrofolate reductase (Mtb-DHFR) has emerged as a promising approach for the treatment of tuberculosis. To identify novel Mtb-DHFR inhibitors, structure-based virtual screening (SBVS) of the Molecular Diversity Preservation International (MolMall) database was performed using Glide against the Mtb-DHFR and h-DHFR enzymes. On the basis of SBVS, receptor fit, drug-like filters, and ADMET (absorption, distribution, metabolism, excretion, and toxicity) analysis, 16 hits were selected and tested for their antitubercular activity against the H₃₇R_V strain of M. tuberculosis. Five compounds showed promising activity with compounds 11436 and 15275 as the most potent hits with IC₅₀ values of 0.65 and 12.51 μM, respectively, against the H₃₇R_V strain of M. tuberculosis. The two compounds were further tested in the Mtb-DHFR and h-DHFR enzymatic assay for selectivity and were found to be three- to eight-fold selective towards Mtb-DHFR over h-DHFR with minimum inhibitory concentration values of 5.50, 73.89 µM and 42.00, 263.00 µM, respectively. In silico simulation studies also supported the stability of the protein–ligand complex formation. The present study demonstrates the successful utilization of in silico SBVS tools for the identification of novel and potential Mtb-DHFR inhibitors and compound 11436 ((2,4-dihydroxyphenyl)(3,4,5-trihydroxyphenyl)methanone) as a potential lead for the development of novel Mtb-DHFR inhibitors.     

Autoradiographic localisation of D3-dopamine receptors in the human brain using the selective D3-dopamine receptor agonist (+)-[3H]PD 128907

The selective D₃-dopamine receptor agonist 4aR,10bR-(+)-trans-3,4,4a,10b-tetrahydro-4-[N-propyl-2,3-³H]-2H,5H-[1]benzopyrano[4,3-b]-1,4-oxazin-9-ol ([³H]PD 128907) was used to visualise D₃-dopamine receptors in whole hemisphere cryosections from post-mortem human brain. [³H]PD 128907 has an 18- to 40-fold selectivity for D₃- over D₂-dopamine receptors as compared to a 7- to 24-fold selectivity of the more commonly used ligand [³H]7-OH-DPAT. [³H]PD 128907 accumulated markedly in the nucleus accumbens and in the ventral parts of caudate nucleus and putamen, with a slightly heterogeneous (patch-matrix like) distribution. The binding in the lateral parts of caudate nucleus and putamen was much less dense. No binding was obtained in any other regions. A very high proportion of [³H]PD 128907 was specifically bound, as judged from the low binding remaining in the presence of the D₂/D₃-dopamine receptor antagonist raclopride. This gives the ligand a potential for the detection of low density D₃-dopamine receptors in the human brain. The binding obtained with [³H]PD 128907 was qualitatively similar to that using [³H]7-OH-DPAT in the presence of GTP. However, [³H]7-OH-DPAT labelled, in contrast to [³H]PD 128907, also D₃-dopamine receptors in neocortex. The new compound [³H]PD 128907 appears to be a suitable radioligand for autoradiographic examination of the D₃-dopamine receptor localisation in the human brain, and should also be useful for pharmacological studies of this receptor subtype. Received: 20 November 1995/Final version: 2 May 1996     

Pharmacophore modeling, 3D-QSAR,synthesis, and anti-lung cancer evaluation of novel thieno[2,3-d][1,2,3]triazines targeting EGFR

