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Paul J Fletcher - One of the best experts on this subject based on the ideXlab platform.
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pharmacological modulation of 5 ht2c Receptor activity produces bidirectional changes in locomotor activity responding for a conditioned reinforcer and mesolimbic da release in c57bl 6 mice
Neuropsychopharmacology, 2017Co-Authors: Guy A Higgins, Paul J Fletcher, Caleb J Browne, Colin HarveylewisAbstract:Converging lines of behavioral, electrophysiological, and biochemical evidence suggest that 5-HT2C Receptor signaling may bidirectionally influence reward-related behavior through an interaction with the mesolimbic dopamine (DA) system. Here we directly test this hypothesis by examining how modulating 5-HT2C Receptor activity affects DA-dependent behaviors and relate these effects to changes in nucleus accumbens (NAc) DA release. In C57BL/6 mice, locomotor activity and responding for a conditioned reinforcer (CRf), a measure of incentive motivation, were examined following treatment with three 5-HT2C Receptor ligands: the agonist CP809101 (0.25–3 mg/kg), the antagonist SB242084 (0.25–1 mg/kg), or the antagonist/inverse agonist SB206553 (1–5 mg/kg). We further tested whether doses of these compounds that changed locomotor activity and responding for a CRf (1 mg/kg CP809101, 0.5 mg/kg SB242084, or 2.5 mg/kg SB206553) also altered NAc DA release using in vivo microdialysis in anesthetized mice. CP809101 reduced locomotor activity, responding for a CRf, and NAc DA release. In contrast, both SB242084 and SB206553 enhanced locomotor activity, responding for a CRf, and NAc DA release, although higher doses of SB206553 produced opposite behavioral effects. Pretreatment with the non-selective DA Receptor antagonist α-flupenthixol prevented SB242084 from enhancing responding for a CRf. Thus blocking tonic 5-HT2C Receptor signaling can release serotonergic inhibition of mesolimbic DA activity and enhance reward-related behavior. The observed bidirectional effects of 5-HT2C Receptor ligands may have important implications when considering the 5-HT2C Receptor as a therapeutic target for psychiatric disorders, particularly those presenting with motivational dysfunctions.
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effects of 5 ht1a 5 ht2a and 5 ht2c Receptor agonists and antagonists on responding for a conditioned reinforcer and its enhancement by methylphenidate
Psychopharmacology, 2017Co-Authors: Fiona D Zeeb, Guy A Higgins, Paul J Fletcher, Caleb J Browne, Ashlie D SokoAbstract:Objectives These experiments examined the effects of selective 5-HT1A, 5-HT2A and 5-HT2C Receptor ligands on responding for a conditioned reinforcer (CRf). Effects of these ligands were measured under basal conditions and following elevated dopamine (DA) activity produced by the DA reuptake inhibitor methylphenidate.
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lorcaserin and cp 809101 reduce motor impulsivity and reinstatement of food seeking behavior in male rats implications for understanding the anti obesity property of 5 ht2c Receptor agonists
Psychopharmacology, 2016Co-Authors: Guy A Higgins, Paul J Fletcher, Leo B. Silenieks, Everett B Altherr, Cam Macmillan, Wayne E PrattAbstract:The 5-HT2C Receptor agonist lorcaserin (Belviq®) has been approved by the FDA for the treatment of obesity. Impulsivity is a contributory feature of some eating disorders. Experiments investigated the effect of lorcaserin and the highly selective 5-HT2C agonist CP-809101 on measures of impulsivity and on reinstatement of food-seeking behaviour, a model of dietary relapse. The effect of both drugs on 22-h deprivation-induced feeding was also examined, as was the effect of prefeeding in each impulsivity test. Lorcaserin (0.3–0.6 mg/kg SC) and CP-809101 (0.6–1 mg/kg SC) reduced premature responding in rats trained on the 5-CSRTT and improved accuracy in a Go-NoGo task by reducing false alarms. At equivalent doses, both drugs also reduced reinstatement for food-seeking behaviour. Neither drug altered impulsive choice measured in a delay-discounting task. Lorcaserin (1–3 mg/kg SC) and CP-809101 (3–6 mg/kg SC) reduced deprivation-induced feeding but only at higher doses. These results suggest that in addition to previously reported effects on satiety and reward, altered impulse control may represent a contributory factor to the anti-obesity property of 5-HT2C Receptor agonists. Lorcaserin may promote weight loss by improving adherence to dietary regimens in individuals otherwise prone to relapse and may be beneficial in cases where obesity is associated with eating disorders tied to impulsive traits, such as binge eating disorder.
