Agonist stimulation at human μ opioid receptors in a [(35)S]GTPγS incorporation assay: observation of "bell-shaped" concentration-response relationships under conditions of strong receptor G protein coupling.

Context: The appearance of "bell"- (or "inverted U"-) shaped agonist concentration-response curves (CRCs) in in vitro pharmacological experiments is a frequently observed but poorly communicated phenomenon. In the context of G protein coupled receptor research, it is commonly attributed to the recruitment of secondary targets or to desensitization or feedback processes, but the concrete background of these observations often remains intriguing.

Objective: Here, we addressed the subject of bell-shaped agonist CRCs at the µ opioid receptor (µOR) by testing the impact of experimental conditions favoring G protein coupling.

Mice with a deletion of the major central myelin protein exhibit hypersensitivity to noxious thermal stimuli: involvement of central sensitization.

Null mutations in the gene encoding the major myelin protein of the central nervous system, proteolipid protein 1 (PLP1), cause an X-linked form of spastic paraplegia (SPG2) associated with axonal degeneration. While motor symptoms are the best known manifestations of this condition, its somatosensory disturbances have been described but poorly characterized. We carried out a longitudinal study in an animal model of SPG2 - mice carrying a deletion of the Plp1 gene (Plp-null mice).

Direct and indirect interactions of the dopamine D₃ receptor with glutamate pathways: implications for the treatment of schizophrenia.

This article, based on original data as well as on previously reported preclinical and clinical data that are reviewed, describes direct and indirect interactions of the D(3) receptor with N-methyl-D-aspartate receptor (NMDA) signaling and their functional consequences and therapeutic implications for schizophrenia. D(3) receptor immunoreactivity at ultrastructural level with electron microscopy was identified at presumably glutamatergic, asymmetric synapses of the medium-sized spiny neurons of the nucleus accumbens. This finding supports the existence of a direct interaction of the D(3) receptor with glutamate, in line with previously described interactions with NMDA signaling involving Ca(2+)/calmodulin-dependent protein kinase II at post-synaptic densities (Liu et al.

Does endoplasmic reticulum stress participate in APD-induced hepatic metabolic dysregulation?

Metabolic side effects caused by certain antipsychotic drugs (APDs), in particular clozapine and olanzapine, are now clinically well-documented. However, the potential mechanisms implicated in the metabolic disturbances of these drugs on peripheral tissues remain obscure. Here, we investigated the effects of five frequently prescribed APDs on the Sterol Regulatory Element Binding Protein (SREBP) transcription factor pathways which control lipogenesis and cholesterogenesis, using the Immortalized Human Hepatocyte cell model (IHH).

Overweight induced by chronic risperidone exposure is correlated with overexpression of the SREBP-1c and FAS genes in mouse liver.

Weight gain and metabolic disturbances, such as dyslipidemia and hyperglycaemia, are common side effects of most antipsychotic drugs, including risperidone. The aim of this study was to investigate the effects of chronic treatment with risperidone on body weight, fat accumulation, liver weight, and hepatic expression of key genes involved in lipid metabolism in female mice. We also addressed the mechanism of risperidone induction of metabolic side effects by exploring its effect on lipid and cholesterol metabolism in primary cultures of rat hepatocytes.

Rigid analogues of the α2-adrenergic blocker atipamezole: small changes, big consequences.

We report the discovery of a new family of α(2) adrenergic receptor antagonists derived from atipamezole. Affinities of the compounds at human α(2) and α(1b) receptors as well as their functional activities at hα(2A) receptors were determined in competition binding and G-protein activation assays, respectively. Central α(2) antagonist activities were confirmed in mice after oral administration.

Antipsychotic drug action on SREBPs-related lipogenesis and cholesterogenesis in primary rat hepatocytes.

The use of some of antipsychotic drugs (APDs) in humans has been hampered by the induction of metabolic disorders such as weight gain, dyslipidemia, and diabetes. In primary rat hepatocytes, we investigated the actions of several APDs on lipid and cholesterol metabolism using [(14)C]acetate incorporation, quantitative reverse transcription-polymerase chain reaction, and western blotting. Clozapine and olanzapine, known to have significant metabolic side effects in man, strongly increased de novo lipid and cholesterol synthesis in rat hepatocytes.

Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo.

Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1.

Na+ currents in cardioprotection: better to be late.

We report the discovery of a selective, potent inhibitor of the late current mediated by the cardiac isoform of the sodium channel (Na(V)1.5). The compound, 3,4-dihydro-N-[(2S)-3-[(2-hydroxy-3-methylphenyl)thio]-2-methylpropyl]-2H-(3R)-1,5-benzoxathiepin-3-amine (2d) (F 15741), blocks the late component of the Na(+) currents and greatly reduces veratridine- or ischemia-induced contracture in isolated tissue and whole heart.

