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Sample records for 2a 5-ht2a receptor

  1. INSIGHTS INTO THE REGULATION OF 5-HT2A RECEPTORS BY SCAFFOLDING PROTEINS AND KINASES

    PubMed Central

    Allen, John A.; Yadav, Prem N.

    2008-01-01

    SUMMARY 5-HT2A serotonin receptors are essential molecular targets for the actions of LSD-like hallucinogens and atypical antipsychotic drugs. 5-HT2A serotonin receptors also mediate a variety of physiological processes in peripheral and central nervous systems including platelet aggregation, smooth muscle contraction, and the modulation of mood and perception. Scaffolding proteins have emerged as important regulators of 5-HT2A receptors and our recent studies suggest multiple scaffolds exist for 5-HT2A receptors including PSD95, arrestin, and caveolin. In addition, a novel interaction has emerged between p90 ribosomal S6 kinase and 5-HT2A receptors which attenuates receptor signaling. This article reviews our recent studies and emphasizes the role of scaffolding proteins and kinases in the regulation of 5-HT2A trafficking, targeting and signaling. PMID:18640136

  2. Evaluation of structural effects on 5-HT2A receptor antagonism by aporphines: identification of a new aporphine with 5-HT2A antagonist activity

    PubMed Central

    Ponnala, Shashikanth; Gonzales, Junior; Kapadia, Nirav; Navarro, Hernan A.; Harding, Wayne W.

    2014-01-01

    A set of aporphine analogs related to nantenine was evaluated for antagonist activity at 5-HT2A and α1A adrenergic receptors. With regards to 5-HT2A receptor antagonism, a C2 allyl group is detrimental to activity. The chiral center of nantenine is not important for 5-HT2A antagonist activity, however the N6 nitrogen atom is a critical feature for 5-HT2A antagonism. Compound 12b was the most potent 5-HT2A aporphine antagonist identified in this study and has similar potency to previously identified aporphine antagonists 2 and 3. The ring A and N6 modifications examined were detrimental to α1A antagonism. A slight eutomeric preference for the R enantiomer of nantenine was observed in relation to α1A antagonism. PMID:24630561

  3. Increased hypothalamic 5-HT2A receptor gene expression and effects of pharmacologic 5-HT2A receptor inactivation in obese A{sup y} mice

    SciTech Connect

    Nonogaki, Katsunori . E-mail: knonogaki-tky@umin.ac.jp; Nozue, Kana; Oka, Yoshitomo

    2006-12-29

    Serotonin (5-hydroxytryptamine; 5-HT) 2A receptors contribute to the effects of 5-HT on platelet aggregation and vascular smooth muscle cell proliferation, and are reportedly involved in decreases in plasma levels of adiponectin, an adipokine, in diabetic subjects. Here, we report that systemic administration of sarpogrelate, a 5-HT2A receptor antagonist, suppressed appetite and increased hypothalamic pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript, corticotropin releasing hormone, 5-HT2C, and 5-HT1B receptor gene expression. A{sup y} mice, which have ectopic expression of the agouti protein, significantly increased hypothalamic 5-HT2A receptor gene expression in association with obesity compared with wild-type mice matched for age. Systemic administration of sarpogrelate suppressed overfeeding, body weight gain, and hyperglycemia in obese A{sup y} mice, whereas it did not increase plasma adiponectin levels. These results suggest that obesity increases hypothalamic 5-HT2A receptor gene expression, and pharmacologic inactivation of 5-HT2A receptors inhibits overfeeding and obesity in A{sup y} mice, but did not increase plasma adiponectin levels.

  4. Expression of serotonin 5-HT(2A) receptors in the human cerebellum and alterations in schizophrenia.

    PubMed

    Eastwood, S L; Burnet, P W; Gittins, R; Baker, K; Harrison, P J

    2001-11-01

    The occurrence of human cerebellar serotonin 5-HT(2A) receptors (5-HT(2A)R) is equivocal and their status in schizophrenia unknown. Using a range of techniques, we investigated cerebellar 5-HT(2A)R expression in 16 healthy subjects and 16 subjects with schizophrenia. Immunocytochemistry with a monoclonal antibody showed labelling of Purkinje cell bodies and dendrites, as well as putative astrocytes. Western blots showed a major band at approximately 45 kDa. Receptor autoradiography and homogenate binding with [(3)H]ketanserin revealed cerebellar 5-HT(2A)R binding sites present at levels approximately a third of that in prefrontal cortex. 5-HT(2A)R mRNA was detected by reverse transcriptase-polymerase chain reaction, with higher relative levels in men than women. Several aspects of 5-HT(2A)R expression were altered in schizophrenia. 5-HT(2A)R immunoreactivity in Purkinje cells was partially redistributed from soma to dendrites and was increased in white matter. 5-HT(2A)R mRNA was decreased in the male patients. 5-HT(2A)R measured by dot blots and [(3)H]ketanserin binding (B(max) and K(d)) were not significantly altered in schizophrenia. These data show that 5-HT(2A)R gene products (mRNA, protein, binding sites) are expressed in the human cerebellum at nonnegligible levels; this bears upon 5-HT(2A)R imaging studies which use the cerebellum as a reference region. 5-HT(2A)R expression is altered in schizophrenia; the shift of 5-HT(2A)R from soma to dendrites is noteworthy since atypical antipsychotics have the opposite effect. Finally, the results emphasise that expression of a receptor gene is a mutifaceted process. Measurement of multiple parameters is necessary to give a clear picture of the normal situation and to show the profile of alterations in a disease. PMID:11574947

  5. Activated astrocytes display increased 5-HT2a receptor expression in pathological states.

    PubMed

    Wu, C; Singh, S K; Dias, P; Kumar, S; Mann, D M

    1999-08-01

    In human brain tissues from patients dying with cerebral infarction, hypertensive encephalopathy, Alzheimer's disease, Huntington's disease, frontotemporal dementia, and Creutzfeldt-Jakob disease there is an activation of astrocytes. Such activated astrocytes display GFAP and strong 5-HT(2A), but not 5-HT(2B) or 5-HT(2C), receptor immunoreactivity; this 5-HT(2A) reaction has not been observed in normal, nonactivated astrocytes. It is suggested that an up-regulation of 5-HT(2A) receptors may be part of an early response reaction in astrocytes, possibly designed to maintain homeostasis or to induce secondary message pathways involving trophic factors or glycogenolysis. PMID:10415157

  6. Reduced 5-HT2A receptor signaling following selective bilateral amygdala damage

    PubMed Central

    Schlaepfer, Thomas E.; Matusch, Andreas; Reich, Harald; Shah, Nadim J.; Zilles, Karl; Maier, Wolfgang; Bauer, Andreas

    2009-01-01

    Neurobiological evidence implicates the amygdala as well as serotonergic (serotonin, 5-HT) signaling via postsynaptic 5-HT2A receptors as essential substrates of anxiety behaviors. Assuming a functional interdependence of these substrates, we hypothesized that a low-fear behavioral phenotype due to bilateral lesion of the amygdala would be associated with significant 5-HT2A receptor changes. Thus, we used [18F]altanserin positron emission tomography (PET) referenced to radioligand plasma levels and corrected for partial volume effects to quantify the spatial distribution of 5-HT2A receptor binding potential (BPP) in a rare patient with Urbach–Wiethe disease and selective bilateral amygdala calcification damage relative to 10 healthy control subjects. Consistent with our a priori hypothesis, we observed a 70% global decrease in 5-HT2A receptor BPP in the Urbach–Wiethe patient relative to controls. Thus, brain abnormalities in this patient are not restricted to the amygdala, but extend to overall 5-HT neurotransmission via 5-HT2A receptors. Our findings provide important insights into the molecular architecture of human anxiety behaviors and suggest the 5-HT2A receptor as a promising pharmacological target to control pathological anxiety. PMID:19015089

  7. Activation of 5-HT2A/2C receptors reduces the excitability of cultured cortical neurons.

    PubMed

    Hu, Lingli; Liu, Chunhua; Dang, Minyan; Luo, Bin; Guo, Yiping; Wang, Haitao

    2016-10-01

    The abundant forebrain serotonergic projections are believed to modulate the activities of cortical neurons. 5-HT2 receptor among multiple subtypes of serotonin receptors contributes to the modulation of excitability, synaptic transmissions and plasticity. In the present study, whole-cell patch-clamp recording was adopted to examine whether activation of 5-HT2A/2C receptors would have any impact on the excitability of cultured cortical neurons. We found that 2,5-Dimethoxy-4-iodoamphetamine (DOI), a selective 5-HT2A/2C receptor agonist, rapidly and reversibly depressed spontaneous action potentials mimicking the effect of serotonin. The decreased excitability was also observed for current-evoked firing. Additionally DOI increased neuronal input resistance. Hyperpolarization-activated cyclic nucleotide-gated cationic channels (HCN) did not account for the inhibition of spontaneous firing. The synaptic contribution was ruled out in that DOI augmented excitation and attenuated inhibition to actually favor an increase in the excitability. Our findings revealed that activation of 5-HT2A/2C receptors reduces neuronal excitability, which would deepen our understanding of serotonergic modulation of cortical activities. PMID:27585751

  8. 5-HT2A receptor activation is necessary for CO2-induced arousal

    PubMed Central

    Smith, Haleigh R.; MacAskill, Amanda; Richerson, George B.

    2015-01-01

    Hypercapnia-induced arousal from sleep is an important protective mechanism pertinent to a number of diseases. Most notably among these are the sudden infant death syndrome, obstructive sleep apnea and sudden unexpected death in epilepsy. Serotonin (5-HT) plays a significant role in hypercapnia-induced arousal. The mechanism of 5-HT's role in this protective response is unknown. Here we sought to identify the specific 5-HT receptor subtype(s) involved in this response. Wild-type mice were pretreated with antagonists against 5-HT receptor subtypes, as well as antagonists against adrenergic, cholinergic, histaminergic, dopaminergic, and orexinergic receptors before challenge with inspired CO2 or hypoxia. Antagonists of 5-HT2A receptors dose-dependently blocked CO2-induced arousal. The 5-HT2C receptor antagonist, RS-102221, and the 5-HT1A receptor agonist, 8-OH-DPAT, attenuated but did not completely block CO2-induced arousal. Blockade of non-5-HT receptors did not affect CO2-induced arousal. None of these drugs had any effect on hypoxia-induced arousal. 5-HT2 receptor agonists were given to mice in which 5-HT neurons had been genetically eliminated during embryonic life (Lmx1bf/f/p) and which are known to lack CO2-induced arousal. Application of agonists to 5-HT2A, but not 5-HT2C, receptors, dose-dependently restored CO2-induced arousal in these mice. These data identify the 5-HT2A receptor as an important mediator of CO2-induced arousal and suggest that, while 5-HT neurons can be independently activated to drive CO2-induced arousal, in the absence of 5-HT neurons and endogenous 5-HT, 5-HT receptor activation can act in a permissive fashion to facilitate CO2-induced arousal via another as yet unidentified chemosensor system. PMID:25925320

  9. Serotonin 5-HT(2A) receptor activation induces 2-arachidonoylglycerol release through a phospholipase c-dependent mechanism.

    PubMed

    Parrish, Jason C; Nichols, David E

    2006-11-01

    To date, several studies have demonstrated that phospholipase C-coupled receptors stimulate the production of endocannabinoids, particularly 2-arachidonoylglycerol. There is now evidence that endocannabinoids are involved in phospholipase C-coupled serotonin 5-HT(2A) receptor-mediated behavioral effects in both rats and mice. The main objective of this study was to determine whether activation of the 5-HT(2A) receptor leads to the production and release of the endocannabinoid 2-arachidonoylglycerol. NIH3T3 cells stably expressing the rat 5-HT(2A) receptor were first incubated with [(3)H]-arachidonic acid for 24 h. Following stimulation with 10 mum serotonin, lipids were extracted from the assay medium, separated by thin layer chromatography, and analyzed by liquid scintillation counting. Our results indicate that 5-HT(2A) receptor activation stimulates the formation and release of 2-arachidonoylglycerol. The 5-HT(2A) receptor-dependent release of 2-arachidonoylglycerol was partially dependent on phosphatidylinositol-specific phospholipase C activation. Diacylglycerol produced downstream of 5-HT(2A) receptor-mediated phospholipase D or phosphatidylcholine-specific phospholipase C activation did not appear to contribute to 2-arachidonoylglycerol formation in NIH3T3-5HT(2A) cells. In conclusion, our results support a functional model where neuromodulatory neurotransmitters such as serotonin may act as regulators of endocannabinoid tone at excitatory synapses through the activation of phospholipase C-coupled G-protein coupled receptors. PMID:17010161

  10. The serotonin 5-HT2A and 5-HT2C receptors interact with specific sets of PDZ proteins.

    PubMed

    Bécamel, Carine; Gavarini, Sophie; Chanrion, Benjamin; Alonso, Gérard; Galéotti, Nathalie; Dumuis, Aline; Bockaert, Joël; Marin, Philippe

    2004-05-01

    The 5-hydroxytryptamine type 2A (5-HT(2A)) receptor and the 5-HT(2C) receptor are closely related members of the G-protein-coupled receptors activated by serotonin that share very similar pharmacological profiles and cellular signaling pathways. These receptors express a canonical class I PDZ ligand (SXV) at their C-terminal extremity. Here, we have identified proteins that interact with the PDZ ligand of the 5-HT(2A) and 5-HT(2C) receptors by a proteomic approach associating affinity chromatography using immobilized synthetic peptides encompassing the PDZ ligand and mass spectrometry. We report that both receptor C termini interact with specific sets of PDZ proteins in vitro. The 5-HT(2C) receptor but not the 5-HT(2A) receptor binds to the Veli-3.CASK.Mint1 ternary complex and to SAP102. In addition, the 5-HT(2C) receptor binds more strongly to PSD-95 and MPP-3 than the 5-HT(2A) receptor. In contrast, a robust interaction between the 5-HT(2A) receptor and the channel-interacting PDZ protein CIPP was found, whereas CIPP did not significantly associate with the 5-HT(2C) receptor. We also show that residues located at the -1 position and upstream the PDZ ligand in the C terminus of the 5-HT(2A) and 5-HT(2C) receptors are major determinants in their interaction with specific PDZ proteins. Immunofluorescence and electron microscopy studies strongly suggested that these specific interactions also take place in living cells and that the 5-HT(2) receptor-PDZ protein complexes occur in intracellular compartments. The interaction of the 5-HT(2A) and the 5-HT(2C) receptor with specific sets of PDZ proteins may contribute to their different signal transduction properties.

  11. The role of serotonin 5-HT2A receptors in memory and cognition

    PubMed Central

    Zhang, Gongliang; Stackman, Robert W.

    2015-01-01

    Serotonin 5-HT2A receptors (5-HT2ARs) are widely distributed in the central nervous system, especially in brain region essential for learning and cognition. In addition to endogenous 5-HT, several hallucinogens, antipsychotics, and antidepressants function by targeting 5-HT2ARs. Preclinical studies show that 5-HT2AR antagonists have antipsychotic and antidepressant properties, whereas agonist ligands possess cognition-enhancing and hallucinogenic properties. Abnormal 5-HT2AR activity is associated with a number of psychiatric disorders and conditions, including depression, schizophrenia, and drug addiction. In addition to its traditional activity as a G protein-coupled receptor (GPCR), recent studies have defined novel operations of 5-HT2ARs. Here we review progress in the (1) receptor anatomy and biology: distribution, signaling, polymerization and allosteric modulation; and (2) receptor functions: learning and memory, hallucination and spatial cognition, and mental disorders. Based on the recent progress in basic research on the 5-HT2AR, it appears that post-training 5-HT2AR activation enhances non-spatial memory consolidation, while pre-training 5-HT2AR activation facilitates fear extinction. Further, the potential influence that 5-HT2AR-elicited visual hallucinations may have on visual cue (i.e., landmark) guided spatial cognition is discussed. We conclude that the development of selective 5-HT2AR modulators to target distinct signaling pathways and neural circuits represents a new possibility for treating emotional, neuropsychiatric, and neurodegenerative disorders. PMID:26500553

  12. Expression of α(1)-adrenergic receptors in rat prefrontal cortex: cellular co-localization with 5-HT(2A) receptors.

    PubMed

    Santana, Noemí; Mengod, Guadalupe; Artigas, Francesc

    2013-06-01

    The prefrontal cortex (PFC) is involved in behavioural control and cognitive processes that are altered in schizophrenia. The brainstem monoaminergic systems control PFC function, yet the cells/networks involved are not fully known. Serotonin (5-HT) and norepinephrine (NE) increase PFC neuronal activity through the activation of α(1)-adrenergic receptors (α(1)ARs) and 5-HT(2A) receptors (5-HT(2A)Rs), respectively. Neurochemical and behavioural interactions between these receptors have been reported. Further, classical and atypical antipsychotic drugs share nm in vitro affinity for α(1)ARs while having preferential affinity for D(2) and 5-HT(2A)Rs, respectively. Using double in situ hybridization we examined the cellular expression of α(1)ARs in pyramidal (vGluT1-positive) and GABAergic (GAD(65/67)-positive) neurons in rat PFC and their co-localization with 5-HT(2A)Rs. α(1)ARs are expressed by a high proportion of pyramidal (59-85%) and GABAergic (52-79%) neurons. The expression in pyramidal neurons exhibited a dorsoventral gradient, with a lower percentage of α(1)AR-positive neurons in infralimbic cortex compared to anterior cingulate and prelimbic cortex. The expression of α(1A), α(1B) and α(1D) adrenergic receptors was segregated in different layers and subdivisions. In all them there is a high co-expression with 5-HT(2A)Rs (∼80%). These observations indicate that NE controls the activity of most PFC pyramidal neurons via α(1)ARs, either directly or indirectly, via GABAergic interneurons. Antipsychotic drugs can thus modulate the activity of PFC via α(1)AR blockade. The high co-expression with 5-HT(2A)Rs indicates a convergence of excitatory serotonergic and noradrenergic inputs onto the same neuronal populations. Moreover, atypical antipsychotics may exert a more powerful control of PFC function through the simultaneous blockade of α(1)ARs and 5-HT(2A)Rs.

  13. 5-HT2A receptors control body temperature in mice during LPS-induced inflammation via regulation of NO production.

    PubMed

    Voronova, Irina P; Khramova, Galina M; Kulikova, Elizabeth A; Petrovskii, Dmitrii V; Bazovkina, Daria V; Kulikov, Alexander V

    2016-01-01

    G protein-coupled 5-HT2A receptors are involved in the regulation of numerous normal and pathological physiological functions. At the same time, its involvement in the regulation of body temperature (Tb) in normal conditions is obscure. Here we study the effect of the 5-HT2A receptor activation or blockade on Tb in sick animals. The experiments were carried out on adult C57BL/6 mouse males. Systemic inflammation and sickness were produced by lipopolysaccharide (LPS, 0.1mg/kg, ip), while the 5-HT2A receptor was stimulated or blocked through the administration of the receptor agonist DOI or antagonist ketanserin (1mg/kg), respectively. LPS, DOI or ketanserin alone produced no effect on Tb. However, administration of LPS together with a peripheral or central ketanserin injection reduced Tb (32.2°C). Ketanserin reversed the LPS-induced expression of inducible NO synthase in the brain. Consequently, an involvement of NO in the mechanism of the hypothermic effect of ketanserin in sick mice was hypothesized. Administration of LPS together with NO synthase inhibitor, l-nitro-arginine methyl ester (60mg/kg, ip) resulted in deep (28.5°C) and prolonged (8h) hypothermia, while administration of l-nitro-arginine methyl ester alone produced no effect on Tb. Thus, 5-HT2A receptors play a key role in Tb control in sick mice. Blockade of this GPCR produces hypothermia in mice with systemic inflammation via attenuation of LPS-induced NO production. These results indicate an unexpected role of 5-HT2A receptors in inflammation and NO production and have a considerable biological impact on understanding the mechanism of animal adaptation to pathogens and parasites. Moreover, adverse side effects of 5-HT2A receptor antagonists in patients with inflammation may be expected. PMID:26621247

  14. 5-HT2A receptors control body temperature in mice during LPS-induced inflammation via regulation of NO production.

    PubMed

    Voronova, Irina P; Khramova, Galina M; Kulikova, Elizabeth A; Petrovskii, Dmitrii V; Bazovkina, Daria V; Kulikov, Alexander V

    2016-01-01

    G protein-coupled 5-HT2A receptors are involved in the regulation of numerous normal and pathological physiological functions. At the same time, its involvement in the regulation of body temperature (Tb) in normal conditions is obscure. Here we study the effect of the 5-HT2A receptor activation or blockade on Tb in sick animals. The experiments were carried out on adult C57BL/6 mouse males. Systemic inflammation and sickness were produced by lipopolysaccharide (LPS, 0.1mg/kg, ip), while the 5-HT2A receptor was stimulated or blocked through the administration of the receptor agonist DOI or antagonist ketanserin (1mg/kg), respectively. LPS, DOI or ketanserin alone produced no effect on Tb. However, administration of LPS together with a peripheral or central ketanserin injection reduced Tb (32.2°C). Ketanserin reversed the LPS-induced expression of inducible NO synthase in the brain. Consequently, an involvement of NO in the mechanism of the hypothermic effect of ketanserin in sick mice was hypothesized. Administration of LPS together with NO synthase inhibitor, l-nitro-arginine methyl ester (60mg/kg, ip) resulted in deep (28.5°C) and prolonged (8h) hypothermia, while administration of l-nitro-arginine methyl ester alone produced no effect on Tb. Thus, 5-HT2A receptors play a key role in Tb control in sick mice. Blockade of this GPCR produces hypothermia in mice with systemic inflammation via attenuation of LPS-induced NO production. These results indicate an unexpected role of 5-HT2A receptors in inflammation and NO production and have a considerable biological impact on understanding the mechanism of animal adaptation to pathogens and parasites. Moreover, adverse side effects of 5-HT2A receptor antagonists in patients with inflammation may be expected.

  15. 5-HT2A Serotonin Receptor Density in Adult Male Rats’ Hippocampus after Morphine-based Conditioned Place Preference

    PubMed Central

    Mohammadi, Rabie; Jahanshahi, Mehrdad; Jameie, Seyed Behnamedin

    2016-01-01

    Introduction: A close interaction exists between the brain opioid and serotonin (5-HT) neurotransmitter systems. Brain neurotransmitter 5-HT plays an important role in the regulation of reward-related processing. However, a few studies have investigated the potential role of 5-HT2A receptors in this behavior. Therefore, the aim of the present study was to assess the influence of morphine and Conditioned Place Preference (CPP) on the density of 5-HT2A receptor in neurons of rat hippocampal formation. Methods: Morphine (10 mg/kg, IP) was injected in male Wistar rats for 7 consecutive days (intervention group), but control rats received just normal saline (1 mL/kg, IP). We used a hotplate test of analgesia to assess induction of tolerance to analgesic effects of morphine on days 1 and 8 of injections. Later, two groups of rats were sacrificed one day after 7 days of injections, their whole brains removed, and the striatum and PFC immediately dissected. Then, the NR1 gene expression was examined with a semi-quantitative RT-PCR method. Results: Our data showed that the maximum response was obtained with 2.5 mg/kg of morphine. The density of 5-HT2A receptor in different areas of the hippocampus increased significantly at sham-morphine and CPP groups (P<0.05). On the other hand, the CPP groups had more 5-HT2A receptors than sham-morphine groups and also the sham-morphine groups had more 5-HT2A receptors than the control groups. Conclusion: We concluded that the phenomenon of conditioned place preference induced by morphine can cause a significant increase in the number of serotonin 5-HT2A receptors in neurons of all areas of hippocampus. PMID:27563418

  16. Reelin influences the expression and function of dopamine D2 and serotonin 5-HT2A receptors: a comparative study.

    PubMed

    Varela, M J; Lage, S; Caruncho, H J; Cadavid, M I; Loza, M I; Brea, J

    2015-04-01

    Reelin is an extracellular matrix protein that plays a critical role in neuronal guidance during brain neurodevelopment and in synaptic plasticity in adults and has been associated with schizophrenia. Reelin mRNA and protein levels are reduced in various structures of post-mortem schizophrenic brains, in a similar way to those found in heterozygous reeler mice (HRM). Reelin is involved in protein expression in dendritic spines that are the major location where synaptic connections are established. Thus, we hypothesized that a genetic deficit in reelin would affect the expression and function of dopamine D2 and serotonin 5-HT2A receptors that are associated with the action of current antipsychotic drugs. In this study, D2 and 5-HT2A receptor expression and function were quantitated by using radioligand binding studies in the frontal cortex and striatum of HRM and wild-type mice (WTM). We observed increased expression (p<0.05) in striatum membranes and decreased expression (p<0.05) in frontal cortex membranes for both dopamine D2 and serotonin 5-HT2A receptors from HRM compared to WTM. Our results show parallel alterations of D2 and 5-HT2A receptors that are compatible with a possible hetero-oligomeric nature of these receptors. These changes are similar to changes described in schizophrenic patients and provide further support for the suitability of using HRM as a model for studying this disease and the effects of antipsychotic drugs. PMID:25637489

  17. Serotonin 5-HT2A receptor gene variants influence antidepressant response to repeated total sleep deprivation in bipolar depression.

    PubMed

    Benedetti, Francesco; Barbini, Barbara; Bernasconi, Alessandro; Fulgosi, Mara Cigala; Colombo, Cristina; Dallaspezia, Sara; Gavinelli, Chiara; Marino, Elena; Pirovano, Adele; Radaelli, Daniele; Smeraldi, Enrico

    2008-12-12

    5-HT2A receptor density in prefrontal cortex was associated with depression and suicide. 5-HT2A receptor gene polymorphism rs6313 was associated with 5-HT2A receptor binding potential, with the ability of individuals to use environmental support in order to prevent depression, and with sleep improvement after antidepressant treatment with mirtazapine. Studies on response to antidepressant drugs gave inconsistent results. Here we studied the effect of rs6313 on response to repeated total sleep deprivation (TSD) in 80 bipolar depressed inpatients treated with three consecutive TSD cycles (each one made of 36 h awake followed by a night of undisturbed sleep). All genotype groups showed comparable acute effects of the first TSD, but patients homozygotes for the T variant had better perceived and observed benefits from treatment than carriers of the C allele. These effects became significant after the first recovery night and during the following days, leading to a 36% higher final response rate (Hamilton depression rating<8). The higher density of postsynaptic excitatory 5-HT2A receptors in T/T homozygotes could have led to higher behavioural effects of increased 5-HT neurotransmission due to repeated TSD. Other possible mechanisms involve allostatic/homeostatic adaptation to sleep loss, and a different effect of the allele variants on epigenetic influences. Results confirm the interest for individual gene variants of the serotonin pathway in shaping clinical characteristics of depression and antidepressant response.

  18. The antidepressant 5-HT2A receptor antagonists pizotifen and cyproheptadine inhibit serotonin-enhanced platelet function.

    PubMed

    Lin, Olivia A; Karim, Zubair A; Vemana, Hari Priya; Espinosa, Enma V P; Khasawneh, Fadi T

    2014-01-01

    There is considerable interest in defining new agents or targets for antithrombotic purposes. The 5-HT2A receptor is a G-protein coupled receptor (GPCR) expressed on many cell types, and a known therapeutic target for many disease states. This serotonin receptor is also known to regulate platelet function. Thus, in our FDA-approved drug repurposing efforts, we investigated the antiplatelet activity of cyproheptadine and pizotifen, two antidepressant 5-HT2A Receptor antagonists. Our results revealed that cyproheptadine and pizotifen reversed serotonin-enhanced ADP-induced platelet aggregation in vitro and ex vivo. And the inhibitory effects of these two agents were found to be similar to that of EMD 281014, a 5-HT2A Receptor antagonist under development. In separate experiments, our studies revealed that these 5-HT2A receptor antagonists have the capacity to reduce serotonin-enhanced ADP-induced elevation in intracellular calcium levels and tyrosine phosphorylation. Using flow cytometry, we also observed that cyproheptadine, pizotifen, and EMD 281014 inhibited serotonin-enhanced ADP-induced phosphatidylserine (PS) exposure, P-selectin expression, and glycoprotein IIb-IIIa activation. Furthermore, using a carotid artery thrombosis model, these agents prolonged the time for thrombotic occlusion in mice in vivo. Finally, the tail-bleeding time was investigated to assess the effect of cyproheptadine and pizotifen on hemostasis. Our findings indicated prolonged bleeding time in both cyproheptadine- and pizotifen-treated mice. Notably, the increases in occlusion and bleeding times associated with these two agents were comparable to that of EMD 281014, and to clopidogrel, a commonly used antiplatelet drug, again, in a fashion comparable to clopidogrel and EMD 281014. Collectively, our data indicate that the antidepressant 5-HT2A antagonists, cyproheptadine and pizotifen do exert antiplatelet and thromboprotective effects, but similar to clopidogrel and EMD 281014, their

  19. Anti-thrombotic and vascular effects of AR246686, a novel 5-HT2A receptor antagonist.

    PubMed

    Adams, John W; Ramirez, Juan; Ortuno, Danny; Shi, Yunqing; Thomsen, William; Richman, Jeremy G; Morgan, Michael; Dosa, Peter; Teegarden, Bradley R; Al-Shamma, Hussien; Behan, Dominic P; Connolly, Daniel T

    2008-05-31

    We have evaluated the anti-platelet and vascular pharmacology of AR246686, a novel 5-hydroxytryptamine2A (5-HT2A) receptor antagonist. AR246686 displayed high affinity binding to membranes of HEK cells stably expressing recombinant human and rat 5-HT2A receptors (Ki=0.2 nM and 0.4 nM, respectively). Functional antagonism (IC50=1.9 nM) with AR246686 was determined by inhibition of ligand-independent inositol phosphate accumulation in the 5-HT2A stable cell line. We observed 8.7-fold and 1360-fold higher affinity of AR246686 for the 5-HT2A receptor vs. 5-HT2C and 5-HT2B receptors, respectively. AR246686 inhibited 5-HT-induced amplification of ADP-stimulated human platelet aggregation (IC50=21 nM). Similar potency was observed for inhibition of 5-HT stimulated DNA synthesis in rat aortic smooth muscle cells (IC(50)=10 nM) and 5-HT-mediated contraction in rat aortic rings. Effects of AR246686 on arterial thrombosis and bleeding time were studied in a rat model of femoral artery occlusion. Oral dosing of AR246686 to rats resulted in prolongation of time to occlusion at 1 mg/kg, whereas increased bleeding time was observed at a dose of 20 mg/kg. In contrast, both bleeding time and time to occlusion were increased at the same dose (10 mg/kg) of clopidogrel. These results demonstrate that AR246686 is a high affinity 5-HT2A receptor antagonist with potent activity on platelets and vascular smooth muscle. Further, oral administration results in anti-thrombotic effects at doses that are free of significant effects on traumatic bleeding time.

