From Oxadiazole to Triazole Analogues: Optimization toward a Dual Orexin Receptor Antagonist with Improved in vivo Efficacy in Dogs.

The orexin system is responsible for regulating the sleep-wake cycle. Suvorexant, a dual orexin receptor antagonist (DORA) is approved by the FDA for the treatment of insomnia disorders. Herein, we report the optimization efforts toward a DORA, where our starting point was (5-methoxy-4-methyl-2-[1,2,3]triazol-2-yl-phenyl)-{(S)-2-[5-(2-trifluoromethoxy-phenyl)-[1,2,4]oxadiazol-3-yl]-pyrrolidin-1-yl}methanone (6), a compound which emerged from our in-house research program.

The Use of Physiology-Based Pharmacokinetic and Pharmacodynamic Modeling in the Discovery of the Dual Orexin Receptor Antagonist ACT-541468.

The identification of new sleep drugs poses particular challenges in drug discovery owing to disease-specific requirements such as rapid onset of action, sleep maintenance throughout major parts of the night, and absence of residual next-day effects. Robust tools to estimate drug levels in human brain are therefore key for a successful discovery program. Animal models constitute an appropriate choice for drugs without species differences in receptor pharmacology or pharmacokinetics.

Novel hexahydrospiro[piperidine-4,1'-pyrrolo[3,4-c]pyrroles]: highly selective small-molecule nociceptin/orphanin FQ receptor agonists.

Novel hexahydrospiro[piperidine-4,1'-pyrrolo[3,4-c]pyrroles that act as potent and selective orphanin FQ/nociceptin (N/OFQ) receptor (NOP) agonists were identified. The best compound, (+)-5a, potently inhibited 3H-N/OFQ binding to the NOP receptor (K(i) = 0.49 nM) but was >1000-fold less potent in binding to MOP, KOP, and DOP opiate receptors.

A combined pharmacological and genetic approach to investigate the role of orphanin FQ in learning and memory.

Using a combination of the selective opioid receptor-like1 (ORL1) receptor agonist, Ro 64-6198, and orphanin FQ/nociceptin (OFQ/N) peptide knockout (KO) mice, the influence of OFQ/N on cognition has been studied in the rodent. In wild type, C57BL/6J mice, Ro 64-6198 (0.3-1 mg/kg i.

Improved Semliki Forest virus vectors for receptor research and gene therapy.

We have modified Semliki Forest virus (SFV) vectors to broaden their application range. Here we describe a series of site-directed mutagenesis experiments on the SFV subgenomic 26S promoter to down-regulate the heterologous gene expression. Several mutants showed a dramatic effect on transgene expression levels in BHK cells.

Drug-induced potentiation of prepulse inhibition of acoustic startle reflex in mice: a model for detecting antipsychotic activity?

Rationale: Schizophrenic patients typically have impaired startle habituation (SH) and prepulse inhibition of the startle reflex (PPI). PPI can be disrupted in rats by psychomimetics, and drug-induced reversal of this deficit is considered to predict potential antipsychotic properties. Certain strains of mice, such as C57BL/6J, naturally display poor PPI.

Pharmacological characterization of the novel nonpeptide orphanin FQ/nociceptin receptor agonist Ro 64-6198: rapid and reversible desensitization of the ORL1 receptor in vitro and lack of tolerance in vivo.

The novel nonpeptide orphanin FQ/nociceptin (OFQ/N) ligand [(1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-one] (Ro 64-6198) was characterized in vitro and in vivo for its agonistic potential. Ro 64-6198 was 130- to 3500-fold selective for the OFQ/N receptor (ORL1) compared with opiate receptors.

Influence of the selective ORL1 receptor agonist, Ro64-6198, on rodent neurological function.

Identification of synthetic agonists and antagonists at orphan receptors represents an important step for understanding their physiological function and therapeutic potential. Accordingly, we have recently described a non-peptide agonist at the opioid receptor like (ORL1) receptor (1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one (Ro64-6198; Jenck et al.

High-affinity, non-peptide agonists for the ORL1 (orphanin FQ/nociceptin) receptor.

The discovery of 8-(5,8-dichloro-1,2,3,4-tetrahydro-naphthalen-2-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one, 1a, as a high-affinity ligand for the human ORL1 (orphanin FQ/nociceptin) receptor led to the synthesis of a series of optimized ligands. These compounds exhibit high affinity for the human ORL1 receptor, exhibit moderate to good selectivity versus opioid receptors, and behave as full agonists in biochemical assays.