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characterization of the 5 ht2c Receptor agonist lorcaserin on efficacy and safety measures in a rat model of diet induced obesity
Pharmacology Research & Perspectives, 2015Co-Authors: Guy A Higgins, Paul J Fletcher, Leo B. Silenieks, Jill Desnoyer, Annalise Van Niekerk, Winnie Lau, Sandy Thevarkunnel, Julia Izhakova, Ines DelannoyAbstract:The 5-HT2C Receptor agonist lorcaserin (Belviq®) has been Food and Drug Administration (FDA) approved for the treatment of obesity. The present study is a back translational investigation into the effect of 28-day lorcaserin treatment in a diet-induced obesity (DIO) model using male, Sprague–Dawley rats. An assessment of drug effect on efficacy and multiple safety endpoints including cardiac function was undertaken. Lorcaserin (1–2 mg/kg SC b.i.d.) significantly reduced percentage body weight gain compared to vehicle-treated controls (VEH: 10.6 ± 0.4%; LOR 1: 7.6 ± 1.2%; LOR 2: 5.4 ± 0.6%). Measurement of body composition using quantitative magnetic resonance (QMR) imaging indicated this change was due to the selective reduction in body fat mass. Modest effects on food intake were recorded. At the completion of the treatment phase, echocardiography revealed no evidence for valvulopathy, that is, no aortic or mitral valve regurgitation. The pharmacokinetics of the present treatment regimen was determined over a 7-day treatment period; plasma Cmin and Cmax were in the range 13–160 ng/mL (1 mg/kg b.i.d.) and 34–264 ng/mL (2 mg/kg b.i.d.) with no evidence for drug accumulation. In sum, these studies show an effect of lorcaserin in the DIO model, that in the context of the primary endpoint measure of % body weight change was similar to that reported clinically (i.e., 3.0–5.2% vs. 3.2%). The present studies highlight the translational value of obesity models such as DIO, and suggest that assuming consideration is paid to nonspecific drug effects such as malaise, the DIO model has reasonable forward translational value to help predict clinical outcomes of a new chemical entity.
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responding for a conditioned reinforcer and its enhancement by nicotine is blocked by dopamine Receptor antagonists and a 5 ht2c Receptor agonist but not by a 5 ht2a Receptor antagonist
Pharmacology Biochemistry and Behavior, 2014Co-Authors: Paul J Fletcher, Elizabeth Glenn GuyAbstract:An aspect of nicotine reinforcement that may contribute to tobacco addiction is the effect of nicotine to enhance the motivational properties of reward-associated cues, or conditioned stimuli (CSs). Several studies have now shown that nicotine enhances responding for a stimulus that has been paired with a natural reinforcer. This effect of nicotine to enhance responding for a conditioned reinforcer is likely due to nicotine-induced enhancements in mesolimbic dopaminergic activity, but this has not been directly assessed. In this study, we assessed roles for dopamine (DA) D1 or D2 Receptors, and two serotonin (5-HT) Receptor subtypes known to modulate DA activity, the 5-HT2C or 5-HT2A subtypes, on nicotine-enhanced responding for a conditioned reinforcer. Water-restricted rats were exposed to Pavlovian conditioning sessions, where a CS was paired with water delivery. Then, in a second phase, animals were required to perform a novel, lever-pressing response for presentations of the CS as a conditioned reinforcer. Nicotine (0.4 mg/kg) enhanced responding for the conditioned reinforcer. To examine potential roles for dopamine (DA) and serotonin (5-HT) Receptors in this effect, separate groups of animals were used to assess the impact of administering the D1 Receptor antagonist SCH 23390, D2 Receptor antagonist eticlopride, 5-HT2C Receptor agonist Ro 60-0175, or 5-HT2A Receptor antagonist M100907 on nicotine-enhanced responding for conditioned reinforcement. SCH 23390, eticlopride, and Ro 60-0175 all reduced responding for conditioned reinforcement, and the ability of nicotine to enhance this effect. M100907 did not alter this behavior. Together, these studies indicate that DA D1 and D2 Receptors, but not 5-HT2A Receptors, contribute to the effect of nicotine to enhance responding for a conditioned reinforcer. This effect can also be modulated by 5-HT2C Receptor activation.
Elaine Sandersbush - One of the best experts on this subject based on the ideXlab platform.
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impact of rna editing on functions of the serotonin 2c Receptor in vivo
Frontiers in Neuroscience, 2010Co-Authors: Uade Olaghere B Da Silva, Michael V Morabito, Clinton E Canal, David C. Airey, Ronald B. Emeson, Elaine SandersbushAbstract:Transcripts encoding 5-HT2C Receptors are modified posttranscriptionally by RNA editing, generating up to 24 protein isoforms. In recombinant cells, the fully edited isoform, 5-HT2C-VGV, exhibits blunted G-protein coupling and reduced constitutive activity. The present studies examine the signal transduction properties of 5-HT2C-VGV Receptors in brain to determine the in vivo consequences of altered editing. Using mice solely expressing the 5-HT2C-VGV Receptor (VGV/Y), we demonstrate reduced G-protein coupling efficiency and high-affinity agonist binding of brain 5-HT2C-VGV Receptors. However, enhanced behavioral sensitivity to a 5-HT2C Receptor agonist was also seen in mice expressing 5-HT2C-VGV Receptors, an unexpected finding given the blunted G-protein coupling. In addition, mice expressing 5-HT2C-VGV Receptors had greater sensitivity to a 5-HT2C inverse agonist/antagonist enhancement of dopamine turnover relative to wild-type mice. These behavioral and biochemical results are most likely explained by increases in 5-HT2C Receptor binding sites in the brains of mice solely expressing -5HT2C-VGV Receptors. We conclude that 5-HT2C-VGV Receptor signaling in brain is blunted, but this deficiency is masked by a marked increase in 5HT2C Receptor binding site density in mice solely expressing the VGV isoform. These findings suggest that RNA editing may regulate the density of 5-HT2C Receptor binding sites in brain. We further caution that the pattern of 5-HT2C Receptor RNA isoforms may not reflect the pattern of protein isoforms, and hence the inferred overall function of the Receptor.