  20. APORPHINOID ANTAGONISTS OF 5-HT2A RECEPTORS: FURTHER EVALUATION OF RING A SUBSTITUENTS AND THE SIZE OF RING C

    PubMed Central

    Ponnala, Shashikanth; Kapadia, Nirav; Navarro, Hernán A.; Harding, Wayne W.

    2014-01-01

    A series of ring A modified analogs of nantenine as well as structural variants in ring C were synthesized and evaluated for antagonist activity at 5-HT2A and α1A receptors. Halogenation improves 5-HT2A antagonist potency in molecules containing a C1 methoxyl/C2 methoxyl or C1 methoxyl/C2 hydroxyl moiety. Bromination or iodination (but not chlorination) with the latter moiety also significantly increased α1A antagonist potency. Homologation or contraction of ring C adversely affected antagonist activity at both receptors, implying that a six-membered ring C motif is beneficial for high antagonist potency at both receptors. Molecular docking studies suggest that the improved antagonist activity (by virtue of improved affinity) of C3 halogenated aporphines in this study, is attributable to favorable interactions with the C3 halogen and F339 and/or F340. PMID:24766771

  1. Chronic treatment with LY341495 decreases 5-HT(2A) receptor binding and hallucinogenic effects of LSD in mice.

    PubMed

    Moreno, José L; Holloway, Terrell; Rayannavar, Vinayak; Sealfon, Stuart C; González-Maeso, Javier

    2013-03-01

    Hallucinogenic drugs, such as lysergic acid diethylamide (LSD), mescaline and psilocybin, alter perception and cognitive processes. All hallucinogenic drugs have in common a high affinity for the serotonin 5-HT(2A) receptor. Metabotropic glutamate 2/3 (mGlu2/3) receptor ligands show efficacy in modulating the cellular and behavioral responses induced by hallucinogenic drugs. Here, we explored the effect of chronic treatment with the mGlu2/3 receptor antagonist 2S-2-amino-2-(1S,2S-2-carboxycyclopropan-1-yl)-3-(xanth-9-yl)-propionic acid (LY341495) on the hallucinogenic-like effects induced by LSD (0.24mg/kg). Mice were chronically (21 days) treated with LY341495 (1.5mg/kg), or vehicle, and experiments were carried out one day after the last injection. Chronic treatment with LY341495 down-regulated [(3)H]ketanserin binding in somatosensory cortex of wild-type, but not mGlu2 knockout (KO), mice. Head-twitch behavior, and expression of c-fos, egr-1 and egr-2, which are responses induced by hallucinogenic 5-HT(2A) agonists, were found to be significantly decreased by chronic treatment with LY341495. These findings suggest that repeated blockade of the mGlu2 receptor by LY341495 results in reduced 5-HT(2A) receptor-dependent hallucinogenic effects of LSD.

  2. N-acetylcysteine modulates hallucinogenic 5-HT(2A) receptor agonist-mediated responses: behavioral, molecular, and electrophysiological studies.

    PubMed

    Lee, Mei-Yi; Chiang, Chun-Cheng; Chiu, Hong-Yi; Chan, Ming-Huan; Chen, Hwei-Hsien

    2014-06-01

    N-acetylcysteine (NAC) has been reported to reverse the psychotomimetic effects in the rodent phencyclidine model of psychosis and shown beneficial effects in treating patients with schizophrenia. The effect of NAC has been associated with facilitating the activity of cystine-glutamate antiporters on glial cells concomitant with the release of non-vesicular glutamate, which mainly stimulates the presynaptic metabotropic glutamate receptor subtype 2 receptors (mGluR2). Recent evidence demonstrated that functional interactions between serotonin 5-HT2A receptor (5-HT(2A)R) and mGluR2 are responsible to unique cellular responses when targeted by hallucinogenic drugs. The present study determined the effects of NAC on hallucinogenic 5-HT(2A)R agonist (±)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-elicited behavioral and molecular responses in mice and DOI-evoked field potentials in the mouse cortical slices. NAC significantly attenuated DOI-induced head twitch response and expression of c-Fos and Egr-2 in the infralimbic and motor cortex and suppressed the increase in the frequency of excitatory field potentials elicited by DOI in the medial prefrontal cortex. In addition, the cystine-glutamate antiporter inhibitor (S)-4-carboxyphenylglycine (CPG) and the mGluR2 antagonist LY341495 reversed the suppressing effects of NAC on DOI-induced head twitch and molecular responses and increased frequency of excitatory field potentials, supporting that NAC attenuates the 5-HT(2A)R-mediated hallucinogenic effects via increased activity of cystine-glutamate antiporter followed by activation of mGluR2 receptors. These findings implicate NAC as a potential therapeutic agent for hallucinations and psychosis associated with hallucinogen use and schizophrenia.

  3. Blockade of 5-HT2A receptors suppresses hyperthermic but not cardiovascular responses to psychosocial stress in rats.

    PubMed

    Beig, M I; Baumert, M; Walker, F R; Day, T A; Nalivaiko, E

    2009-03-31

    The aim of this study was to determine whether 5-HT2A receptors mediate cardiovascular and thermogenic responses to acute psychological stresses. For this purpose, adult male Wistar hooded rats instrumented for telemetric recordings of either electrocardiogram (ECG) (n=12) or arterial pressure (n=12) were subjected, on different days, to four 15-min episodes of social defeat. Prior to stress, animals received s.c. injection of the selective 5-HT2A receptor antagonist SR-46349B (trans-4-((3Z)3-[(2-dimethylaminoethyl)oxyimino]-3-(2-fluorophenyl)propen-1-yl)-phenol, hemifumarate) (at doses of 0.3, 1.0 and 3.0 mg/kg) or vehicle. The drug had no effect on basal heart rate or heart rate variability indexes, arterial pressure, and core body temperature. Social defeat elicited significant and substantial tachycardic (347+/-7 to 500+/-7 bpm), pressor (77+/-4 to 97+/-4 mm Hg) and hyperthermic (37.0+/-0.3 to 38.5+/-0.1 degrees C) responses. Blockade of 5-HT2A receptors, at all doses of the antagonist, completely prevented stress-induced hyperthermia. In contrast, stress-induced cardiovascular responses were not affected by the blockade (except small reduction of tachycardia by the highest dose of the drug). We conclude that in rats, 5-HT2A receptors mediate stress-induced hyperthermic responses, but are not involved in the genesis of stress-induced rises in heart rate or arterial pressure, and do not participate in cardiovascular control at rest. PMID:19356699

  4. Clozapine, but not olanzapine, disrupts conditioned avoidance response in rats by antagonizing 5-HT2A/2C receptors.

    PubMed

    Li, Ming; Sun, Tao; Mead, Alexa

    2012-04-01

    The present study was designed to assess the role of 5-HT(2A/2C) receptors in the acute and repeated effect of clozapine and olanzapine in a rat conditioned avoidance response model, a validated model of antipsychotic activity. Male Sprague-Dawley rats that were previously treated with either phencyclidine (0.5-2.0 mg/kg, sc), amphetamine (1.25-5.0 mg/kg, sc), or saline and tested in a prepulse inhibition of acoustic startle study were used. They were first trained to acquire avoidance response to a white noise (CS1) and a pure tone (CS2) that differed in their ability to predict the occurrence of footshock. Those who acquired avoidance response were administered with clozapine (10.0 mg/kg, sc) or olanzapine (1.0 mg/kg, sc) together with either saline or 1-2,5-dimethoxy-4-iodo-amphetamine (DOI, a selective 5-HT(2A/2C) agonist, 1.0 or 2.5 mg/kg, sc), and their conditioned avoidance responses were tested for four consecutive days. After two drug-free retraining days, the long-term repeated effect was assessed in a challenge test during which all rats were injected with a low dose of clozapine (5 mg/kg, sc) or olanzapine (0.5 mg/kg). Results show that pretreatment of DOI dose-dependently reversed the acute disruptive effect of clozapine on both CS1 and CS2 avoidance responses, whereas it had little effect in reversing the acute effect of olanzapine. On the challenge test, pretreatment of DOI did not alter the clozapine-induced tolerance or the olanzapine-induced sensitization effect. These results confirmed our previous findings and suggest that clozapine, but not olanzapine, acts on through 5-HT(2A/2C) receptors to achieve its acute avoidance disruptive effect and likely its therapeutic effects. The long-term clozapine tolerance and olanzapine sensitization effects appear to be mediated by non-5-HT(2A/2C) receptors.

  5. Latent inhibition is attenuated by noise and partially restored by a 5-HT2A receptor antagonist.

    PubMed

    McDonald, L M; Moran, P M; Vythelingum, G N; Joseph, M H; Stephenson, J D; Gray, J A

    2002-12-01

    Latent inhibition (LI) is a model of attention, which is a cognitive process that can be modulated by stressors such as chronic intermittent broadband noise, e.g. caused by building work, which is particularly stressful to rats. The aim of this study was to analyse the effect of chronic noise stress, caused by a building project, on LI, and its interaction with SR 46,349B, a 5-HT2A receptor antagonist. Control groups from LI experiments conducted during periods of chronic intermittent noise were compared with control groups from LI experiments conducted in normal quiet conditions. The interaction of SR 46,349B with the effects of chronic noise stress was then tested. Chronic intermittent noise attenuated LI, an effect which was partially reversed by SR 46,349B, 2.4 mg/kg i.p. Attenuation of LI by chronic intermittent noise and reversal of this effect by SR 46,349B support suggestions that stress can modulate attention and that 5-HT2A receptors are involved in mediating the effects of chronic stress.

  6. C-(4,5,6-trimethoxyindan-1-yl)methanamine: a mescaline analogue designed using a homology model of the 5-HT2A receptor.

    PubMed

    McLean, Thomas H; Chambers, James J; Parrish, Jason C; Braden, Michael R; Marona-Lewicka, Danuta; Kurrasch-Orbaugh, Deborah; Nichols, David E

    2006-07-13

    A conformationally restricted analogue of mescaline, C-(4,5,6-trimethoxyindan-1-yl)-methanamine, was designed using a 5-HT(2A) receptor homology model. The compound possessed 3-fold higher affinity and potency than and efficacy equal to that of mescaline at the 5-HT(2A) receptor. The new analogue substituted fully for LSD in drug discrimination studies and was 5-fold more potent than mescaline. Resolution of this analogue into its enantiomers corroborated the docking experiments, showing the R-(+) isomer to have higher affinity and potency and to have efficacy similar to that of mescaline at the 5-HT(2A) receptor.

  7. The 5-HT2A serotonin receptor in executive function: Implications for neuropsychiatric and neurodegenerative diseases.

    PubMed

    Aznar, Susana; Hervig, Mona El-Sayed

    2016-05-01

    Executive function entails the interplay of a group of cognitive processes enabling the individual to anticipate consequences, attain self-control, and undertake appropriate goal-directed behaviour. Serotonin signalling at serotonin 2A receptors (5-HT2AR) has important effects on these behavioural and cognitive pathways, with the prefrontal cortex (PFC) as the central actor. Indeed, the 5-HT2ARs are highly expressed in PFC, where they modulate cortical activity and local network oscillations (brain waves). Numerous psychiatric and neurodegenerative diseases result in disrupted executive function. Animal and human studies have linked these disorders with alterations in the 5-HT2AR system, making this an important pharmacological target for the treatment of disorders with impaired cognitive function. This review aims to describe the current state of knowledge on the role of 5-HT2AR signalling in components of executive function, and how 5-HT2AR systems may relate to executive dysfunctions occurring in psychiatric and neurodegenerative diseases. We hope thereby to provide insight into how pharmacotherapy targeting the 5-HT2AR may ameliorate (or exacerbate) aspects of these disorders. PMID:26891819

  8. Effects of dominance status on conditioned defeat and expression of 5-HT1A and 5-HT2A receptors

    PubMed Central

    Morrison, Kathleen E.; Swallows, Cody L.; Cooper, Matthew A.

    2011-01-01

    Past experience can alter how individuals respond to stressful events. The brain serotonin system is a key factor modulating stress-related behavior and may contribute to individual variation in coping styles. In this study we investigated whether dominant and subordinate hamsters respond differently to social defeat and whether their behavioral responses are associated with changes in 5-HT1A and 5-HT2A receptor immunoreactivity in several limbic brain regions. We paired weight-matched hamsters in daily aggressive encounters for two weeks so that they formed a stable dominance relationship. We also included controls that were exposed to an empty cage each day for two weeks. Twenty-four hours after the final pairing or empty cage exposure, subjects were socially defeated in 3, 5-min encounters with a more aggressive hamster. Twenty-four hours after social defeat, animals were tested for conditioned defeat in a 5-min social interaction test with a non-aggressive intruder. We collected brains following conditioned defeat testing and performed immunohistochemistry for 5-HT1A and 5-HT2A receptors. We found that dominants showed less submissive and defensive behavior at conditioned defeat testing compared to both subordinates and controls. Additionally, both dominants and subordinates had an increased number of 5-HT1A immunopositive cells in the basolateral amygdala compared to controls. Subordinates also had more 5-HT1A immunopositive cells in the dorsal medial amygdala than did controls. Finally, dominants had fewer 5-HT1A immunopositive cells in the paraventricular nucleus of the hypothalamus compared to controls. Our results indicate that dominant social status results in a blunted conditioned defeat response and a distinct pattern of 5-HT1A receptor expression, which may contribute to resistance to conditioned defeat. PMID:21362435

  9. Effects of dominance status on conditioned defeat and expression of 5-HT1A and 5-HT2A receptors.

    PubMed

    Morrison, Kathleen E; Swallows, Cody L; Cooper, Matthew A

    2011-08-01

    Past experience can alter how individuals respond to stressful events. The brain serotonin system is a key factor modulating stress-related behavior and may contribute to individual variation in coping styles. In this study we investigated whether dominant and subordinate hamsters respond differently to social defeat and whether their behavioral responses are associated with changes in 5-HT1A and 5-HT2A receptor immunoreactivity in several limbic brain regions. We paired weight-matched hamsters in daily aggressive encounters for two weeks so that they formed a stable dominance relationship. We also included controls that were exposed to an empty cage each day for two weeks. Twenty-four hours after the final pairing or empty cage exposure, subjects were socially defeated in 3, 5-min encounters with a more aggressive hamster. Twenty-four hours after social defeat, animals were tested for conditioned defeat in a 5-min social interaction test with a non-aggressive intruder. We collected brains following conditioned defeat testing and performed immunohistochemistry for 5-HT1A and 5-HT2A receptors. We found that dominants showed less submissive and defensive behavior at conditioned defeat testing compared to both subordinates and controls. Additionally, both dominants and subordinates had an increased number of 5-HT1A immunopositive cells in the basolateral amygdala compared to controls. Subordinates also had more 5-HT1A immunopositive cells in the dorsal medial amygdala than did controls. Finally, dominants had fewer 5-HT1A immunopositive cells in the paraventricular nucleus of the hypothalamus compared to controls. Our results indicate that dominant social status results in a blunted conditioned defeat response and a distinct pattern of 5-HT1A receptor expression, which may contribute to resistance to conditioned defeat.

  10. 5-HT2A Receptor Binding in the Frontal Cortex of Parkinson's Disease Patients and Alpha-Synuclein Overexpressing Mice: A Postmortem Study.

    PubMed

    Rasmussen, Nadja Bredo; Olesen, Mikkel Vestergaard; Brudek, Tomasz; Plenge, Per; Klein, Anders Bue; Westin, Jenny E; Fog, Karina; Wörtwein, Gitta; Aznar, Susana

    2016-01-01

    The 5-HT2A receptor is highly involved in aspects of cognition and executive function and seen to be affected in neurodegenerative diseases like Alzheimer's disease and related to the disease pathology. Even though Parkinson's disease (PD) is primarily a motor disorder, reports of impaired executive function are also steadily being associated with this disease. Not much is known about the pathophysiology behind this. The aim of this study was thereby twofold: (1) to investigate 5-HT2A receptor binding levels in Parkinson's brains and (2) to investigate whether PD associated pathology, alpha-synuclein (AS) overexpression, could be associated with 5-HT2A alterations. Binding density for the 5-HT2A-specific radioligand [(3)H]-MDL 100.907 was measured in membrane suspensions of frontal cortex tissue from PD patients. Protein levels of AS were further measured using western blotting. Results showed higher AS levels accompanied by increased 5-HT2A receptor binding in PD brains. In a separate study, we looked for changes in 5-HT2A receptors in the prefrontal cortex in 52-week-old transgenic mice overexpressing human AS. We performed region-specific 5-HT2A receptor binding measurements followed by gene expression analysis. The transgenic mice showed lower 5-HT2A binding in the frontal association cortex that was not accompanied by changes in gene expression levels. This study is one of the first to look at differences in serotonin receptor levels in PD and in relation to AS overexpression. PMID:27579212

  11. 5-HT2A Receptor Binding in the Frontal Cortex of Parkinson's Disease Patients and Alpha-Synuclein Overexpressing Mice: A Postmortem Study.

    PubMed

    Rasmussen, Nadja Bredo; Olesen, Mikkel Vestergaard; Brudek, Tomasz; Plenge, Per; Klein, Anders Bue; Westin, Jenny E; Fog, Karina; Wörtwein, Gitta; Aznar, Susana

    2016-01-01

    The 5-HT2A receptor is highly involved in aspects of cognition and executive function and seen to be affected in neurodegenerative diseases like Alzheimer's disease and related to the disease pathology. Even though Parkinson's disease (PD) is primarily a motor disorder, reports of impaired executive function are also steadily being associated with this disease. Not much is known about the pathophysiology behind this. The aim of this study was thereby twofold: (1) to investigate 5-HT2A receptor binding levels in Parkinson's brains and (2) to investigate whether PD associated pathology, alpha-synuclein (AS) overexpression, could be associated with 5-HT2A alterations. Binding density for the 5-HT2A-specific radioligand [(3)H]-MDL 100.907 was measured in membrane suspensions of frontal cortex tissue from PD patients. Protein levels of AS were further measured using western blotting. Results showed higher AS levels accompanied by increased 5-HT2A receptor binding in PD brains. In a separate study, we looked for changes in 5-HT2A receptors in the prefrontal cortex in 52-week-old transgenic mice overexpressing human AS. We performed region-specific 5-HT2A receptor binding measurements followed by gene expression analysis. The transgenic mice showed lower 5-HT2A binding in the frontal association cortex that was not accompanied by changes in gene expression levels. This study is one of the first to look at differences in serotonin receptor levels in PD and in relation to AS overexpression.

  12. 5-HT2A Receptor Binding in the Frontal Cortex of Parkinson's Disease Patients and Alpha-Synuclein Overexpressing Mice: A Postmortem Study

    PubMed Central

    Rasmussen, Nadja Bredo; Olesen, Mikkel Vestergaard; Plenge, Per; Klein, Anders Bue; Westin, Jenny E.; Fog, Karina

    2016-01-01

    The 5-HT2A receptor is highly involved in aspects of cognition and executive function and seen to be affected in neurodegenerative diseases like Alzheimer's disease and related to the disease pathology. Even though Parkinson's disease (PD) is primarily a motor disorder, reports of impaired executive function are also steadily being associated with this disease. Not much is known about the pathophysiology behind this. The aim of this study was thereby twofold: (1) to investigate 5-HT2A receptor binding levels in Parkinson's brains and (2) to investigate whether PD associated pathology, alpha-synuclein (AS) overexpression, could be associated with 5-HT2A alterations. Binding density for the 5-HT2A-specific radioligand [3H]-MDL 100.907 was measured in membrane suspensions of frontal cortex tissue from PD patients. Protein levels of AS were further measured using western blotting. Results showed higher AS levels accompanied by increased 5-HT2A receptor binding in PD brains. In a separate study, we looked for changes in 5-HT2A receptors in the prefrontal cortex in 52-week-old transgenic mice overexpressing human AS. We performed region-specific 5-HT2A receptor binding measurements followed by gene expression analysis. The transgenic mice showed lower 5-HT2A binding in the frontal association cortex that was not accompanied by changes in gene expression levels. This study is one of the first to look at differences in serotonin receptor levels in PD and in relation to AS overexpression. PMID:27579212

  13. Discovering the mechanisms underlying serotonin (5-HT)2A and 5-HT2C receptor regulation following nicotine withdrawal in rats.

    PubMed

    Zaniewska, Magdalena; Alenina, Natalia; Wydra, Karolina; Fröhler, Sebastian; Kuśmider, Maciej; McCreary, Andrew C; Chen, Wei; Bader, Michael; Filip, Małgorzata

    2015-08-01

    We have previously demonstrated that nicotine withdrawal produces depression-like behavior and that serotonin (5-HT)2A/2C receptor ligands modulate that mood-like state. In the present study we aimed to identify the mechanisms (changes in radioligand binding, transcription or RNA-editing) related to such a behavioral outcome. Rats received vehicle or nicotine (0.4 mg/kg, s.c.) for 5 days in home cages. Brain 5-HT2A/2C receptors were analyzed on day 3 of nicotine withdrawal. Nicotine withdrawal increased [(3)H]ketanserin binding to 5-HT2A receptors in the ventral tegmental area and ventral dentate gyrus, yet decreased binding in the nucleus accumbens shell. Reduction in [(3)H]mesulergine binding to 5-HT2C receptors was seen in the ventral dentate gyrus. Profound decrease in the 5-HT2A receptor transcript level was noted in the hippocampus and ventral tegmental area. Out of five 5-HT2C receptor mRNA editing sites, deep sequencing data showed a reduction in editing at the E site and a trend toward reduction at the C site in the hippocampus. In the ventral tegmental area, a reduction for the frequency of CD 5-HT2C receptor transcript was seen. These results show that the reduction in the 5-HT2A receptor transcript level may be an auto-regulatory response to the increased receptor density in the hippocampus and ventral tegmental area during nicotine withdrawal, while decreased 5-HT2C receptor mRNA editing may explain the reduction in receptor labeling in the hippocampus. Serotonin (5-HT)2A/2C receptor ligands alleviate depression-like state in nicotine-withdrawn rats. Here, we show that the reduction in 5-HT2A receptor transcript level may be an auto-regulatory response to the increased receptor number in the hippocampus and ventral tegmental area during nicotine withdrawal, while attenuated 5-HT2C receptor mRNA editing in the hippocampus might explain reduced inverse agonist binding to 5-HT2C receptor and suggest a shift toward a population of more active receptors. 5

  14. 4-Bromo-2,5-dimethoxyphenethylamine (2C-B) and structurally related phenylethylamines are potent 5-HT2A receptor antagonists in Xenopus laevis oocytes

    PubMed Central

    Villalobos, Claudio A; Bull, Paulina; Sáez, Patricio; Cassels, Bruce K; Huidobro-Toro, J Pablo

    2004-01-01

    We recently described that several 2-(2,5-dimethoxy-4-substituted phenyl)ethylamines (PEAs), including 4-I=2C-I, 4-Br=2C-B, and 4-CH3=2C-D analogs, are partial agonists at 5-HT2C receptors, and show low or even negligible intrinsic efficacy at 5-HT2A receptors. These results raised the proposal that these drugs may act as 5-HT2 antagonists. To test this hypothesis, Xenopus laevis oocytes were microinjected with the rat clones for 5-HT2A or 5-HT2C receptors. The above-mentioned PEAs and its 4-H analog (2C-H) blocked the 5-HT-induced currents at 5-HT2A, but not at the 5-HT2C receptor, revealing 5-HT2 receptor subtype selectivity. The 5-HT2A receptor antagonism required a 2-min preincubation to attain maximum inhibition. All PEAs tested shifted the 5-HT concentration–response curves to the right and downward. Their potencies varied with the nature of the C(4) substituent; the relative rank order of their 5-HT2A receptor antagonist potency was 2C-I>2C-B>2C-D>2C-H. The present results demonstrate that in X. laevis oocytes, a series of 2,5-dimethoxy-4-substituted PEAs blocked the 5-HT2A but not the 5-HT2C receptor-mediated responses. As an alternative hypothesis, we suggest that the psychostimulant activity of the PEAs may not be exclusively associated with partial or full 5-HT2A receptor agonism. PMID:15006903

  15. Small molecule drug screening in Drosophila identifies the 5HT2A receptor as a feeding modulation target

    PubMed Central

    Gasque, Gabriel; Conway, Stephen; Huang, Juan; Rao, Yi; Vosshall, Leslie B.

    2013-01-01

    Dysregulation of eating behavior can lead to obesity, which affects 10% of the adult population worldwide and accounts for nearly 3 million deaths every year. Despite this burden on society, we currently lack effective pharmacological treatment options to regulate appetite. We used Drosophila melanogaster larvae to develop a high-throughput whole organism screen for drugs that modulate food intake. In a screen of 3630 small molecules, we identified the serotonin (5-hydroxytryptamine or 5-HT) receptor antagonist metitepine as a potent anorectic drug. Using cell-based assays we show that metitepine is an antagonist of all five Drosophila 5-HT receptors. We screened fly mutants for each of these receptors and found that serotonin receptor 5-HT2A is the sole molecular target for feeding inhibition by metitepine. These results highlight the conservation of molecular mechanisms controlling appetite and provide a method for unbiased whole-organism drug screens to identify novel drugs and molecular pathways modulating food intake. PMID:23817146

  16. Pyramidal Neurons in Rat Prefrontal Cortex Projecting to Ventral Tegmental Area and Dorsal Raphe Nucleus Express 5-HT2A Receptors

    PubMed Central

    Vázquez-Borsetti, Pablo; Cortés, Roser

    2009-01-01

    The prefrontal cortex (PFC) is involved in higher brain functions altered in schizophrenia. Classical antipsychotics modulate cortico-limbic circuits mainly through subcortical D2 receptor blockade, whereas second generation (atypical) antipsychotics preferentially target cortical 5-HT receptors. Anatomical and functional evidence supports a PFC-based control of the brainstem monoaminergic nuclei. Using a combination of retrograde tracing experiments and in situ hybridization we report that a substantial proportion of PFC pyramidal neurons projecting to the dorsal raphe (DR) and/or ventral tegmental area (VTA) express 5-HT2A receptors. Cholera-toxin B application into the DR and the VTA retrogradely labeled projection neurons in the medial PFC (mPFC) and in orbitofrontal cortex (OFC). In situ hybridization of 5-HT2A receptor mRNA in the same tissue sections labeled a large neuronal population in mPFC and OFC. The percentage of DR-projecting neurons expressing 5-HT2A receptor mRNA was ∼60% in mPFC and ∼75% in OFC (n = 3). Equivalent values for VTA-projecting neurons were ∼55% in both mPFC and ventral OFC. Thus, 5-HT2A receptor activation/blockade in PFC may have downstream effects on dopaminergic and serotonergic systems via direct descending pathways. Atypical antipsychotics may distally modulate monoaminergic cells through PFC 5-HT2A receptor blockade, presumably decreasing the activity of neurons receiving direct cortical inputs. PMID:19029064

  17. Potential role of cortical 5-HT(2A) receptors in the anxiolytic action of cyamemazine in benzodiazepine withdrawal.

    PubMed

    Benyamina, Amine; Naassila, Mickaël; Bourin, Michel

    2012-07-30

    The antipsychotic cyamemazine is a potent serotonin 5-HT(2A) receptor (5-HT(2AR)) antagonist. A positron emission tomography (PET) study in human patients showed that therapeutic doses of cyamemazine produced near saturation of 5-HT(2AR) occupancy in the frontal cortex, whereas dopamine D(2) occupancy remained below the level for motor side effects observed with typical antipsychotics. Recently, numerous studies have revealed the involvement of 5-HT(2AR) in the pathophysiology of anxiety and a double-blind, randomized clinical trial showed similar efficacy of cyamemazine and bromazepam in reducing the anxiety associated with benzodiazepine withdrawal. Therefore, we reviewed the above articles about 5-HT(2AR) and anxiety in order to understand better the anxiolytic mechanisms of cyamemazine in benzodiazepine withdrawal. The 5-HT(2AR) is the most abundant serotonin receptor subtype in the cortex. Non-pharmacological studies with antisense oligodeoxynucleotides and genetically modified mice clearly showed that cortical 5-HT(2AR) signaling positively modulates anxiety-like behavior. With a few exceptions, most other studies reviewed here further support this view. Therefore, the anxiolytic efficacy of cyamemazine in benzodiazepine withdrawal can be due to a 5-HT(2AR) antagonistic activity at the cortical level.