Two series of thieno[2,3-d][1,2,3]triazine derivatives were designed, synthesized, and biologically evaluated as potential epidermal growth factor receptor (EGFR) inhibitors targeting the non-small-cell lung cancer cell line H1299. Most of the synthesized compounds displayed IC₅₀ values ranging from 25 to 58 nM against H1299, which are superior to that of gefitinib (40 µM). 3-(5,6,7,8-Tetrahydro-7H-cyclohexa[4:5]thieno[2,3-d]-1,2,3-triazin-4-ylamino)benzene-1,3-diamine ( 6b ) achieved the highest cytotoxic activity against H1299 with an IC₅₀ value of 25 nM; it had the ability to decrease the EGFR concentration in H1299 cells from 7.22 to 2.67 pg/ml. In vitro, the IC₅₀ value of compound 6b was 0.33 nM against EGFR, which is superior to that of gefitinib at 1.9 nM and erlotinib at 4 nM. The three-dimensional quantitative structure–activity relationships and molecular modeling studies revealed comparable binding modes of compound 6b , gefitinib, and erlotinib in the EGFR active site. The in silico ADME (absorption, distribution, metabolism, and excretion) prediction parameters of this compound revealed promising pharmacokinetic and physicochemical properties. Moreover, DFT (density functional theory) calculations showed the high reactivity of compound 6b toward the EGFR compared with other compounds. The designed compound 6b might serve as an encouraging lead compound for the discovery of promising anti-lung cancer agents targeting EGFR.     

Binding of [H]MSX-2 (3-(3-hydroxypropyl)-7-methyl-8-(m-methoxystyryl)-1-propargylxanthine) to rat striatal membranes — a new, selective antagonist radioligand for A2A adenosine receptors

The present study describes the preparation and binding properties of a new, potent, and selective A_2A adenosine receptor (AR) antagonist radioligand, [³H]3-(3-hydroxypropyl)-7-methyl-8-(m-methoxystyryl)-1-propargylxanthine ([³H]MSX-2). [³H]MSX-2 binding to rat striatal membranes was saturable and reversible. Saturation experiments showed that [³H]MSX-2 labeled a single class of binding sites with high affinity (K_d=8.0 nM) and limited capacity (B_max=1.16 fmol·mg⁻¹ of protein). The presence of 100 μM GTP, or 10 mM magnesium chloride, respectively, had no effect on [³H]MSX-2 binding. AR agonists competed with the binding of 1 nM [³H]MSX-2 with the following order of potency: 5′-N-ethylcarboxamidoadenosine (NECA)>2-[4-(carboxyethyl)phenylethylamino]-5′-N-ethylcarboxamidoadenosine (CGS-21680)>2-chloroadenosine (2-CADO)>N⁶-cyclopentyladenosine (CPA). AR antagonists showed the following order of potency: 8-(m-bromostyryl)-3,7-dimethyl-1-propargylxanthine (BS-DMPX)>1,3-dipropyl-8-cyclopentylxanthine (DPCPX)>(R)-5,6-dimethyl-7-(1-phenylethyl)-2-(4-pyridyl)-7H-pyrrolo[2,3-d]pyrimidine-4-amine (SH-128)>3,7-dimethyl-1-propargylxanthine (DMPX)>caffeine. The K_i values for antagonists were in accordance with data from binding studies with the agonist radioligand [³H]CGS21680, while agonist affinities were 3–7-fold lower. [³H]MSX-2 is a highly selective A_2A AR antagonist radioligand exhibiting a selectivity of at least two orders of magnitude versus all other AR subtypes. The new radioligand shows high specific radioactivity (85 Ci/mmol, 3150 GBq/mmol) and acceptable nonspecific binding at rat striatal membranes of 20–30%, at 1 nM.     

Modulation of Opioid Receptor Ligand Affinity and Efficacy Using Active and Inactive State Receptor Models

Mu opioid receptor (MOR) agonists are widely used for the treatment of pain; however, chronic use results in the development of tolerance and dependence. It has been demonstrated that coadministration of a MOR agonist with a delta opioid receptor (DOR) antagonist maintains the analgesia associated with MOR agonists, but with reduced negative side‐effects. Using our newly refined opioid receptor models for structure‐based ligand design, we have synthesized several pentapeptides with tailored affinity and efficacy profiles. In particular, we have obtained pentapeptides 8 , Tyr‐c(S‐S)[DCys‐1Nal‐Nle‐Cys]NH₂, and 12 , Tyr‐c(S‐S)[DCys‐1Nal‐Nle‐Cys]OH, which demonstrates high affinity and full agonist behavior at MOR, high affinity but very low efficacy for DOR, and minimal affinity for the kappa opioid receptor (KOR). Functional properties of these peptides as MOR agonists/DOR antagonists lacking undesired KOR activity make them promising candidates for future in vivo studies of MOR/DOR interactions. Subtle structural variation of 12 , by substituting D‐Cys⁵ for L‐Cys⁵, generated analog 13, which maintains low nanomolar MOR and DOR affinity, but which displays no efficacy at either receptor. These results demonstrate the power and utility of accurate receptor models for structure‐based ligand design, as well as the profound sensitivity of ligand function on its structure.     