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the serotonin 2c Receptor potently modulates the head twitch response in mice induced by a phenethylamine hallucinogen
Psychopharmacology, 2010Co-Authors: Paul J Gresch, Elaine Sandersbush, Uade Olaghere B Da Silva, Clinton E Canal, Erin E Watt, David C. AireyAbstract:Hallucinogenic serotonin 2A (5-HT2A) Receptor partial agonists, such as (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), induce a frontal cortex-dependent head-twitch response (HTR) in rodents, a behavioral proxy of a hallucinogenic response that is blocked by 5-HT2A Receptor antagonists. In addition to 5-HT2A Receptors, DOI and most other serotonin-like hallucinogens have high affinity and potency as partial agonists at 5-HT2C Receptors. We tested for involvement of 5-HT2C Receptors in the HTR induced by DOI. Comparison of 5-HT2C Receptor knockout and wild-type littermates revealed an approximately 50% reduction in DOI-induced HTR in knockout mice. Also, pretreatment with either the 5-HT2C Receptor antagonist SB206553 or SB242084 eradicated a twofold difference in DOI-induced HTR between the standard inbred mouse strains C57BL/6J and DBA/2J, and decreased the DOI-induced HTR by at least 50% in both strains. None of several measures of 5-HT2A Receptors in frontal cortex explained the strain difference, including 5-HT2A Receptor density, Gαq or Gαi/o protein levels, phospholipase C activity, or DOI-induced expression of Egr1 and Egr2. 5-HT2C Receptor density in the brains of C57BL/6J and DBA/2J was also equivalent, suggesting that 5-HT2C Receptor-mediated intracellular signaling or other physiological modulators of the HTR may explain the strain difference in response to DOI. We conclude that the HTR to DOI in mice is strongly modulated by 5-HT2C Receptor activity. This novel finding invites reassessment of hallucinogenic mechanisms involving 5-HT2 Receptors.
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rna editing of the serotonin 2c Receptor and expression of gαq protein genetic mouse models do not support a role for regulation or compensation
Journal of Neurochemistry, 2009Co-Authors: Clinton E Canal, Elaine Sandersbush, Kontip Connie Mahautmr, David C. AireyAbstract:The serotonin 2C (5-HT2C) Receptor undergoes RNA editing at five bases in a region of the pre-mRNA encoding the second intracellular loop, generating many unique 5-HT2C Receptor isoforms. Mechanisms regulating in vivo expression of different edited 5-HT2C Receptor isoforms are poorly understood, as are the adaptive consequences of variation in editing profiles. Recent findings suggest a putative relationship between expression levels of Gαq/11 protein and the degree of editing of 5-HT2C Receptor transcripts. To elucidate the potential regulatory or adaptive role of Gαq/11 protein levels, we quantified editing of 5-HT2C Receptor RNA transcripts in Gαq null mice and protein levels of Gαq and Gα11 in transgenic male mice solely expressing either the non-edited (INI) or the fully edited (VGV) isoforms of the 5-HT2C Receptor. Pyrosequencing of RNA isolated from amygdaloid cortex in Gαq null and wild-type mice revealed no significant differences in 5-HT2C Receptor mRNA editing profiles. Cortical tissue from INI/y, VGV/y, and wild-type mice was assayed for expression of Gαq and Gα11 subunits by Western blotting. No differences in signal density between wild-type and INI/y or VGV/y groups were found, indicating equivalent levels of Gαq and Gα11 protein. Together, these data do not support a causal or compensatory relationship between 5-HT2C Receptor RNA editing and Gq protein levels.
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rna editing of the human serotonin 5 ht2c Receptor alters Receptor mediated activation of g13 protein
Journal of Biological Chemistry, 2001Co-Authors: Raymond D Price, David M Weiner, Mike S S Chang, Elaine SandersbushAbstract:Abstract The recent completion of the human genome predicted the presence of only 30,000 genes, stressing the importance of mechanisms that increase molecular diversity at the post-transcriptional level. One such post-transcriptional event is RNA editing, which generates multiple protein isoforms from a single gene, often with profound functional consequences. The human serotonin 5-HT2C Receptor undergoes RNA editing that creates multiple Receptor isoforms. One consequence of RNA editing of cell surface Receptors may be to alter the pattern of activation of heterotrimeric G-proteins and thereby shift preferred intracellular signaling pathways. We examined the ability of the nonedited 5-HT2C Receptor isoform (INI) and two extensively edited isoforms, VSV and VGV, to interact with various G-protein α subunits. Two functional assays were utilized: the cell-based functional assay, Receptor Selection/Amplification TechnologyTM, in which the pharmacological consequences of co-expression of 5HT2C Receptor isoforms with G-protein α subunits in fibroblasts were studied, and 5HT2CReceptor-mediated rearrangements of the actin cytoskeleton in stable cell lines. These studies revealed that the nonedited 5-HT2C Receptor functionally couples to Gq and G13. In contrast, coupling to G13 was not detected for the extensively edited 5-HT2C Receptors. Thus, RNA editing represents a novel mechanism for regulating the pattern of activation of heterotrimeric G-proteins, molecular switches that control an enormous variety of biological processes.