  18. Cartography of 5-HT1A and 5-HT2A Receptor Subtypes in Prefrontal Cortex and Its Projections.

    PubMed

    Mengod, Guadalupe; Palacios, José M; Cortés, Roser

    2015-07-15

    Since the development of chemical neuroanatomical tools in the 1960s, a tremendous wealth of information has been generated on the anatomical components of the serotonergic system, at the microscopic level in the brain including the prefrontal cortex (PFC). The PFC receives a widespread distribution of serotonin (5-hydroxytryptamine, 5-HT) terminals from the median and dorsal raphe nuclei. 5-HT receptors were first visualized using radioligand autoradiography in the late 1980s and early 1990s and showed, in contrast to 5-HT innervation, a differential distribution of binding sites associated with different 5-HT receptor subtypes. Due to the cloning of the different 5-HT receptor subtype genes in the late 1980s and early 1990s, it was possible, using in situ hybridization histochemistry, to localize cells expressing mRNA for these receptors. Double in situ hybridization histochemistry and immunohistochemistry allowed for the chemical characterization of the phenotype of cells expressing 5-HT receptors. Tract tracing technology allowed a detailed cartography of the neuronal connections of PFC and other brain areas. Based on these data, maps have been constructed that reflect our current understanding of the different circuits where 5-HT receptors can modulate the electrophysiological, pharmacological, and behavioral functions of the PFC. We will review current knowledge regarding the cellular localization of 5-HT1A and 5-HT2A receptors in mammalian PFC and their possible functions in the neuronal circuits of the PFC. We will discuss data generated in our laboratory as well as in others, focusing on localization in the pyramidal and GABAergic neuronal cell populations in different mammalian species using molecular neuroanatomy and on the connections with other brain regions. PMID:25739427

  19. Cartography of 5-HT1A and 5-HT2A Receptor Subtypes in Prefrontal Cortex and Its Projections.

    PubMed

    Mengod, Guadalupe; Palacios, José M; Cortés, Roser

    2015-07-15

    Since the development of chemical neuroanatomical tools in the 1960s, a tremendous wealth of information has been generated on the anatomical components of the serotonergic system, at the microscopic level in the brain including the prefrontal cortex (PFC). The PFC receives a widespread distribution of serotonin (5-hydroxytryptamine, 5-HT) terminals from the median and dorsal raphe nuclei. 5-HT receptors were first visualized using radioligand autoradiography in the late 1980s and early 1990s and showed, in contrast to 5-HT innervation, a differential distribution of binding sites associated with different 5-HT receptor subtypes. Due to the cloning of the different 5-HT receptor subtype genes in the late 1980s and early 1990s, it was possible, using in situ hybridization histochemistry, to localize cells expressing mRNA for these receptors. Double in situ hybridization histochemistry and immunohistochemistry allowed for the chemical characterization of the phenotype of cells expressing 5-HT receptors. Tract tracing technology allowed a detailed cartography of the neuronal connections of PFC and other brain areas. Based on these data, maps have been constructed that reflect our current understanding of the different circuits where 5-HT receptors can modulate the electrophysiological, pharmacological, and behavioral functions of the PFC. We will review current knowledge regarding the cellular localization of 5-HT1A and 5-HT2A receptors in mammalian PFC and their possible functions in the neuronal circuits of the PFC. We will discuss data generated in our laboratory as well as in others, focusing on localization in the pyramidal and GABAergic neuronal cell populations in different mammalian species using molecular neuroanatomy and on the connections with other brain regions.

  20. THE SEROTONIN (5-HT) 5-HT2A RECEPTOR: ASSOCIATION WITH INHERENT AND COCAINE-EVOKED BEHAVIORAL DISINHIBITION IN RATS

    PubMed Central

    Anastasio, Noelle C.; Stoffel, Erin C.; Fox, Robert G.; Bubar, Marcy J.; Rice, Kenner C.; Moeller, F. Gerard; Cunningham, Kathryn A.

    2011-01-01

    Alterations in the balance of functional activity within the serotonin (5-HT) system are hypothesized to underlie impulse control. Cocaine-dependent subjects consistently demonstrate greater impulsivity relative to non-drug using control subjects. Preclinical studies suggest that the 5-HT2A receptor (5-HT2AR) contributes to the regulation of impulsive behavior and also mediates some of the behavioral effects of cocaine. We hypothesized that the selective 5-HT2AR antagonist M100907 would reduce inherent levels of impulsivity and attenuate impulsive responding induced by cocaine in two animal models of impulsivity, the differential reinforcement of low rate (DRL) task and the one-choice serial reaction time (1-CSRT) task. M100907 reduced rates of responding in the DRL task and premature responding in the 1-CSRT task. Conversely, cocaine disrupted rates of responding in the DRL task and increased premature responding in the 1-CSRT task. M100907 attenuated cocaine-induced increases in specific markers of behavioral disinhibition in the DRL and 1-CSRT tasks. These results suggest that the 5-HT2AR regulates inherent impulsivity, and that blockade of the 5-HT2AR alleviates specific aspects of elevated levels of impulsivity induced by cocaine exposure. These data point to the 5-HT2AR as an important regulatory substrate in impulse control. PMID:21499079

  1. Maternal lipopolysaccharide treatment differentially affects 5-HT(2A) and mGlu2/3 receptor function in the adult male and female rat offspring.

    PubMed

    Wischhof, Lena; Irrsack, Ellen; Dietz, Frank; Koch, Michael

    2015-10-01

    Maternal infection during pregnancy increases the risk for the offspring to develop schizophrenia. However, it is still not fully understood which biochemical mechanisms are responsible for the emergence of neuropsychiatric symptoms following prenatal immune activation. The serotonin (5-hydroxytryptamine, 5-HT) and glutamate system have prominently been associated with the schizophrenia pathophysiology but also with the mechanism of antipsychotic drug actions. Here, we investigated the behavioral and cellular response to 5-HT2A and metabotropic glutamate (mGlu)2/3 receptor stimulation in male and female offspring born to lipopolysaccharide (LPS)-treated mothers. Additionally, we assessed protein expression levels of prefrontal 5-HT2A and mGlu2 receptors. Prenatally LPS-exposed male and female offspring showed locomotor hyperactivity and increased head-twitch behavior in response to the 5-HT2A receptor agonist DOI. In LPS-exposed male offspring, the mGlu2/3 receptor agonist LY379268 failed to reduce DOI-induced prepulse inhibition deficits. In LPS-males, the behavioral changes were further accompanied by enhanced DOI-induced c-Fos protein expression and an up-regulation of prefrontal 5-HT2A receptors. No changes in either 5-HT2A or mGlu2 receptor protein levels were found in female offspring. Our data support the hypothesis of an involvement of maternal infection during pregnancy contributing, at least partially, to the pathology of schizophrenia. Identifying biochemical alterations that parallel the behavioral deficits may help to improve therapeutic strategies in the treatment of this mental illness. Since most studies in rodents almost exclusively include male subjects, our data further contribute to elucidating possible gender differences in the effects of prenatal infection on 5-HT2A and mGlu2/3 receptor function. PMID:26051401

  2. Activation of 5-HT2a Receptors in the Basolateral Amygdala Promotes Defeat-Induced Anxiety and the Acquisition of Conditioned Defeat in Syrian Hamsters

    PubMed Central

    Clinard, Catherine T.; Bader, Lauren R.; Sullivan, Molly A.; Cooper, Matthew A.

    2014-01-01

    Conditioned defeat is a model in Syrian hamsters (Mesocricetus auratus) in which normal territorial aggression is replaced by increased submissive and defensive behavior following acute social defeat. The conditioned defeat response involves both a fear-related memory for a specific opponent as well as anxiety-like behavior indicated by avoidance of novel conspecifics. We have previously shown that systemic injection of a 5-HT2a receptor antagonist reduces the acquisition of conditioned defeat. Because neural activity in the basolateral amygdala (BLA) is critical for the acquisition of conditioned defeat and BLA 5-HT2a receptors can modulate anxiety but have a limited effect on emotional memories, we investigated whether 5-HT2a receptor modulation alters defeat-induced anxiety but not defeat-related memories. We injected the 5-HT2a receptor antagonist MDL 11,939 (0 mM, 1.7 mM or 17 mM) or the 5-HT2a receptor agonist TCB-2 (0 mM, 8 mM or 80 mM) into the BLA prior to social defeat. We found that injection of MDL 11,939 into the BLA impaired acquisition of the conditioned defeat response and blocked defeat-induced anxiety in the open field, but did not significantly impair avoidance of former opponents in the Y-maze. Furthermore, we found that injection of TCB-2 into the BLA increased the acquisition of conditioned defeat and increased anxiety-like behavior in the open field, but did not alter avoidance of former opponents. Our data suggest that 5-HT2a receptor signaling in the BLA is both necessary and sufficient for the development of conditioned defeat, likely via modulation of defeat-induced anxiety. PMID:25458113

  3. Extensive Rigid Analogue Design Maps the Binding Conformation of Potent N-Benzylphenethylamine 5-HT2A Serotonin Receptor Agonist Ligands

    PubMed Central

    2012-01-01

    Based on the structure of the superpotent 5-HT2A agonist 2-(4-bromo-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamine, which consists of a ring-substituted phenethylamine skeleton modified with an N-benzyl group, we designed and synthesized a small library of constrained analogues to identify the optimal arrangement of the pharmacophoric elements of the ligand. Structures consisted of diversely substituted tetrahydroisoquinolines, piperidines, and one benzazepine. Based on the structure of (S,S)-9b, which showed the highest affinity of the series, we propose an optimal binding conformation. (S,S)-9b also displayed 124-fold selectivity for the 5-HT2A over the 5-HT2C receptor, making it the most selective 5-HT2A receptor agonist ligand currently known. PMID:23336049

  4. Lack of Association between the Serotonin Transporter (5-HTT) and Serotonin Receptor (5-HT2A) Gene Polymorphisms with Smoking Behavior among Malaysian Malays

    PubMed Central

    Rozak, Nur Iwani A; Ahmad, Imran; Gan, Siew Hua; Abu Bakar, Ruzilawati

    2014-01-01

    Abstract An insertion/deletion polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) and a polymorphism (rs6313) in the serotonin 2A receptor gene (5-HT2A) have previously been linked to smoking behavior. The objective of this study was to determine the possible association of the 5-HTTLPR and 5-HT2A gene polymorphisms with smoking behavior within a population of Malaysian male smokers (n=248) and non-smokers (n=248). The 5-HTTLPR genotypes were determined using the polymerase chain reaction (PCR) and were classified as short (S) alleles or long (L) alleles. The 5HT2A genotypes were determined using PCR-restriction fragment length polymorphisms (PCR-RFLP). No significant differences in the distribution frequencies of the alleles were found between the smokers and the non-smokers for the 5-HTTLPR polymorphism (x2 = 0.72, P>0.05) or the 5HT2A polymorphism (x2 = 0.73, P>0.05). This is the first study conducted on Malaysian Malay males regarding the association of 5-HTTLPR and 5HT2A polymorphisms and smoking behavior. However, the genes were not found to be associated with smoking behavior in our population. PMID:25853073

  5. Genotype-Dependent Difference in 5-HT2C Receptor-Induced Hypolocomotion: Comparison with 5-HT2A Receptor Functional Activity

    PubMed Central

    Bazovkina, Darya V.; Kondaurova, Elena M.; Naumenko, Vladimir S.; Ponimaskin, Evgeni

    2015-01-01

    In the present study behavioral effects of the 5-HT2C serotonin receptor were investigated in different mouse strains. The 5-HT2C receptor agonist MK-212 applied intraperitoneally induced significant dose-dependent reduction of distance traveled in the open field test in CBA/Lac mice. This effect was receptor-specific because it was inhibited by the 5-HT2C receptor antagonist RS102221. To study the role of genotype in 5-HT2C receptor-induced hypolocomotion, locomotor activity of seven inbred mouse strains was measured after MK-212 acute treatment. We found that the 5-HT2C receptor stimulation by MK-212 decreased distance traveled in the open field test in CBA/Lac, C57Bl/6, C3H/He, and ICR mice, whereas it failed to affect locomotor activity in DBA/2J, Asn, and Balb/c mice. We also compared the interstrain differences in functional response to 5-HT2C and 5-HT2A receptors activation measured by the quantification of receptor-mediated head-twitches. These experiments revealed significant positive correlation between 5-HT2C and 5-HT2A receptors functional responses for all investigated mouse strains. Moreover, we found that 5-HT2A receptor activation with DOI did not change locomotor activity in CBA/Lac mice. Taken together, our data indicate the implication of 5-HT2C receptors in regulation of locomotor activity and suggest the shared mechanism for functional responses mediated by 5-HT2C and 5-HT2A receptors. PMID:26380122

  6. Genotype-Dependent Difference in 5-HT2C Receptor-Induced Hypolocomotion: Comparison with 5-HT2A Receptor Functional Activity.

    PubMed

    Bazovkina, Darya V; Kondaurova, Elena M; Naumenko, Vladimir S; Ponimaskin, Evgeni

    2015-01-01

    In the present study behavioral effects of the 5-HT2C serotonin receptor were investigated in different mouse strains. The 5-HT2C receptor agonist MK-212 applied intraperitoneally induced significant dose-dependent reduction of distance traveled in the open field test in CBA/Lac mice. This effect was receptor-specific because it was inhibited by the 5-HT2C receptor antagonist RS102221. To study the role of genotype in 5-HT2C receptor-induced hypolocomotion, locomotor activity of seven inbred mouse strains was measured after MK-212 acute treatment. We found that the 5-HT2C receptor stimulation by MK-212 decreased distance traveled in the open field test in CBA/Lac, C57Bl/6, C3H/He, and ICR mice, whereas it failed to affect locomotor activity in DBA/2J, Asn, and Balb/c mice. We also compared the interstrain differences in functional response to 5-HT2C and 5-HT2A receptors activation measured by the quantification of receptor-mediated head-twitches. These experiments revealed significant positive correlation between 5-HT2C and 5-HT2A receptors functional responses for all investigated mouse strains. Moreover, we found that 5-HT2A receptor activation with DOI did not change locomotor activity in CBA/Lac mice. Taken together, our data indicate the implication of 5-HT2C receptors in regulation of locomotor activity and suggest the shared mechanism for functional responses mediated by 5-HT2C and 5-HT2A receptors. PMID:26380122

  7. Genotype-Dependent Difference in 5-HT2C Receptor-Induced Hypolocomotion: Comparison with 5-HT2A Receptor Functional Activity.

    PubMed

    Bazovkina, Darya V; Kondaurova, Elena M; Naumenko, Vladimir S; Ponimaskin, Evgeni

    2015-01-01

    In the present study behavioral effects of the 5-HT2C serotonin receptor were investigated in different mouse strains. The 5-HT2C receptor agonist MK-212 applied intraperitoneally induced significant dose-dependent reduction of distance traveled in the open field test in CBA/Lac mice. This effect was receptor-specific because it was inhibited by the 5-HT2C receptor antagonist RS102221. To study the role of genotype in 5-HT2C receptor-induced hypolocomotion, locomotor activity of seven inbred mouse strains was measured after MK-212 acute treatment. We found that the 5-HT2C receptor stimulation by MK-212 decreased distance traveled in the open field test in CBA/Lac, C57Bl/6, C3H/He, and ICR mice, whereas it failed to affect locomotor activity in DBA/2J, Asn, and Balb/c mice. We also compared the interstrain differences in functional response to 5-HT2C and 5-HT2A receptors activation measured by the quantification of receptor-mediated head-twitches. These experiments revealed significant positive correlation between 5-HT2C and 5-HT2A receptors functional responses for all investigated mouse strains. Moreover, we found that 5-HT2A receptor activation with DOI did not change locomotor activity in CBA/Lac mice. Taken together, our data indicate the implication of 5-HT2C receptors in regulation of locomotor activity and suggest the shared mechanism for functional responses mediated by 5-HT2C and 5-HT2A receptors.

  8. APD125, a Selective Serotonin 5-HT2A Receptor Inverse Agonist, Significantly Improves Sleep Maintenance in Primary Insomnia

    PubMed Central

    Rosenberg, Russell; Seiden, David J.; Hull, Steven G.; Erman, Milton; Schwartz, Howard; Anderson, Christen; Prosser, Warren; Shanahan, William; Sanchez, Matilde; Chuang, Emil; Roth, Thomas

    2008-01-01

    Introduction: Insomnia is a condition affecting 10% to 15% of the adult population and is characterized by difficulty falling asleep, difficulty staying asleep, or nonrestorative sleep, accompanied by daytime impairment or distress. This study evaluates APD125, a selective inverse agonist of the 5-HT2A receptor, for treatment of chronic insomnia, with particular emphasis on sleep maintenance. In phase 1 studies, APD125 improved sleep maintenance and was well tolerated. Methodology: Adult subjects (n = 173) with DSM-IV defined primary insomnia were randomized into a multicenter, double-blind, placebo-controlled, 3-way crossover study to compare 2 doses of APD125 (10 mg and 40 mg) with placebo. Each treatment period was 7 days with a 7- to 9-day washout period between treatments. Polysomnographic recordings were performed at the initial 2 screening nights and at nights (N) 1/2 and N 6/7 of each treatment period. Results: APD125 was associated with significant improvements in key sleep maintenance parameters measured by PSG. Wake time after sleep onset decreased (SEM) by 52.5 (3.2) min (10 mg) and 53.5 (3.5) min (40 mg) from baseline to N 1/2 vs. 37.8 (3.4) min for placebo, (P < 0.0001 for both doses vs placebo), and by 51.7 (3.4) min (P = 0.01) and 48.0 (3.6) min (P = 0.2) at N 6/7 vs. 44.0 (3.8) min for placebo. Significant APD125 effects on wake time during sleep were also seen (P < 0.0001 N 1/2, P < 0.001 N 6/7). The number of arousals and number of awakenings decreased significantly with APD125 treatment compared to placebo. Slow wave sleep showed a statistically significant dose-dependent increase. There was no significant decrease in latency to persistent sleep. No serious adverse events were reported, and no meaningful differences in adverse event profiles were observed between either dose of APD125 and placebo. APD125 was not associated with next-day psychomotor impairment as measured by Digit Span, Digit Symbol Copy, and Digit Symbol Coding Tests

  9. Involvement of 5-HT2A receptors in MDMA reinforcement and cue-induced reinstatement of MDMA-seeking behaviour.

    PubMed

    Orejarena, María Juliana; Lanfumey, Laurence; Maldonado, Rafael; Robledo, Patricia

    2011-08-01

    The serotonergic system appears crucial for (±)-3,4-methylenedioxymethamphetamine (MDMA) reinforcing properties. Current evidence indicates that serotonin 5-HT2A receptors (5-HT2ARs) modulate mesolimbic dopamine (DA) activity and several behavioural responses related to the addictive properties of psychostimulants. This study evaluated the role of 5-HT2ARs in MDMA-induced reinforcement and hyperlocomotion, and the reinstatement of MDMA-seeking behaviour. Basal and MDMA-stimulated extracellular levels of DA in the nucleus accumbens (NAc) and serotonin and noradrenaline in the prefrontal cortex were also assessed. Self-administration of MDMA was blunted in 5-HT2AR knockout (KO) mice compared to wild-type (WT) littermates at both doses tested (0.125 and 0.25 mg/kg per infusion). Horizontal locomotion was increased by MDMA (10 and 20 mg/kg i.p.) to a higher extent in KO than in WT mice. DA outflow in the NAc was lower in KO compared to WT mice under basal conditions and after MDMA (20 mg/kg) challenge. In WT mice, MDMA (5 and 10 mg/kg i.p.) priming did not reinstate MDMA-seeking behaviour, while cue-induced reinstatement was prominent. This cue-induced reinstatement was blocked by administration of the selective 5-HT2AR antagonist, SR46349B (eplivanserin) at a dose of 0.5 mg/kg, but not at 0.25 mg/kg. Our results indicate that 5-HT2ARs are crucial for MDMA-induced reinforcement and cue-induced reinstatement of MDMA-seeking behaviour. These effects are probably due to the modulation of mesolimbic dopaminergic activity.

  10. Allosteric signaling through an mGlu2 and 5-HT2A heteromeric receptor complex and its potential contribution to schizophrenia.

    PubMed

    Moreno, José L; Miranda-Azpiazu, Patricia; García-Bea, Aintzane; Younkin, Jason; Cui, Meng; Kozlenkov, Alexey; Ben-Ezra, Ariel; Voloudakis, Georgios; Fakira, Amanda K; Baki, Lia; Ge, Yongchao; Georgakopoulos, Anastasios; Morón, José A; Milligan, Graeme; López-Giménez, Juan F; Robakis, Nikolaos K; Logothetis, Diomedes E; Meana, J Javier; González-Maeso, Javier

    2016-01-12

    Heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) can form multiprotein complexes (heteromers), which can alter the pharmacology and functions of the constituent receptors. Previous findings demonstrated that the Gq/11-coupled serotonin 5-HT2A receptor and the Gi/o-coupled metabotropic glutamate 2 (mGlu2) receptor-GPCRs that are involved in signaling alterations associated with psychosis-assemble into a heteromeric complex in the mammalian brain. In single-cell experiments with various mutant versions of the mGlu2 receptor, we showed that stimulation of cells expressing mGlu2-5-HT2A heteromers with an mGlu2 agonist led to activation of Gq/11 proteins by the 5-HT2A receptors. For this crosstalk to occur, one of the mGlu2 subunits had to couple to Gi/o proteins, and we determined the relative location of the Gi/o-contacting subunit within the mGlu2 homodimer of the heteromeric complex. Additionally, mGlu2-dependent activation of Gq/11, but not Gi/o, was reduced in the frontal cortex of 5-HT2A knockout mice and was reduced in the frontal cortex of postmortem brains from schizophrenic patients. These findings offer structural insights into this important target in molecular psychiatry.

  11. Functional selectivity of hallucinogenic phenethylamine and phenylisopropylamine derivatives at human 5-hydroxytryptamine (5-HT)2A and 5-HT2C receptors.

    PubMed

    Moya, Pablo R; Berg, Kelly A; Gutiérrez-Hernandez, Manuel A; Sáez-Briones, Patricio; Reyes-Parada, Miguel; Cassels, Bruce K; Clarke, William P

    2007-06-01

    2,5-Dimethoxy-4-substituted phenylisopropylamines and phenethylamines are 5-hydroxytryptamine (serotonin) (5-HT)(2A/2C) agonists. The former are partial to full agonists, whereas the latter are partial to weak agonists. However, most data come from studies analyzing phospholipase C (PLC)-mediated responses, although additional effectors [e.g., phospholipase A(2) (PLA(2))] are associated with these receptors. We compared two homologous series of phenylisopropylamines and phenethylamines measuring both PLA(2) and PLC responses in Chinese hamster ovary-K1 cells expressing human 5-HT(2A) or 5-HT(2C) receptors. In addition, we assayed both groups of compounds as head shake inducers in rats. At the 5-HT(2C) receptor, most compounds were partial agonists for both pathways. Relative efficacy of some phenylisopropylamines was higher for both responses compared with their phenethylamine counterparts, whereas for others, no differences were found. At the 5-HT(2A) receptor, most compounds behaved as partial agonists, but unlike findings at 5-HT(2C) receptors, all phenylisopropylamines were more efficacious than their phenethylamine counterparts. 2,5-Dimethoxyphenylisopropylamine activated only the PLC pathway at both receptor subtypes, 2,5-dimethoxyphenethylamine was selective for PLC at the 5-HT(2C) receptor, and 2,5-dimethoxy-4-nitrophenethylamine was PLA(2)-specific at the 5-HT(2A) receptor. For both receptors, the rank order of efficacy of compounds differed depending upon which response was measured. The phenylisopropylamines were strong head shake inducers, whereas their phenethylamine congeners were not, in agreement with in vitro results and the involvement of 5-HT(2A) receptors in the head shake response. Our results support the concept of functional selectivity and indicate that subtle changes in ligand structure can result in significant differences in the cellular signaling profile.

  12. Tolerance to LSD and DOB induced shaking behaviour: differential adaptations of frontocortical 5-HT(2A) and glutamate receptor binding sites.

    PubMed

    Buchborn, Tobias; Schröder, Helmut; Dieterich, Daniela C; Grecksch, Gisela; Höllt, Volker

    2015-03-15

    Serotonergic hallucinogens, such as lysergic acid diethylamide (LSD) and dimethoxy-bromoamphetamine (DOB), provoke stereotype-like shaking behaviour in rodents, which is hypothesised to engage frontocortical glutamate receptor activation secondary to serotonin2A (5-HT2A) related glutamate release. Challenging this hypothesis, we here investigate whether tolerance to LSD and DOB correlates with frontocortical adaptations of 5-HT2A and/or overall-glutamate binding sites. LSD and DOB (0.025 and 0.25 mg/kg, i.p.) induce a ketanserin-sensitive (0.5 mg/kg, i.p., 30-min pretreatment) increase in shaking behaviour (including head twitches and wet dog shakes), which with repeated application (7× in 4 ds) is undermined by tolerance. Tolerance to DOB, as indexed by DOB-sensitive [(3)H]spiroperidol and DOB induced [(35)S]GTP-gamma-S binding, is accompanied by a frontocortical decrease in 5-HT2A binding sites and 5-HT2 signalling, respectively; glutamate-sensitive [(3)H]glutamate binding sites, in contrast, remain unchanged. As to LSD, 5-HT2 signalling and 5-HT2A binding, respectively, are not or only marginally affected, yet [(3)H]glutamate binding is significantly decreased. Correlation analysis interrelates tolerance to DOB to the reduced 5-HT2A (r=.80) as well as the unchanged [(3)H]glutamate binding sites (r=.84); tolerance to LSD, as opposed, shares variance with the reduction in [(3)H]glutamate binding sites only (r=.86). Given that DOB and LSD both induce tolerance, one correlating with 5-HT2A, the other with glutamate receptor adaptations, it might be inferred that tolerance can arise at either level. That is, if a hallucinogen (like LSD in our study) fails to induce 5-HT2A (down-)regulation, glutamate receptors (activated postsynaptic to 5-HT2A related glutamate release) might instead adapt and thus prevent further overstimulation of the cortex. PMID:25513973

  13. Tolerance to LSD and DOB induced shaking behaviour: differential adaptations of frontocortical 5-HT(2A) and glutamate receptor binding sites.

    PubMed

    Buchborn, Tobias; Schröder, Helmut; Dieterich, Daniela C; Grecksch, Gisela; Höllt, Volker

    2015-03-15

    Serotonergic hallucinogens, such as lysergic acid diethylamide (LSD) and dimethoxy-bromoamphetamine (DOB), provoke stereotype-like shaking behaviour in rodents, which is hypothesised to engage frontocortical glutamate receptor activation secondary to serotonin2A (5-HT2A) related glutamate release. Challenging this hypothesis, we here investigate whether tolerance to LSD and DOB correlates with frontocortical adaptations of 5-HT2A and/or overall-glutamate binding sites. LSD and DOB (0.025 and 0.25 mg/kg, i.p.) induce a ketanserin-sensitive (0.5 mg/kg, i.p., 30-min pretreatment) increase in shaking behaviour (including head twitches and wet dog shakes), which with repeated application (7× in 4 ds) is undermined by tolerance. Tolerance to DOB, as indexed by DOB-sensitive [(3)H]spiroperidol and DOB induced [(35)S]GTP-gamma-S binding, is accompanied by a frontocortical decrease in 5-HT2A binding sites and 5-HT2 signalling, respectively; glutamate-sensitive [(3)H]glutamate binding sites, in contrast, remain unchanged. As to LSD, 5-HT2 signalling and 5-HT2A binding, respectively, are not or only marginally affected, yet [(3)H]glutamate binding is significantly decreased. Correlation analysis interrelates tolerance to DOB to the reduced 5-HT2A (r=.80) as well as the unchanged [(3)H]glutamate binding sites (r=.84); tolerance to LSD, as opposed, shares variance with the reduction in [(3)H]glutamate binding sites only (r=.86). Given that DOB and LSD both induce tolerance, one correlating with 5-HT2A, the other with glutamate receptor adaptations, it might be inferred that tolerance can arise at either level. That is, if a hallucinogen (like LSD in our study) fails to induce 5-HT2A (down-)regulation, glutamate receptors (activated postsynaptic to 5-HT2A related glutamate release) might instead adapt and thus prevent further overstimulation of the cortex.

  14. 3,4-methylenedioxymethamphetamine increases excitability in the dentate gyrus: role of 5HT2A receptor-induced PGE2 signaling.

    PubMed

    Collins, Stuart A; Huff, Courtney; Chiaia, Nicolas; Gudelsky, Gary A; Yamamoto, Bryan K

    2016-03-01

    3,4-methylenedioxymethamphetamine (MDMA) is a widely abused psychostimulant, which causes release of serotonin in various forebrain regions. Recently, we reported that MDMA increases extracellular glutamate concentrations in the dentate gyrus, via activation of 5HT2A receptors. We examined the role of prostaglandin signaling in mediating the effects of 5HT2A receptor activation on the increases in extracellular glutamate and the subsequent long-term loss of parvalbumin interneurons in the dentate gyrus caused by MDMA. Administration of MDMA into the dentate gyrus of rats increased PGE2 concentrations which was prevented by coadministration of MDL100907, a 5HT2A receptor antagonist. MDMA-induced increases in extracellular glutamate were inhibited by local administration of SC-51089, an inhibitor of the EP1 prostaglandin receptor. Systemic administration of SC-51089 during injections of MDMA prevented the decreases in parvalbumin interneurons observed 10 days later. The loss of parvalbumin immunoreactivity after MDMA exposure coincided with a decrease in paired-pulse inhibition and afterdischarge threshold in the dentate gyrus. These changes were prevented by inhibition of EP1 and 5HT2A receptors during MDMA. Additional experiments revealed an increased susceptibility to kainic acid-induced seizures in MDMA-treated rats, which could be prevented with SC51089 treatments during MDMA exposure. Overall, these findings suggest that 5HT2A receptors mediate MDMA-induced PGE2 signaling and subsequent increases in glutamate. This signaling mediates parvalbumin cell losses as well as physiologic changes in the dentate gyrus, suggesting that the lack of the inhibition provided by these neurons increases the excitability within the dentate gyrus of MDMA-treated rats. We hypothesized that the widely abused psychostimulant MDMA causes a loss of parvalbumin (PV) cells and increases excitability in the dentate gyrus. MDMA increases serotonin (5HT) release and activates 5HT2A

  15. A comparison of the behavioural effects of 5-HT2A and 5-HT2C receptor agonists in the pigeon.

    PubMed

    Wolff, M C; Leander, J D

    2000-08-01

    Activity at the 5-HT2A receptor versus that of the 5-HT2C receptor was studied in three behavioural paradigms. In pigeons trained to discriminate 0.32 mg/kg of 1-(2,5-diemethoxy-4-iodophenyl)-2-aminopropane (DOI) (a mixed 5-HT2A/C receptor agonist) from vehicle, quipazine (0.1-1 mg/kg) and m-chlorophenylpiperazine (mCPP) (1-3 mg/kg) substituted for DOI in a dose-related manner, and this generalization was blocked by MDL100907 (0.0001-0.01 mg/kg), a selective 5-HT2A receptor antagonist. RO60-0175 (a relatively selective 5-HT2C agonist) induced partial substitution at 3 mg/kg that was antagonized by both MDL100907 and by 3 mg/kg of SB242084, a relatively selective 5-HT2C antagonist. MK212 (a mixed 5-HT2C/A agonist) induced partial substitution that was antagonized by SB242084, but not by MDL100907. On a progressive ratio 5 operant schedule (PR5) for food reinforcement, DOI, quipazine, mCPP, MK212 and R060-0175 decreased the break point; mCPP, DOI, MK212 and quipazine also induced vomiting. Although MDL100907 antagonized both the reductions of break point and vomiting, SB242084 only partially attenuated the decrease in break point observed with MK212 and DOI, and was unable to eliminate vomiting. Thus pharmacological activity at the 5-HT2A receptor can be behaviourally distinguished from pharmacological activity at the 5-HT2C receptor in the pigeon. Furthermore, the decrease in the break point of a PR5 schedule induced by 5-HT2C receptor agonists may be related to decreased appetite, whereas that induced by 5-HT2A receptor agonists may be due to unrelated factors, such as emesis. PMID:11103887

  16. The role of the 5-HT2A and 5-HT2C receptors in the stimulus effects of hallucinogenic drugs. I: Antagonist correlation analysis.