A novel kainate receptor ligand [H]-(2S,4R)-4-methylglutamate: Pharmacological characterization in rabbit brain membranes

Since kainate evokes large non-desensitizing currents at α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, kainate is of limited use in discriminating between AMPA and kainate receptors. Following recent reports that (2S,4R)-4-methylglutamate is a kainate receptor-selective agonist, we have radiolabelled and subsequently characterized the binding of [³H]-(2S,4R)-4-methylglutamate to rabbit whole-brain membranes. [³H]-(2S,4R)-4-methylglutamate binding was rapid, reversible and labelled two sites (KD1 = 3.67 ± 0.50 nM/B_max1 = 0.54 ± 0.03 pmol/mg protein and K_D2 = 281.66 ± 12.33 nM/ B_max2 = 1.77 ± 0.09 pmol/mg protein). [³H]-(2S,4R)-4-methylglutamate binding was displaced by several non-NMDA receptor ligands: domoate > kainate -quisqualate -glutamate > 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX) (S)-AMPA = (S)-5-fluorowillardiine > NMDA. Neither the metabotropic glutamate receptor agonists (1S,3R)-ACPD or -AP4, together with the -glutamate uptake inhibitor -trans-2,4-PDC, influenced binding when tested at 100 μM. We conclude that [³H]-(2S,4R)-4-methylglutamate is a useful radioligand for labelling kainate receptors. It possesses high selectivity, and possesses a pharmacology similar to that for rat cloned low-affinity (Glu5 and 6) kainate receptor subunits.     

Synthesis and antibacterial activity of 4-benzoyl-1-(4-carboxy-phenyl)-5-phenyl-1H-pyrazole-3-carboxylic acid and derivatives

A new 1H-pyrazole-3-carboxylic acid 2, along with hydrazono-pyridazinone 3, a by-product, and its derivatives 4–7 were synthesized and the structures confirmed by infrared (IR) and ¹H and ¹³C nuclear magnetic resonance (NMR) data. These new compounds were evaluated for their antibacterial activities against Gram-positive and Gram-negative bacteria using the tube dilution method. The minimal inhibitory concentrations (MICs) experiments revealed that most compounds exerted inhibitor effects against Klebsiella pneumonia, Escherichia coli, Bacillus subtilus, and Xanthomonas compestris test microorganisms. Moreover, the results showed that the pyrazolo[3,4-d]pyridazine compounds were the best compounds of the series, exhibiting antibacterial activity against both Gram-positive and Gram-negative bacteria.     

Characterization of Peptide 20–30 of Follicle Stimulating Hormone Receptor as an Antagonist of Receptor Activity: Significance of Charged Residues

We had previously reported the region (20–30) from follicle stimulating hormone receptor as being an immunodominant epitope and the smallest reported peptide capable of inhibiting hormone binding. We now report it to be an effective antagonist of ligand‐induced cAMP signalling as well. The region (20–30) of follicle stimulating hormone receptor has three charged residues, namely, E²², D²⁶ and R²⁹ that are specific to follicle stimulating hormone receptor and are conserved in mammals. This study aimed to verify whether the charged residues contribute to the activity of the follicle stimulating hormone receptor peptide (20–30). This was done using analogs of follicle stimulating hormone receptor peptide (20–30), each having an alanine substitution for a corresponding charged residue. The analog peptides displayed a loss of activity and could not inhibit hormone binding or the subsequent signal transduction. The ability of follicle stimulating hormone receptor peptide (20–30) to bind antipeptide antibodies against follicle stimulating hormone receptor peptide (9–30) was either decreased or abolished with the alanine substituted analog peptides of follicle stimulating hormone receptor peptide (20–30). The loss of function led us to verify whether there was a conformational change as well. CD spectral analysis did not reveal a significant change. These observations indicate that the charged aminoacids present in follicle stimulating hormone receptor peptide (20–30) are crucial for the observed follicle stimulating hormone antagonistic activity. This information could form the basis for the design of novel compounds capable of functioning as follicle stimulating hormone antagonists.     