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rna editing of the 5 ht2c Receptor alters agonist Receptor effector coupling specificity
British Journal of Pharmacology, 2001Co-Authors: Jodie Cropper, Elaine Sandersbush, Colleen M Niswender, Ronald B. EmesonAbstract:The serotonin2C (5-HT2C) Receptor couples to both phospholipase C (PLC)-inositol phosphate (IP) and phospholipase A2 (PLA2)-arachidonic acid (AA) signalling cascades. Agonists can differentially activate these effectors (i.e. agonist-directed trafficking of Receptor stimulus) perhaps due to agonist-specific Receptor conformations which differentially couple to/activate transducer molecules (e.g. G proteins). Since editing of RNA transcripts of the human 5-HT2C Receptor leads to substitution of amino acids at positions 156, 158 and 160 of the putative second intracellular loop, a region important for G protein coupling, we examined the capacity of agonists to activate both the PLC-IP and PLA2-AA pathways in CHO cells stably expressing two major, fully RNA-edited isoforms (5-HT2C-VSV, 5-HT2C-VGV) of the h5-HT2C Receptor. 5-HT increased AA release and IP accumulation in both 5-HT2C-VSV and 5-HT2C-VGV expressing cells. As expected, the potency of 5-HT for both RNA-edited isoforms for both responses was 10 fold lower relative to that of the non-edited Receptor (5-HT2C-INI) when Receptors were expressed at similar levels. Consistent with our previous report, the efficacy order of two 5-HT Receptor agonists (TFMPP and bufotenin) was reversed for AA release and IP accumulation at the non-edited Receptor thus demonstrating agonist trafficking of Receptor stimulus. However, with the RNA-edited Receptor isoforms there was no difference in the relative efficacies of TFMPP or bufotenin for AA release and IP accumulation suggesting that the capacity for 5-HT2C agonists to traffic Receptor stimulus is lost as a result of RNA editing. These results suggest an important role for the second intracellular loop in transmitting agonist-specific information to signalling molecules. British Journal of Pharmacology (2001) 134, 386–392; doi:10.1038/sj.bjp.0704255
Kathryn A. Cunningham - One of the best experts on this subject based on the ideXlab platform.
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discovery of 4 phenylpiperidine 2 carboxamide analogues as serotonin 5 ht2c Receptor positive allosteric modulators with enhanced drug like properties
Journal of Medicinal Chemistry, 2020Co-Authors: Eric A Wold, Noelle C. Anastasio, Erik J Garcia, Christopher Wild, Joanna Miszkiel, Claudia A Soto, Jianping Chen, Konrad Pazdrak, Robert G Fox, Kathryn A. CunninghamAbstract:Targeting the serotonin (5-HT) 5-HT2C Receptor (5-HT2CR) allosteric site to potentiate endogenous 5-HT tone may provide novel therapeutics to alleviate the impact of costly, chronic diseases such as obesity and substance use disorders. Expanding upon our recently described 5-HT2CR-positive allosteric modulators (PAMs) based on the 4-alkylpiperidine-2-carboxamide scaffold, we optimized the undecyl moiety at the 4-position with variations of cyclohexyl- or phenyl-containing fragments to reduce rotatable bonds and lipophilicity. Compound 12 (CTW0415) was discovered as a 5-HT2CR PAM with improved pharmacokinetics and reduced off-target interactions relative to our previous series of molecules. The in vivo efficacy of compound 12 to potentiate the effects of a selective 5-HT2CR agonist was established in a drug discrimination assay. Thus, 12 is reported as a 5-HT2CR PAM with characteristics suitable for in vivo pharmacological studies to further probe the biological and behavioral mechanisms of allosteric modulation of a Receptor important in several chronic diseases.
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design synthesis and characterization of 4 undecylpiperidine 2 carboxamides as positive allosteric modulators of the serotonin 5 ht 5 ht2c Receptor
Journal of Medicinal Chemistry, 2019Co-Authors: Christopher Wild, Kathryn A. Cunningham, Noelle C. Anastasio, Rachel M. Hartley, Eric A Wold, Joanna Miszkiel, Claudia A Soto, Chunyong Ding, Mark A White, Jia ZhouAbstract:An impaired signaling capacity of the serotonin (5-HT) 5-HT2C Receptor (5-HT2CR) has been implicated in the neurobehavioral processes that promote relapse vulnerability in cocaine use disorder (CUD). Restoration of the diminished 5-HT2CR signaling through positive allosteric modulation presents a novel therapeutic approach. Several new molecules with the 4-alkylpiperidine-2-carboxamide scaffold were designed, synthesized, and pharmacologically evaluated, leading to the discovery of selective 5-HT2CR positive allosteric modulators (PAMs). Compound 16 (CYD-1-79) potentiated 5-HT-evoked intracellular calcium release in cells stably expressing the human 5-HT2CR but not the 5-HT2AR cells. A topographically distinct allosteric site was identified based on the newly solved 5-HT2CR structure. Compound 16 modulated 5-HT2CR-mediated spontaneous ambulation, partially substituted for the training dose of the 5-HT2CR agonist WAY163909, synergized with a low dose of WAY163909 to substitute fully for the stimulus effect...