    PubMed

    Fiorella, D; Rabin, R A; Winter, J C

    1995-10-01

    Investigations conducted over the past 3 decades have demonstrated that serotonergic receptors, specifically the 5-HT2A and 5-HT2C subtypes, play an important role in the behavioral effects of hallucinogenic compounds. The present study was designed to determine the respective significance of these two receptors in the stimulus effects of LSD and (-)DOM in the rat. Specifically, the interactions of a series of serotonergic antagonists (risperidone, pirenpirone, metergoline, ketanserin, loxapine, LY53857, pizotyline, spiperone, cyprohepatadine, mesulergine, promethazine, and thioridazine) with the LSD stimulus and the (-)DOM stimulus in LSD-trained subjects was defined. From these data, IC50 values were determined for the inhibition of the LSD-appropriate responding elicited by either 0.1 mg/kg LSD (15-min pretreatment time) or 0.4 mg/kg (-)DOM (75-min pretreatment). In addition, the affinities of these antagonists for 5-HT2A and 5-HT2C receptors were determined in radioligand competition studies, 5-HT2A affinity correlated significantly with IC50 values for the blockade of the LSD (r = +0.75, P < 0.05) and (-)DOM (r = +0.95, P < 0.001) stimuli in the LSD trained subjects. 5-HT2C affinity did not correlate significantly with either series of IC50 values. These data indicate that (1) the stimulus effects of LSD, and (2) the substitution of (-)DOM for the LSD stimulus are mediated by agonist activity at 5-HT2A receptors.

  17. Effect of fluvoxamine on platelet 5-HT2A receptors as studied by [3H]lysergic acid diethylamide ([3H]LSD) binding in healthy volunteers.

    PubMed

    Spigset, O; Mjörndal, T

    1997-09-01

    Alterations in platelet 5-HT2A receptor characteristics have been reported in major depression as well as in other psychiatric diseases, and some effort has been made to utilize platelet 5-HT2A receptor status as a biological correlate to antidepressant drug response. In order to investigate whether treatment with a selective serotonin reuptake inhibitor affects platelet 5-HT2A receptors, we have studied platelet [3H]lysergic acid diethylamide ([3H]LSD) binding in healthy subjects treated with fluvoxamine in increasing dosage once weekly for 4 weeks. After 1 week of fluvoxamine treatment (25 mg/day), both Bmax and Kd were significantly lower than before the start of the treatment (19.9 versus 25.5 fmol/mg protein, P = 0.005 for Bmax; 0.45 versus 0.93 nM, P = 0.006 for Kd). Bmax returned to baseline during week 2, whereas Kd was lower than the baseline value throughout the treatment period. After discontinuation of fluvoxamine treatment, there was a significant increase in Kd (0.50 nM before discontinuation vs. 1.14 nM after discontinuation; P = 0.001), but not in Bmax. The study demonstrates that fluvoxamine affects platelet 5-HT2A receptor status irrespective of underlying psychiatric disease, and that this effect is evident already after 1 week at a subtherapeutic fluvoxamine dose.

  18. Exploring the relationship between binding modes of 9-(aminomethyl)-9,10-dihydroanthracene and cyproheptadine analogues at the 5-HT2A serotonin receptor.

    PubMed

    Westkaemper, R B; Runyon, S P; Savage, J E; Roth, B L; Glennon, R A

    2001-02-26

    Comparison of the serotonin 5-HT2A receptor affinities of a parallel series of structural analogues of the novel ligand 9-aminomethyl-9,10-dihydroanthracene (AMDA) and a structurally similar prototypical tricyclic amine cyproheptadine suggests that the two agents bind to the receptor in different fashions. Examination of ligand-receptor model complexes supports the experimental data and suggests a potential origin for the differences in binding modes.

  19. Development of a Multiplex Assay for Studying Functional Selectivity of Human Serotonin 5-HT2A Receptors and Identification of Active Compounds by High-Throughput Screening.

    PubMed

    Iglesias, Alba; Lage, Sonia; Cadavid, Maria Isabel; Loza, Maria Isabel; Brea, José

    2016-09-01

    G protein-coupled receptors (GPCRs) exist as collections of conformations in equilibrium, and the efficacy of drugs has been proposed to be associated with their absolute and relative affinities for these different conformations. The serotonin 2A (5-HT2A) receptor regulates multiple physiological functions, is involved in the pathophysiology of schizophrenia, and serves as an important target of atypical antipsychotic drugs. This receptor was one of the first GPCRs for which the functional selectivity phenomenon was observed, with its various ligands exerting differential effects on the phospholipase A2 (PLA2) and phospholipase C (PLC) signaling pathways. We aimed to develop a multiplex functional assay in 96-well plates for the simultaneous measurement of the PLA2 and PLC pathways coupled to 5-HT2A receptors; this approach enables the detection of either functional selectivity or cooperativity phenomena in early drug screening stages. The suitability of the method for running screening campaigns was tested using the Prestwick Chemical Library, and 22 confirmed hits with activities of more than 90% were identified; 11 of these hits produced statistically significant differences between the two effector pathways. Thus, we have developed a miniaturized multiplex assay in 96-well plates to measure functional selectivity for 5-HT2A receptors in the early stages of the drug discovery process. PMID:27095818

  20. MDMA-induced loss of parvalbumin interneurons within the dentate gyrus is mediated by 5HT2A and NMDA receptors.

    PubMed

    Collins, Stuart A; Gudelsky, Gary A; Yamamoto, Bryan K

    2015-08-15

    MDMA is a widely abused psychostimulant which causes a rapid and robust release of the monoaminergic neurotransmitters dopamine and serotonin. Recently, it was shown that MDMA increases extracellular glutamate concentrations in the dorsal hippocampus, which is dependent on serotonin release and 5HT2A/2C receptor activation. The increased extracellular glutamate concentration coincides with a loss of parvalbumin-immunoreactive (PV-IR) interneurons of the dentate gyrus region. Given the known susceptibility of PV interneurons to excitotoxicity, we examined whether MDMA-induced increases in extracellular glutamate in the dentate gyrus are necessary for the loss of PV cells in rats. Extracellular glutamate concentrations increased in the dentate gyrus during systemic and local administration of MDMA. Administration of the NMDA receptor antagonist, MK-801, during systemic injections of MDMA, prevented the loss of PV-IR interneurons seen 10 days after MDMA exposure. Local administration of MDL100907, a selective 5HT2A receptor antagonist, prevented the increases in glutamate caused by reverse dialysis of MDMA directly into the dentate gyrus and prevented the reduction of PV-IR. These findings provide evidence that MDMA causes decreases in PV within the dentate gyrus through a 5HT2A receptor-mediated increase in glutamate and subsequent NMDA receptor activation.

  1. Synthesis and in vitro evaluation of [18F]FECIMBI-36: A potential agonist PET ligand for 5-HT2A/2C receptors

    PubMed Central

    Prabhakaran, Jaya; Underwood, Mark D.; Dileep Kumar, J. S.; Simpson, Norman R.; Kassir, Suham A.; Bakalian, Mihran J.; Mann, J. John; Arango, Victoria

    2016-01-01

    Radiosynthesis and in vitro evaluation of [18F]-2-(4-bromo-2,5-dimethoxyphenyl)-N-(2-(2-fluoroethoxy)benzyl)ethanamine, ([18F]FECIMBI-36) or ([18F]1), a potential agonist PET imaging agent for 5-HT2A/2C receptors is described. Syntheses of reference standard 1 and the corresponding des-fluoroethyl radiolabeling precursor (2) were achieved with 75% and 65% yields, respectively. In vitro pharmacology assay of FECIMBI-36 by [3H]-ketanserin competition binding assay obtained from NIMH-PDSP showed high affinities to 5-HT2AR (Ki = 1 nM) and 5-HT2CR (Ki = 1.7 nM). Radiolabeling of FECIMBI-36 was achieved from the boc-protected precursor 2 using [18F]-fluoroethyltosylate in presence of Cs2CO3 in DMSO followed by removal of the protective group. [18F]1 was isolated using RP-HPLC in 25 ± 5% yield, purity ≥95% and specific activity 1–2 Ci/μmol (N = 6). In vitro autoradiography studies demonstrate that [18F]1 selectively label 5-HT2A and 5-HT2C receptors in slide-mounted sections of postmortem human brain using phosphor imaging. Our results indicate the potential of [18F]1 for imaging 5-HT2A/2C receptors in the high affinity state in vivo using PET imaging. PMID:26253634

  2. Synthesis and in vitro evaluation of [18F]FECIMBI-36: A potential agonist PET ligand for 5-HT2A/2C receptors.

    PubMed

    Prabhakaran, Jaya; Underwood, Mark D; Kumar, J S Dileep; Simpson, Norman R; Kassir, Suham A; Bakalian, Mihran J; Mann, J John; Arango, Victoria

    2015-09-15

    Radiosynthesis and in vitro evaluation of [(18)F]-2-(4-bromo-2,5-dimethoxyphenyl)-N-(2-(2-fluoroethoxy)benzyl)ethanamine, ([(18)F]FECIMBI-36) or ([(18)F]1), a potential agonist PET imaging agent for 5-HT2A/2C receptors is described. Syntheses of reference standard 1 and the corresponding des-fluoroethyl radiolabeling precursor (2) were achieved with 75% and 65% yields, respectively. In vitro pharmacology assay of FECIMBI-36 by [(3)H]-ketanserin competition binding assay obtained from NIMH-PDSP showed high affinities to 5-HT2AR (Ki = 1nM) and 5-HT2CR (Ki=1.7 nM). Radiolabeling of FECIMBI-36 was achieved from the boc-protected precursor 2 using [(18)F]-fluoroethyltosylate in presence of Cs2CO3 in DMSO followed by removal of the protective group. [(18)F]1 was isolated using RP-HPLC in 25 ± 5% yield, purity > 95% and specific activity 1-2Ci/μmol (N = 6). In vitro autoradiography studies demonstrate that [(18)F]1 selectively label 5-HT2A and 5-HT2C receptors in slide-mounted sections of postmortem human brain using phosphor imaging. Our results indicate the potential of [(18)F]1 for imaging 5-HT2A/2C receptors in the high affinity state in vivo using PET imaging.

  3. Role of 5-HT2A and 5-HT2C receptors in the stimulus effects of hallucinogenic drugs. II: Reassessment of LSD false positives.

    PubMed

    Fiorella, D; Rabin, R A; Winter, J C

    1995-10-01

    In the context of animal studies of hallucinogens, an LSD-false positive is defined as a drug known to be devoid of hallucinogenic activity in humans but which nonetheless fully mimics LSD in animals. Quipazine, MK-212, lisuride, and yohimbine have all been reported to be LSD false positives. The present study was designed to determine whether these compounds also substitute for the stimulus effects of the more pharmacologically selective hallucinogen (-)DOM (0.56 mg/kg, 75-min pretreatment time). The LSD and (-)DOM stimuli fully generalized to quipazine (3.0 mg/kg) and lisuride (0.2 mg/kg), but only partially generalized to MK-212 (0.1-1.0 mg/kg) and yohimbine (2-20 mg/kg). In combination tests, pirenpirone (0.08 mg/kg), a compound with both D2 and 5-HT2A affinity, blocked the substitution of quipazine and lisuride for the (-)DOM stimulus. Ketanserin (2.5 mg/kg), an antagonist with greater than 1 order of magnitude higher affinity for 5-HT2A receptors than either 5-HT2C or D2 receptors, also fully blocked the substitution of these compounds for the (-)DOM stimulus, while the selective D2 antagonist thiothixene (0.1-1.0 mg/kg) failed to block the substitution of lisuride for the (-)DOM stimulus. These results suggest that quipazine and lisuride substitute for the stimulus properties of the phenylalkglamine hallucinogen (-)DOM via agonist activity at 5-HT2A receptors. In addition, these results suggest that 5-HT2A agonist activity may be required, but is not in itself sufficient, for indolamine and phenylalkglamine compounds to elicit hallucinations in humans. Finally, it is concluded that MK-212 and yohimbine are neither LSD nor (-)DOM false positives.

  4. Role for serotonin2A (5-HT2A) and 2C (5-HT2C) receptors in experimental absence seizures.

    PubMed

    Venzi, Marcello; David, François; Bellet, Joachim; Cavaccini, Anna; Bombardi, Cristiano; Crunelli, Vincenzo; Di Giovanni, Giuseppe

    2016-09-01

    Absence seizures (ASs) are the hallmark of childhood/juvenile absence epilepsy. Monotherapy with first-line anti-absence drugs only controls ASs in 50% of patients, indicating the need for novel therapeutic targets. Since serotonin family-2 receptors (5-HT2Rs) are known to modulate neuronal activity in the cortico-thalamo-cortical loop, the main network involved in AS generation, we investigated the effect of selective 5-HT2AR and 5-HT2CR ligands on ASs in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well established polygenic rat model of these non-convulsive seizures. GAERS rats were implanted with fronto-parietal EEG electrodes under general anesthesia, and their ASs were later recorded under freely moving conditions before and after intraperitoneal administration of various 5-HT2AR and 5-HT2CR ligands. The 5-HT2A agonist TCB-2 dose-dependently decreased the total time spent in ASs, an effect that was blocked by the selective 5-HT2A antagonist MDL11,939. Both MDL11,939 and another selective 5-HT2A antagonist (M100,907) increased the length of individual seizures when injected alone. The 5-HT2C agonists lorcaserin and CP-809,101 dose-dependently suppressed ASs, an effect blocked by the selective 5-HT2C antagonist SB 242984. In summary, 5-HT2ARs and 5-HT2CRs negatively control the expression of experimental ASs, indicating that selective agonists at these 5-HT2R subtypes might be potential novel anti-absence drugs.

  5. Role for serotonin2A (5-HT2A) and 2C (5-HT2C) receptors in experimental absence seizures.

    PubMed

    Venzi, Marcello; David, François; Bellet, Joachim; Cavaccini, Anna; Bombardi, Cristiano; Crunelli, Vincenzo; Di Giovanni, Giuseppe

    2016-09-01

    Absence seizures (ASs) are the hallmark of childhood/juvenile absence epilepsy. Monotherapy with first-line anti-absence drugs only controls ASs in 50% of patients, indicating the need for novel therapeutic targets. Since serotonin family-2 receptors (5-HT2Rs) are known to modulate neuronal activity in the cortico-thalamo-cortical loop, the main network involved in AS generation, we investigated the effect of selective 5-HT2AR and 5-HT2CR ligands on ASs in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well established polygenic rat model of these non-convulsive seizures. GAERS rats were implanted with fronto-parietal EEG electrodes under general anesthesia, and their ASs were later recorded under freely moving conditions before and after intraperitoneal administration of various 5-HT2AR and 5-HT2CR ligands. The 5-HT2A agonist TCB-2 dose-dependently decreased the total time spent in ASs, an effect that was blocked by the selective 5-HT2A antagonist MDL11,939. Both MDL11,939 and another selective 5-HT2A antagonist (M100,907) increased the length of individual seizures when injected alone. The 5-HT2C agonists lorcaserin and CP-809,101 dose-dependently suppressed ASs, an effect blocked by the selective 5-HT2C antagonist SB 242984. In summary, 5-HT2ARs and 5-HT2CRs negatively control the expression of experimental ASs, indicating that selective agonists at these 5-HT2R subtypes might be potential novel anti-absence drugs. PMID:27085605

  6. Implication of 5-HT2A subtype receptors in DOI activity in the four-plates test-retest paradigm in mice.

    PubMed

    Ripoll, Nadège; Hascoët, Martine; Bourin, Michel

    2006-01-01

    The four-plates test (FPT) is an animal model of anxiety which allows the detection of anxiolytic effect not only of benzodiazepines (BZDs) but also of other non-BZDs anxiolytic compounds such as antidepressants (ADs). Furthermore, DOI, a 5-HT(2A/2C) agonist, has been shown to exert an anxiolytic-like effect in this model. Retesting mice in animal models of anxiety (test-retest paradigm) induces an anxiogenic-like and a loss of anxiolytic-like effects in response to BZDs and ADs. On the contrary, DOI has been reported to oppose the fear potentiation induced by trial 1 in the FPT. Despite DOI is considered as one of the most selective 5-HT(2A) available, it acts as agonist at all three 5-HT(2) receptor subtypes (5-HT(2A), 5-HT(2B) and 5-HT(2C)). The aim of this study was thus to investigate in the FPT test-retest paradigm, which 5-HT(2) receptor subtype(s) was involved in the DOI-induced effect in experienced mice. The effect of DOI (0.25-4 mg/kg) and the agonists, 5-HT(2B), BW 723C86 (1-16 mg/kg) and 5-HT(2C), RO 60-0175 (0.25-4 mg/kg) have also been studied. Then, antagonism studies were conducted combinating the 5-HT(2A) receptor antagonist SR 46349B, the 5-HT(2B/2C) receptor antagonist SB 206553 or the selective 5-HT(2C) receptor antagonist RS 10-2221 (at the doses of 0.1 and 1 mg/kg) with the DOI (1 mg/kg). Our study shows that the BW 723C86 had no effect on retesting mice, whereas it exerted an anxiolytic-like effect in naive mice. By contrast to DOI, the RO 60-0175 had no effect neither in naive nor experienced mice. Furthermore, only the SR 46349B antagonized the DOI-induced anti-punishment effect. Diazepam included as a positive control also increased in each case the number of punished passages in naive mice. Our findings altogether also suggest that DOI exerts its anxiolytic-like effect in the FPT test-retest paradigm through 5-HT(2A) receptors.

  7. Participation of 5-HT1-like and 5-HT2A receptors in the contraction of human temporal artery by 5-hydroxytryptamine and related drugs.

    PubMed Central

    Verheggen, R.; Freudenthaler, S.; Meyer-Dulheuer, F.; Kaumann, A. J.

    1996-01-01

    1. We investigated the hypothesis that, as in some other large human arteries, 5-HT-induced contraction of the temporal artery is mediated through two co-existing receptor populations, 5-HT1-like- and 5-HT2A. Temporal arterial segments were obtained from patients undergoing brain surgery and rings prepared set up to contract with 5-HT and related agents. Fractions of maximal 5-HT responses mediated through 5-HT1-like and 5-HT2A receptors, f1 and f2 = 1-f1, were estimated by use of the 5-HT2A-selective antagonist ketanserin. 2. In rings with intact endothelium 5-HT evoked contractions with a -log EC50, M of 7.0. Ketanserin (10-1000 nM) antagonized part of the 5-HT-induced contractions. Ketanserin-resistant components of 5-HT-induced contractions were found with -log EC50, M of 6.9 and f1 of 0.17 (100 nM ketanserin) and -log EC50, M of 6.4 and f1 of 0.20 (1000 nM ketanserin). 3. In rings with endothelial function attenuated by enzymatic treatment, 5-HT caused contractions with a -log EC50, M of 7.2 that were partially blocked by ketanserin. Ketanserin-resistant components of 5-HT-induced contractions were found with -log EC50, M 7.4 and f1 of 0.16 (100 nM ketanserin) and -log EC50, M of 7.5 and f1 of 0.14 (1000 nM ketanserin). 4. The ketanserin-resistant component of 5-HT-evoked contraction was blocked by methiothepin (100-1000 nM) consistent with mediation through 5-HT1-like receptors. 5. In rings with intact endothelium the 5-HT1-like-selective agonist, sumatriptan, caused small contractions with a -log EC50, M of 6.5 and intrinsic activity of 0.21 with respect to 5-HT that were resistant to blockade by 1000 nM ketanserin but antagonized by 100 nM methiothepin. 6. In rings with intact endothelium the 5-HT2A receptor partial agonist SK&F 103829 (2,3,4,5-tetrahydro-8[methyl sulphonyl]-1H3-benzazepin-7-ol methensulphonate) contracted rings with a -log EC50, M of 5.0 and an intrinsic activity of 0.49 with respect to 5-HT; the effects were antagonized by ketanserin 1000

  8. Evidence for a 5-HT2A receptor mode of action in the anxiolytic-like properties of DOI in mice.

    PubMed

    Nic Dhonnchadha, Bríd Aine; Hascoët, Martine; Jolliet, Pascale; Bourin, Michel

    2003-12-17

    DOI [(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane] displays a high affinity for the rat 5-HT2A, 5-HT2B and 5-HT2C receptors (pKi 7.3, 7.4 and 7.8, respectively) and acts as an agonist. DOI (0.5-4 mg/kg, i.p. 30 min pre-test) increased the number of punished passages in the mouse four plates test (FPT). The anti-punishment action of DOI (1 mg/kg, i.p. 30 min pre-test) was abolished by prior treatment with the selective 5-HT2A receptor antagonist SR 46949B (0.1 and 1 mg/kg, i.p. 45 min pre-test) but not by the selective 5-HT2C receptor antagonist RS 10-2221 (0.1 and 1 mg/kg, i.p. 45 min pre-test) nor the selective 5-HT2C/2B receptor antagonist SB 206553 (0.1 and 1 mg/kg, i.p. 45 min pre-test). An anxiolytic-like action was also observed for DOI (1 mg/kg) in the elevated plus maze (EPM). The anxiolytic-like action of DOI (1 mg/kg, i.p. 30 min pre-test) was antagonised by pre-treatment with SR 46949B (0.125 and 0.5 mg/kg, i.p. 45 min pre-test) but not by RS 10-2221 (0.1 and 1 mg/kg, i.p. 45 min pre-test) nor SB 206553 (0.1 and 1 mg/kg, i.p. 45 min pre-test). In conclusion, DOI produced an anxiolytic-like profile in the mouse FPT and EPM. These effects are likely to be 5-HT2A receptor mediated.

  9. A Model of Post-Infection Fatigue Is Associated with Increased TNF and 5-HT2A Receptor Expression in Mice.

    PubMed

    Couch, Yvonne; Xie, Qin; Lundberg, Louise; Sharp, Trevor; Anthony, Daniel C

    2015-01-01

    It is well documented that serotonin (5-HT) plays an important role in psychiatric illness. For example, myalgic encephalomyelitis (ME/CFS), which is often provoked by infection, is a disabling illness with an unknown aetiology and diagnosis is based on symptom-specific criteria. However, 5-HT2A receptor expression and peripheral cytokines are known to be upregulated in ME. We sought to examine the relationship between the 5-HT system and cytokine expression following systemic bacterial endotoxin challenge (LPS, 0.5 mg/kg i.p.), at a time when the acute sickness behaviours have largely resolved. At 24 hours post-injection mice exhibit no overt changes in locomotor behaviour, but do show increased immobility in a forced swim test, as well as decreased sucrose preference and reduced marble burying activity, indicating a depressive-like state. While peripheral IDO activity was increased after LPS challenge, central activity levels remained stable and there was no change in total brain 5-HT levels or 5-HIAA/5-HT. However, within the brain, levels of TNF and 5-HT2A receptor mRNA within various regions increased significantly. This increase in receptor expression is reflected by an increase in the functional response of the 5-HT2A receptor to agonist, DOI. These data suggest that regulation of fatigue and depressive-like moods after episodes of systemic inflammation may be regulated by changes in 5-HT receptor expression, rather than by levels of enzyme activity or cytokine expression in the CNS. PMID:26147001

  10. A Model of Post-Infection Fatigue Is Associated with Increased TNF and 5-HT2A Receptor Expression in Mice

    PubMed Central

    Couch, Yvonne; Xie, Qin; Lundberg, Louise; Sharp, Trevor; Anthony, Daniel C.

    2015-01-01

    It is well documented that serotonin (5-HT) plays an important role in psychiatric illness. For example, myalgic encephalomyelitis (ME/CFS), which is often provoked by infection, is a disabling illness with an unknown aetiology and diagnosis is based on symptom-specific criteria. However, 5-HT2A receptor expression and peripheral cytokines are known to be upregulated in ME. We sought to examine the relationship between the 5-HT system and cytokine expression following systemic bacterial endotoxin challenge (LPS, 0.5mg/kg i.p.), at a time when the acute sickness behaviours have largely resolved. At 24 hours post-injection mice exhibit no overt changes in locomotor behaviour, but do show increased immobility in a forced swim test, as well as decreased sucrose preference and reduced marble burying activity, indicating a depressive-like state. While peripheral IDO activity was increased after LPS challenge, central activity levels remained stable and there was no change in total brain 5-HT levels or 5-HIAA/5-HT. However, within the brain, levels of TNF and 5-HT2A receptor mRNA within various regions increased significantly. This increase in receptor expression is reflected by an increase in the functional response of the 5-HT2A receptor to agonist, DOI. These data suggest that regulation of fatigue and depressive-like moods after episodes of systemic inflammation may be regulated by changes in 5-HT receptor expression, rather than by levels of enzyme activity or cytokine expression in the CNS. PMID:26147001

  11. Multiple conformations of 5-HT2A and 5-HT 2C receptors in rat brain: an autoradiographic study with [125I](±)DOI.

    PubMed

    López-Giménez, Juan F; Vilaró, M Teresa; Palacios, José M; Mengod, Guadalupe

    2013-10-01

    Earlier autoradiographic studies with the 5-HT2 receptor agonist [(125)I](±)DOI in human brain showed unexpected biphasic competition curves for various 5-HT2A antagonists. We have performed similar studies in rat brain regions with selective 5-HT2A (M100907) and 5-HT2C (SB242084) antagonists together with ketanserin and mesulergine. The effect of GTP analogues on antagonist competition was also studied. Increasing concentrations of Gpp(NH)p or GTPγS resulted in a maximal inhibition of [(125)I](±)DOI-specific binding of approximately 50 %. M100907 competed biphasically in all regions. In the presence of 100 μM Gpp(NH)p, M100907 still displaced biphasically the remaining [(125)I](±)DOI binding. Ketanserin showed biphasic curves in some regions and monophasic curves in others. In the latter, Gpp(NH)p evidenced an additional high-affinity site. SB242084 competed biphasically in brainstem nuclei and monophasically in the other regions. In most areas, SB242084 affinities were not notably altered by Gpp(NH)p. Mesulergine competed monophasically in all regions without alteration by Gpp(NH)p. These results conform with the extended ternary complex model of receptor action: receptor exists as an equilibrium of multiple conformations, i.e. ground (R), partly activated (R*) and activated G-protein-coupled (R*G) conformation/s. Thus, [(125)I](±)DOI would label multiple conformations of both 5-HT2A and 5-HT2C receptors in rat brain, and M100907 and ketanserin would recognise these conformations with different affinities.

  12. Differential effects of neonatal handling on anxiety, corticosterone response to stress, and hippocampal glucocorticoid and serotonin (5-HT)2A receptors in Lewis rats.

    PubMed

    Durand, M; Sarrieau, A; Aguerre, S; Mormède, P; Chaouloff, F

    1998-05-01

    Neonatal handling (during the first 3 weeks of age) has been reported by others to diminish the hypothalamo-pituitary-adrenal (HPA) responsivity to stress in adult Long Evans rats, an effect involving a serotonin (5-HT)2A receptor-mediated increase in glucocorticoid receptor (GR) gene expression in the frontal cortex and the hippocampus. In addition, handled animals may also display enduring reductions in anxiety-related behaviours, including in the elevated plus-maze. We have thus analysed the aforementioned neuroendocrine and behavioural consequences of neonatal stress in male and female adult Lewis rats, a strain characterised by its high anxiety and its hyporesponsive HPA axis. Plasma corticosterone, but not behavioural, responses to an elevated plus-maze test were decreased in handled rats. Besides, hippocampal mineralocorticoid receptor (MR) and GR binding capacities were not different between handled and non-handled Lewis rats, an observation which could be extended to our adult Long Evans rats. Lastly, neither hippocampal nor cortical 5-HT2A receptor binding capacities in adult Lewis rats were affected by prior handling. In keeping with the failure to detect early handling-induced increases in hippocampal GR binding in 3-week old Lewis and Long Evans rats, the present study reinforces past findings indicating that environmental and genetic factors are crucial variables in the neonatal handling paradigm.

  13. The 5-HT(2A) receptor and serotonin transporter in Asperger's disorder: A PET study with [¹¹C]MDL 100907 and [¹¹C]DASB.