抗胆碱能化合物3-甲基-3-氮杂双环[3,3,1]壬-9-酯类α,β异构体的合成

本文报道了一系列抗胆碱能化合物3-甲基-3-氮杂双环[3,3,1]壬-9-酯类α和β异构体的合成。将3-甲基-3-氮杂双环[3,3,1]壬-9-酮还原为相应的醇后,分离成9α和9β两种异构醇,再分别与各种取代羧酸甲酯进行酯交换,而得α和β酯类。对所有产物的立体构型与¹H核磁共振谱的关系进行了讨论。初步药理实验结果表明,除化合物Ⅲ₉,Ⅲ₁₀外,所有化合物均具有较强的中枢抗胆碱能作用,其中6个化合物的抗摈榔碱震颤作用强度接近或超过阿托品,相应的α和β异构体之间作用强度差别较小。     

Allosteric modulation of metabotropic glutamate receptor 5 affects phosphorylation, internalization, and desensitization of the μ-opioid receptor

Recent evidence suggests that opioid analgesia and tolerance can be modulated by metabotropic glutamate receptors. Therefore, we studied the functional coupling and desensitization of the μ-opioid receptor (MOR) in human embryonic kidney (HEK) 293 cells which co-express metabotropic glutamate receptor 5 (mGluR5). As demonstrated by the D-Ala²,N-MePhe⁴,Gl-ol⁵-enkephalin (DAMGO)-induced inhibition of intracellular cAMP level and by binding studies, the co-expression of mGluR5 had no substantial effect on the agonist binding sites and functional coupling of the MOR. However, in MOR/mGluR5 co-expressing cells, the non-competitive mGluR5 antagonist MPEP (2-methyl-6-(phenylethynyl)-pyridine) decreases the DAMGO-induced MOR phosphorylation, internalization, and desensitization, whereas non-selective competitive mGluR antagonists or agonists had no effects. These findings indicate that an allosteric modulation of mGluR5 can affect the agonist-induced MOR signalling and regulation. As a mechanistic basis for the observed effects we suggested an interaction/heterodimerization of MOR and mGluR5, which is supported by the DAMGO-induced co-internalization of MOR and mGluR5 and by the increase of MPEP binding sites (B_max) and a change of the binding affinity (K_D) of mGluR5 receptors after the co-expression of MOR. In addition, co-immunoprecipitation experiments revealed evidence for an interaction between MOR and mGluR5 which is facilitated by MPEP treatment.     

Synthesis of 2-(3-Substituted-1,2,4-oxadiazol-5-yl)-8-methyl-8-azabicyclo[3.2.1]octanes and 2α-(3-Substituted-1,2,4-oxadiazol-5-yl)-8-methyl-8-azabicyclo[3.2.1]oct-2-enes as Potential Muscarinic Agonists

