Development of 2-Aminotetralin-Type Serotonin 5-HT Agonists: Molecular Determinants for Selective Binding and Signaling at 5-HT, 5-HT, 5-HT, and 5-HT Receptors.

The serotonin (5-hydroxytryptamine, 5-HT) 5-HT G-protein coupled receptor subtypes (5-HT) share a high sequence homology, confounding development of subtype-specific ligands. This study used a 5-HT structure-based ligand design approach to develop subtype-selective ligands using a 5-substituted-2-aminotetralin (5-SAT) chemotype, leveraging results from pharmacological, molecular modeling, and mutagenesis studies to delineate molecular determinants for 5-SAT binding and function at 5-HT subtypes. 5-SATs demonstrated high affinity ( ≤ 25 nM) and at least 50-fold stereoselective preference ([2] > [2]) at 5-HT, 5-HT and 5-HT receptors but essentially nil affinity ( > 1 μM) at 5-HT receptors.

Effects of (-)-MBP, a novel 5-HT agonist and 5-HT antagonist/inverse agonist on brain activity: A phMRI study on awake mice.

A novel serotonin ligand (-)-MBP was developed for the treatment of schizophrenia that has 5-HT antagonist activity together with 5-HT agonist activity. The multi-functional activity of this novel drug candidate was characterized using pharmacological magnetic resonance imaging. It was hypothesized (-)-MBP would affect activity in brain areas associated with sensory perception.

Conformationally Selective 2-Aminotetralin Ligands Targeting the alpha2A- and alpha2C-Adrenergic Receptors.

Many important physiological processes are mediated by alpha2A- and alpha2C-adrenergic receptors (α2Rs), a subtype of class A G protein-coupled receptors (GPCRs). However, α2R signaling is poorly understood, and there are few approved medications targeting these receptors. Drug discovery aimed at α2Rs is complicated by the high degree of binding pocket homology between α2AR and α2CR, which confounds ligand-mediated selective activation or inactivation of signaling associated with a particular subtype.

Oxycodone self-administration and reinstatement in male and female squirrel monkeys: Effects of alternative reinforcer availability.

The use of non-drug alternative reinforcers has long been utilized as a component of therapeutic interventions for the management of substance use disorder; however, the conditions under which alternative reinforcers are most effective are not well characterized. This study evaluated the impact of varying the magnitude of an alternative reinforcer on oxycodone self-administration and reinstatement in male and female squirrel monkeys. Subjects (n=4/sex) were trained under concurrent second-order schedules of reinforcement for intravenous oxycodone (0.

FPT, a 2-Aminotetralin, Is a Potent Serotonin 5-HT, 5-HT, and 5-HT Receptor Agonist That Modulates Cortical Electroencephalogram Activity in Adult Knockout Mice.

There are no approved medicines for fragile X syndrome (FXS), a monogenic, neurodevelopmental disorder. Electroencephalogram (EEG) studies show alterations in resting-state cortical EEG spectra, such as increased gamma-band power, in patients with FXS that are also observed in knockout models of FXS, offering putative biomarkers for drug discovery. Genes encoding serotonin receptors (5-HTRs), including 5-HT, 5-HT, and 5-HTRs, are differentially expressed in FXS, providing a rationale for investigating them as pharmacotherapeutic targets.

"Selective" serotonin 5-HT receptor antagonists.

Blockade of the serotonin 5-HT G protein-coupled receptor (5-HTR) is a fundamental pharmacological characteristic of numerous antipsychotic medications, which are FDA-approved to treat schizophrenia, bipolar disorder, and as adjunctive therapies in major depressive disorder. Meanwhile, activation of the 5-HTR by serotonergic psychedelics may be useful in treating neuropsychiatric indications, including major depressive and substance use disorders. Serotonergic psychedelics and other 5-HTR agonists, however, often bind other receptors, and standard 5-HTR antagonists lack sufficient selectivity to make well-founded mechanistic conclusions about the 5-HTR-dependent effects of these compounds and the general neurobiological function of 5-HTRs.

A new class of 5-HT /5-HT receptor inverse agonists: Synthesis, molecular modeling, in vitro and in vivo pharmacology of novel 2-aminotetralins.