    PubMed

    Girgis, Ragy R; Slifstein, Mark; Xu, Xiaoyan; Frankle, W Gordon; Anagnostou, Evdokia; Wasserman, Stacey; Pepa, Lauren; Kolevzon, Alexander; Abi-Dargham, Anissa; Laruelle, Marc; Hollander, Eric

    2011-12-30

    Evidence from biochemical, imaging, and treatment studies suggest abnormalities of the serotonin system in autism spectrum disorders, in particular in frontolimbic areas of the brain. We used the radiotracers [(11)C]MDL 100907 and [(11)C]DASB to characterize the 5-HT(2A) receptor and serotonin transporter in Asperger's Disorder. Seventeen individuals with Asperger's Disorder (age=34.3 ± 11.1 years) and 17 healthy controls (age=33.0 ± 9.6 years) were scanned with [(11)C]MDL 100907. Of the 17 patients, eight (age=29.7 ± 7.0 years) were also scanned with [¹¹C]DASB, as were eight healthy controls (age=28.7 ± 7.0 years). Patients with Asperger's Disorder and healthy control subjects were matched for age, gender, and ethnicity, and all had normal intelligence. Metabolite-corrected arterial plasma inputs were collected and data analyzed by two-tissue compartment modeling. The primary outcome measure was regional binding potential BP(ND). Neither regional [¹¹C]MDL 100907 BP(ND) nor [¹¹C]DASB BP(ND) was statistically different between the Asperger's and healthy subjects. This study failed to find significant alterations in binding parameters of 5-HT(2A) receptors and serotonin transporters in adult subjects with Asperger's disorder.

  14. A double dissociation in the effects of 5-HT2A and 5-HT2C receptors on the acquisition and expression of conditioned defeat in Syrian hamsters

    PubMed Central

    Harvey, Marquinta L.; Swallows, Cody L.; Cooper, Matthew A.

    2012-01-01

    Previous research indicates that serotonin enhances the development of stress-induced changes in behavior, although it is unclear which serotonin receptors mediate this effect. 5-HT2 receptors are potential candidates because activation at these receptors is associated with increased fear and anxiety. In this study we investigated whether pharmacological treatments targeting 5-HT2 receptors would alter the acquisition and expression of conditioned defeat. Conditioned defeat is a social defeat model in Syrian hamsters in which individuals display increased submissive and defensive behavior and a loss of territorial aggression when tested with a novel intruder 24 hours after an acute social defeat. The nonselective 5-HT2 receptor agonist mCPP (0.0, 0.3, 1.0 or 3.0 mg/kg) was injected either prior to social defeat training or prior to conditioned defeat testing. Also, the 5-HT2A receptor antagonist MDL 11,939 (0.0, 0.5 or 2.0 mg/kg) was injected either prior to social defeat training or prior to conditioned defeat testing. Injection of mCPP prior to testing increased the expression of conditioned defeat, but injection of mCPP prior to training did not alter the acquisition of conditioned defeat. Conversely, injection of MDL 11,939 prior to training reduced the acquisition of conditioned defeat, but injection of MDL 11,939 prior to testing did not alter the expression of conditioned defeat. Our data suggest that mCPP activates 5-HT2C receptors during testing to enhance the display of submissive and defensive behavior, whereas MDL 11,939 blocks 5-HT2A receptors during social defeat to disrupt the development of the conditioned defeat response. In sum, these results suggest that serotonin acts at separate 5-HT2 receptors to facilitate the acquisition and expression of defeat-induced changes in social behavior. PMID:22708954

  15. Serotonin (5-HT) and 5-HT2A receptor agonists suppress lipolysis in primary rat adipose cells.

    PubMed

    Hansson, Björn; Medina, Anya; Fryklund, Claes; Fex, Malin; Stenkula, Karin G

    2016-05-27

    Serotonin (5-HT) is a biogenic monoamine that functions both as a neurotransmitter and a circulating hormone. Recently, the metabolic effects of 5-HT have gained interest and peripheral 5-HT has been proposed to influence lipid metabolism in various ways. Here, we investigated the metabolic effects of 5-HT in isolated, primary rat adipose cells. Incubation with 5-HT suppressed β-adrenergically stimulated glycerol release and decreased phosphorylation of protein kinase A (PKA)-dependent substrates, hormone sensitive lipase (Ser563) and perilipin (Ser522). The inhibitory effect of 5-HT on lipolysis enhanced the anti-lipolytic effect of insulin, but sustained in the presence of phosphodiesterase inhibitors, OPC3911 and isobuthylmethylxanthine (IBMX). The relative expression of 5-HT1A, -2B and -4 receptor class family were significantly higher in adipose tissue compared to adipose cells, whereas 5-HT1D, -2A and -7 were highly expressed in isolated adipose cells. Similar to 5-HT, 5-HT2 receptor agonists reduced lipolysis while 5-HT1 receptor agonists rather decreased non-stimulated and insulin-stimulated glucose uptake. Together, these data provide evidence of a direct effect of 5-HT on adipose cells, where 5-HT suppresses lipolysis and glucose uptake, which could contribute to altered systemic lipid- and glucose metabolism. PMID:27109474

  16. Cardiac baroreflex facilitation evoked by hypothalamus and prefrontal cortex stimulation: role of the nucleus tractus solitarius 5-HT2A receptors.

    PubMed

    Sévoz-Couche, C; Comet, M A; Bernard, J F; Hamon, M; Laguzzi, R

    2006-10-01

    We previously showed that serotonin (5-HT2) receptor activation in the nucleus of the tractus solitarius (NTS) produced hypotension, bradycardia, and facilitation of the baroreflex bradycardia. Activation of the preoptic area (POA) of the hypothalamus, which is involved in shock-evoked passive behaviors, induces similar modifications. In addition, previous studies showed that blockade of the infralimbic (IL) part of the medial prefrontal cortex, which sends projections to POA, produced an inhibitory influence on the baroreflex cardiac response. Thus, to assess the possible implication of NTS 5-HT2 receptors in passive cardiovascular responses, we analyzed in anesthetized rats the effects of NTS inhibition and NTS 5-HT2 receptor blockade on the cardiovascular modifications induced by chemical (0.3 M D,L-homocysteic acid) and electrical (50 Hz, 150-200 microA) stimulation of IL or POA. Intra-NTS microinjections of muscimol, a GABAA receptor agonist, prevented the decreases in blood pressure and heart rate normally evoked by IL or POA activation. In addition, we found that intra-NTS microinjection of R(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol, a specific 5-HT2A receptor antagonist, did not affect the decreases in cardiovascular baseline parameters induced by IL or POA stimulation but prevented the facilitation of the aortic baroreflex bradycardia normally observed during IL (+65 and +60%) or POA (+70 and +69%) electrical and chemical stimulation, respectively. These results show that NTS 5-HT2A receptors play a key role in the enhancement of the cardiac response of the baroreflex but not in the changes in basal heart rate and blood pressure induced by IL or POA stimulation. PMID:16763082

  17. Effects of imipramine and bupropion on the duration of immobility of ACTH-treated rats in the forced swim test: involvement of the expression of 5-HT2A receptor mRNA.

    PubMed

    Kitamura, Yoshihisa; Fujitani, Yoshika; Kitagawa, Kouhei; Miyazaki, Toshiaki; Sagara, Hidenori; Kawasaki, Hiromu; Shibata, Kazuhiko; Sendo, Toshiaki; Gomita, Yutaka

    2008-02-01

    We examined the effect of chronic administration of imipramine and bupropion, monoamine reuptake inhibitors, on the duration of immobility in the forced swim test and serotonin (5-HT)(2A) receptor function in the form of 5-HT(2A) receptor mRNA levels in rats chronically treated with adrenocorticotropic hormone (ACTH). The immobility-decreasing effect of bupropion without imipramine did not influence the chronic ACTH treatment. The effect on the expression of 5-HT(2A) receptor mRNA of chronic ACTH treatment was decreased by bupropion, but not imipramine. These results suggest that bupropion has the effect of reducing immobility time in the forced swim test in the tricyclic antidepressant-resistant depressive model induced by chronic ACTH treatment in rats, and that decreased 5-HT(2A) receptor mRNA levels may be involved in this phenomenon.

  18. In Vivo Quantification of 5-HT2A Brain Receptors in Mdr1a KO Rats with 123I-R91150 Single-Photon Emission Computed Tomography.

    PubMed

    Dumas, Noé; Moulin-Sallanon, Marcelle; Fender, Pascal; Tournier, Benjamin B; Ginovart, Nathalie; Charnay, Yves; Millet, Philippe

    2015-01-01

    Our goal was to identify suitable image quantification methods to image 5-hydroxytryptamine2A (5-HT2A) receptors in vivo in Mdr1a knockout (KO) rats (i.e., P-glycoprotein KO) using 123I-R91150 single-photon emission computed tomography (SPECT). The 123I-R91150 binding parameters estimated with different reference tissue models (simplified reference tissue model [SRTM], Logan reference tissue model, and tissue ratio [TR] method) were compared to the estimates obtained with a comprehensive three-tissue/seven-parameter (3T/7k)-based model. The SRTM and Logan reference tissue model estimates of 5-HT2A receptor (5-HT2AR) nondisplaceable binding potential (BPND) correlated well with the absolute receptor density measured with the 3T/7k gold standard (r > .89). Quantification of 5-HT2AR using the Logan reference tissue model required at least 90 minutes of scanning, whereas the SRTM required at least 110 minutes. The TR method estimates were also highly correlated to the 5-HT2AR density (r > .91) and only required a single 20-minute scan between 100 and 120 minutes postinjection. However, a systematic overestimation of the BPND values was observed. The Logan reference tissue method is more convenient than the SRTM for the quantification of 5-HT2AR in Mdr1a KO rats using 123I-R91150 SPECT. The TR method is an interesting and simple alternative, despite its bias, as it still provides a valid index of 5-HT2AR density. PMID:26105563

  19. Serotonin contracts the rat mesenteric artery by inhibiting 4-aminopyridine-sensitive Kv channels via the 5-HT2A receptor and Src tyrosine kinase.

    PubMed

    Sung, Dong Jun; Noh, Hyun Ju; Kim, Jae Gon; Park, Sang Woong; Kim, Bokyung; Cho, Hana; Bae, Young Min

    2013-01-01

    Serotonin (5-hydroxytryptamine (5-HT)) is a neurotransmitter that regulates a variety of functions in the nervous, gastrointestinal and cardiovascular systems. Despite such importance, 5-HT signaling pathways are not entirely clear. We demonstrated previously that 4-aminopyridine (4-AP)-sensitive voltage-gated K(+) (Kv) channels determine the resting membrane potential of arterial smooth muscle cells and that the Kv channels are inhibited by 5-HT, which depolarizes the membranes. Therefore, we hypothesized that 5-HT contracts arteries by inhibiting Kv channels. Here we studied 5-HT signaling and the detailed role of Kv currents in rat mesenteric arteries using patch-clamp and isometric tension measurements. Our data showed that inhibiting 4-AP-sensitive Kv channels contracted arterial rings, whereas inhibiting Ca(2+)-activated K(+), inward rectifier K(+) and ATP-sensitive K(+) channels had little effect on arterial contraction, indicating a central role of Kv channels in the regulation of resting arterial tone. 5-HT-induced arterial contraction decreased significantly in the presence of high KCl or the voltage-gated Ca(2+) channel (VGCC) inhibitor nifedipine, indicating that membrane depolarization and the consequent activation of VGCCs mediate the 5-HT-induced vasoconstriction. The effects of 5-HT on Kv currents and arterial contraction were markedly prevented by the 5-HT2A receptor antagonists ketanserin and spiperone. Consistently, α-methyl 5-HT, a 5-HT2 receptor agonist, mimicked the 5-HT action on Kv channels. Pretreatment with a Src tyrosine kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, prevented both the 5-HT-mediated vasoconstriction and Kv current inhibition. Our data suggest that 4-AP-sensitive Kv channels are the primary regulator of the resting tone in rat mesenteric arteries. 5-HT constricts the arteries by inhibiting Kv channels via the 5-HT2A receptor and Src tyrosine kinase pathway. PMID:24336234

  20. 5-HT2A and 5-HT2C receptors as hypothalamic targets of developmental programming in male rats

    PubMed Central

    Martin-Gronert, Malgorzata S.; Stocker, Claire J.; Wargent, Edward T.; Cripps, Roselle L.; Garfield, Alastair S.; Jovanovic, Zorica; D'Agostino, Giuseppe; Yeo, Giles S. H.; Cawthorne, Michael A.; Arch, Jonathan R. S.; Heisler, Lora K.; Ozanne, Susan E.

    2016-01-01

    ABSTRACT Although obesity is a global epidemic, the physiological mechanisms involved are not well understood. Recent advances reveal that susceptibility to obesity can be programmed by maternal and neonatal nutrition. Specifically, a maternal low-protein diet during pregnancy causes decreased intrauterine growth, rapid postnatal catch-up growth and an increased risk for diet-induced obesity. Given that the synthesis of the neurotransmitter 5-hydroxytryptamine (5-HT) is nutritionally regulated and 5-HT is a trophic factor, we hypothesised that maternal diet influences fetal 5-HT exposure, which then influences development of the central appetite network and the subsequent efficacy of 5-HT to control energy balance in later life. Consistent with our hypothesis, pregnant rats fed a low-protein diet exhibited elevated serum levels of 5-HT, which was also evident in the placenta and fetal brains at embryonic day 16.5. This increase was associated with reduced levels of 5-HT2CR, the primary 5-HT receptor influencing appetite, in the fetal, neonatal and adult hypothalamus. As expected, a reduction of 5-HT2CR was associated with impaired sensitivity to 5-HT-mediated appetite suppression in adulthood. 5-HT primarily achieves effects on appetite by 5-HT2CR stimulation of pro-opiomelanocortin (POMC) peptides within the arcuate nucleus of the hypothalamus (ARC). We show that 5-HT2ARs are also anatomically positioned to influence the activity of ARC POMC neurons and that mRNA encoding 5-HT2AR is increased in the hypothalamus of in utero growth-restricted offspring that underwent rapid postnatal catch-up growth. Furthermore, these animals at 3 months of age are more sensitive to appetite suppression induced by 5-HT2AR agonists. These findings not only reveal a 5-HT-mediated mechanism underlying the programming of susceptibility to obesity, but also provide a promising means to correct it, by treatment with a 5-HT2AR agonist. PMID:26769798

  1. Synthesis and structure-affinity relationships of novel small molecule natural product derivatives capable of discriminating between serotonin 5-HT1A, 5-HT2A, 5-HT2C receptor subtypes

    PubMed Central

    Cummings, David F.; Canseco, Diana C.; Sheth, Pratikkumar; Johnson, James E.; Schetz, John A.

    2010-01-01

    Efforts to develop ligands that distinguish between clinically relevant 5-HT2A and 5-HT2C serotonin receptor subtypes have been challenging, because their sequences have high homology. Previous studies reported that a novel aplysinopsin belonging to a chemical class of natural products isolated from a marine sponge was selective for the 5-HT2C over the 5-HT2A receptor subtype. Our goal was to explore the 5-HT2A/2C receptor structure-affinity relationships of derivatives based on the aplysinopsin natural product pharmacophore. Twenty aplysinopsin derivatives were synthesized, purified and tested for their affinities for cloned human serotonin 5-HT1A, 5-HT2A and 5-HT2C receptor subtypes. Four compounds in this series had >30-fold selectivity for 5-HT2A or 5-HT2C receptors. The compound (E)-5-((5,6-dichloro-1H-indol-3-yl)methylene)-2-imino-1,3-dimethylimidazolidin-4-one (UNT-TWU-22, 16) had approximately 2100-fold selectivity for the serotonin 5-HT2C receptor subtype: an affinity for 5-HT2C equal to 46 nM and no detectable affinity for the 5-HT1A or 5-HT2A receptor subtypes. The two most important factors controlling 5-HT2A or 5-HT2C receptor subtype selectivity were the combined R1, R3-alkylation of the imidazolidinone ring and the type and number of halogens on the indole ring of the aplysinopsin pharmacophore. PMID:20570529

  2. Potential Modes of Interaction of 9-Aminomethyl-9,10-dihydroanthracene (AMDA) Derivatives with the 5-HT2A Receptor: A Ligand Structure-Affinity Relationship, Receptor Mutagenesis and Receptor Modeling Investigation⊕

    PubMed Central

    Runyon, Scott P.; Mosier, Philip D.; Roth, Bryan L.; Glennon, Richard A.; Westkaemper, Richard B.

    2011-01-01

    The effects of 3-position substitution of 9-aminomethyl-9,10-dihydroanthracene (AMDA) on 5-HT2A receptor affinity were determined and compared to a parallel series of DOB-like 1-(2,5-dimethoxyphenyl)-2-aminopropanes substituted at the 4-position. The results were interpreted within the context of 5-HT2A receptor models that suggest that members of the DOB-like series can bind to the receptor in two distinct modes that correlate with the compounds’ functional activity. Automated ligand docking and molecular dynamics suggest that all of the AMDA derivatives, the parent of which is a 5-HT2A antagonist, bind in a fashion analogous to that for the sterically demanding antagonist DOB-like compounds. The failure of the F3406.52L mutation to adversely affect the affinity of AMDA and the 3-bromo derivative is consistent with the proposed modes of orientation. Evaluation of ligand-receptor complex models suggest that a valine/threonine exchange between the 5-HT2A and D2 receptors may be the origin of selectivity for AMDA and two substituted derivatives. PMID:18847250

  3. Metabotropic glutamate mGlu2 receptor is necessary for the pharmacological and behavioral effects induced by hallucinogenic 5-HT2A receptor agonists.

    PubMed

    Moreno, José L; Holloway, Terrell; Albizu, Laura; Sealfon, Stuart C; González-Maeso, Javier

    2011-04-15

    Hallucinogenic drugs, including mescaline, psilocybin and lysergic acid diethylamide (LSD), act at serotonin 5-HT2A receptors (5-HT2ARs). Metabotropic glutamate receptor 2/3 (mGluR2/3) ligands show efficacy in modulating the responses induced by activation of 5-HT2ARs. The formation of a 5-HT2AR-mGluR2 complex suggests a functional interaction that affects the hallucinogen-regulated cellular signaling pathways. Here, we tested the cellular and behavioral effects of hallucinogenic 5-HT2AR agonists in mGluR2 knockout (mGluR2-KO) mice. Mice were intraperitoneally injected with the hallucinogens DOI (2 mg/kg) and LSD (0.24 mg/kg), or vehicle. Head-twitch behavioral response, expression of c-fos, which is induced by all 5-HT2AR agonists, and expression of egr-2, which is hallucinogen-specific, were determined in wild type and mGluR2-KO mice. [(3)H]Ketanserin binding displacement curves by DOI were performed in mouse frontal cortex membrane preparations. Head twitch behavior was abolished in mGluR2-KO mice. The high-affinity binding site of DOI was undetected in mGluR2-KO mice. The hallucinogen DOI induced c-fos in both wild type and mGluR2-KO mice. However, the induction of egr-2 by DOI was eliminated in mGlu2-KO mice. These findings suggest that the 5-HT2AR-mGluR2 complex is necessary for the neuropsychological responses induced by hallucinogens.

  4. Potentiation of 5-methoxy-N,N-dimethyltryptamine-induced hyperthermia by harmaline and the involvement of activation of 5-HT1A and 5-HT2A receptors.

    PubMed

    Jiang, Xi-Ling; Shen, Hong-Wu; Yu, Ai-Ming

    2015-02-01

    5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) and harmaline are serotonin (5-HT) analogs often abused together, which alters thermoregulation that may indicate the severity of serotonin toxicity. Our recent studies have revealed that co-administration of monoamine oxidase inhibitor harmaline leads to greater and prolonged exposure to 5-HT agonist 5-MeO-DMT that might be influenced by cytochrome P450 2D6 (CYP2D6) status. This study was to define the effects of harmaline and 5-MeO-DMT on thermoregulation in wild-type and CYP2D6-humanized (Tg-CYP2D6) mice, as well as the involvement of 5-HT receptors. Animal core body temperatures were monitored noninvasively in the home cages after implantation of telemetry transmitters and administration of drugs. Harmaline (5 and 15 mg/kg, i.p.) alone was shown to induce hypothermia that was significantly affected by CYP2D6 status. In contrast, higher doses of 5-MeO-DMT (10 and 20 mg/kg) alone caused hyperthermia. Co-administration of harmaline (2, 5 or 15 mg/kg) remarkably potentiated the hyperthermia elicited by 5-MeO-DMT (2 or 10 mg/kg), which might be influenced by CYP2D6 status at certain dose combination. Interestingly, harmaline-induced hypothermia was only attenuated by 5-HT1A receptor antagonist WAY-100635, whereas 5-MeO-DMT- and harmaline-5-MeO-DMT-induced hyperthermia could be suppressed by either WAY-100635 or 5-HT2A receptor antagonists (MDL-100907 and ketanserin). Moreover, stress-induced hyperthermia under home cage conditions was not affected by WAY-100635 but surprisingly attenuated by MDL-100907 and ketanserin. Our results indicate that co-administration of monoamine oxidase inhibitor largely potentiates 5-MeO-DMT-induced hyperthermia that involves the activation of both 5-HT1A and 5-HT2A receptors. These findings shall provide insights into development of anxiolytic drugs and new strategies to relieve the lethal hyperthermia in serotonin toxicity.

  5. Serotonin 5-HT2A receptor binding in platelets from healthy subjects as studied by [3H]-lysergic acid diethylamide ([3H]-LSD): intra- and interindividual variability.

    PubMed

    Spigset, O; Mjörndal, T

    1997-04-01

    In studies on platelet 5-HT2A receptor binding in patients with neuropsychiatric disorders, there has been a marked variability and a considerable overlap of values between patients and controls. The causes of the large variability in 5-HT2A receptor parameters is still unsettled. In the present study, we have quantified the intra- and interindividual variability of platelet 5-HT2A receptor binding in 112 healthy subjects and explored factors that may influence 5-HT2A receptor binding, using [3H]-lysergic acid diethylamide as radioligand. Age, gender, blood pressure, and metabolic capacity of the liver enzymes CYP2D6 and CYP2C19 did not influence Bmax and Kd values. Body weight and body mass index (BMI) showed a negative correlation with Kd (p = .04 and .03, respectively), but not with Bmax. Bmax was significantly lower in the light half of the year than in the dark half of the year (p = .001), and Kd was significantly lower in the fall than in the summer and winter (p < .001). In females, there was a significant increase in Bmax from week 1 to week 2 of the menstrual cycle (p = .03). Females taking contraceptive pills had significantly higher Kd than drug-free females in weeks 1 and 4 of the menstrual cycle (p = .04). This study shows that a number of factors should be taken into account when using platelet 5-HT2A receptor binding in studies of neuropsychiatric disorders.

  6. Cognitive Impairment Induced by Delta9-tetrahydrocannabinol Occurs through Heteromers between Cannabinoid CB1 and Serotonin 5-HT2A Receptors

    PubMed Central

    Lanfumey, Laurence; Cordomí, Arnau; Pastor, Antoni; de La Torre, Rafael; Gasperini, Paola; Navarro, Gemma; Howell, Lesley A.; Pardo, Leonardo; Lluís, Carmen; Canela, Enric I.; McCormick, Peter J.; Maldonado, Rafael; Robledo, Patricia

    2015-01-01

    Activation of cannabinoid CB1 receptors (CB1R) by delta9-tetrahydrocannabinol (THC) produces a variety of negative effects with major consequences in cannabis users that constitute important drawbacks for the use of cannabinoids as therapeutic agents. For this reason, there is a tremendous medical interest in harnessing the beneficial effects of THC. Behavioral studies carried out in mice lacking 5-HT2A receptors (5-HT2AR) revealed a remarkable 5-HT2AR-dependent dissociation in the beneficial antinociceptive effects of THC and its detrimental amnesic properties. We found that specific effects of THC such as memory deficits, anxiolytic-like effects, and social interaction are under the control of 5-HT2AR, but its acute hypolocomotor, hypothermic, anxiogenic, and antinociceptive effects are not. In biochemical studies, we show that CB1R and 5-HT2AR form heteromers that are expressed and functionally active in specific brain regions involved in memory impairment. Remarkably, our functional data shows that costimulation of both receptors by agonists reduces cell signaling, antagonist binding to one receptor blocks signaling of the interacting receptor, and heteromer formation leads to a switch in G-protein coupling for 5-HT2AR from Gq to Gi proteins. Synthetic peptides with the sequence of transmembrane helices 5 and 6 of CB1R, fused to a cell-penetrating peptide, were able to disrupt receptor heteromerization in vivo, leading to a selective abrogation of memory impairments caused by exposure to THC. These data reveal a novel molecular mechanism for the functional interaction between CB1R and 5-HT2AR mediating cognitive impairment. CB1R-5-HT2AR heteromers are thus good targets to dissociate the cognitive deficits induced by THC from its beneficial antinociceptive properties. PMID:26158621

  7. Antidepressant-like activity of Tagetes lucida Cav. is mediated by 5-HT(1A) and 5-HT(2A) receptors.

    PubMed

    Bonilla-Jaime, H; Guadarrama-Cruz, G; Alarcon-Aguilar, F J; Limón-Morales, O; Vazquez-Palacios, G

    2015-10-01

    It has been demonstrated that the aqueous extract of Tagetes lucida Cav. shows an antidepressant-like effect on the forced swimming test (FST) in rats. The aim of this study was to analyze the participation of the serotoninergic system in the antidepressant-like effect of the aqueous extract of T. lucida. Different doses of the extract of T. lucida were administered at 72, 48, 24, 18 and 1 h before FST. The animals were pretreated with a 5-HT1A receptor antagonist (WAY-100635, 0.5 mg/kg), a 5-HT2A receptor antagonist (ketanserin, 5 mg/kg), a β-noradrenergic receptor antagonist (propranolol, 200 mg/kg), and with a α2-noradrenergic receptor antagonist (yohimbine, 1 mg/kg) alone or combined with the extract and pretreated with a serotonin synthesis inhibitor (PCPA) before treatment with 8-OH-DPAT + the extract of T. lucida. In addition, suboptimal doses of the 5-HT1A agonist (8-OH-DPAT) + non-effective dose of extract was analyzed in the FST. To determine the presence of flavonoids, the aqueous extract of T. lucida (20 µl, 4 mg/ml) was injected in HPLC; however, a quercetin concentration of 7.72 mg/g of extract weight was detected. A suboptimal dose of 8-OH-DPAT + extract of T. lucida decreased immobility and increased swimming and climbing. An antidepressant-like effect with the aqueous extract of T. lucida at doses of 100 and 200 mg/kg was observed on the FST with decreased immobility behavior and increased swimming; however, this effect was blocked by WAY-100635, ketanserin and PCPA but not by yohimbine and propranolol, suggesting that the extract of T. lucida could be modulating the release/reuptake of serotonin.

  8. Examination of the hippocampal contribution to serotonin 5-HT2A receptor-mediated facilitation of object memory in C57BL/6J mice.

    PubMed

    Zhang, Gongliang; Cinalli, David; Cohen, Sarah J; Knapp, Kristina D; Rios, Lisa M; Martínez-Hernández, José; Luján, Rafael; Stackman, Robert W

    2016-10-01

    The rodent hippocampus supports non-spatial object memory. Serotonin 5-HT2A receptors (5-HT2AR) are widely expressed throughout the hippocampus. We previously demonstrated that the activation of 5-HT2ARs enhanced the strength of object memory assessed 24 h after a limited (i.e., weak memory) training procedure. Here, we examined the subcellular distribution of 5-HT2ARs in the hippocampal CA1 region and underlying mechanisms of 5-HT2AR-mediated object memory consolidation. Analyses with immuno-electron microscopy revealed the presence of 5-HT2ARs on the dendritic spines and shafts of hippocampal CA1 neurons, and presynaptic terminals in the CA1 region. In an object recognition memory procedure that places higher demand on the hippocampus, only post-training systemic or intrahippocampal administration of the 5-HT2AR agonist TCB-2 enhanced object memory. Object memory enhancement by TCB-2 was blocked by the 5-HT2AR antagonist, MDL 11,937. The memory-enhancing dose of systemic TCB-2 increased extracellular glutamate levels in hippocampal dialysate samples, and increased the mean in vivo firing rate of hippocampal CA1 neurons. In summary, these data indicate a pre- and post-synaptic distribution of 5-HT2ARs, and activation of 5-HT2ARs selectively enhanced the consolidation of object memory, without affecting encoding or retrieval. The 5-HT2AR-mediated facilitation of hippocampal memory may be associated with an increase in hippocampal neuronal firing and glutamate efflux during a post-training time window in which recently encoded memories undergo consolidation.

  9. 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

    PubMed Central

    Cordova-Sintjago, Tania; Liu, Yue; Kim, Myong S.; Morgan, Drake; Booth, Raymond G.

