Publications by authors named "Daniel Langenegger"

Orexin receptor antagonists represent attractive targets for the development of drugs for the treatment of insomnia. Both efficacy and safety are crucial in clinical settings and thorough investigations of pharmacokinetics and pharmacodynamics can predict contributing factors such as duration of action and undesirable effects. To this end, we studied the interactions between various "dual" orexin receptor antagonists and the orexin receptors, OX1R and OX2R, over time using saturation and competition radioligand binding with [(3)H]-BBAC ((S)-N-([1,1'-biphenyl]-2-yl)-1-(2-((1-methyl-1H-benzo[d]imidazol-2-yl)thio)acetyl)pyrrolidine-2-carboxamide).

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In search for peptidic [FeFe] hydrogenase mimics, the cyclic disulfide Sandostatin (octreotide) was allowed to react with Fe(3)(CO)(12). An octreotide-Fe(2)(CO)(6) complex was isolated and characterized spectroscopically as well as by elemental and thermochemical analysis. The complex catalyzes the electrochemical reduction of H(+) to H(2).

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Starting from non-peptidic sst(1)-selective somatostatin receptor antagonists, first compounds with mixed sst(1)/sst(3) affinity were identified by directed structural modifications. Systematic optimization of these initial leads afforded novel, enantiomerically pure, highly potent and sst(3)-subtype selective somatostatin antagonists based on a (4S,4aS,8aR)-decahydroisoquinoline-4-carboxylic acid core moiety. These compounds can efficiently be synthesized and show promising PK properties in rodents.

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Structural simplification of the core moieties of obeline and ergoline somatostatin sst(1) receptor antagonists, followed by systematic optimization, led to the identification of novel, highly potent and selective sst(1) receptor antagonists. These achiral, non-peptidic compounds are easily prepared and show promising PK properties in rodents.

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Octreotate (1b) is the octreotide (SANDOSTATIN; 1a) analogue, carrying a C-terminal CO(2)H (Thr) instead of the CH(2)OH (threoninol) group. In pursuit of our interest in unnatural peptides, we have now synthesized (by the solid-phase Fmoc method) the enantiomeric form 2 of octreotate and determined its affinity for the five human somatostatin (SRIF) receptors (hsst(1-5)). The binding was found to be 9.

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Non-peptidic compounds containing the octahydro-indolo[4,3-fg]quinoline (ergoline) structural element have been optimized into derivatives with high affinity (pK(d) r sst(1)>9) and selectivity (>1000-fold for h sst(1) over h sst(2)-h sst(5)) for the somatostatin sst(1) receptor. In functional assays, these ergolines act as antagonists at human recombinant sst(1) receptors. Pharmacokinetic studies in rodents reveal good oral bioavailability and brain penetration for some of these compounds.

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The SAR of over 50 derivatives of octahydrobenzo[g]quinoline (obeline)-type somatostatin sst(1) receptor antagonist 1 is presented, focusing on the modification of its arylpiperazine moiety. Sst(1) affinities in this series cover a range of five orders of magnitude with the best derivatives displaying subnanomolar sst(1) affinities and >10,000-fold selectivities over the sst(2) receptor subtype as well as promising pharmacokinetic properties.

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A novel class of non-peptide somatostatin receptor ligands bearing the octahydrobenzo[g]quinoline (obeline) structural element has been identified. SAR studies have been performed that led to the discovery of derivatives with high affinity (pK(d) r sst(1) > or = 9) and selectivity (> or = 150-fold for h sst(1) over h sst(2)-h sst(5)) for somatostatin receptor subtype sst(1). In a functional assay, the compounds act as antagonists at human recombinant sst(1) receptors.

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Somatostatin-14 (SRIF) co-localizes with gamma-aminobutyric acid (GABA) in the hippocampus and regulates neuronal excitability. A role of SRIF in the control of seizures has been proposed, although its exact contribution requires some clarification. In particular, SRIF knockout (KO) mice do not exhibit spontaneous seizures, indicating that compensatory changes may occur in KO.

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Clinically used somatostatin (SRIF) analogs, octreotide and lanreotide, act primarily by binding to SRIF receptor subtype 2 (sst2). In contrast, the recently described multiligand SOM230 binds with high affinity to sst(1-3) and sst5 and KE 108 is characterised as a high affinity ligand for all five SRIF receptors. In tumoural mouse corticotrophs (AtT-20 cells) and in mouse hippocampus, binding and functional features of KE 108 were examined and compared to SRIF-14, octreotide and SOM230.

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Somatostatin-14 [somatotropin release-inhibiting factor (SRIF)] reduces hippocampal epileptiform activity but the contribution of its specific receptors (sst1-5) is poorly understood. We have focused on the role of sst1 and sst2 in mediating SRIF modulation of epilepsy using hippocampal slices of wild-type (WT) and sst1 or sst2 knockout (KO) mice. Recordings of epileptiform discharge induced by Mg2+ -free medium with 4-aminopyridine were performed from the CA3 region before and after the application of SRIF compounds.

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1. Somatostatin (somatotropin release inhibiting factor; SRIF) acts via five G protein-coupled receptors (sst(1)-sst(5)) that modulate multiple cellular effectors. The aim of this study was to compare two functional effects of the human sst(2) receptor stably expressed in CHO-K1 cells in a single experiment using a duplex assay for intracellular calcium and serum response element (SRE)-driven luciferase expression.

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1. The mouse corticotroph tumour cell line AtT-20 is a useful model to investigate the physiological role of native somatostatin (SRIF, Somatotropin release inhibitory factor) receptor subtypes (sst(1) - sst(5)). The objective of this study was to characterise the pharmacological features and the functional effects of SRIF receptors expressed by AtT-20 cells using radioligand binding and cAMP accumulation.

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The availability of antagonist ligands for somatostatin receptors is very limited, with those that are available often displaying agonist properties or limited receptor subtype selectivity. Hay et al. [Bioorg.

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The two forms (DTyr8 and LTyr8) of the putative somatostatin sst2 receptor antagonist CYN 154806 (Ac-4NO2-Phe-c(DCys-Tyr-DTrp-Lys-Thr-Cys)-D/LTyr-NH2) were investigated on recombinant human somatostatin receptors and endogenous guinea-pig ileum receptors. In radioligand binding studies using the agonist radioligands [125I]LTT-SRIF-28, [125I][Tyr10]cortistatin-14, [125I]CGP 23996 and [125I][Tyr3]octreotide in Chinese hamster lung fibroblast (CCL39) and Chinese hamster ovary (CHO) cells expressing human somatostatin receptors (hsst1-5), CYN 154806 binds to sst2 receptors with nanomolar affinity (pKD=8.14-8.

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Four linear beta(2)/beta(3)-di- and alpha/beta(3)-tetrapeptides (1-4) were investigated as somatostatin sst(4) receptor agonists on recombinant human and mouse somatostatin receptors. Human somatostatin receptor subtypes 1-5 (sst(1-5)), and mouse somatostatin receptor subtypes 1,3,4 and 5, were characterised using the agonist radioligands [(125)I]LTT-SRIF-28, [(125)I][Tyr(10)]CST(14) and [(125)I]CGP 23996 in stably transfected Chinese hamster lung fibroblast (CCL39) cells. The peptides bound selectively to sst(4) receptors with nanomolar affinity (pK(d)=5.

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