Background And Purpose: The 5-HT receptor subtypes 5-HT and 5-HT are important neurotherapeutic targets, though, obtaining selectivity over 5-HT and H receptors is challenging. Here, we delineated molecular determinants of selective binding to 5-HT and 5-HT receptors for novel 4-phenyl-2-dimethylaminotetralins (4-PATs).

Experimental Approach: We synthesized 42 novel 4-PATs with halogen or aryl moieties at the C(4)-phenyl meta-position.

Evaluation of lorcaserin as an anticonvulsant in juvenile Fmr1 knockout mice.

Recent preclinical and clinical studies suggest that lorcaserin, a preferential serotonin 2C receptor (5-HTR) agonist that was approved for the treatment of obesity, possesses antiepileptic properties. Here, we tested whether lorcaserin (1, 3, 5.6, 10 mg/kg) is prophylactic against audiogenic seizures (AGSs) in juvenile Fmr1 knockout mice, a mouse model of fragile X syndrome (FXS).

()-5-(2'-Fluorophenyl)-,-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine, a Serotonin Receptor Modulator, Possesses Anticonvulsant, Prosocial, and Anxiolytic-like Properties in an Knockout Mouse Model of Fragile X Syndrome and Autism Spectrum Disorder.

Fragile X syndrome (FXS) is a neurodevelopmental disorder characterized by intellectual disabilities and a plethora of neuropsychiatric symptoms. FXS is the leading monogenic cause of autism spectrum disorder (ASD), which is defined clinically by repetitive and/or restrictive patterns of behavior and social communication deficits. Epilepsy and anxiety are also common in FXS and ASD.

Synthesis of novel 5-substituted-2-aminotetralin analogs: 5-HT and 5-HT G protein-coupled receptor affinity, 3D-QSAR and molecular modeling.

The serotonin 5-HT G protein-coupled receptor (GPCR) is a proposed pharmacotherapeutic target for a variety of central and peripheral indications, albeit, there are no approved drugs selective for binding 5-HT. We previously reported that a lead analog based on the 5-substituted-N,N-disubstituted-1,2,3,4-tetrahydronaphthalen-2-amine (5-substituted-2-aminotetralin, 5-SAT) scaffold binds with high affinity at the 5-HT GPCR, and can treat symptoms of autism in mouse models; subsequently, the lead was found to have high affinity at the 5-HT GPCR. Herein, we report the synthesis of novel 5-SAT analogs to develop a 3-dimensional quantitative structure-affinity relationship (3D-QSAR) at the human 5-HT receptor for comparison with similar studies at the highly homologous 5-HT receptor.

Ligand-directed serotonin 5-HT receptor desensitization and sensitization.

Exposure of G protein-coupled receptors (GPCRs) to agonists can desensitize receptor signaling and lead to drug tolerance, whereas inverse agonists can sensitize signaling. For example, activation of serotonin 5-HT GPCRs is pharmacotherapeutic for obesity, but there is tolerance to the anorectic effect of the only approved 5-HT agonist, lorcaserin. We tested the hypothesis that different agonists or inverse agonists differentially desensitize or sensitize, respectively, canonical 5-HT-mediated activation of phospholipase C (PLC) signaling in vitro.

Homology Modeling Inspired Synthesis of 5-HT2A Receptor Inhibitors: A Diazepine Analogue of the Atypical Antipsychotic JL13.

Background: The benzoxazepine JL13 is an analogue of the clozapine family of antipsychotic agents which target the 5-HT2A receptor, and has showed promise as an atypical antipsychotic agent. Based on the dearth of clinically effective anti-psychotic agents available, we sought to design and chemically synthesize additional analogues.

Methods: Structure function analysis was conducted using state of art computational methods, which were designed to highlight new candidates for chemical synthesis.

Mutagenesis Analysis Reveals Distinct Amino Acids of the Human Serotonin 5-HT Receptor Underlying the Pharmacology of Distinct Ligands.

While exploring the structure-activity relationship of 4-phenyl-2-dimethylaminotetralins (PATs) at serotonin 5-HT receptors, we discovered that relatively minor modification of PAT chemistry impacts function at 5-HT receptors. In HEK293 cells expressing human 5-HT receptors, for example, (-)-trans-3'-Br-PAT and (-)-trans-3'-Cl-PAT are agonists regarding Gα-inositol phosphate signaling, whereas (-)-trans-3'-CF-PAT is an inverse agonist. To investigate the ligand-receptor interactions that govern this change in function, we performed site-directed mutagenesis of 14 amino acids of the 5-HT receptor based on molecular modeling and reported G protein-coupled receptor crystal structures, followed by molecular pharmacology studies.