Spatial and associative learning deficits induced by neonatal excitotoxic hippocampal damage in rats: further evaluation of an animal model of schizophrenia.

Neonatal ventral hippocampal lesions in the rat result in post-pubertal onset of behavioural abnormalities, modelling some aspects of schizophrenia. We further assessed the behavioural effects of neonatal lesions in rats in a variety of cognitive tasks and in the prepulse inhibition (PPI) of startle response paradigm. Prepubescent, lesioned rats exhibited startle responses and PPI similar to controls whereas, at adulthood, they showed a deficit in PPI.

Synthesis of (1S,3aS)-8-(2,3,3a,4,5, 6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triaza-spiro[4. 5]decan-4-one, a potent and selective orphanin FQ (OFQ) receptor agonist with anxiolytic-like properties.

The development of 8-(2,3,3a,4,5, 6-hexahydro-1H-phenalen1-yl)-1-phenyl-1,3,8-triaza-spiro[4. 5]decan-4-ones 3 starting from (RS)-8-acenaphten-1-yl-1-phenyl-1,3, 8-triazaspiro[4.5]decan-4-one 1 is reported.

Functional consequences of reduction in NMDA receptor glycine affinity in mice carrying targeted point mutations in the glycine binding site.

We have used site-directed mutagenesis in conjunction with homologous recombination to generate two mouse lines carrying point mutations in the glycine binding site of the NMDAR1 subunit (Grin1). Glycine concentration-response curves from acutely dissociated hippocampal neurons revealed a 5- and 86-fold reduction in receptor glycine affinity in mice carrying Grin1(D481N) and Grin1(K483Q) mutations, respectively, whereas receptor glutamate affinity remained unaffected. Homozygous mutant Grin1(D481N) animals are viable and fertile and appear to develop normally.

ORL1 receptor ligands: structure-activity relationships of 8-cycloalkyl-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-ones.

We have investigated 8-cycloalkyl-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-o nes as ligands for the ORL1 receptor. These unsophisticated, achiral compounds show remarkable affinity for the ORL1 receptor.

8-acenaphthen-1-yl-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-one derivatives as orphanin FQ receptor agonists.

A series of 8-acenaphthen-1-yl-1-phenyl-1,3,8-triaza-spiro[4.5]decan+ ++-4-one derivatives 1 was studied with respect to the binding affinity for the orphanin FQ (OFQ) and opioid (mu, kappa, delta) receptors. The influence of stereochemistry as well as the substitution pattern of the phenyl-ring in position 1 on the affinity for the orphanin FQ receptor and selectivity to opioid (mu, kappa, delta) receptors is discussed.

Targeted disruption of the orphanin FQ/nociceptin gene increases stress susceptibility and impairs stress adaptation in mice.

The neuropeptide orphanin FQ (also known as nociceptin; OFQ/N) has been implicated in modulating stress-related behavior. OFQ/N was demonstrated to reverse stress-induced analgesia and possess anxiolytic-like activity after central administration. To further study physiological functions of OFQ/N, we have generated OFQ/N-deficient mice by targeted disruption of the OFQ/N gene.

5-HT2C receptor agonists: pharmacological characteristics and therapeutic potential.

In vitro, (S)-2-(chloro-5-fluoro-indol-1-yl)-1-methylethylamine 1:1 C4H4O4 and (S)-2-(4,4,7-trimethyl-1,4-dihydro-indeno[1, 2-b]pyrrol-1-yl)-1-methylethylamine 1:1 C4H4O4 exhibited high-affinity binding to the serotonin2C (5HT2C) receptors and stimulated turnover of inositol 1,4,5-triphosphate. Affinity to several of the other 5-HT receptor subtypes and to numerous nonserotonergic receptors was much lower. In rats, both compounds elicited behavioral signs of 5-HT2C receptor agonism but not 5-HT2A receptor agonism.

Sarmazenil-precipitated withdrawal: a reliable method for assessing dependence liability of benzodiazepine receptor ligands.