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Serotonin 5-HT2C Receptor Activation Suppresses Binge Intake and the Reinforcing and Motivational Properties of High-Fat Food
Frontiers in Pharmacology, 2018Co-Authors: Amanda E. Price, Sonja J. Stutz, Noelle C. Anastasio, Jonathan D Hommel, Kathryn A. CunninghamAbstract:Binge eating disorder (BED) is characterized by dysfunctional hedonic food intake and reward-related processes. Activation of the serotonin (5-HT) 5-HT2C Receptor (5-HT2CR) suppresses both food intake and reward-related behaviors and is thus poised to regulate BED. This study assessed the effects of 5-HT2CR activation via the selective 5-HT2CR agonist WAY163909 on binge eating-related behaviors in adult male Sprague-Dawley rats. Low doses of WAY163909 (1.0, 2.0 mg/kg) suppressed high fat food (HFF) binge intake, but not standard food non-binge intake. WAY163909 (1.0 mg/kg) also attenuated operant responding for self-administered HFF pellets on fixed and progressive ratio schedules of reinforcement, indicating that 5-HT2CR activation suppresses the reinforcing and motivational properties of HFF, respectively. These findings suggest that activation of the 5-HT2CR may be effective at suppressing binge eating in patients with BED via suppression of the reinforcing and motivational properties of HFF. This work supports future studies targeting the 5-HT2CR in the treatment of BED.
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Biophysical validation of serotonin 5-HT2A and 5-HT2C Receptor interaction
2018Co-Authors: Daniel E. Felsing, Scott R Gilbertson, Noelle C. Anastasio, Joanna M. Miszkiel, John A. Allen, Kathryn A. CunninghamAbstract:The serotonin (5-HT) 5-HT2A Receptor (5-HT2AR) and 5-HT2C Receptor (5-HT2CR) in the central nervous system are implicated in a range of normal behaviors (e.g., appetite, sleep) and physiological functions (e.g., endocrine secretion) while dysfunctional 5-HT2AR and/or 5-HT2CR are implicated in neuropsychiatric disorders (e.g., addiction, obesity, schizophrenia). Preclinical studies suggest that the 5-HT2AR and 5-HT2CR may act in concert to regulate the neural bases for behavior. Here, we utilize three distinct biophysical and immunocytochemistry-based approaches to identify and study this Receptor complex in cultured cells. Employing a split luciferase complementation assay (LCA), we demonstrated that formation of the 5-HT2AR:5-HT2CR complex exists within 50 nm, increases proportionally to the 5-HT2CR:5-HT2AR protein expression ratio, and is specific to the Receptor interaction and not due to random complementation of the luciferase fragments. Using a proximity ligation assay (PLA), we found that cells stably expressing both the 5-HT2AR and 5-HT2CR exhibit 5-HT2AR:5-HT2CR heteroReceptor complexes within 40 nm of each other. Lastly, bioluminescence resonance energy transfer (BRET) analyses indicates the formation of a specific and saturable 5-HT2AR:5-HT2CR interaction, suggesting that the 5-HT2AR and 5-HT2CR form a close interaction within 10 nm of each other in intact live cells. The bioengineered Receptors generated for the LCA and the BRET exhibit 5-HT-mediated intracellular calcium signaling as seen for the native Receptors. Taken together, this study validates a very close 5-HT2AR:5-HT2CR interaction in cultured cells.
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Design, Synthesis, and Characterization of 4‑Undecylpiperidine-2-carboxamides as Positive Allosteric Modulators of the Serotonin (5-HT) 5‑HT2C Receptor
2018Co-Authors: Christopher T. Wild, Kathryn A. Cunningham, Noelle C. Anastasio, Rachel M. Hartley, Joanna M. Miszkiel, Eric A Wold, Claudia A Soto, Chunyong Ding, Mark A White, Jia ZhouAbstract:An impaired signaling capacity of the serotonin (5-HT) 5-HT2C Receptor (5-HT2CR) has been implicated in the neurobehavioral processes that promote relapse vulnerability in cocaine use disorder (CUD). Restoration of the diminished 5-HT2CR signaling through positive allosteric modulation presents a novel therapeutic approach. Several new molecules with the 4-alkylpiperidine-2-carboxamide scaffold were designed, synthesized, and pharmacologically evaluated, leading to the discovery of selective 5-HT2CR positive allosteric modulators (PAMs). Compound 16 (CYD-1-79) potentiated 5-HT-evoked intracellular calcium release in cells stably expressing the human 5-HT2CR but not the 5-HT2AR cells. A topographically distinct allosteric site was identified based on the newly solved 5-HT2CR structure. Compound 16 modulated 5-HT2CR-mediated spontaneous ambulation, partially substituted for the training dose of the 5-HT2CR agonist WAY163909, synergized with a low dose of WAY163909 to substitute fully for the stimulus effects of WAY163909, and attenuated relapse vulnerability as assessed in a rodent self-administration model, indicating its therapeutic promise for CUD
Clinton E Canal - One of the best experts on this subject based on the ideXlab platform.