    2013-01-01

    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. It was discovered that (+)-6-OH-7-Cl-PAT (only) had ∼40-fold-lower affinity at mouse (m) compared with h5-HT2A receptors. Molecular modeling and computational ligand docking studies indicated that the 6-OH moiety of (+)- but not (−)-6-OH-7-Cl-PAT could form a hydrogen bond with serine residue 5.46 of the h5-HT2A receptor. The m5-HT2A as well as m5-HT2B, h5-HT2B, m5-HT2C, and h5-HT2C receptors have alanine at position 5.46, obviating this interaction; (+)-6-OH-7-Cl-PAT also showed ∼50-fold lower affinity than (−)-6-OH-7-Cl-PAT at m5-HT2C and h5-HT2C receptors. Mutagenesis studies confirmed that 5-HT2A S5.46 is critical for (+)- but not (−)-6-OH-7-Cl-PAT binding, as well as function. The (+)-6-OH-7-Cl-PAT enantiomer showed partial agonist effects at h5-HT2A wild-type (WT) and m5-HT2A A5.46S point-mutated receptors but did not activate m5-HT2A WT and h5-HT2A S5.46A point-mutated receptors, or h5-HT2B, h5-HT2C, and m5-HT2C receptors; (−)-6-OH-7-Cl-PAT did not activate any of the 5-HT2 receptors. Experiments also included the (2R,4S)-trans-(+)- and (2S,4R)-trans-(−)-enantiomers of 6-methoxy-7-chloro-PAT to validate hydrogen bonding interactions proposed for the corresponding 6-OH analogs. Results indicate that PAT ligand three-dimensional structure impacts target receptor binding and translational

  10. Blonanserin Ameliorates Phencyclidine-Induced Visual-Recognition Memory Deficits: the Complex Mechanism of Blonanserin Action Involving D3-5-HT2A and D1-NMDA Receptors in the mPFC

    PubMed Central

    Hida, Hirotake; Mouri, Akihiro; Mori, Kentaro; Matsumoto, Yurie; Seki, Takeshi; Taniguchi, Masayuki; Yamada, Kiyofumi; Iwamoto, Kunihiro; Ozaki, Norio; Nabeshima, Toshitaka; Noda, Yukihiro

    2015-01-01

    Blonanserin differs from currently used serotonin 5-HT2A/dopamine-D2 receptor antagonists in that it exhibits higher affinity for dopamine-D2/3 receptors than for serotonin 5-HT2A receptors. We investigated the involvement of dopamine-D3 receptors in the effects of blonanserin on cognitive impairment in an animal model of schizophrenia. We also sought to elucidate the molecular mechanism underlying this involvement. Blonanserin, as well as olanzapine, significantly ameliorated phencyclidine (PCP)-induced impairment of visual-recognition memory, as demonstrated by the novel-object recognition test (NORT) and increased extracellular dopamine levels in the medial prefrontal cortex (mPFC). With blonanserin, both of these effects were antagonized by DOI (a serotonin 5-HT2A receptor agonist) and 7-OH-DPAT (a dopamine-D3 receptor agonist), whereas the effects of olanzapine were antagonized by DOI but not by 7-OH-DPAT. The ameliorating effect was also antagonized by SCH23390 (a dopamine-D1 receptor antagonist) and H-89 (a protein kinase A (PKA) inhibitor). Blonanserin significantly remediated the decrease in phosphorylation levels of PKA at Thr197 and of NR1 (an essential subunit of N-methyl-D-aspartate (NMDA) receptors) at Ser897 by PKA in the mPFC after a NORT training session in the PCP-administered mice. There were no differences in the levels of NR1 phosphorylated at Ser896 by PKC in any group. These results suggest that the ameliorating effect of blonanserin on PCP-induced cognitive impairment is associated with indirect functional stimulation of the dopamine-D1-PKA-NMDA receptor pathway following augmentation of dopaminergic neurotransmission due to inhibition of both dopamine-D3 and serotonin 5-HT2A receptors in the mPFC. PMID:25120077

  11. Combined serotonin (5-HT)1A agonism, 5-HT(2A) and dopamine D₂ receptor antagonism reproduces atypical antipsychotic drug effects on phencyclidine-impaired novel object recognition in rats.

    PubMed

    Oyamada, Yoshihiro; Horiguchi, Masakuni; Rajagopal, Lakshmi; Miyauchi, Masanori; Meltzer, Herbert Y

    2015-05-15

    Subchronic administration of an N-methyl-D-aspartate receptor (NMDAR) antagonist, e.g. phencyclidine (PCP), produces prolonged impairment of novel object recognition (NOR), suggesting they constitute a hypoglutamate-based model of cognitive impairment in schizophrenia (CIS). Acute administration of atypical, e.g. lurasidone, but not typical antipsychotic drugs (APDs), e.g. haloperidol, are able to restore NOR following PCP (acute reversal model). Furthermore, atypical APDs, when co-administered with PCP, have been shown to prevent development of NOR deficits (prevention model). Most atypical, but not typical APDs, are more potent 5-HT(2A) receptor inverse agonists than dopamine (DA) D2 antagonists, and have been shown to enhance cortical and hippocampal efflux and to be direct or indirect 5-HT(1A) agonists in vivo. To further clarify the importance of these actions to the restoration of NOR by atypical APDs, sub-effective or non-effective doses of combinations of the 5-HT(1A) partial agonist (tandospirone), the 5-HT(2A) inverse agonist (pimavanserin), or the D2 antagonist (haloperidol), as well as the combination of all three agents, were studied in the acute reversal and prevention PCP models of CIS. Only the combination of all three agents restored NOR and prevented the development of PCP-induced deficit. Thus, this triple combination of 5-HT(1A) agonism, 5-HT(2A) antagonism/inverse agonism, and D2 antagonism is able to mimic the ability of atypical APDs to prevent or ameliorate the PCP-induced NOR deficit, possibly by stimulating signaling cascades from D1 and 5-HT(1A) receptor stimulation, modulated by D2 and 5-HT(2A) receptor antagonism. PMID:25448429

  12. Changes in the 5-HT2A receptor system in the pre-mammillary hypothalamus of the ewe are related to regulation of LH pulsatile secretion by an endogenous circannual rhythm

    PubMed Central

    Chemineau, Philippe; Daveau, Agnès; Pelletier, Jean; Malpaux, Benoît; Karsch, Fred J; Viguié, Catherine

    2003-01-01

    Background We wanted to determine if changes in the expression of serotonin 2A receptor (5HT2A receptor) gene in the premammillary hypothalamus are associated with changes in reproductive neuroendocrine status. Thus, we compared 2 groups of ovariectomized-estradiol-treated ewes that expressed high vs low LH pulsatility in two different paradigms (2 groups per paradigm): (a) refractoriness (low LH secretion) or not (high LH secretion) to short days in pineal-intact Ile-de-France ewes (RSD) and (b) endogenous circannual rhythm (ECR) in free-running pinealectomized Suffolk ewes in the active or inactive stage of their reproductive rhythm. Results In RSD ewes, density of 5HT2A receptor mRNA (by in situ hybridization) was significantly higher in the high LH group (25.3 ± 1.4 vs 21.4 ± 1.5 grains/neuron, P < 0.05) and 3H-Ketanserin binding (a specific radioligand) of the median part of the premammillary hypothalamus tended to be higher in the high group (29.1 ± 4.0 vs 24.6 ± 4.2 fmol/mg tissu-equivalent; P < 0.10). In ECR ewes, density of 5HT2A receptor mRNA and 3H-Ketanserin binding were both significantly higher in the high LH group (20.8 ± 1.6 vs 17.0 ± 1.5 grains/neuron, P < 0.01, and 19.7 ± 5.0 vs 7.4 ± 3.4 fmol/mg tissu-equivalent; P < 0.05, respectively). Conclusions We conclude that these higher 5HT2A receptor gene expression and binding activity of 5HT2A receptor in the premammillary hypothalamus are associated with stimulation of LH pulsatility expressed before the development of refractoriness to short days and prior to the decline of reproductive neuroendocrine activity during expression of the endogenous circannual rhythm. PMID:12553884

  13. Synthesis and Structure–Activity Relationships of N-Benzyl Phenethylamines as 5-HT2A/2C Agonists

    PubMed Central

    2014-01-01

    N-Benzyl substitution of 5-HT2A receptor agonists of the phenethylamine structural class of psychedelics (such as 4-bromo-2,5-dimethoxyphenethylamine, often referred to as 2C-B) confer a significant increase in binding affinity as well as functional activity of the receptor. We have prepared a series of 48 compounds with structural variations in both the phenethylamine and N-benzyl part of the molecule to determine the effects on receptor binding affinity and functional activity at 5-HT2A and 5-HT2C receptors. The compounds generally had high affinity for the 5-HT2A receptor with 8b having the highest affinity at 0.29 nM but with several other compounds also exhibiting subnanomolar binding affinities. The functional activity of the compounds was distributed over a wider range with 1b being the most potent at 0.074 nM. Most of the compounds exhibited low to moderate selectivity (1- to 40-fold) for the 5-HT2A receptor in the binding assays, although one compound 6b showed an impressive 100-fold selectivity for the 5-HT2A receptor. In the functional assay, selectivity was generally higher with 1b being more than 400-fold selective for the 5-HT2A receptor. PMID:24397362

  14. Heterocomplex formation of 5-HT2A-mGlu2 and its relevance for cellular signaling cascades.

    PubMed

    Delille, Hannah K; Becker, Judith M; Burkhardt, Sabrina; Bleher, Barbara; Terstappen, Georg C; Schmidt, Martin; Meyer, Axel H; Unger, Liliane; Marek, Gerard J; Mezler, Mario

    2012-06-01

    Dopamine, serotonin and glutamate play a role in the pathophysiology of schizophrenia. In the brain a functional crosstalk between the serotonin receptor 5-HT(2A) and the metabotropic glutamate receptor mGlu(2) has been demonstrated. Such a crosstalk may be mediated indirectly through neuronal networks or directly by receptor oligomerization. A direct link of the 5-HT(2A)-mGlu(2) heterocomplex formation to receptor function, i.e. to intracellular signaling, has not been fully demonstrated yet. Here we confirm the formation of 5-HT(2A)-mGlu(2) heterocomplexes using quantitative Snap/Clip-tag based HTRF methods. Additionally, mGlu(2) formed complexes with 5-HT(2B) and mGlu(5) but not 5-HT(2C) indicating that complex formation is not specific to the 5-HT(2A)-mGlu(2) pair. We studied the functional consequences of the 5-HT(2A)-mGlu(2) heterocomplex addressing cellular signaling pathways. Co-expression of receptors in HEK-293 cells had no relevant effects on signaling mediated by the individual receptors when mGlu(2) agonists, antagonists and PAMs, or 5-HT(2A) hallucinogenic and non-hallucinogenic agonists and antagonists were used. Hallucinogenic 5-HT(2A) agonists induced signaling through G(q/11), but not G(i) and thus did not lead to modulation of intracellular cAMP levels. In membranes of the medial prefrontal cortex [(3)H]-LY341495 binding competition of mGlu(2/3) agonist LY354740 was not influenced by 2,5-dimethoxy-4-iodoamphetamine (DOI). Taken together, the formation of GPCR heterocomplexes does not necessarily translate into second messenger effects. These results do not put into question the well-documented functional cross-talk of the two receptors in the brain, but do challenge the biological relevance of the 5-HT(2A)-mGlu(2) heterocomplex.

  15. The antidepressant-like activity of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one involves serotonergic 5-HT(1A) and 5-HT(2A/C) receptors activation.

    PubMed

    Pytka, Karolina; Walczak, Maria; Kij, Agnieszka; Rapacz, Anna; Siwek, Agata; Kazek, Grzegorz; Olczyk, Adrian; Gałuszka, Adam; Waszkielewicz, Anna; Marona, Henryk; Sapa, Jacek; Filipek, Barbara

    2015-10-01

    Xanthone derivatives have been shown to posses many biological properties. Some of them act within the central nervous system and show neuroprotective or antidepressant-like properties. Taking this into account we investigated antidepressant-like activity in mice and the possible mechanism of action of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-11) - a new xanthone derivative. We demonstrated that HBK-11 produced antidepressant-like effects in the forced swim test and tail suspension test, comparable to that of venlafaxine. The combined treatment with sub-effective doses of HBK-11 and fluoxetine (but not reboxetine or bupropion) significantly reduced the immobility in the forced swim test. Moreover, the antidepressant-like activity of HBK-11 in the aforementioned test was blocked by p-chlorophenylalanine, and significantly reduced by serotonergic 5HT1A receptor antagonist - WAY-1006335 and 5HT2A/C receptor antagonist - ritanserin. As none of the above treatments influenced the spontaneous locomotor activity, it can be concluded that HBK-11 mediates its activity through a serotonergic system, and its antidepressant-like effect involves 5HT1A and 5HT2A/C receptor activation. Furthermore, at antidepressant-like doses HBK-11 did not cause the mice to display locomotor deficits in rotarod or chimney tests. Considering the pharmacokinetic profile, HBK-11 demonstrated rapid absorption after i.p. administration, high clearance value, short terminal half-life, very high volume of distribution and incomplete bioavailability. The compound studied had good penetration into the brain tissue of mice. Since studied xanthone derivative seems to present interesting, untypical mechanism of antidepressant-like action i.e. 5HT2A/C receptor activation, it may have a potential in the treatment of depressive disorders, and surely requires further studies. PMID:26210317

  16. Inhibition of SNL-induced upregulation of CGRP and NPY in the spinal cord and dorsal root ganglia by the 5-HT(2A) receptor antagonist ketanserin in rats.

    PubMed

    Wang, Dongmei; Chen, Tingjun; Gao, Yun; Quirion, Rémi; Hong, Yanguo

    2012-05-01

    Our previous study has demonstrated that topical and systemic administration of the 5-HT(2A) receptor antagonist ketanserin attenuates neuropathic pain. To explore the mechanisms involved, we examined whether ketanserin reversed the plasticity changes associated with calcitonin gene-related peptides (CGRP) and neuropeptide Y (NPY) which may reflect distinct mechanisms: involvement and compensatory protection. Behavioral responses to thermal and tactile stimuli after spinal nerve ligation (SNL) at L5 demonstrated neuropathic pain and its attenuation in the vehicle- and ketanserin-treated groups, respectively. SNL surgery induced an increase in CGRP and NPY immunoreactivity (IR) in laminae I-II of the spinal cord. L5 SNL produced an expression of NPY-IR in large, medium and small diameter neurons in dorsal root ganglion (DRG) only at L5, but not adjacent L4 and L6. Daily injection of ketanserin (0.3 mg/kg, s.c.) for two weeks suppressed the increase in CGRP-IR and NPY-IR in the spinal cord or DRG. The present study demonstrated that: (1) the expression of CGRP was enhanced in the spinal dorsal horn and NPY was expressed in the DRG containing injured neurons, but not in the adjacent DRG containing intact neurons, following L5 SNL; (2) the maladaptive changes in CGRP and NPY expression in the spinal cord and DRG mediated the bioactivity of 5-HT/5-HT(2A) receptors in neuropathic pain and (3) the blockade of 5-HT(2A) receptors by ketanserin reversed the evoked upregulation of both CGRP and NPY in the spinal cord and DRG contributing to the inhibition of neuropathic pain.

  17. The highly selective 5-hydroxytryptamine (5-HT)2A receptor antagonist, EMD 281014, significantly increases swimming and decreases immobility in male congenital learned helpless rats in the forced swim test.

    PubMed

    Patel, Jignesh G; Bartoszyk, Gerd D; Edwards, Emmeline; Ashby, Charles R

    2004-04-01

    We examined the effect of the highly selective 5-hydroxytryptamine (5-HT)(2A) receptor antagonist 7-[4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl]-1H-indole-3-carbonitrile HCl (EMD 281014) in congenital learned helpless male rats in the forced swim test. The administration of EMD-281014 (0.3-30 mg/kg i.p.) to congenital learned helpless rats dose-dependently and significantly (at 10 and 30 mg/kg) decreased immobility and increased swimming compared to vehicle-treated animals. Thus, EMD 281014 produces effects in the forced swim test resembling those of antidepressants.

  18. The role of the 5-HT2A and 5-HT2C receptors in the stimulus effects of hallucinogenic drugs. III: The mechanistic basis for supersensitivity to the LSD stimulus following serotonin depletion.

    PubMed

    Fiorella, D; Helsley, S; Lorrain, D S; Rabin, R A; Winter, J C

    1995-10-01

    The present study was designed to determine the effects of p-chlorophenylalanine (PCPA) and p-chloroamphetamine (PCA) administration on (1) the levels of serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in rat brain, (2) the sensitivity of LSD-trained rats to the stimulus effects of LSD, and (3) the maximal levels of 5-HT2A and 5-HT2C receptor mediated phosphoinositide (PI) hydrolysis in rat brain. PCA and PCPA both produced a significant depletion of whole brain 5-HT and 5-HIAA concentrations. The depletion of serotonin with PCPA, but not PCA, resulted in supersensitivity of LSD-trained subjects to the stimulus effects of LSD. Neither PCPA nor PCA treatment altered the maximal level of 5-HT2A receptor-mediated PI hydrolysis. However, PCPA, but not PCA, treatment resulted in a significant upregulation (46%, P < 0.05) of the maximal level of 5-HT2C receptor mediated PI hydrolysis. These data suggest that upregulation of the 5-HT2C receptor mediates the supersensitivity to LSD discriminative stimulus which follows the depletion of central nervous system serotonin by PCPA.

  19. Binding of [(3)H]lysergic acid diethylamide to serotonin 5-HT(2A) receptors and of [(3)H]paroxetine to serotonin uptake sites in platelets from healthy children, adolescents and adults.

    PubMed

    Sigurdh, J; Spigset, O; Allard, P; Mjörndal, T; Hägglöf, B

    1999-11-01

    Possible age effects on binding of [(3)H]lysergic acid diethylamide ([(3)H]LSD) to serotonin 5-HT(2A) receptors and of [(3)H]paroxetine to serotonin uptake sites were studied in platelets from healthy children (11-12 years of age), adolescents (16-17 years of age) and adults. Significant overall age effects were found both for the number of binding sites (B(max)) for [(3)H]LSD binding (p < 0.001), the affinity constant (K(d)) for [(3)H]LSD binding (p < 0.001), B(max) for [(3)H]paroxetine binding (p < 0.001) and K(d) for [(3)H] paroxetine binding (p = 0.006). In general, there was a decrease in B(max) with increasing age, which predominantly occurred between the ages 11-12 years and 16-17 years for the 5-HT(2A) receptor, and after 16-17 years of age for the serotonin uptake site. These developmental changes might have an impact on the effect of treatment with serotonergic drugs in children and adolescents. When the platelet serotonin variables investigated are employed in studies in children or adolescents, age matching or, alternatively, introduction of age control in the statistical analysis should be performed.

  20. 5-HT(2A) and mGlu2 receptor binding levels are related to differences in impulsive behavior in the Roman Low- (RLA) and High- (RHA) avoidance rat strains.

    PubMed

    Klein, A B; Ultved, L; Adamsen, D; Santini, M A; Tobeña, A; Fernandez-Teruel, A; Flores, P; Moreno, M; Cardona, D; Knudsen, G M; Aznar, S; Mikkelsen, J D

    2014-03-28

    The Roman Low- and High-Avoidance rat strains (RLA-I vs RHA-I) have been bidirectionally selected and bred according to their performance in the two-way active avoidance response in the shuttle-box test. Numerous studies have reported a pronounced divergence in emotionality between the two rat strains including differences in novelty seeking, anxiety, stress coping, and susceptibility to addictive substances. However, the underlying molecular mechanisms behind these divergent phenotypes are not known. Here, we determined impulsivity using the 5-choice serial reaction time task and levels of serotonin transporter (SERT), 5-HT(2A) and 5-HT(1A) receptor binding using highly specific radioligands ((3)H-escitalopram, (3)H-MDL100907 and (3)H-WAY100635) and mGlu2/3 receptor binding ((3)H-LY341495) using receptor autoradiography in fronto-cortical sections from RLA-I (n=8) and RHA-I (n=8) male rats. In the more impulsive RHA-I rats, 5-HT(2A), 5-HT(1A) and SERT binding in the frontal cortex was significantly higher compared to RLA-I rats. In contrast, mGlu2/3 receptor binding was decreased by 40% in RHA-I rats compared to RLA-I rats. To differentiate between mGlu2 and mGlu3 receptor protein levels, these were further studied using western blotting, which showed non-detectable levels of mGlu2 receptor protein in RHA rats, while no differences were observed for mGlu3 receptor protein levels. Collectively, these data show general congenital differences in the serotonergic system and a pronounced difference in mGlu2 receptor protein levels. We suggest that the differences in the serotonergic system may mediate some of the phenotypic characteristics in this strain such as hyper-impulsivity and susceptibility to drug addiction. PMID:24412375

  1. D-serine deficiency attenuates the behavioral and cellular effects induced by the hallucinogenic 5-HT(2A) receptor agonist DOI.

    PubMed

    Santini, Martin A; Balu, Darrick T; Puhl, Matthew D; Hill-Smith, Tiffany E; Berg, Alexandra R; Lucki, Irwin; Mikkelsen, Jens D; Coyle, Joseph T

    2014-02-01

    Both the serotonin and glutamate systems have been implicated in the pathophysiology of schizophrenia, as well as in the mechanism of action of antipsychotic drugs. Psychedelic drugs act through the serotonin 2A receptor (5-HT2AR), and elicit a head-twitch response (HTR) in mice, which directly correlates to 5-HT2AR activation and is absent in 5-HT2AR knockout mice. The precise mechanism of this response remains unclear, but both an intrinsic cortico-cortical pathway and a thalamo-cortical pathway involving glutamate release have been proposed. Here, we used a genetic model of NMDAR hypofunction, the serine racemase knockout (SRKO) mouse, to explore the role of glutamatergic transmission in regulating 5-HT2AR-mediated cellular and behavioral responses. SRKO mice treated with the 5-HT2AR agonist (±)-2,5-dimethoxy-4-iodoamphetamine (DOI) showed a clearly diminished HTR and lower induction of c-fos mRNA. These altered functional responses in SRKO mice were not associated with changes in cortical or hippocampal 5-HT levels or in 5-HT2AR and metabotropic glutamate-2 receptor (mGluR2) mRNA and protein expression. Together, these findings suggest that D-serine-dependent NMDAR activity is involved in mediating the cellular and behavioral effects of 5-HT2AR activation.

  2. The Combination of Marketed Antagonists of α1b-Adrenergic and 5-HT2A Receptors Inhibits Behavioral Sensitization and Preference to Alcohol in Mice: A Promising Approach for the Treatment of Alcohol Dependence

    PubMed Central

    Trovero, Fabrice; David, Sabrina; Bernard, Philippe; Puech, Alain; Bizot, Jean-Charles; Tassin, Jean-Pol

    2016-01-01

    Alcohol-dependence is a chronic disease with a dramatic and expensive social impact. Previous studies have indicated that the blockade of two monoaminergic receptors, α1b-adrenergic and 5-HT2A, could inhibit the development of behavioral sensitization to drugs of abuse, a hallmark of drug-seeking and drug-taking behaviors in rodents. Here, in order to develop a potential therapeutic treatment of alcohol dependence in humans, we have blocked these two monoaminergic receptors by a combination of antagonists already approved by Health Agencies. We show that the association of ifenprodil (1 mg/kg) and cyproheptadine (1 mg/kg) (α1-adrenergic and 5-HT2 receptor antagonists marketed as Vadilex ® and Periactine ® in France, respectively) blocks behavioral sensitization to amphetamine in C57Bl6 mice and to alcohol in DBA2 mice. Moreover, this combination of antagonists inhibits alcohol intake in mice habituated to alcohol (10% v/v) and reverses their alcohol preference. Finally, in order to verify that the effect of ifenprodil was not due to its anti-NMDA receptors property, we have shown that a combination of prazosin (0.5 mg/kg, an α1b-adrenergic antagonist, Mini-Press ® in France) and cyproheptadine (1 mg/kg) could also reverse alcohol preference. Altogether these findings strongly suggest that combined prazosin and cyproheptadine could be efficient as a therapy to treat alcoholism in humans. Finally, because α1b-adrenergic and 5-HT2A receptors blockade also inhibits behavioral sensitization to psychostimulants, opioids and tobacco, it cannot be excluded that this combination will exhibit some efficacy in the treatment of addiction to other abused drugs. PMID:26968030

  3. 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

    PubMed Central

    Morgan, Drake; Felsing, Daniel; Kondabolu, Krishnakanth; Rowland, Neil E.; Robertson, Kimberly L.; Sakhuja, Rajeev; Booth, Raymond G.

    2014-01-01

    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. (−)-MBP, however, does not alter locomotion when administered alone, distinguishing it from clozapine, which suppresses locomotion. Finally, consumption of highly palatable food by mice was not increased by (−)-MBP at a dose that produced at least 50% maximal efficacy in the psychoses models. Compared with (−)-MBP, the enantiomer (+)-MBP was much less active across in vitro affinity and functional assays using mouse and human receptors and also translated in vivo with comparably lower potency and efficacy. Results indicate a 5-HT2C receptor-specific agonist, such as (−)-MBP, may be pharmacotherapeutic for psychoses, without liability for obesity, hallucinations, heart disease, sedation, or motoric disorders. PMID:24563531

  4. Effects of the 5-HT₆ receptor antagonists SB-399885 and RO-4368554 and of the 5-HT(2A) receptor antagonist EMD 281014 on sleep and wakefulness in the rat during both phases of the light-dark cycle.

    PubMed

    Monti, Jaime M; Jantos, Héctor

    2011-01-01

    The effects of the 5-HT₆ receptor antagonists SB-399885 (2.5, 5 and 10 mg/kg) and RO-4368554 (2.5, 5 and 10 mg/kg) and of the 5-HT(2A) receptor antagonist EMD 281014 (2.5, 5 and 10 mg/kg) were studied in rats implanted for chronic sleep procedures. Administration of 10 mg/kg SB-399885, i.p., to rats 2 h after the beginning of the light phase of the light-dark cycle caused a significant increase of wakefulness (W) and a reduction of slow wave sleep (SWS), REM sleep (REMS) and the number of REM periods during 6-h recording sessions. Light sleep was increased after the whole range of doses. The increase of W and reduction of SWS and REMS occurred predominantly during the first 2-h period whereas light sleep was augmented over the first and the second 2-h recording periods. Injection of RO-4368554 (10 mg/kg, i.p.) 2 h after the beginning of the light period significantly increased W and reduced SWS and REMS during the first 2-h recording period. Administration of EMD 281014 (10 mg/kg, i.p.) during the light phase significantly increased SWS and reduced light sleep during 6-h sessions. REMS and the number of REM period were reduced with the entire range of doses. The reduction of REMS and light sleep and the increase of SWS occurred predominantly during the first and the second 2-h of recording, respectively. Injection of SB-399885 (10 mg/kg, i.p.) 2 h after the beginning of the dark period induced a significant reduction of REMS during the first 2-h of recording. In contrast, RO-4368554 did not modify values corresponding to sleep variables during the dark period. Treatment with EMD 281014 (2.5-10 mg/kg, i.p.) during the dark phase significantly increased SWS during the second 2-h period. Our study supports the proposal that blockade of postsynaptic 5-HT₆ receptors with systemic administration of SB-399885 and RO-4368554 increases W and reduces SWS and REMS during the light phase of the sleep-wake cycle. SB-399885 also induces a suppression of REMS during the dark

  5. Distinct effect of 5-HT1A and 5-HT2A receptors in the medial nucleus of the amygdala on tonic immobility behavior.

    PubMed

    de Paula, Bruna Balbino; Leite-Panissi, Christie Ramos Andrade

    2016-07-15

    The tonic immobility (TI) response is an innate fear behavior associated with intensely dangerous situations, exhibited by many species of invertebrate and vertebrate animals. In humans, it is possible that TI predicts the severity of posttraumatic stress disorder symptoms. This behavioral response is initiated and sustained by the stimulation of various groups of neurons distributed in the telencephalon, diencephalon and brainstem. Previous research has found the highest Fos-IR in the posteroventral part of the medial nucleus of the amygdala (MEA) during TI behavior; however, the neurotransmission of this amygdaloid region involved in the modulation of this innate fear behavior still needs to be clarified. Considering that a major drug class used for the treatment of psychopathology is based on serotonin (5-HT) neurotransmission, we investigated the effects of serotonergic receptor activation in the MEA on the duration of TI. The results indicate that the activation of the 5HT1A receptors or the blocking of the 5HT2 receptors of the MEA can promote a reduction in fear and/or anxiety, consequently decreasing TI duration in guinea pigs. In contrast, blocking the 5HT1A receptors or activating the 5HT2 receptors in this amygdalar region increased the TI duration, suggesting an increase in fear and/or anxiety. These alterations do not appear to be due to a modification of spontaneous motor activity, which might non-specifically affect TI duration. Thus, these results suggest a distinct role of the 5HT receptors in the MEA in innate fear modulation. PMID:27150816

  6. Hallucinogen-like effects of 2-([2-(4-cyano-2,5-dimethoxyphenyl) ethylamino]methyl)phenol (25CN-NBOH), a novel N-benzylphenethylamine with 100-fold selectivity for 5-HT2A receptors, in mice

    PubMed Central

    Gray, Bradley W.; Bailey, Jessica M.; Smith, Douglas; Hansen, Martin; Kristensen, Jesper L.