Synthetic studies on cyclobuta[a]indanes: stereocontrolled access to C9-substituted derivatives.

We report the preparation of novel ethyl cyclobuta[a]indane derivatives of pharmacological interest. The synthesis of compounds 5 was used as a model to study stereocontrolled access to C9-substituted cyclobutane from the corresponding cyclobutanone 1. Progress was made on two complementary aspects: (1) catalytic hydrogenation from the appropriate cyclobutene precursors; and (2) delivery of the C9 substituent through an intramolecular process.

Region-specific changes in 5-HT1A agonist-induced Extracellular signal-Regulated Kinases 1/2 phosphorylation in rat brain: a quantitative ELISA study.

Brain serotonin 5-HT(1A) receptor, a traditional target for the treatment of mood disorders, modulates intracellular signalling pathways, such as the Extracellular signal-Regulated Kinases 1/2 (ERK1/2) pathway. The present studies are the first to determine levels of phospho-ERK1/2 (pERK1/2) in brain using a quantitative Enzyme Linked-Immuno-Sorbent Assay. We examined pERK1/2 levels in rat brain following administration of (+)8-OH-DPAT, buspirone as well as of the more selective, high-efficacy 5-HT(1A) agonists F13640 and F13714.

Sodium late current blockers in ischemia reperfusion: is the bullet magic?

We describe the discovery of the first selective, potent, and voltage-dependent inhibitor of the late current mediated by the cardiac sodium channel Na V1.5. The compound 3,4-dihydro- N-[(2 S)-3-[(2-methoxyphenyl)thio]-2-methylpropyl]-2 H-(3 R)-1,5-benzoxathiepin-3-amine, 2a (F 15845), was identified from a novel family of 3-amino-1,5-benzoxathiepine derivatives.

Antipsychotics differ in their ability to internalise human dopamine D2S and human serotonin 5-HT1A receptors in HEK293 cells.

Antipsychotic drugs act preferentially via dopamine D(2) receptor blockade, but interaction with serotonin 5-HT(1A) receptors has attracted interest as additional target for antipsychotic treatment. As receptor internalisation is considered crucial for drug action, we tested the propensity of antipsychotics to internalise human (h)D(2S) receptors and h5-HT(1A) receptors. Agonist-induced internalisation of hemaglutinin (HA)-tagged hD(2S) and HA-h5-HT(1A) receptors expressed in HEK293 cells was increased by coexpression of G-protein coupled receptor kinase 2 and beta-arrestin2.

High-efficacy 5-HT1A agonists for antidepressant treatment: a renewed opportunity.

We report the discovery of novel 5-HT1A receptor agonists and describe the process that led to the antidepressant candidate 9 (F 15599). 9 has nanomolar affinity for 5-HT1A binding sites and is over 1000-fold selective with respect to the other 5-HT1 receptor subtypes, 5-HT2-7 receptor families, and also numerous GPCRs, transporters, ion channels, and enzymes. In a cellular model of signal transduction, 9 activates h5-HT1A receptors with an efficacy superior to that of the prototypical 5-HT1A agonist (+/-)-8-OH-DPAT and comparators undergoing clinical trials.

Towards a new generation of potential antipsychotic agents combining D2 and 5-HT1A receptor activities.

We report the discovery and the synthesis of novel, potential antipsychotic compounds combining potent dopamine D2 receptor antagonist and serotonin 5-HT1A receptor agonist properties in the same molecule. We describe the structure-activity relationship that lead us to the promising derivative: N-[(2,2-dimethyl-2,3-dihydro-benzofuran-7-yloxy)ethyl]-3-(cyclopent-1-enyl)-benzylamine 16. The latter has high affinity for D2 and 5-HT1A receptors, whereas it possesses only a weak affinity for 5-HT2A sites.

Differential agonist and inverse agonist profile of antipsychotics at D2L receptors coupled to GIRK potassium channels.

The D(2) dopaminergic receptor represents a major target of antipsychotic drugs. Using the coupling of the human D(2long) (hD(2L)) receptor to G protein-coupled inward rectifier potassium (GIRK) channels in Xenopus laevis oocytes, we examined the activity of antipsychotic agents of different classes - typical, atypical, and a "new generation" of compounds, exhibiting a preferential D(2) and 5-HT(1A) receptor profile. When the hD(2L) receptor was coexpressed with GIRK channels, a series of reference compounds exhibited full agonist (dopamine, and quinpirole), partial agonist (apomorphine, (-)3-PPP, and (+)-UH232) or inverse agonist (raclopride, and L741626) properties.