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Mutagenesis Analysis Reveals Distinct Amino Acids of the Human Serotonin 5‑HT2C Receptor Underlying the Pharmacology of Distinct Ligands
2016Co-Authors: Yue Liu, Clinton E Canal, Tania C. Cordova-sintjago, Wanying Zhu, Raymond G. BoothAbstract:While exploring the structure–activity relationship of 4-phenyl-2-dimethylaminotetralins (PATs) at serotonin 5-HT2C Receptors, we discovered that relatively minor modification of PAT chemistry impacts function at 5-HT2C Receptors. In HEK293 cells expressing human 5-HT2C‑INI Receptors, for example, (−)-trans-3′-Br-PAT and (−)-trans-3′-Cl-PAT are agonists regarding Gαq-inositol phosphate signaling, whereas (−)-trans-3′-CF3-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-HT2C Receptor based on molecular modeling and reported G protein-coupled Receptor crystal structures, followed by molecular pharmacology studies. We found that S3.36, T3.37, and F5.47 in the orthosteric binding pocket are critical for affinity (Ki) of all PATs tested, we also found that F6.44, M6.47, C7.45, and S7.46 are primarily involved in regulating EC/IC50 functional potencies of PATs. We discovered that when residue S5.43, N6.55, or both are mutated to alanine, (−)-trans-3′-CF3-PAT switches from inverse agonist to agonist function, and when N6.55 is mutated to leucine, (−)-trans-3′-Br-PAT switches from agonist to inverse agonist function. Notably, most point-mutations that affected PAT pharmacology did not significantly alter affinity (KD) of the antagonist radioligand [3H]mesulergine, but every mutation tested negatively impacted serotonin binding. Also, amino acid mutations differentially affected the pharmacology of other commercially available 5-HT2C ligands tested. Collectively, the data show that functional outcomes shared by different ligands are mediated by different amino acids and that some 5-HT2C Receptor residues important for pharmacology of one ligand are not necessarily important for another ligand
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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
Neuropharmacology, 2013Co-Authors: Clinton E Canal, Raymond G Booth, Drake MorganAbstract: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. The expected results were considered in accordance with ligand functional selectivity. Commercially-available 5-HT2C agonists (CP 809101, Ro 60-0175, WAY 161503, mCPP, and 1-methylpsilocin), novel 4-phenyl-2-N,N-dimethyl-aminotetralin (PAT)-type 5-HT2C agonists (with 5-HT2A/2B antagonist activity), and antagonists selective for 5-HT2A (M100907), 5-HT2C (SB-242084), and 5-HT2B/2C (SB-206553) Receptors attenuated the DOI-elicited-HTR. In contrast, there were differential effects on locomotion across classes of compounds. The 5-HT2C agonists and M100907 decreased locomotion, SB-242084 increased locomotion, SB-206553 resulted in dose-dependent biphasic effects on locomotion, and the PATs did not alter locomotion. In vitro molecular pharmacology studies showed that 5-HT2C agonists potent for attenuating the DOI-elicited-HTR also reduced the efficacy of DOI to activate mouse 5-HT2C Receptor-mediated PLC signaling in HEK cells. Although there were differences in affinities of a few compounds at mouse compared to human 5-HT2A or 5-HT2C Receptors, all compounds tested retained their selectivity for either Receptor, regardless of Receptor species. Results indicate that 5-HT2C Receptor agonists and antagonists attenuate the DOI-elicited-HTR in C57Bl/6J mice, and suggest that structurally diverse 5-HT2C ligands result in different 5-HT2C Receptor signaling outcomes compared to DOI.
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impact of rna editing on functions of the serotonin 2c Receptor in vivo
Frontiers in Neuroscience, 2010Co-Authors: Uade Olaghere B Da Silva, Michael V Morabito, Clinton E Canal, David C. Airey, Ronald B. Emeson, Elaine SandersbushAbstract:Transcripts encoding 5-HT2C Receptors are modified posttranscriptionally by RNA editing, generating up to 24 protein isoforms. In recombinant cells, the fully edited isoform, 5-HT2C-VGV, exhibits blunted G-protein coupling and reduced constitutive activity. The present studies examine the signal transduction properties of 5-HT2C-VGV Receptors in brain to determine the in vivo consequences of altered editing. Using mice solely expressing the 5-HT2C-VGV Receptor (VGV/Y), we demonstrate reduced G-protein coupling efficiency and high-affinity agonist binding of brain 5-HT2C-VGV Receptors. However, enhanced behavioral sensitivity to a 5-HT2C Receptor agonist was also seen in mice expressing 5-HT2C-VGV Receptors, an unexpected finding given the blunted G-protein coupling. In addition, mice expressing 5-HT2C-VGV Receptors had greater sensitivity to a 5-HT2C inverse agonist/antagonist enhancement of dopamine turnover relative to wild-type mice. These behavioral and biochemical results are most likely explained by increases in 5-HT2C Receptor binding sites in the brains of mice solely expressing -5HT2C-VGV Receptors. We conclude that 5-HT2C-VGV Receptor signaling in brain is blunted, but this deficiency is masked by a marked increase in 5HT2C Receptor binding site density in mice solely expressing the VGV isoform. These findings suggest that RNA editing may regulate the density of 5-HT2C Receptor binding sites in brain. We further caution that the pattern of 5-HT2C Receptor RNA isoforms may not reflect the pattern of protein isoforms, and hence the inferred overall function of the Receptor.