Radioligand binding affinities of seven muscarinic receptor ligands which possess an oxadiazole ring side chain have been determined in rat heart, rat brain, and m₁- or m₃-transfected CHO cell membrane preparations to determine the selectivity for subtypes of muscarinic receptor. The ratios of binding constants in brain membranes were measured as an indicator of potential agonist activity against [³H]QNB and [³H]Oxo-M. These muscarinic ligands did not discriminate the subtypes of muscarinic receptors. Six muscarinic ligands which have a 3-amino- or 3-methyl-1,2,4-oxadiazol-5-yl groups attached to the 8-methyl-8-azabicyclo[3.2.1]oct-2-ene or 8-methyl-8-azabicyclo[3.2.1]octane head group show binding constants between 2.04 x 10^–6 and 1.79 x 10^–5 M in rat heart, rat brain, and m₁- or m₃-transfected CHO cell membrane preparations. 1-Methyl-2-[3-amino-1,2,4-oxadiazol-5-yl]piperidine shows low binding constants of approximately 10^–4 M in rat heart and rat brain. (1R,5S)-2-[3-Amino-1,2,4-oxadiazol-5-yl]-8-methyl-8-azabicyclo-[3.2.1]oct-2-ene [(1R,5S)-17] was the most active compound.     

Design,Synthesis and Evaluation of Antidepressant Activity of Novel 2‐Methoxy 1, 8 Naphthyridine 3‐Carboxamides as 5‐HT3 Receptor Antagonists

A series of novel 1,8‐naphthyridine‐3‐carboxamides as 5‐HT₃ receptor antagonists were synthesized with an intention to explore the antidepressant activity of these compounds. The title carboxamides were designed using ligand‐based approach keeping in consideration the structural requirement of the pharmacophore of 5‐HT₃ receptor antagonists. The compounds were synthesized using appropriate synthetic route from the starting material nicotinamide. 5‐HT₃ receptor antagonism of all the compounds, which was denoted in the form of pA₂ value, was determined in longitudinal muscle myenteric plexus preparation from guinea‐pig ileum against 5‐HT₃ agonist, 2‐methyl‐5‐HT. Compound 8g (2‐methoxy‐1, 8‐naphthyridin‐3‐yl) (2‐methoxy phenyl piperazine‐1‐yl) methanone was identified as the most active compound, which expressed a pA₂ value of 7.67. The antidepressant activity of all the compounds was examined in mice model of forced swim test (FST); importantly, none of the compounds was found to cause any significant changes in the locomotor activity of mice at the tested dose levels. In FST, the compounds with considerably higher pA₂ value exhibited promising antidepressant‐like activity, whereas compounds with lower pA₂ value did not show antidepressant‐like activity as compared to the control group.     

Effect of aromatic amino acid substitutions in the 3-position of cyclic β-casomorphin analogues on μ-opioid agonist/δ-opioid antagonist properties*

The β-casomorphin-5 analog H-Tyr-c[-D-Orn-2-Nal-D-Pro-Gly-] (2-Nal = 2-naphthylalanine) was the first reported cyclic opioid peptide with mixed μ agonist/δ antagonist properties [R. Schmidt et al. (1994) J. Med. Chem. 37 , 1136-1144]. The 2-Na1³ residue in this peptide was replaced with benzothienylalanine (Bta) (3), His(Bz1) (4), Tyr(Bz1) (5), 4′-benzoylphenylalanine (Bpa) (6), 4′-benzylphenylalanine (Bzp) (7), thyrnine (Thy) (8), thyroxine (Thx) (9), 4′-biphenylalanine (Bip) (10), 4′-biphenylglycine (Bpg) (12) and 3,3-diphenylalanine (Dip) (14), and the in vitro opioid activity profiles of the resulting compounds were determined in μ and δ receptor-representative binding assays and bioassays. Analogues 3, 12 and 14 were full agonists in the μ receptor-representative guinea-pig ileum (GPI) assay and also were agonists in the δ receptor-representative mouse vas deferens (MVD) assay. The agonist effects of the latter compounds in the MVD assay were antagonized by the highly selective δ antagonist H-Tyr-Tic-Phe-Phe-OH (TIPP), indicating that they were triggered by δ receptor activation. The Bzp³- and Bip³-containing peptides 7 and 10 turned out to be μ antagonists against the μ selective agonist H-Tyr-D-Ala-Phe-Phe-NH₂, in the GPI assay. The other analogues were weak partial μ agonists which displayed remarkably decreased μ receptor affinity as compared to parent peptide 1. Compounds 4-10 were found to be δ antagonists in the MVD assay. Analogues 4 and 9 exhibited δ antagonist potency similar to that of parent peptide 1, while compounds 5-8 and 10 showed 3-12-fold higher δ antagonist potency against DPDPE and deltorphin I and, in most cases, increased δ receptor affinity. These results indicate that the & delta; receptor tolerates bulky aromatic side chains in the 3-position of cyclic β-casomorphin analogs with either δ agonist or δ antagonist properties. However, these compounds displayed drastically reduced μ receptor affinity in nearly all cases. © Munksgaard 1996.     