The benzodiazepine receptor partial inverse agonist sarmazenil exhibits in vivo proconvulsive, but not convulsant, effects in different paradigms in rodents. Intravenous sarmazenil challenge given at several fixed intervals following the termination of repeated treatment with a markedly sedative dose of diazepam in squirrel monkeys was effective in precipitating withdrawal signs, but had no comparable effects in vehicle-treated controls. The precipitated withdrawal reaction was not only robust, but it was consistently observed in all of the diazepam-treated monkeys.

Novel agonists of 5HT2C receptors. Synthesis and biological evaluation of substituted 2-(indol-1-yl)-1-methylethylamines and 2-(indeno[1,2-b]pyrrol-1-yl)-1-methylethylamines. Improved therapeutics for obsessive compulsive disorder.

The syntheses of a series of substituted 2-(indol-1-yl)-1-methylethylamines and 2-(indeno[1,2- b]pyrrol-1-yl)-1-methylethylamines are reported. The binding affinities of the compounds at 5HT2C and 5HT2A receptors (79% homology in the transmembrane domain) were determined. The ligands displayed selectivity for 5HT2C receptors relative to 5HT2A receptors.

Urocortin, a novel neuropeptide with anxiogenic-like properties.

Potential anxiogenic-like properties of urocortin, a corticotropin-releasing factor (CRF)-related neuropeptide, were investigated in models of anxiety in rodents. In the elevated plus-maze, CRF- and urocortin-treated rats (0.1 nmol, i.

Behavioral effects of CCKB receptor ligands in a validated simulation of panic anxiety in rats.

Animals or human subjects receiving brain stimulation in the dorsal periaqueductal gray matter (dPAG) show sudden fear-suggestive behavioral reactions and physical signs of autonomic activation which are reminiscent of the symptom profile characterizing a panic attack. An experimental situation in rats measuring dPAG stimulation self-interruption thresholds has been validated as realistically simulating several aspects of panic anxiety with objective signs of symptomatic and predictive validity using established antipanic and panicogenic agents; it was utilized here to evaluate the effects of various cholecystokinin B receptor ligands. A dose-dependent increase in self-interruption thresholds (antipanic-like effect) was recorded following injection of L-365,260 (3.

5HT2C receptor agonists exhibit antidepressant-like properties in the anhedonia model of depression in rats.

Potential antidepressant properties of preferential 5HT2C receptor agonists were investigated in stress-induced anhedonia, a validated simulation of depression. This simulation evaluates the hedonic state of stressed rats by recording variations in self-stimulation threshold measured before, during, and after exposure to intermittent, unpredictable, mild stressors. This stress regimen gradually elevates self-stimulation threshold, suggesting the development of an anhedonic state.

Chronic mild stress-induced anhedonia model of depression; sleep abnormalities and curative effects of electroshock treatment.

A core symptom of human depressive disorder is anhedonia, the loss of interest or pleasure in daily activities. Anhedonia, measured as subsensitivity to reward, can be induced in rats by a regimen of repeated, mild, unpredictable stressors. Here, the hedonic state of rats was assessed using an intracranial self-stimulation (ICSS) procedure.

Comparison of benzodiazepine receptor ligands with partial agonistic, antagonistic or partial inverse agonistic properties in precipitating withdrawal in squirrel monkeys.

Benzodiazepine receptor (BZR) ligands previously characterized as differing in intrinsic efficacy were evaluated first for potency in antagonizing flunitrazepam-induced sleep in monkeys. Data from these experiments were used to define approximately equieffective doses for subsequent use in precipitating withdrawal in diazepam-treated monkeys. It was shown that partial agonists with intermediate intrinsic efficacy (bretazenil, Ro 41-7812) were relatively ineffective in precipitating withdrawal reactions in diazepam-treated squirrel monkeys.

Dorsal periaqueductal gray-induced aversion as a simulation of panic anxiety: elements of face and predictive validity.

Neurosurgical stimulation of the dorsal periaqueductal gray (dPAG) matter in man induces acute signs of autonomic arousal and feelings of subjective anxiety; those signs have phenomenological similarity with the symptom profile characterizing a panic attack. Animals undergoing dPAG stimulation show comparable physical signs of autonomic activation and sudden fear-suggestive behavioral reactions that can be shaped into operant self-interruption behavior. Drugs known to acutely reduce (alprazolam, clonazepam) or precipitate (yohimbine, caffeine) panic attacks in patients were found to acutely and dose-dependently reduce or enhance, respectively, aversion induced by dPAG stimulation in rats.