    2014-01-01

    Rationale 2-([2-(4-cyano-2,5-dimethoxyphenyl)ethylamino]methyl)phenol (25CN-NBOH) is structurally similar to N-benzyl substituted phenethylamine hallucinogens currently emerging as drugs of abuse. 25CN-NBOH exhibits dramatic selectivity for 5-HT2A receptors in vitro, but has not been behaviorally characterized. Objective 25CN-NBOH was compared to the traditional phenethylamine hallucinogen R(−)-2,5-dimethoxy-4-iodoamphetamine (DOI) using mouse models of drug-elicited head twitch behavior and drug discrimination. Methods Drug-elicited head twitches were quantified for 10 min following administration of various doses of either DOI or 25CN-NBOH, with and without pretreatments of 0.01 mg/kg 5-HT2A antagonist M100907 or 3.0 mg/kg 5-HT2C antagonist RS102221. The capacity of 25CN-NBOH to attenuate DOI-elicited head twitch was also investigated. Mice were trained to discriminate DOI or M100907 from saline, and 25CN-NBOH was tested for generalization. Results 25CN-NBOH induced a head twitch response in the mouse that was lower in magnitude than that of DOI, blocked by M100907, but not altered by RS102221. DOI-elicited head twitch was dose-dependently attenuated by 25CN-NBOH pretreatment. 25CN-NBOH produced an intermediate degree of generalization (55%) for the DOI training dose, and these interoceptive effects were attenuated by M100907. Finally, 25CN-NBOH did not generalize to M100907 at any dose, but ketanserin fully substituted in these animals. Conclusions 25CN-NBOH was behaviorally active, but less effective than DOI in two mouse models of hallucinogenic effects. The effectiveness with which M100907 antagonized the behavioral actions of 25CN-NBOH strongly suggests that the 5-HT2A receptor is an important site of agonist action for this compound in vivo. PMID:25224567

  7. Effects of central activation of serotonin 5-HT2A/2C or dopamine D2/3 receptors on the acute and repeated effects of clozapine in the conditioned avoidance response test

    PubMed Central

    Feng, Min; Gao, Jun; Sui, Nan; Li, Ming

    2014-01-01

    Rationale: Acute administration of clozapine (a gold standard of atypical antipsychotics) disrupts avoidance response in rodents, while repeated administration often causes a tolerance effect. Objective: The present study investigated the neuroanatomical basis and receptor mechanisms of acute and repeated effects of clozapine treatment in the conditioned avoidance response test in male Sprague-Dawley rats. Methods: DOI (2,5-dimethoxy-4-iodo-amphetamine, a preferential 5-HT2A/2C agonist) or quinpirole (a preferential dopamine D2/3 agonist) was microinjected into the medial prefrontal cortex (mPFC) or nucleus accumbens shell (NAs), and their effects on the acute and long-term avoidance-disruptive effect of clozapine were tested. Results: Intra-mPFC microinjection of quinpirole enhanced the acute avoidance disruptive effect of clozapine (10 mg/kg, sc), while DOI microinjections reduced it marginally. Repeated administration of clozapine (10 mg/kg, sc) daily for 5 days caused a progressive decrease in its inhibition of avoidance responding, indicating tolerance development. Intra-mPFC microinjection of DOI at 25.0 (but not 5.0) μg/side during this period completely abolished the expression of clozapine tolerance. This was indicated by the finding that clozapine-treated rats centrally infused with 25.0 μg/side DOI did not show higher levels of avoidance responses than the vehicle-treated rats in the clozapine challenge test. Microinjection of DOI into the mPFC immediately before the challenge test also decreased the expression of clozapine tolerance. Conclusions: Acute behavioral effect of clozapine can be enhanced by activation of the D2/3 receptors in the mPFC. Clozapine tolerance expression relies on the neuroplasticity initiated by its antagonist action against 5-HT2A/2C receptors in the mPFC. PMID:25288514

  8. Dual role of serotonin in the acquisition and extinction of reward-driven learning: involvement of 5-HT1A, 5-HT2A and 5-HT3 receptors.

    PubMed

    Frick, Luciana Romina; Bernardez-Vidal, Micaela; Hocht, Christian; Zanutto, Bonifacio Silvano; Rapanelli, Maximiliano

    2015-01-15

    Serotonin (5-HT) has been proposed as a possible encoder of reward. Nevertheless, the role of this neurotransmitter in reward-based tasks is not well understood. Given that the major serotonergic circuit in the rat brain comprises the dorsal raphe nuclei and the medial prefrontal cortex (mPFC), and because the latter structure is involved in the control of complex behaviors and expresses 1A (5-HT1A), 2A (5-HT2A), and 3 (5-HT3) receptors, the aim was to study the role of 5-HT and of these receptors in the acquisition and extinction of a reward-dependent operant conditioning task. Long Evans rats were trained in an operant conditioning task while receiving fluoxetine (serotonin reuptake inhibitor, 10mg/kg), tianeptine (serotonin reuptake enhancer, 10mg/kg), buspirone (5-HT1A partial agonist, 10mg/kg), risperidone (5-HT2A antagonist, 1mg/kg), ondansetron (5-HT3 antagonist, 2mg/kg) or vehicle. Then, animals that acquired the operant conditioning without any treatment were trained to extinct the task in the presence of the pharmacological agents. Fluoxetine impaired acquisition but improved extinction. Tianeptine administration induced the opposite effects. Buspirone induced a mild deficit in acquisition and had no effects during the extinction phase. Risperidone administration resulted in learning deficits during the acquisition phase, although it promoted improved extinction. Ondansetron treatment showed a deleterious effect in the acquisition phase and an overall improvement in the extinction phase. These data showed a differential role of 5-HT in the acquisition and extinction of an operant conditioning task, suggesting that it may have a dual function in reward encoding. PMID:24949809

  9. 4-Fluorosulfonylpiperidines: selective 5-HT2A ligands for the treatment of insomnia.

    PubMed

    Fish, L Rebecca; Gilligan, Myra T; Humphries, Alexander C; Ivarsson, Magnus; Ladduwahetty, Tammy; Merchant, Kevin J; O'Connor, Desmond; Patel, Smita; Philipps, Elisabeth; Vargas, Hugo M; Hutson, Peter H; MacLeod, Angus M

    2005-08-15

    Incorporation of fluorine at the 4-position of an existing series of sulfonyl piperidine 5-HT2A antagonists gave compounds with increased selectivity over the IKr potassium channel. This work led to the identification of 3b, a compound that gave no increase in QTc in the anesthetized dog up to plasma levels as high as 148 microM. Furthermore, 3b has been shown to increase slow-wave sleep bout duration and to decrease the number of awakenings in rats, indicating the potential utility of 5-HT2A antagonists in the treatment of insomnia.

  10. Binding of [3H]paroxetine to serotonin uptake sites and of [3H]lysergic acid diethylamide to 5-HT2A receptors in platelets from women with premenstrual dysphoric disorder during gonadotropin releasing hormone treatment.

    PubMed

    Bixo, M; Allard, P; Bäckström, T; Mjörndal, T; Nyberg, S; Spigset, O; Sundström-Poromaa, I

    2001-08-01

    Changes in serotonergic parameters have been reported in psychiatric conditions such as depression but also in the premenstrual dysphoric disorder (PMDD). In addition, hormonal effects on serotonergic activity have been established. In the present study, binding of [3H]paroxetine to platelet serotonin uptake sites and binding of [3H]lysergic acid diethylamide ([3H]LSD) to platelet serotonin (5-HT)2A receptors were studied in patients with PMDD treated with a low dose of a gonadotropin releasing hormone (GnRH) agonist (buserelin) or placebo and compared to controls. The PMDD patients were relieved of premenstrual symptoms like depression and irritability during buserelin treatment. The number of [3H]paroxetine binding sites (Bmax) were significantly higher in the follicular phase in untreated PMDD patients compared to controls. When treated with buserelin the difference disappeared. No differences in [3H]LSD binding between the three groups were shown. The present study demonstrated altered platelet [3H]paroxetine binding characteristics in women with PMDD compared to controls. Furthermore, [3H]paroxetine binding was affected by PMDD treatment with a low dose of buserelin. The results are consistent with the hypothesis that changes in serotonergic transmission could be a trait in the premenstrual dysphoric disorder.

  11. The serotonergic hallucinogen 5-methoxy-N,N-dimethyltryptamine disrupts cortical activity in a regionally-selective manner via 5-HT(1A) and 5-HT(2A) receptors.

    PubMed

    Riga, Maurizio S; Bortolozzi, Analia; Campa, Letizia; Artigas, Francesc; Celada, Pau

    2016-02-01

    5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a natural hallucinogen, acting as a non-selective serotonin 5-HT(1A)/5-HT(2A)-R agonist. Psychotomimetic agents such as the non-competitive NMDA-R antagonist phencyclidine and serotonergic hallucinogens (DOI and 5-MeO-DMT) disrupt cortical synchrony in the low frequency range (<4 Hz) in rat prefrontal cortex (PFC), an effect reversed by antipsychotic drugs. Here we extend these observations by examining the effect of 5-MeO-DMT on low frequency cortical oscillations (LFCO, <4 Hz) in PFC, visual (V1), somatosensory (S1) and auditory (Au1) cortices, as well as the dependence of these effects on 5-HT(1A)-R and 5-HT(2A)-R, using wild type (WT) and 5-HT(2A)-R knockout (KO2A) anesthetized mice. 5-MeO-DMT reduced LFCO in the PFC of WT and KO2A mice. The effect in KO2A mice was fully prevented by the 5-HT(1A)-R antagonist WAY-100635. Systemic and local 5-MeO-DMT reduced 5-HT release in PFC mainly via 5-HT(1A)-R. Moreover, 5-MeO-DMT reduced LFCO in S1, Au1 and V1 of WT mice and only in V1 of KO2A mice, suggesting the involvement of 5-HT(1A)-R activation in the 5-MeO-DMT-induced disruption of V1 activity. In addition, antipsychotic drugs reversed 5-MeO-DMT effects in WT mice. The present results suggest that the hallucinogen action of 5-MeO-DMT is mediated by simultaneous alterations of the activity of sensory (S1, Au1, V1) and associative (PFC) cortical areas, also supporting a role of 5-HT(1A)-R stimulation in V1 and PFC, in addition to the well-known action on 5-HT(2A)-R. Moreover, the reversal by antipsychotic drugs of 5-MeO-DMT effects adds to previous literature supporting the usefulness of the present model in antipsychotic drug development.

  12. Extending David Horrobin's membrane phospholipid theory of schizophrenia: overactivity of cytosolic phospholipase A(2) in the brain is caused by overdrive of coupled serotonergic 5HT(2A/2C) receptors in response to stress.

    PubMed

    Eggers, Arnold E

    2012-12-01

    David Horrobin's membrane phospholipid theory of schizophrenia has held up well over time because his therapeutic prediction that dietary supplementation with eicosapentaenoic acid (EPA) would have a therapeutic effect has been partially verified and undergoes continued testing. In the final version of his theory, he hypothesized that there was hyperactivity of phosphoslipase A(2) (PLA(2)) or a related enzyme but did not explain how the hyperactivity came about. It is known that serotonergic 5HT(2A/2C) receptors are coupled to PLA(2), which hydrolyzes both arachidonic acid (AA) and EPA from diacylglycerides at the sn-2 position. In this paper, Horrobin's theory is combined with a previously published theory of chronic stress in which it was hypothesized that a disinhibited dorsal raphe nucleus, the principal nucleus of the serotonergic system, can organize the neuropathology of diseases such as migraine, hypertension, and the metabolic syndrome. The new or combined theory is that schizophrenia is a disease of chronic stress in which a disinhibited DRN causes widespread serotonergic overdrive in the cerebral cortex. This in turn causes overdrive of cPLA(2) and both central and peripheral depletion of AA and EPA. Because EPA is present in smaller amounts, it falls below threshold for maintaining an intracellular balance between AA-derived and EPA-derived second messenger cascades, which leads to abnormal patterns of neuronal firing. There are two causes of neuronal dysfunction: the disinhibited DRN and EPA depletion. Schizophrenia is statistically associated with metabolic syndrome, hypertension, and migraine because they form a cluster of diseases with similar pathophysiology. The theory provides an explanation for both the central and peripheral phospholipid abnormalities in schizophrenia. It also explains the role of stress in schizophrenia, elevated serum PLA(2) activity in schizophrenia, the relationship between untreated schizophrenia and metabolic syndrome

  13. Molecular Determinants for Ligand Binding at Serotonin 5-HT2A and 5-HT2C GPCRs: Experimental Affinity Results Analyzed by Molecular Modeling and Ligand Docking Studies

    PubMed Central

    Sakhuja, Rajeev; Kondabolu, Krishnakanth; Canal, Clinton E.; Booth, Raymond G.

    2013-01-01

    Ligands that activate the serotonin 5-HT2C G protein-coupled receptor (GPCR) may be therapeutic for psychoses, addiction, and other neuropsychiatric disorders. Ligands that are antagonists at the closely related 5-HT2A GPCR also may treat neuropsychiatric disorders; in contrast, 5-HT2A activation may cause hallucinations. 5-HT2C-specific agonist drug design is challenging because 5-HT2 GPCRs share 80% transmembrane (TM) homology, same second messenger signaling, and no crystal structures are reported. To help delineate molecular determinants underlying differential binding and activation of 5-HT2 GPCRs, 5-HT2A, and 5-HT2C homology models were built from the β2-adrenergic GPCR crystal structure and equilibrated in a lipid phosphatidyl choline bilayer performing molecular dynamics simulations. Ligand docking studies at the 5-HT2 receptor models were conducted with the (2R, 4S)- and (2S, 4R)-enantiomers of the novel 5-HT2C agonist/5-HT2A/2B antagonist trans-4-phenyl-N,N-dimethyl-2-aminotetralin (PAT) and its 4′-chlorophenyl congners. Results indicate PAT–5-HT2 molecular interactions especially in TM domain V are important for the (2R, 4S) enantiomer, whereas, TM domain VI and VII interactions are more important for the (2S, 4R) enantiomer. PMID:23913978

  14. 1,4-Disubstituted aromatic piperazines with high 5-HT2A/D2 selectivity: Quantitative structure-selectivity investigations, docking, synthesis and biological evaluation.

    PubMed

    Möller, Dorothee; Salama, Ismail; Kling, Ralf C; Hübner, Harald; Gmeiner, Peter

    2015-09-15

    Simultaneous targeting of dopamine D2 and 5-HT2A receptors for the treatment of schizophrenia is one key feature of typical and atypical antipsychotics. In most of the top-selling antipsychotic drugs like aripiprazole and risperidone, high affinity to both receptors can be attributed to the presence of 1,4-disubstituted aromatic piperazines or piperidines as primary receptor recognition elements. Taking advantage of our in-house library of phenylpiperazine-derived dopamine receptor ligands and experimental data, we established highly significant CoMFA and CoMSIA models for the prediction of 5-HT2A over D2 selectivity. Subsequently, the models were applied to identify the selective candidates 55-57 from our newly synthesized library of GPCR ligands comprising a pyrazolo[1,5-a]pyridine head group and a 1,2,3-triazole based linker unit. The test compound 57 showed subnanomolar a Ki value (0.64 nM) for 5-HT2A and more than 10- and 30-fold selectivity over the dopamine receptor isoforms D2S and D2L, respectively. PMID:26299826

  15. 5-HT2A Gene Variants Moderate the Association between PTSD and Reduced Default Mode Network Connectivity.

    PubMed

    Miller, Mark W; Sperbeck, Emily; Robinson, Meghan E; Sadeh, Naomi; Wolf, Erika J; Hayes, Jasmeet P; Logue, Mark; Schichman, Steven A; Stone, Angie; Milberg, William; McGlinchey, Regina

    2016-01-01

    The default mode network (DMN) has been used to study disruptions of functional connectivity in a wide variety of psychiatric and neurological conditions, including posttraumatic stress disorder (PTSD). Studies indicate that the serotonin system exerts a modulatory influence on DMN connectivity; however, no prior study has examined associations between serotonin receptor gene variants and DMN connectivity in either clinical or healthy samples. We examined serotonin receptor single nucleotide polymorphisms (SNPs), PTSD, and their interactions for association with DMN connectivity in 134 White non-Hispanic veterans. We began by analyzing candidate SNPs identified in prior meta-analyses of relevant psychiatric traits and found that rs7997012 (an HTR2A SNP), implicated previously in anti-depressant medication response in the Sequenced Treatment Alternatives for Depression study (STAR(*)D; McMahon et al., 2006), interacted with PTSD to predict reduced connectivity between the posterior cingulate cortex (PCC) and the right medial prefrontal cortex and right middle temporal gyrus (MTG). rs130058 (HTR1B) was associated with connectivity between the PCC and right angular gyrus. We then expanded our analysis to 99 HTR1B and HTR2A SNPs and found two HTR2A SNPs (rs977003 and rs7322347) that significantly moderated the association between PTSD severity and the PCC-right MTG component of the DMN after correcting for multiple testing. Finally, to obtain a more precise localization of the most significant SNP × PTSD interaction, we performed a whole cortex vertex-wise analysis of the rs977003 effect. This analysis revealed the locus of the pre-frontal effect to be in portions of the superior frontal gyrus, while the temporal lobe effect was centered in the middle and inferior temporal gyri. These findings point to the influence of HTR2A variants on DMN connectivity and advance knowledge of the role of 5-HT2A receptors in the neurobiology of PTSD. PMID:27445670

  16. 5-HT2A Gene Variants Moderate the Association between PTSD and Reduced Default Mode Network Connectivity

    PubMed Central

    Miller, Mark W.; Sperbeck, Emily; Robinson, Meghan E.; Sadeh, Naomi; Wolf, Erika J.; Hayes, Jasmeet P.; Logue, Mark; Schichman, Steven A.; Stone, Angie; Milberg, William; McGlinchey, Regina

    2016-01-01

    The default mode network (DMN) has been used to study disruptions of functional connectivity in a wide variety of psychiatric and neurological conditions, including posttraumatic stress disorder (PTSD). Studies indicate that the serotonin system exerts a modulatory influence on DMN connectivity; however, no prior study has examined associations between serotonin receptor gene variants and DMN connectivity in either clinical or healthy samples. We examined serotonin receptor single nucleotide polymorphisms (SNPs), PTSD, and their interactions for association with DMN connectivity in 134 White non-Hispanic veterans. We began by analyzing candidate SNPs identified in prior meta-analyses of relevant psychiatric traits and found that rs7997012 (an HTR2A SNP), implicated previously in anti-depressant medication response in the Sequenced Treatment Alternatives for Depression study (STAR*D; McMahon et al., 2006), interacted with PTSD to predict reduced connectivity between the posterior cingulate cortex (PCC) and the right medial prefrontal cortex and right middle temporal gyrus (MTG). rs130058 (HTR1B) was associated with connectivity between the PCC and right angular gyrus. We then expanded our analysis to 99 HTR1B and HTR2A SNPs and found two HTR2A SNPs (rs977003 and rs7322347) that significantly moderated the association between PTSD severity and the PCC-right MTG component of the DMN after correcting for multiple testing. Finally, to obtain a more precise localization of the most significant SNP × PTSD interaction, we performed a whole cortex vertex-wise analysis of the rs977003 effect. This analysis revealed the locus of the pre-frontal effect to be in portions of the superior frontal gyrus, while the temporal lobe effect was centered in the middle and inferior temporal gyri. These findings point to the influence of HTR2A variants on DMN connectivity and advance knowledge of the role of 5-HT2A receptors in the neurobiology of PTSD. PMID:27445670

  17. Hallucinogenic 5-HT2AR agonists LSD and DOI enhance dopamine D2R protomer recognition and signaling of D2-5-HT2A heteroreceptor complexes.

    PubMed

    Borroto-Escuela, Dasiel O; Romero-Fernandez, Wilber; Narvaez, Manuel; Oflijan, Julia; Agnati, Luigi F; Fuxe, Kjell

    2014-01-01

    Dopamine D2LR-serotonin 5-HT2AR heteromers were demonstrated in HEK293 cells after cotransfection of the two receptors and shown to have bidirectional receptor-receptor interactions. In the current study the existence of D2L-5-HT2A heteroreceptor complexes was demonstrated also in discrete regions of the ventral and dorsal striatum with in situ proximity ligation assays (PLA). The hallucinogenic 5-HT2AR agonists LSD and DOI but not the standard 5-HT2AR agonist TCB2 and 5-HT significantly increased the density of D2like antagonist (3)H-raclopride binding sites and significantly reduced the pKiH values of the high affinity D2R agonist binding sites in (3)H-raclopride/DA competition experiments. Similar results were obtained in HEK293 cells and in ventral striatum. The effects of the hallucinogenic 5-HT2AR agonists on D2R density and affinity were blocked by the 5-HT2A antagonist ketanserin. In a forskolin-induced CRE-luciferase reporter gene assay using cotransfected but not D2R singly transfected HEK293 cells DOI and LSD but not TCB2 significantly enhanced the D2LR agonist quinpirole induced inhibition of CRE-luciferase activity. Haloperidol blocked the effects of both quinpirole alone and the enhancing actions of DOI and LSD while ketanserin only blocked the enhancing actions of DOI and LSD. The mechanism for the allosteric enhancement of the D2R protomer recognition and signalling observed is likely mediated by a biased agonist action of the hallucinogenic 5-HT2AR agonists at the orthosteric site of the 5-HT2AR protomer. This mechanism may contribute to the psychotic actions of LSD and DOI and the D2-5-HT2A heteroreceptor complex may thus be a target for the psychotic actions of hallunicogenic 5-HT2A agonists.

  18. Effects of the 5-HT2A agonist psilocybin on mismatch negativity generation and AX-continuous performance task: implications for the neuropharmacology of cognitive deficits in schizophrenia.

    PubMed

    Umbricht, Daniel; Vollenweider, Franz X; Schmid, Liselotte; Grübel, Claudia; Skrabo, Anja; Huber, Theo; Koller, Rene

    2003-01-01

    Previously the NMDA (N-methyl-D-aspartate) receptor (NMDAR) antagonist ketamine was shown to disrupt generation of the auditory event-related potential (ERP) mismatch negativity (MMN) and the performance of an 'AX'-type continuous performance test (AX-CPT)--measures of auditory and visual context-dependent information processing--in a similar manner as observed in schizophrenia. This placebo-controlled study investigated effects of the 5-HT(2A) receptor agonist psilocybin on the same measures in 18 healthy volunteers. Psilocybin administration induced significant performance deficits in the AX-CPT, but failed to reduce MMN generation significantly. These results indirectly support evidence that deficient MMN generation in schizophrenia may be a relatively distinct manifestation of deficient NMDAR functioning. In contrast, secondary pharmacological effects shared by NMDAR antagonists and the 5-HT(2A) agonist (ie disruption of glutamatergic neurotransmission) may be the mechanism underlying impairments in AX-CPT performance observed during both psilocybin and ketamine administration. Comparable deficits in schizophrenia may result from independent dysfunctions of 5-HT(2A) and NMDAR-related neurotransmission.

  19. Pharmacogenetic Study of Serotonin Transporter and 5HT2A Genotypes in Autism

    PubMed Central

    Najjar, Fedra; Owley, Thomas; Mosconi, Matthew W.; Jacob, Suma; Hur, Kwan; Guter, Stephen J.; Sweeney, John A.; Gibbons, Robert D; Bishop, Jeffrey R.

    2015-01-01

    Abstract Objective: The purpose of this study was to determine whether polymorphisms in the serotonin transporter (SLC6A4) and serotonin-2A receptor (HTR2A) genes are associated with response to escitalopram in patients with autism spectrum disorder (ASD). Methods: Forty-four participants with ASD were enrolled in a 6 week, forced titration, open label examination of the selective serotonin reuptake inhibitor (SSRI) escitalopram. Doses increased at weekly intervals starting at 2.5mg daily with a maximum possible dose of 20 mg daily achieved by the end of the study. If adverse events were experienced, participants subsequently received the previously tolerated dose for the duration of study. SLC6A4 (5-HTTLPR) and HTR2A (rs7997012) genotype groups were assessed in relation to treatment outcomes and drug doses. Results: Insistence on sameness and irritability symptoms significantly improved over the course of the 6 week treatment period (p<0.0001) in this open-label trial. There were no significant differences observed in the rate of symptom improvement over time across genotype groups. Similarly, dosing trajectory was not significantly associated with genotype groups. Conclusions: Previous studies have identified SLC6A4 and HTR2A associations with SSRI response in patients with depression and 5-HTTLPR (SLC6A4) associations with escitalopram response in ASD. We did not observe evidence for similar relationships in this ASD study. PMID:26262902

  20. The influence of 5-HT(2A) activity on a 5-HT(2C) specific in vivo assay used for early identification of multiple acting SERT and 5-HT(2C) receptor ligands.

    PubMed

    Éliás, Olivér; Nógrádi, Katalin; Domány, György; Szakács, Zoltán; Kóti, János; Szántay, Csaba; Tarcsay, Ákos; Keserű, György M; Gere, Anikó; Kiss, Béla; Kurkó, Dalma; Kolok, Sándor; Némethy, Zsolt; Kapui, Zoltán; Hellinger, Éva; Vastag, Mónika; Sághy, Katalin; Kedves, Rita; Gyertyán, István

    2016-02-01

    As a result of our exploratory programme aimed at elaborating dually acting compounds towards the serotonin (5-HT) transporter (SERT) and the 5-HT2C receptor a novel series of 3-amino-1-phenylpropoxy substituted diphenylureas was identified. From that collection two promising compounds (2 and 3) exhibiting highest 5-HT2C receptor affinity strongly inhibited the 5-HT2C receptor agonist 1-(3-chlorophenyl)piperazine (mCPP) induced hypomotility in mice. In further pursuance of that objective (2-aminoethyl)(benzyl)sulfamoyl diphenylureas and diphenylpiperazines have also been elaborated. Herein we report the synthesis of potent multiple-acting compounds from this new class. However, when two optimized representatives (6 and 14) possessing the desired in vitro profile were tested neither reduced the motor activity of mCPP treated animals. Comparative albeit limited in vitro structure-activity relationship (SAR) analysis and detailed in vivo studies are discussed and explanation for their intricate behaviour is proposed.

  1. Association study of T102C 5-HT2A polymorphism in schizophrenic patients: diagnosis, psychopathology, and suicidal behavior

    PubMed Central

    Correa, Humberto; De Marco, Luiz; Boson, Wolfanga; Nicolato, Rodrigo; Teixeira, Antó L.; Campo, Valdir R.; Romano-Silva, Marco A.

    2007-01-01

    The objective of this study was to examine the association between the serotonin (5-HT)2A gene polymorphism (102T/C) and suicidal behavior in schizophrenic inpatients. We studied 129 subjects who met the diagnostic criteria for schizophrenia according to a structured clinicai interview (MINI-PLUS), Patients underwent a semistructured interview to assess suicide attempt history and its characteristics, in addition, at least one close relative of the patient was interviewed to assess prohand and family suicidal behavior. Healthy controls were students and hospital staff members free of psychiatric and medical illness. Genotypes were determined after polymerase chain reaction amplification of the region of 5-HT2A/T102C containing the polymorphic site and digestion with the restriction enzyme Hpall, We found no association between suicidal attempt history and suicide attempt characteristics and genotypic or aileie frequencies. Suicidal behavior was also not associated with demographic or psychopathological characteristics. These results suggest that the S-HT2A gene polymorphism (102T/C) is not involved in genetic susceptibility to suicidal behavior, but further studies in a larger sample are needed. PMID:17506229

  2. Effect of GABAergic ligands on the anxiolytic-like activity of DOI (a 5-HT(2A/2C) agonist) in the four-plate test in mice.

    PubMed

    Massé, Fabienne; Hascoët, Martine; Bourin, Michel

    2007-01-01

    5-HTergic and GABAergic systems are involved in neurobiology of anxiety. Precedent studies have demonstrated that SSRIs possessed an anxiolytic-like effect in the four-plate test (FPT) at doses that did not modify spontaneous locomotor activity. This effect seems to be mediated through the activation of 5-HT(2A) postsynaptic receptors. The purpose of the present study was to examine the implication of GABA system in the anxiolytic-like activity of DOI in the FPT. To achieve this, the co-administration of DOI (5-HT(2A/2C) receptor agonists) with GABA(A) and GABA(B) receptor ligands was evaluated in the FPT. Alprazolam, diazepam and muscimol (for higher dose) potentiated the anxiolytic-like effect of DOI. Bicuculline, picrotoxin and baclofen inhibited the anxiolytic-like effect of DOI. Flumazenil and CGP 35348 had no effect on the anxiolytic-like activity of DOI. These results suggest that the GABA system seems to be strongly implicated in the anxiolytic-like activity of DOI in the FPT.

  3. Evidence for a common biological basis of the Absorption trait, hallucinogen effects, and positive symptoms: epistasis between 5-HT2a and COMT polymorphisms.

    PubMed

    Ott, Ulrich; Reuter, Martin; Hennig, Juergen; Vaitl, Dieter

    2005-08-01

    Absorption represents a disposition to experience altered states of consciousness characterized by intensively focused attention. It is correlated with hypnotic susceptibility and includes phenomena ranging from vivid perceptions and imaginations to mystical experiences. Based on the assumption that drug-induced and naturally occurring mystical experiences share common neural mechanisms, we hypothesized that Absorption is influenced by the T102C polymorphism affecting the 5-HT2a receptor, which is known to be an important target site of hallucinogens like LSD. Based on the pivotal role ascribed to the prefrontal executive control network for absorbed attention and positive symptoms in schizophrenia, it was further hypothesized that Absorption is associated with the VAL158MET polymorphism of the catechol-O-methyltransferase (COMT) gene affecting the dopaminergic neurotransmitter system. The Tellegen Absorption Scale was administered to 336 subjects (95 male, 241 female). Statistical analysis revealed that the group with the T/T genotype of the T102C polymorphism, implying a stronger binding potential of the 5-HT2a receptor, indeed had significantly higher Absorption scores (F = 10.00, P = 0.002), while no main effect was found for the COMT polymorphism. However, the interaction between T102C and COMT genotypes yielded significance (F = 3.89; P = 0.049), underlining the known functional interaction between the 5-HT and the dopaminergic system. These findings point to biological foundations of the personality trait of Absorption.

  4. The effects of the preferential 5-HT2A agonist psilocybin on prepulse inhibition of startle in healthy human volunteers depend on interstimulus interval.

    PubMed

    Vollenweider, Franz X; Csomor, Philipp A; Knappe, Bernhard; Geyer, Mark A; Quednow, Boris B

    2007-09-01

    Schizophrenia patients exhibit impairments in prepulse inhibition (PPI) of the startle response. Hallucinogenic 5-HT(2A) receptor agonists are used for animal models of schizophrenia because they mimic some symptoms of schizophrenia in humans and induce PPI deficits in animals. Nevertheless, one report indicates that the 5-HT(2A) receptor agonist psilocybin increases PPI in healthy humans. Hence, we investigated these inconsistent results by assessing the dose-dependent effects of psilocybin on PPI in healthy humans. Sixteen subjects each received placebo or 115, 215, and 315 microg/kg of psilocybin at 4-week intervals in a randomized and counterbalanced order. PPI at 30-, 60-, 120-, 240-, and 2000-ms interstimulus intervals (ISIs) was measured 90 and 165 min after drug intake, coinciding with the peak and post-peak effects of psilocybin. The effects of psilocybin on psychopathological core dimensions and sustained attention were assessed by the Altered States of Consciousness Rating Scale (5D-ASC) and the Frankfurt Attention Inventory (FAIR). Psilocybin dose-dependently reduced PPI at short (30 ms), had no effect at medium (60 ms), and increased PPI at long (120-2000 ms) ISIs, without affecting startle reactivity or habituation. Psilocybin dose-dependently impaired sustained attention and increased all 5D-ASC scores with exception of Auditory Alterations. Moreover, psilocybin-induced impairments in sustained attention performance were positively correlated with reduced PPI at the 30 ms ISI and not with the concomitant increases in PPI observed at long ISIs. These results confirm the psilocybin-induced increase in PPI at long ISIs and reveal that psilocybin also produces a decrease in PPI at short ISIs that is correlated with impaired attention and consistent with deficient PPI in schizophrenia.