1,3,4-Thiadiazole and 1,2,4-triazole-5-thione derivatives bearing 2-pentyl-5-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-one ring: Synthesis,molecular docking,urease inhibition,and crystal structure

Two series of 1,3,4-thiadiazole ( 40a–o ) and 1,2,4-triazole-5-thione ( 41a–l ) derivatives bearing a 2-pentyl-5-phenyl-1,2,4-triazole-3-one ring were synthesized and then studied for their urease inhibitory activities using thiourea as a standard drug. Among the two groups, the first group ( 40a–o ) did not show good activity while the second group ( 41a–l ) showed excellent activity. Compound 41j (1091.24 ± 14.02 µM) of the second series of compounds showed lower activity than thiourea, while the remaining 11 compounds ( 41a–i , k , and l ) showed better activity than thiourea (183.92 ± 13.14 µM). Among the 11 compounds, 41b (15.96 ± 2.28 µM) having the 3-F group on the phenyl ring showed the highest inhibitory activity. Urease kinetic studies of 41b , which is the most active compound, determined it to have an un-competitive inhibition potential. Moreover, in silico analysis against urease from jack bean with 27 new heterocyclic compounds and the reference molecule was carried out to see the necessary interactions responsible for urease activity. The docking calculations of all compounds supported stronger binding to the receptor than the reference molecule, with high inhibition constants. In addition, compound 40m was characterized by single-crystal X-ray diffraction analysis. X-ray analysis reveals that the structures of the compound 40m crystallize in the monoclinic P21/c space group with the cell parameters: a = 10.2155(9) Å, b = 22.1709(18) Å, c = 21.4858(17) Å, β = 99.677(8)°, V = 4797.0(7) ų. X-ray diffraction analyses were also performed to gain insights into the role of weak intermolecular interactions and C-H…X (halogen) interactions in compound 40m that influence the crystal packing.     

[3H]ICS 205-930 labels 5-HT3 recognition sites in membranes of cat and rabbit vagus nerve and superior cervical ganglion

Summary The binding characteristics of [³H]ICS 205-930, a 5-hydroxytryptamine 5-HT₃ receptor antagonist, were investigated in membranes prepared from cat and rabbit vagus nerve (VN) and superior cervical ganglion (SCG). The autoradiographic localisation of 5-HT₃ recognition sites was also assessed using [³H]ICS 205-930 in slices from cat medulla oblongata, nodose ganglion and vagus nerve.[³H]ICS 205-930 bound to a homogeneous population of high affinity recognition sites in cat VN: B_max = 201 ± 43 fmol/mg protein, pK_D = 9.26 ± 0.17 and SCG: B_max = 291 ± 40 fmol/mg, pK_D = 9.35 ± 0.80 (n = 3). Competition experiments performed in membranes from cat VN and SCG with agonists and antagonists suggested the presence of a homogeneous population of [³H]ICS 205-930 recognition sites. Competition curves were steep and monophasic and were best fitted by a 1 receptor site model. The following rank order of affinity for [³H]ICS 205-930 binding sites was observed with antagonists: SDZ 206-830 = ICS 205-930 > BRL 43694 > SDZ 206–792 > quipazine > MDL 72222 > metoclopramide > mCPP and agonists: 2-methyl-5-HT = 5-HT > phenylbiguanide. A similar profile was observed for a limited series of compounds in rabbit membranes. Drugs acting at 5-HT₁, 5-HT₂ and dopamine receptors (domperidone, spiperone and metergoline) showed very low affinities for [³H]ICS 205-930 recognition sites. The sites labelled with [³H]ICS 205-930 in vagus nerve and superior cervical ganglion of both species displayed the pharmacological profile of a 5-HT₃ receptor. There was a significant correlation between the rank order of affinity of the tested compounds for [³H]ICS 205-930 recognition sites in cat and rabbit membranes and their rank order of affinity for 5-HT₃ receptors from neuroblastoma-glioma NG 108-15 cells. Autoradiographic studies suggest that [³H]ICS 205-930 binding sites are present over and around the nodose ganglion cell somata, along certain fibers of the vagus nerve and in the terminal areas of this nerve in the medullar nucleus of the vagus.The present data demonstrate that [³H]ICS 205-930 identifies 5-HT₃ receptors in preparations of cat and rabbit vagus nerve and superior cervical ganglion.Send offprint requests to D. Hoyer at the above addressThe present results have been presented in part at the Winter Meeting of the British Pharmacological Society, London, December 20–22, 1988 (Hoyer et al. 1989)     