An Orally Active Phenylaminotetralin-Chemotype Serotonin 5-HT7 and 5-HT1A Receptor Partial Agonist that Corrects Motor Stereotypy in Mouse Models.

Stereotypy (e.g., repetitive hand waving) is a key phenotype of autism spectrum disorder, Fragile X and Rett syndromes, and other neuropsychiatric disorders, and its severity correlates with cognitive and attention deficits.

Novel 4-substituted-N,N-dimethyltetrahydronaphthalen-2-amines: synthesis, affinity, and in silico docking studies at serotonin 5-HT2-type and histamine H1 G protein-coupled receptors.

Syntheses were undertaken of derivatives of (2S,4R)-(-)-trans-4-phenyl-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (4-phenyl-2-dimethylaminotetralin, PAT), a stereospecific agonist at the serotonin 5-HT2C G protein-coupled receptor (GPCR), with inverse agonist activity at 5-HT2A and 5-HT2B GPCRs. Molecular changes were made at the PAT C(4)-position, while preserving N,N-dimethyl substitution at the 2-position as well as trans-stereochemistry, structural features previously shown to be optimal for 5-HT2 binding. Affinities of analogs were determined at recombinant human 5-HT2 GPCRs in comparison to the phylogenetically closely-related histamine H1 GPCR, and in silico ligand docking studies were conducted at receptor molecular models to help interpret pharmacological results and guide future ligand design.

Serotonin-2C receptor agonists decrease potassium-stimulated GABA release in the nucleus accumbens.

The serotonin 5-HT2C receptor has shown promise in vivo as a pharmacotherapeutic target for alcoholism. For example, recently, a novel 4-phenyl-2-N,N-dimethylaminotetralin (PAT) drug candidate, that demonstrates 5-HT2C receptor agonist activity together with 5-HT2A/2B receptor inverse agonist activity, was shown to reduce operant responding for ethanol after peripheral administration to rats. Previous studies have shown that the 5-HT2C receptor is found throughout the mesoaccumbens pathway and that 5-HT2C receptor agonism causes activation of ventral tegmental area (VTA) GABA neurons.

Aromatic interactions impact ligand binding and function at serotonin 5-HT G protein-coupled receptors: Receptor homology modeling, ligand docking, and molecular dynamics results validated by experimental studies.

The serotonin (5-hydroxytryptamine, 5-HT) 5-HT G protein-coupled receptor (GPCR) family consists of types 2A, 2B, and 2C that share ~75% transmembrane (TM) sequence identity. Agonists for 5-HT receptors are under development for psychoses, whereas, at 5-HT receptors, antipsychotic effects are associated with antagonists-in fact, 5-HT agonists can cause hallucinations and 5-HT agonists cause cardiotoxicity. It is known that 5-HT TM6 residues W6.

A novel aminotetralin-type serotonin (5-HT) 2C receptor-specific agonist and 5-HT2A competitive antagonist/5-HT2B inverse agonist with preclinical efficacy for psychoses.

Development of 5-HT2C agonists for treatment of neuropsychiatric disorders, including psychoses, substance abuse, and obesity, has been fraught with difficulties, because the vast majority of reported 5-HT2C selective agonists also activate 5-HT2A and/or 5-HT2B receptors, potentially causing hallucinations and/or cardiac valvulopathy. Herein is described a novel, potent, and efficacious human 5-HT2C receptor agonist, (-)-trans-(2S,4R)-4-(3'[meta]-bromophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (-)-MBP), that is a competitive antagonist and inverse agonist at human 5-HT2A and 5-HT2B receptors, respectively. (-)-MBP has efficacy comparable to the prototypical second-generation antipsychotic drug clozapine in three C57Bl/6 mouse models of drug-induced psychoses: the head-twitch response elicited by [2,5]-dimethoxy-4-iodoamphetamine; hyperlocomotion induced by MK-801 [(5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (dizocilpine maleate)]; and hyperlocomotion induced by amphetamine.