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the serotonin 2c Receptor potently modulates the head twitch response in mice induced by a phenethylamine hallucinogen
Psychopharmacology, 2010Co-Authors: Paul J Gresch, Elaine Sandersbush, Uade Olaghere B Da Silva, Clinton E Canal, Erin E Watt, David C. AireyAbstract:Hallucinogenic serotonin 2A (5-HT2A) Receptor partial agonists, such as (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), induce a frontal cortex-dependent head-twitch response (HTR) in rodents, a behavioral proxy of a hallucinogenic response that is blocked by 5-HT2A Receptor antagonists. In addition to 5-HT2A Receptors, DOI and most other serotonin-like hallucinogens have high affinity and potency as partial agonists at 5-HT2C Receptors. We tested for involvement of 5-HT2C Receptors in the HTR induced by DOI. Comparison of 5-HT2C Receptor knockout and wild-type littermates revealed an approximately 50% reduction in DOI-induced HTR in knockout mice. Also, pretreatment with either the 5-HT2C Receptor antagonist SB206553 or SB242084 eradicated a twofold difference in DOI-induced HTR between the standard inbred mouse strains C57BL/6J and DBA/2J, and decreased the DOI-induced HTR by at least 50% in both strains. None of several measures of 5-HT2A Receptors in frontal cortex explained the strain difference, including 5-HT2A Receptor density, Gαq or Gαi/o protein levels, phospholipase C activity, or DOI-induced expression of Egr1 and Egr2. 5-HT2C Receptor density in the brains of C57BL/6J and DBA/2J was also equivalent, suggesting that 5-HT2C Receptor-mediated intracellular signaling or other physiological modulators of the HTR may explain the strain difference in response to DOI. We conclude that the HTR to DOI in mice is strongly modulated by 5-HT2C Receptor activity. This novel finding invites reassessment of hallucinogenic mechanisms involving 5-HT2 Receptors.
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rna editing of the serotonin 2c Receptor and expression of gαq protein genetic mouse models do not support a role for regulation or compensation
Journal of Neurochemistry, 2009Co-Authors: Clinton E Canal, Elaine Sandersbush, Kontip Connie Mahautmr, David C. AireyAbstract:The serotonin 2C (5-HT2C) Receptor undergoes RNA editing at five bases in a region of the pre-mRNA encoding the second intracellular loop, generating many unique 5-HT2C Receptor isoforms. Mechanisms regulating in vivo expression of different edited 5-HT2C Receptor isoforms are poorly understood, as are the adaptive consequences of variation in editing profiles. Recent findings suggest a putative relationship between expression levels of Gαq/11 protein and the degree of editing of 5-HT2C Receptor transcripts. To elucidate the potential regulatory or adaptive role of Gαq/11 protein levels, we quantified editing of 5-HT2C Receptor RNA transcripts in Gαq null mice and protein levels of Gαq and Gα11 in transgenic male mice solely expressing either the non-edited (INI) or the fully edited (VGV) isoforms of the 5-HT2C Receptor. Pyrosequencing of RNA isolated from amygdaloid cortex in Gαq null and wild-type mice revealed no significant differences in 5-HT2C Receptor mRNA editing profiles. Cortical tissue from INI/y, VGV/y, and wild-type mice was assayed for expression of Gαq and Gα11 subunits by Western blotting. No differences in signal density between wild-type and INI/y or VGV/y groups were found, indicating equivalent levels of Gαq and Gα11 protein. Together, these data do not support a causal or compensatory relationship between 5-HT2C Receptor RNA editing and Gq protein levels.
Guy A Higgins - One of the best experts on this subject based on the ideXlab platform.
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pharmacological modulation of 5 ht2c Receptor activity produces bidirectional changes in locomotor activity responding for a conditioned reinforcer and mesolimbic da release in c57bl 6 mice
Neuropsychopharmacology, 2017Co-Authors: Guy A Higgins, Paul J Fletcher, Caleb J Browne, Colin HarveylewisAbstract:Converging lines of behavioral, electrophysiological, and biochemical evidence suggest that 5-HT2C Receptor signaling may bidirectionally influence reward-related behavior through an interaction with the mesolimbic dopamine (DA) system. Here we directly test this hypothesis by examining how modulating 5-HT2C Receptor activity affects DA-dependent behaviors and relate these effects to changes in nucleus accumbens (NAc) DA release. In C57BL/6 mice, locomotor activity and responding for a conditioned reinforcer (CRf), a measure of incentive motivation, were examined following treatment with three 5-HT2C Receptor ligands: the agonist CP809101 (0.25–3 mg/kg), the antagonist SB242084 (0.25–1 mg/kg), or the antagonist/inverse agonist SB206553 (1–5 mg/kg). We further tested whether doses of these compounds that changed locomotor activity and responding for a CRf (1 mg/kg CP809101, 0.5 mg/kg SB242084, or 2.5 mg/kg SB206553) also altered NAc DA release using in vivo microdialysis in anesthetized mice. CP809101 reduced locomotor activity, responding for a CRf, and NAc DA release. In contrast, both SB242084 and SB206553 enhanced locomotor activity, responding for a CRf, and NAc DA release, although higher doses of SB206553 produced opposite behavioral effects. Pretreatment with the non-selective DA Receptor antagonist α-flupenthixol prevented SB242084 from enhancing responding for a CRf. Thus blocking tonic 5-HT2C Receptor signaling can release serotonergic inhibition of mesolimbic DA activity and enhance reward-related behavior. The observed bidirectional effects of 5-HT2C Receptor ligands may have important implications when considering the 5-HT2C Receptor as a therapeutic target for psychiatric disorders, particularly those presenting with motivational dysfunctions.