A novel sulphur glycoside from the seeds of Descurainia sophia (L.)

A new sulphur glycoside, named descurainoside (1), and the known compound sinapic acid (2) have been isolated from the seeds of Descurainia sophia (L.) Webb ex Prantl. The structure of 1 has been identified as (1R,6S,8R,9S,10S)-9,10-dihydroxy-4-[(4-hydroxy-3,5-dimethoxyphenyl)methylene]-8-(hydroxymethyl)-2,7-dioxa-5-thiabicyclo[4.4.0]decan-3-one by means of physico-chemical properties and spectroscopic methods (1D and 2D NMR, HRMS, ESI-MS).     

Efficient synthesis of 13C‐labelled erythromycin biosynthetic intermediate. 1: S‐2‐acetylaminoethyl (2R,3R,4R,5R)‐3,5‐diacetoxy‐2,4‐dimethyl‐4‐([13C]methoxy)‐heptanethioate

An efficient ¹³C‐labelling synthesis of the putative erythromycin biosynthetic intermediate, S‐2‐acetylaminoethyl (2R,3R,4R,5R)‐3,5‐diacetoxy‐2,4‐dimethyl‐4‐([¹³C]methoxy)heptanethioate, which would be useful for the investigation of the chain elongation mechanism in erythromycin biosynthesis, was achieved by utilizing iodo[¹³C]methane and (2S,3R,4R,5R)‐4‐hydroxy‐3,5‐O‐isopropylidene‐2,4‐dimethylheptanol, obtained in our previous studies on erythromycin A synthesis. Copyright © 2008 John Wiley & Sons, Ltd.     

3-(ω-Aminoalkyl)-5,5-dialkyl(or spirocycloalkyl-1′,5-)hydantoins as New 5-HT1A and 5-HT2A Receptor Ligands

A series of new 3-(ω-aminoalkyl)-5,5-disubstituted hydantoins, containing 1-phenylpiperazine, 1-(o-methoxyphenyl)piperazine or 1,2,3,4-tetrahydroisoquinoline fragments, were synthesized by standard alkylation procedures and their 5-HT_1A and 5-HT_2A receptor affinities were determined. It has been shown that the investigated derivatives are recognized by 5-HT_1A and 5-HT_2A receptors due to the presence of a 1-arylpiperazine fragment; however, the terminal hydantoin moiety plays an important role in stabilization of the receptor-ligand complex. It has also been found that the two 1-phenylpiperazine derivatives 32 and 36 are new, selective 5-HT_2A receptor ligands (K_i = 34 and 37 nM, respectively), whereas the derivative of 1-(o-methoxyphenyl)piperazine ( 38 ) is a new, highly potent 5-HT_1A receptor ligand (K_i = 0.51 nM) with a moderate affinity for 5-HT_2A receptors (K_i = 213 nM).