Molecular pharmacology and ligand docking studies reveal a single amino acid difference between mouse and human serotonin 5-HT2A receptors that impacts behavioral translation of novel 4-phenyl-2-dimethylaminotetralin ligands.

During translational studies to develop 4-phenyl-2-dimethylaminotetralin (PAT) compounds for neuropsychiatric disorders, the (2R,4S)-trans-(+)- and (2S,4R)-trans-(-)-enantiomers of the analog 6-hydroxy-7-chloro-PAT (6-OH-7-Cl-PAT) demonstrated unusual pharmacology at serotonin (5-HT) 5-HT2 G protein-coupled receptors (GPCRs). The enantiomers had similar affinities (Ki) at human (h) 5-HT2A receptors (≈ 70 nM). In an in vivo mouse model of 5-HT2A receptor activation [(±)-(2,5)-dimethoxy-4-iodoamphetamine (DOI)-elicited head twitch], however, (-)-6-OH-7-Cl-PAT was about 5-fold more potent than the (+)-enantiomer at attenuating the DOI-elicited response.

The serotonin-2 receptor modulator, (-)-trans-PAT, decreases voluntary ethanol consumption in rats.

Serotonin (5-HT) 5-HT2C receptor agonists have shown promise as novel alcoholism pharmacotherapies, but developing selective agonists has been problematic. Female Sprague Dawley rats were given ethanol in a palatable gel vehicle during operant sessions. 5-HT2C receptor modulators (Ro60-0175, SB242,084, and (-)-trans-PAT) were administered before operant sessions.

Molecular Determinants for Ligand Binding at Serotonin 5-HT and 5-HT GPCRs: Experimental Affinity Results Analyzed by Molecular Modeling and Ligand Docking Studies.

Ligands that activate the serotonin 5-HT G protein-coupled receptor (GPCR) may be therapeutic for psychoses, addiction, and other neuropsychiatric disorders. Ligands that are antagonists at the closely related 5-HT GPCR also may treat neuropsychiatric disorders; in contrast, 5-HT activation may cause hallucinations. 5-HT-specific agonist drug design is challenging because 5-HT GPCRs share 80% transmembrane (TM) homology, same second messenger signaling, and no crystal structures are reported.

Molecular and behavioral pharmacology of two novel orally-active 5HT2 modulators: potential utility as antipsychotic medications.

Background: Desired serotonin 5HT2 receptor pharmacology for treatment of psychoses is 5HT2A antagonism and/or 5HT2C agonism. No selective 5HT2A antagonist has been approved for psychosis and the only approved 5HT2C agonist (for obesity) also activates 5HT2A and 5HT2B receptors, which can lead to clinical complications. Studies herein tested the hypothesis that a dual-function 5HT2A antagonist/5HT2C agonist that does not activate 5HT2B receptors would be suitable for development as an antipsychotic drug, without liability for weight gain.

Support for 5-HT2C receptor functional selectivity in vivo utilizing structurally diverse, selective 5-HT2C receptor ligands and the 2,5-dimethoxy-4-iodoamphetamine elicited head-twitch response model.

There are seemingly conflicting data in the literature regarding the role of serotonin (5-HT) 5-HT2C receptors in the mouse head-twitch response (HTR) elicited by the hallucinogenic 5-HT2A/2B/2C receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI). Namely, both 5-HT2C receptor agonists and antagonists, regarding 5-HT2C receptor-mediated Gq-phospholipase C (PLC) signaling, reportedly attenuate the HTR response. The present experiments tested the hypothesis that both classes of 5-HT2C receptor compounds could attenuate the DOI-elicited-HTR in a single strain of mice, C57Bl/6J.

Molecular determinants of ligand binding at the human histamine H receptor: Site-directed mutagenesis results analyzed with ligand docking and molecular dynamics studies at H homology and crystal structure models.

The human histamine H G-protein coupled receptor (GPCR) is an important drug target for inflammatory, sleep, and other neuropsychiatric disorders. To delineate molecular determinants for ligand binding for drug discovery purposes, human H receptor models were built by homology to the crystal structure of the human β adrenoceptor (βAR) and from the recently reported crystal structure of the human H receptor complex with doxepin at 3.1 Å (PDB code 3RZE).