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effects of 5 ht1a 5 ht2a and 5 ht2c Receptor agonists and antagonists on responding for a conditioned reinforcer and its enhancement by methylphenidate
Psychopharmacology, 2017Co-Authors: Fiona D Zeeb, Guy A Higgins, Paul J Fletcher, Caleb J Browne, Ashlie D SokoAbstract:Objectives These experiments examined the effects of selective 5-HT1A, 5-HT2A and 5-HT2C Receptor ligands on responding for a conditioned reinforcer (CRf). Effects of these ligands were measured under basal conditions and following elevated dopamine (DA) activity produced by the DA reuptake inhibitor methylphenidate.
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lorcaserin and cp 809101 reduce motor impulsivity and reinstatement of food seeking behavior in male rats implications for understanding the anti obesity property of 5 ht2c Receptor agonists
Psychopharmacology, 2016Co-Authors: Guy A Higgins, Paul J Fletcher, Leo B. Silenieks, Everett B Altherr, Cam Macmillan, Wayne E PrattAbstract:The 5-HT2C Receptor agonist lorcaserin (Belviq®) has been approved by the FDA for the treatment of obesity. Impulsivity is a contributory feature of some eating disorders. Experiments investigated the effect of lorcaserin and the highly selective 5-HT2C agonist CP-809101 on measures of impulsivity and on reinstatement of food-seeking behaviour, a model of dietary relapse. The effect of both drugs on 22-h deprivation-induced feeding was also examined, as was the effect of prefeeding in each impulsivity test. Lorcaserin (0.3–0.6 mg/kg SC) and CP-809101 (0.6–1 mg/kg SC) reduced premature responding in rats trained on the 5-CSRTT and improved accuracy in a Go-NoGo task by reducing false alarms. At equivalent doses, both drugs also reduced reinstatement for food-seeking behaviour. Neither drug altered impulsive choice measured in a delay-discounting task. Lorcaserin (1–3 mg/kg SC) and CP-809101 (3–6 mg/kg SC) reduced deprivation-induced feeding but only at higher doses. These results suggest that in addition to previously reported effects on satiety and reward, altered impulse control may represent a contributory factor to the anti-obesity property of 5-HT2C Receptor agonists. Lorcaserin may promote weight loss by improving adherence to dietary regimens in individuals otherwise prone to relapse and may be beneficial in cases where obesity is associated with eating disorders tied to impulsive traits, such as binge eating disorder.
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characterization of the 5 ht2c Receptor agonist lorcaserin on efficacy and safety measures in a rat model of diet induced obesity
Pharmacology Research & Perspectives, 2015Co-Authors: Guy A Higgins, Paul J Fletcher, Leo B. Silenieks, Jill Desnoyer, Annalise Van Niekerk, Winnie Lau, Sandy Thevarkunnel, Julia Izhakova, Ines DelannoyAbstract:The 5-HT2C Receptor agonist lorcaserin (Belviq®) has been Food and Drug Administration (FDA) approved for the treatment of obesity. The present study is a back translational investigation into the effect of 28-day lorcaserin treatment in a diet-induced obesity (DIO) model using male, Sprague–Dawley rats. An assessment of drug effect on efficacy and multiple safety endpoints including cardiac function was undertaken. Lorcaserin (1–2 mg/kg SC b.i.d.) significantly reduced percentage body weight gain compared to vehicle-treated controls (VEH: 10.6 ± 0.4%; LOR 1: 7.6 ± 1.2%; LOR 2: 5.4 ± 0.6%). Measurement of body composition using quantitative magnetic resonance (QMR) imaging indicated this change was due to the selective reduction in body fat mass. Modest effects on food intake were recorded. At the completion of the treatment phase, echocardiography revealed no evidence for valvulopathy, that is, no aortic or mitral valve regurgitation. The pharmacokinetics of the present treatment regimen was determined over a 7-day treatment period; plasma Cmin and Cmax were in the range 13–160 ng/mL (1 mg/kg b.i.d.) and 34–264 ng/mL (2 mg/kg b.i.d.) with no evidence for drug accumulation. In sum, these studies show an effect of lorcaserin in the DIO model, that in the context of the primary endpoint measure of % body weight change was similar to that reported clinically (i.e., 3.0–5.2% vs. 3.2%). The present studies highlight the translational value of obesity models such as DIO, and suggest that assuming consideration is paid to nonspecific drug effects such as malaise, the DIO model has reasonable forward translational value to help predict clinical outcomes of a new chemical entity.
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impulsive action in the 5 choice serial reaction time test in 5 ht2c Receptor null mutant mice
Psychopharmacology, 2013Co-Authors: Ashlie D Soko, Paul J Fletcher, Guy A HigginsAbstract:Rationale Depletion of brain serotonin (5-HT) results in impulsive behaviour as measured by increased premature responding in the five-choice serial reaction time (5-CSRT) test. Acute selective blockade of 5-HT2C Receptors also increases this form of impulsive action, whereas 5-HT2C Receptor stimulation reduces premature responding.