Decreased nucleotide excision repair activity and alterations of topoisomerase IIalpha are associated with the in vivo resistance of a P388 leukemia subline to F11782, a novel catalytic inhibitor of topoisomerases I and II.

Purpose: The purpose of the study was to investigate the mechanisms associated with antitumor activity and resistance to F11782, a novel dual catalytic inhibitor of topoisomerases with DNA repair-inhibitory properties.

Experimental Design: For that purpose, an F11782-resistant P388 leukemia subline (P388/F11782) has been developed in vivo and characterized.

Results: Weekly subtherapeutic doses of F11782 (10 mg/kg) induced complete resistance to F11782 after 8 weekly passages.

Novel derivatives of 2-pyridinemethylamine as selective, potent, and orally active agonists at 5-HT1A receptors.

The aim of this work was to improve the oral bioavailability of a recently discovered, novel structural class of 5-HT1A receptor agonists: aryl-{[4-(6-R-pyridin-2-ylmethyl)-amino]-methyl}-piperidin-1 -yl-metha none. Incorporation of a fluorine atom in the beta-position to the amino function in the side chain led to analogues that exhibited, in general, enhanced and long-lasting 5-HT1A agonist activity in rats after oral administration. Location of the fluorine atom at the C-4 position of the piperidine ring was the most favorable, and among the various substituents tested, the ability of the fluorine was unique in improving the oral activity of this family of ligands.

Design and synthesis of a series of 6-substituted-2-pyridinylmethylamine derivatives as novel, high-affinity, selective agonists at 5-HT1A receptors.

A search for novel, selective agonists with high intrinsic activity at the 5-HT1A subtype of serotonin (5-HT) receptors was undertaken. Mechanistic and thermodynamic considerations led to the design of 6-substituted-2-pyridinylmethylamine as a potential 5-HT1A pharmacophore. Various adducts derived from the 6-substituted-2-pyridinylmethylamine moiety were tested for their affinity at 5-HT1A, alpha1-adrenergic, and D2-dopaminergic receptors.

Preclinical in vivo antitumor activity of vinflunine, a novel fluorinated Vinca alkaloid.

Vinflunine, or 20',20'-difluoro-3',4'-dihydrovinorelbine, is a novel Vinca alkaloid obtained by hemisynthesis using superacidic chemistry. The most impressive structural modification of this vinorelbine derivative was the selective introduction of two fluorine atoms at the 20' position, a part of the molecule previously inaccessible by classic chemistry. The antitumor activity of vinflunine was evaluated against a range of transplantable murine and human tumors.

5-HT autoreceptors in the regulation of 5-HT release from guinea pig raphe nucleus and hypothalamus.

5-HT autoreceptors involved in the regulation of 5-HT release in the guinea pig dorsal raphe nucleus have been studied in comparison with those in the hypothalamus. In vitro release was measured in slices of raphe and hypothalamus prelabelled with [3H]5-HT, superfused with Krebs solution and depolarized electrically. The non-selective 5-HT receptor agonist, 5-carboxamidotryptamine (5-CT) (0.

Effects of milnacipran and pindolol on extracellular noradrenaline and serotonin levels in guinea pig hypothalamus.

Milnacipran, a dual noradrenaline (NA) and serotonin (5-hydroxytryptamine, 5-HT) uptake inhibitor, increased extracellular levels of NA and 5-HT in hypothalamus of freely moving guinea pigs as measured by microdialysis. The basal levels of both monoamines, which were tetrodotoxin sensitive, were increased in a dose-dependent manner and to a similar extent after the intraperitoneal administration of milnacipran (10 and 40 mg/ kg i.p.

Biochemical changes and morphological alterations of liver and kidney in hamsters after administration of the HMG-coenzyme A reductase inhibitor, simvastatin: prevention and reversibility by mevalonate.

The present study analyses the effects of simvastatin, a specific inhibitor of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA reductase) in male Syrian hamsters fed a standard diet or a diet supplemented with 0.12% cholesterol and 20% coconut oil. In hamsters fed the standard diet, gastric administration of simvastatin (10 mg/kg/day) during 12 days was found to be lethal and to have hepatotoxic and nephrotoxic effects.

Neuropharmacology of 5-hydroxytryptamine1B/D receptor ligands.

In spite of a lack of compounds acting selectively at the 5-hydroxytryptamine (5-HT)1B and 5-HT1D receptor subtypes, by cross-relating the available data, this review attempts to tentatively assign behavioural and other in vivo correlates of these receptor subtypes. In addition, a summary of data from microdialysis studies is included to develop an integrated view. Finally, a suggestion is made as to the possible pathophysiological consequences of 5-HT1D receptor dysfunction in man.