  5. Contrasting mechanisms of action and sensitivity to antipsychotics of phencyclidine versus amphetamine: importance of nucleus accumbens 5-HT2A sites for PCP-induced locomotion in the rat.

    PubMed

    Millan, M J; Brocco, M; Gobert, A; Joly, F; Bervoets, K; Rivet, J; Newman-Tancredi, A; Audinot, V; Maurel, S

    1999-12-01

    In the present study, the comparative mechanisms of action of phencyclidine (PCP) and amphetamine were addressed employing the parameter of locomotion in rats. PCP-induced locomotion (PLOC) was potently blocked by the selective serotonin (5-HT)2A vs. D2 antagonists, SR46349, MDL100,907, ritanserin and fananserin, which barely affected amphetamine-induced locomotion (ALOC). In contrast, the selective D2 vs. 5-HT2A antagonists, eticlopride, raclopride and amisulpride, preferentially inhibited ALOC vs. PLOC. The potency of these drugs and 12 multireceptorial antipsychotics in inhibiting PLOC vs. ALOC correlated significantly with affinities at 5-HT2A vs. D2 receptors, respectively. Amphetamine and PCP both dose dependently increased dialysate levels of dopamine (DA) and 5-HT in the nucleus accumbens, striatum and frontal cortex (FCX) of freely moving rats, but PCP was proportionally more effective than amphetamine in elevating levels of 5-HT vs. DA in the accumbens. Further, whereas microinjection of PCP into the accumbens elicited locomotion, its introduction into the striatum or FCX was ineffective. The action of intra-accumbens PCP, but not intra-accumbens amphetamine, was abolished by SR46349 and clozapine. Parachloroamphetamine, which depleted accumbens pools of 5-HT but not DA, likewise abolished PLOC without affecting ALOC. In contrast, intra-accumbens 6-hydroxydopamine (6-OHDA), which depleted DA but not 5-HT, abolished ALOC but only partially attenuated PLOC. In conclusion, PLOC involves (indirect) activation of accumbens-localized 5-HT2A receptors by 5-HT. PLOC is, correspondingly, more potently blocked than ALOC by antipsychotics displaying marked affinity at 5-HT2A receptors.

  6. The effect of intrahippocampal injections of ritanserin (5HT2A/2C antagonist) and granisetron (5HT3 antagonist) on learning as assessed in the spatial version of the water maze.

    PubMed

    Naghdi, Nasser; Harooni, Hooman E

    2005-02-28

    5HT(2A/2C) and 5HT(3) receptors have an important role in cognitive behavior specially in spatial learning and memory but the literature concerning the role of these receptors in hippocampus in cognition remains controversial. In the present study a 5HT(2A/2C) antagonist ritanserin (0, 2, 4, 8 microg/0.5 microl) and a 5HT(3) antagonist granisetron (0.0, 0.05, 0.25, 0.5 microg/0.5 microl) were injected bilaterally into the CA1 region of rat hippocampus, 20 min before each training session in Morris Water Maze (MWM) task. Compare with control group, ritanserin (4 microg/0.5 microl) significantly reduced the escape latency and traveled distance of swimming to platform, but granisetron (0.25 microg/0.5 microl) significantly increased those parameters. Both drugs had no effect on escape latency and traveled distance of a non-spatial visual discrimination task. These results suggest a differential role of 5HT(2A/2C) and 5HT(3) receptors during spatial learning that ritanserin improves rat performance in spatial discrimination task whereas granisetron impairs it.

  7. Modulating the rate and rhythmicity of perceptual rivalry alternations with the mixed 5-HT2A and 5-HT1A agonist psilocybin.

    PubMed

    Carter, Olivia L; Pettigrew, John D; Hasler, Felix; Wallis, Guy M; Liu, Guang B; Hell, Daniel; Vollenweider, Franz X

    2005-06-01

    Binocular rivalry occurs when different images are presented simultaneously to corresponding points within the left and right eyes. Under these conditions, the observer's perception will alternate between the two perceptual alternatives. Motivated by the reported link between the rate of perceptual alternations, symptoms of psychosis and an incidental observation that the rhythmicity of perceptual alternations during binocular rivalry was greatly increased 10 h after the consumption of LSD, this study aimed to investigate the pharmacology underlying binocular rivalry and to explore the connection between the timing of perceptual switching and psychosis. Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine, PY) was chosen for the study because, like LSD, it is known to act as an agonist at serotonin (5-HT)1A and 5-HT2A receptors and to produce an altered state sometimes marked by psychosis-like symptoms. A total of 12 healthy human volunteers were tested under placebo, low-dose (115 microg/kg) and high-dose (250 microg/kg) PY conditions. In line with predictions, under both low- and high-dose conditions, the results show that at 90 min postadministration (the peak of drug action), rate and rhythmicity of perceptual alternations were significantly reduced from placebo levels. Following the 90 min testing period, the perceptual switch rate successively increased, with some individuals showing increases well beyond pretest levels at the final testing, 360 min postadministration. However, as some subjects had still not returned to pretest levels by this time, the mean phase duration at 360 min was not found to differ significantly from placebo. Reflecting the drug-induced changes in rivalry phase durations, subjects showed clear changes in psychological state as indexed by the 5D-ASC (altered states of consciousness) rating scales. This study suggests the involvement of serotonergic pathways in binocular rivalry and supports the previously proposed role of a brainstem

  8. Clonidine potentiates the effects of 5-HT1A, 5-HT1B and 5-HT2A/2C antagonists and 8-OH-DPAT in the mouse forced swimming test.

    PubMed

    Redrobe, J P; Bourin, M

    1998-08-01

    The present study was undertaken to identify the receptor subtypes involved in clonidine's ability to enhance the effects of antidepressant drugs in the mouse forced swimming test. Clonidine (0.06 mg/kg, i.p.) significantly enhanced the antidepressant-like effects of subactive doses of the 5-HT1A receptor agonist, 8-OH-DPAT (1 mg/kg, i.p.; P<0.01); the 5-HT1A receptor antagonist, NAN 190 (0.5 mg/kg, i.p.; P<0.01); the 5-HT1A/1B autoreceptor antagonist, (+/-) pindolol (32 mg/kg, i.p.; P<0.01); the 5-HT2A/2C receptor antagonist, ritanserin (4 mg/kg, i.p.; P<0.01). Pretreatment with clonidine failed to increase mobility when administered in combination with the 5-HT1B receptor agonist, RU 24969 (1 mg/kg, i.p.) or the 5-HT2A receptor antagonist, ketanserin (8 mg/kg, i.p.). In conclusion, clonidine-induced anti-immobility effects are more likely mediated by 5-HT1A and 5-HT2C receptors, as well as alpha-2-adrenergic autoreceptors situated on noradrenergic neurones. The results of the present study also demonstrate that serotonergic receptor function can influence alpha-2-adrenoreceptor mediated responses in the mouse forced swimming test.

  9. The Relationship Between Single Nucleotide Polymorphisms in 5-HT2A Signal Transduction-Related Genes and the Response Efficacy to Selective Serotonin Reuptake Inhibitor Treatments in Chinese Patients with Major Depressive Disorder

    PubMed Central

    Li, Heng-Fen; Yu, Xue; He, Cha-Ye; Kou, Shao-Jie; Cao, Su-Xia

    2012-01-01

    Objective: To explore the possible relationship between six single nucleotide polymorphisms (SNPs) (rs6311 and rs6305 of 5-HT2A, rs5443 of Gβ3, rs2230739 of ACDY9, rs1549870 of PDE1A and rs255163 of CREB1, which are all related with 5-HT2A the signal transduction pathway) and the response efficacy to selective serotonin reuptake inhibitor (SSRI) treatments in major depressive disorder (MDD) Chinese. Methods: This study included 194 depressed patients to investigate the influence of 6 polymorphisms in 5-HT2A signal transduction-related genes on the efficacy of SSRIs assessed over 1 year. The efficacies of SSRIs on 194 MDD patients were evaluated in an 8-week open-trial study. Over 1 year, a follow-up study was completed for 174 of them to observe the long-term efficacy of SSRIs. The optimal-scaling regression analysis was used for testing the relationship between the different genotypes of five SNPs and the efficacy in MDD. Results: It showed that the patients with rs5443TT and rs2230739GG have a relatively good efficacy in response to short-term SSRIs. We also found that good efficacy appeared in depressed patients with rs2230739GG in response to long-term SSRIs. Conclusions: It suggested that different genotypes of rs5443 and rs2230739 might influence the signal transduction pathways of second message and affect therapeutic efficacy. PMID:22480177

  10. Brain structures implicated in the four-plate test in naïve and experienced Swiss mice using injection of diazepam and the 5-HT2A agonist DOI.

    PubMed

    Petit-Demoulière, Benoit; Massé, Fabienne; Cogrel, Nicolas; Hascoët, Martine; Bourin, Michel

    2009-12-01

    Four-plate test-retest (FPT-R) is a useful tool to study aversive memory and abolishment of benzodiazepine effects in experienced mice to four-plate test (FPT), namely one-trial tolerance. In the present study, we have used local injections paradigm, in order to localize structures implied in anxiolytic-like effects of two drugs in naïve and experienced mice: a benzodiazepine, diazepam that is only active in naïve mice; and a 5-HT(2A/2C) agonist, DOI that exert its anxiolytic-like effect both in naïve and experienced mice. Periacqueductal grey substance, three sub-regions of hippocampus (CA1, CA2 and CA3) and two nuclei of amygdala (BLA and LA) have been studied. Local injections did not cause any modifications of ambulatory activity. DOI injections elicit anxiolytic-like effects only when injected into CA2, in naïve and experienced mice. Diazepam had an anxiolytic-like effect in naïve mice, only when injected into lateral nucleus of amygdala; and in experienced mice when injected into PAG. These results help us to better understand the way of action of these two compounds and the structures functionally involved in their effects and in one-trial tolerance (OTT).

  11. 5-Hydroxytryptamine 2A receptor signaling cascade modulates adiponectin and plasminogen activator inhibitor 1 expression in adipose tissue.

    PubMed

    Uchida-Kitajima, Shoko; Yamauchi, Toshimasa; Takashina, Youko; Okada-Iwabu, Miki; Iwabu, Masato; Ueki, Kohjiro; Kadowaki, Takashi

    2008-09-01

    Knowledge of the regulatory factors associated with down-regulation of adiponectin gene expression and up-regulation of PAI-1 gene expression is crucial to understand the pathophysiological basis of obesity and metabolic diseases, and could establish new treatment strategies for these conditions. We showed that expression of 5-HT(2A) receptors was up-regulated in hypertrophic 3T3-L1 adipocytes, which exhibited decreased expression of adiponectin and increased expression of PAI-1. 5-HT(2A) receptor antagonists and suppression of 5-HT(2A) receptor gene expression enhanced adiponectin expression. Activation of Gq negatively regulated adiponectin expression, and inhibition of mitogen-activated protein kinase reversed the Gq-induced effect. Moreover, the 5-HT(2A) receptor blockade reduced PAI-1 expression. These findings indicate that antagonism of 5-HT(2A) receptors in adipocytes could improve the obesity-linked decreases in adiponectin expression and increases in PAI-1 expression.

  12. Regulation of rat cortical 5-hydroxytryptamine2A-receptor mediated electrophysiological responses by repeated daily treatment with electroconvulsive shock or imipramine

    PubMed Central

    Marek, Gerard J.

    2008-01-01

    Down-regulation of 5-hydroxytryptamine2A (5-HT2A) receptors has been a consistent effect induced by most antidepressant drugs. In contrast, electroconvulsive shock (ECS) up-regulates the number of 5-HT2A receptor binding sites. However, the effects of antidepressants on 5-HT2A receptor-mediated responses on identified cells of the cerebral cortex has not been examined. The purpose of the present study was to compare the effects of the tricyclic antidepressant imipramine and ECS on 5-HT2A receptor-mediated electrophysiological responses involving glutamatergic and GABAergic neurotransmission in the rat medial prefrontal cortex (mPFC) and piriform cortex, respectively. The electrophysiological effects of activating 5-HT2A receptors was consistent with 5-HT2A receptor binding regulation for imipramine and ECS except for the mPFC where chronic ECS decreased the potency of 5-HT at a 5-HT2A receptor-mediated response. These findings are consistent with the general hypothesis that chronic antidepressant treatments shift the balance of serotonergic neurotransmission towards inhibitory effects in the cortex. PMID:18294819

  13. Regulation of rat cortical 5-hydroxytryptamine2A receptor-mediated electrophysiological responses by repeated daily treatment with electroconvulsive shock or imipramine.

    PubMed

    Marek, Gerard J

    2008-07-01

    Down-regulation of 5-hydroxytryptamine(2A) (5-HT(2A)) receptors has been a consistent effect induced by most antidepressant drugs. In contrast, electroconvulsive shock (ECS) up-regulates the number of 5-HT(2A) receptor binding sites. However, the effects of antidepressants on 5-HT(2A) receptor-mediated responses on identified cells of the cerebral cortex have not been examined. The purpose of the present study was to compare the effects of the tricyclic antidepressant imipramine and ECS on 5-HT(2A) receptor-mediated electrophysiological responses involving glutamatergic and GABAergic neurotransmission in the rat medial prefrontal cortex (mPFC) and piriform cortex, respectively. The electrophysiological effects of activating 5-HT(2A) receptors were consistent with 5-HT(2A) receptor binding regulation for imipramine and ECS except for the mPFC where chronic ECS decreased the potency of 5-HT at a 5-HT(2A) receptor-mediated response. These findings are consistent with the general hypothesis that chronic antidepressant treatments shift the balance of serotonergic neurotransmission towards inhibitory effects in the cortex.

  14. Serotonin 2a Receptor and Serotonin 1a Receptor Interact Within the Medial Prefrontal Cortex During Recognition Memory in Mice.

    PubMed

    Morici, Juan F; Ciccia, Lucia; Malleret, Gaël; Gingrich, Jay A; Bekinschtein, Pedro; Weisstaub, Noelia V

    2015-01-01

    Episodic memory, can be defined as the memory for unique events. The serotonergic system one of the main neuromodulatory systems in the brain appears to play a role in it. The serotonin 2a receptor (5-HT2aR) one of the principal post-synaptic receptors for 5-HT in the brain, is involved in neuropsychiatric and neurological disorders associated with memory deficits. Recognition memory can be defined as the ability to recognize if a particular event or item was previously encountered and is thus considered, under certain conditions, a form of episodic memory. As human data suggest that a constitutively decrease of 5-HT2A signaling might affect episodic memory performance we decided to compare the performance of mice with disrupted 5-HT2aR signaling (htr2a (-/-)) with wild type (htr2a (+/+)) littermates in different recognition memory and working memory tasks that differed in the level of proactive interference. We found that ablation of 5-HT2aR signaling throughout development produces a deficit in tasks that cannot be solved by single item strategy suggesting that 5-HT2aR signaling is involved in interference resolution. We also found that in the absence of 5-HT2aR signaling serotonin has a deleterious effect on recognition memory retrieval through the activation of 5-HT1aR in the medial prefrontal cortex. PMID:26779016

  15. 5-Hydroxytryptamine2A serotonin receptors in the primate cerebral cortex: possible site of action of hallucinogenic and antipsychotic drugs in pyramidal cell apical dendrites.

    PubMed

    Jakab, R L; Goldman-Rakic, P S

    1998-01-20

    To identify the cortical sites where 5-hydroxytryptamine2A (5-HT2A) serotonin receptors respond to the action of hallucinogens and atypical antipsychotic drugs, we have examined the cellular and subcellular distribution of these receptors in the cerebral cortex of macaque monkeys (with a focus on prefrontal areas) by using light and electron microscopic immunocytochemical techniques. 5-HT2A receptor immunoreactivity was detected in all cortical layers, among which layers II and III and layers V and VI were intensely stained, and layer IV was weakly labeled. The majority of the receptor-labeled cells were pyramidal neurons and the most intense immunolabeling was consistently confined to their parallelly aligned proximal apical dendrites that formed two intensely stained bands above and below layer IV. In double-label experiments, 5-HT2A label was found in calbindin D28k-positive, nonphosphorylated-neurofilament-positive, and immuno-negative pyramidal cells, suggesting that probably all pyramidal cells express 5-HT2A receptors. 5-HT2A label was also found in large- and medium-size interneurons, some of which were immuno-positive for calbindin. 5-HT2A receptor label was also associated with axon terminals. These findings reconcile the data on the receptor's cortical physiology and localization by (i) establishing that 5-HT2A receptors are located postsynaptically and presynaptically, (ii) demonstrating that pyramidal neurons constitute the major 5-HT2A-receptor-expressing cells in the cortex, and (iii) supporting the view that the apical dendritic field proximal to the pyramidal cell soma is the "hot spot" for 5-HT2A-receptor-mediated physiological actions relevant to normal and "psychotic" functional states of the cerebral cortex.

  16. Serotonin 2a Receptor and Serotonin 1a Receptor Interact Within the Medial Prefrontal Cortex During Recognition Memory in Mice

    PubMed Central

    Morici, Juan F.; Ciccia, Lucia; Malleret, Gaël; Gingrich, Jay A.; Bekinschtein, Pedro; Weisstaub, Noelia V.

    2015-01-01

    Episodic memory, can be defined as the memory for unique events. The serotonergic system one of the main neuromodulatory systems in the brain appears to play a role in it. The serotonin 2a receptor (5-HT2aR) one of the principal post-synaptic receptors for 5-HT in the brain, is involved in neuropsychiatric and neurological disorders associated with memory deficits. Recognition memory can be defined as the ability to recognize if a particular event or item was previously encountered and is thus considered, under certain conditions, a form of episodic memory. As human data suggest that a constitutively decrease of 5-HT2A signaling might affect episodic memory performance we decided to compare the performance of mice with disrupted 5-HT2aR signaling (htr2a−/−) with wild type (htr2a+/+) littermates in different recognition memory and working memory tasks that differed in the level of proactive interference. We found that ablation of 5-HT2aR signaling throughout development produces a deficit in tasks that cannot be solved by single item strategy suggesting that 5-HT2aR signaling is involved in interference resolution. We also found that in the absence of 5-HT2aR signaling serotonin has a deleterious effect on recognition memory retrieval through the activation of 5-HT1aR in the medial prefrontal cortex. PMID:26779016

  17. Lysergic acid diethylamide-induced Fos expression in rat brain: role of serotonin-2A receptors.

    PubMed

    Gresch, P J; Strickland, L V; Sanders-Bush, E

    2002-01-01

    Lysergic acid diethylamide (LSD) produces altered mood and hallucinations in humans and binds with high affinity to serotonin-2A (5-HT(2A)) receptors. Although LSD interacts with other receptors, the activation of 5-HT(2A) receptors is thought to mediate the hallucinogenic properties of LSD. The goal of this study was to identify the brain sites activated by LSD and to determine the influence of 5-HT(2A) receptors in this activation. Rats were pretreated with the 5-HT(2A) receptor antagonist MDL 100907 (0.3 mg/kg, i.p.) or vehicle 30 min prior to LSD (500 microg/kg, i.p.) administration and killed 3 h later. Brain tissue was examined for Fos protein expression by immunohistochemistry. LSD administration produced a five- to eight-fold increase in Fos-like immunoreactivity in medial prefrontal cortex, anterior cingulate cortex, and central nucleus of amygdala. However, in dorsal striatum and nucleus accumbens no increase in Fos-like immunoreactivity was observed. Pretreatment with MDL 100907 completely blocked LSD-induced Fos-like immunoreactivity in medial prefrontal cortex and anterior cingulate cortex, but only partially blocked LSD-induced Fos-like immunoreactivity in amygdala. Double-labeled immunohistochemistry revealed that LSD did not induce Fos-like immunoreactivity in cortical cells expressing 5-HT(2A) receptors, suggesting an indirect activation of cortical neurons. These results indicate that the LSD activation of medial prefrontal cortex and anterior cingulate cortex is mediated by 5-HT(2A) receptors, whereas in amygdala 5-HT(2A) receptor activation is a component of the response. These findings support the hypothesis that the medial prefrontal cortex, anterior cingulate cortex, and perhaps the amygdala, are important regions involved in the production of hallucinations.

  18. Presynaptic serotonin 2A receptors modulate thalamocortical plasticity and associative learning

    PubMed Central

    Barre, Alexander; Berthoux, Coralie; De Bundel, Dimitri; Valjent, Emmanuel; Bockaert, Joël; Marin, Philippe; Bécamel, Carine

    2016-01-01

    Higher-level cognitive processes strongly depend on a complex interplay between mediodorsal thalamus nuclei and the prefrontal cortex (PFC). Alteration of thalamofrontal connectivity has been involved in cognitive deficits of schizophrenia. Prefrontal serotonin (5-HT)2A receptors play an essential role in cortical network activity, but the mechanism underlying their modulation of glutamatergic transmission and plasticity at thalamocortical synapses remains largely unexplored. Here, we show that 5-HT2A receptor activation enhances NMDA transmission and gates the induction of temporal-dependent plasticity mediated by NMDA receptors at thalamocortical synapses in acute PFC slices. Expressing 5-HT2A receptors in the mediodorsal thalamus (presynaptic site) of 5-HT2A receptor-deficient mice, but not in the PFC (postsynaptic site), using a viral gene-delivery approach, rescued the otherwise absent potentiation of NMDA transmission, induction of temporal plasticity, and deficit in associative memory. These results provide, to our knowledge, the first physiological evidence of a role of presynaptic 5-HT2A receptors located at thalamocortical synapses in the control of thalamofrontal connectivity and the associated cognitive functions. PMID:26903620

  19. Quantitative phosphoproteomics unravels biased phosphorylation of serotonin 2A receptor at Ser280 by hallucinogenic versus nonhallucinogenic agonists.

    PubMed

    Karaki, Samah; Becamel, Carine; Murat, Samy; Mannoury la Cour, Clotilde; Millan, Mark J; Prézeau, Laurent; Bockaert, Joël; Marin, Philippe; Vandermoere, Franck

    2014-05-01

    The serotonin 5-HT(2A) receptor is a primary target of psychedelic hallucinogens such as lysergic acid diethylamine, mescaline, and psilocybin, which reproduce some of the core symptoms of schizophrenia. An incompletely resolved paradox is that only some 5-HT(2A) receptor agonists exhibit hallucinogenic activity, whereas structurally related agonists with comparable affinity and activity lack such a psychoactive activity. Using a strategy combining stable isotope labeling by amino acids in cell culture with enrichment in phosphorylated peptides by means of hydrophilic interaction liquid chromatography followed by immobilized metal affinity chromatography, we compared the phosphoproteome in HEK-293 cells transiently expressing the 5-HT(2A) receptor and exposed to either vehicle or the synthetic hallucinogen 1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane (DOI) or the nonhallucinogenic 5-HT(2A) agonist lisuride. Among the 5995 identified phosphorylated peptides, 16 sites were differentially phosphorylated upon exposure of cells to DOI versus lisuride. These include a serine (Ser(280)) located in the third intracellular loop of the 5-HT(2A) receptor, a region important for its desensitization. The specific phosphorylation of Ser(280) by hallucinogens was further validated by quantitative mass spectrometry analysis of immunopurified receptor digests and by Western blotting using a phosphosite specific antibody. The administration of DOI, but not of lisuride, to mice, enhanced the phosphorylation of 5-HT(2A) receptors at Ser(280) in the prefrontal cortex. Moreover, hallucinogens induced a less pronounced desensitization of receptor-operated signaling in HEK-293 cells and neurons than did nonhallucinogenic agonists. The mutation of Ser(280) to aspartic acid (to mimic phosphorylation) reduced receptor desensitization by nonhallucinogenic agonists, whereas its mutation to alanine increased the ability of hallucinogens to desensitize the receptor. This study reveals a biased

  20. Quantitative Phosphoproteomics Unravels Biased Phosphorylation of Serotonin 2A Receptor at Ser280 by Hallucinogenic versus Nonhallucinogenic Agonists*

    PubMed Central

    Karaki, Samah; Becamel, Carine; Murat, Samy; Mannoury la Cour, Clotilde; Millan, Mark J.; Prézeau, Laurent; Bockaert, Joël; Marin, Philippe; Vandermoere, Franck

    2014-01-01

    The serotonin 5-HT2A receptor is a primary target of psychedelic hallucinogens such as lysergic acid diethylamine, mescaline, and psilocybin, which reproduce some of the core symptoms of schizophrenia. An incompletely resolved paradox is that only some 5-HT2A receptor agonists exhibit hallucinogenic activity, whereas structurally related agonists with comparable affinity and activity lack such a psychoactive activity. Using a strategy combining stable isotope labeling by amino acids in cell culture with enrichment in phosphorylated peptides by means of hydrophilic interaction liquid chromatography followed by immobilized metal affinity chromatography, we compared the phosphoproteome in HEK-293 cells transiently expressing the 5-HT2A receptor and exposed to either vehicle or the synthetic hallucinogen 1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane (DOI) or the nonhallucinogenic 5-HT2A agonist lisuride. Among the 5995 identified phosphorylated peptides, 16 sites were differentially phosphorylated upon exposure of cells to DOI versus lisuride. These include a serine (Ser280) located in the third intracellular loop of the 5-HT2A receptor, a region important for its desensitization. The specific phosphorylation of Ser280 by hallucinogens was further validated by quantitative mass spectrometry analysis of immunopurified receptor digests and by Western blotting using a phosphosite specific antibody. The administration of DOI, but not of lisuride, to mice, enhanced the phosphorylation of 5-HT2A receptors at Ser280 in the prefrontal cortex. Moreover, hallucinogens induced a less pronounced desensitization of receptor-operated signaling in HEK-293 cells and neurons than did nonhallucinogenic agonists. The mutation of Ser280 to aspartic acid (to mimic phosphorylation) reduced receptor desensitization by nonhallucinogenic agonists, whereas its mutation to alanine increased the ability of hallucinogens to desensitize the receptor. This study reveals a biased phosphorylation of

  1. G-protein Receptor Kinase 5 Regulates the Cannabinoid Receptor 2-induced Up-regulation of Serotonin 2A Receptors*

    PubMed Central

    Franklin, Jade M.; Carrasco, Gonzalo A.

    2013-01-01

    We have recently reported that cannabinoid agonists can up-regulate and enhance the activity of serotonin 2A (5-HT2A) receptors in the prefrontal cortex (PFCx). Increased expression and activity of cortical 5-HT2A receptors has been associated with neuropsychiatric disorders, such as anxiety and schizophrenia. Here we report that repeated CP55940 exposure selectively up-regulates GRK5 proteins in rat PFCx and in a neuronal cell culture model. We sought to examine the mechanism underlying the regulation of GRK5 and to identify the role of GRK5 in the cannabinoid agonist-induced up-regulation and enhanced activity of 5-HT2A receptors. Interestingly, we found that cannabinoid agonist-induced up-regulation of GRK5 involves CB2 receptors, β-arrestin 2, and ERK1/2 signaling because treatment with CB2 shRNA lentiviral particles, β-arrestin 2 shRNA lentiviral particles, or ERK1/2 inhibitor prevented the cannabinoid agonist-induced up-regulation of GRK5. Most importantly, we found that GRK5 shRNA lentiviral particle treatment prevented the cannabinoid agonist-induced up-regulation and enhanced 5-HT2A receptor-mediated calcium release. Repeated cannabinoid exposure was also associated with enhanced phosphorylation of CB2 receptors and increased interaction between β-arrestin 2 and ERK1/2. These latter phenomena were also significantly inhibited by GRK5 shRNA lentiviral treatment. Our results suggest that sustained activation of CB2 receptors, which up-regulates 5-HT2A receptor signaling, enhances GRK5 expression; the phosphorylation of CB2 receptors; and the β-arrestin 2/ERK interactions. These data could provide a rationale for some of the adverse effects associated with repeated cannabinoid agonist exposure. PMID:23592773

  2. Serotonin 2A receptor agonist binding in the human brain with [11C]Cimbi-36

    PubMed Central

    Ettrup, Anders; da Cunha-Bang, Sophie; McMahon, Brenda; Lehel, Szabolcs; Dyssegaard, Agnete; Skibsted, Anine W; Jørgensen, Louise M; Hansen, Martin; Baandrup, Anders O; Bache, Søren; Svarer, Claus; Kristensen, Jesper L; Gillings, Nic; Madsen, Jacob; Knudsen, Gitte M

    2014-01-01

    [11C]Cimbi-36 was recently developed as a selective serotonin 2A (5-HT2A) receptor agonist radioligand for positron emission tomography (PET) brain imaging. Such an agonist PET radioligand may provide a novel, and more functional, measure of the serotonergic system and agonist binding is more likely than antagonist binding to reflect 5-HT levels in vivo. Here, we show data from a first-in-human clinical trial with [11C]Cimbi-36. In 29 healthy volunteers, we found high brain uptake and distribution according to 5-HT2A receptors with [11C]Cimbi-36 PET. The two-tissue compartment model using arterial input measurements provided the most optimal quantification of cerebral [11C]Cimbi-36 binding. Reference tissue modeling was feasible as it induced a negative but predictable bias in [11C]Cimbi-36 PET outcome measures. In five subjects, pretreatment with the 5-HT2A receptor antagonist ketanserin before a second PET scan significantly decreased [11C]Cimbi-36 binding in all cortical regions with no effects in cerebellum. These results confirm that [11C]Cimbi-36 binding is selective for 5-HT2A receptors in the cerebral cortex and that cerebellum is an appropriate reference tissue for quantification of 5-HT2A receptors in the human brain. Thus, we here describe [11C]Cimbi-36 as the first agonist PET radioligand to successfully image and quantify 5-HT2A receptors in the human brain. PMID:24780897

  3. Genetic dysfunction of serotonin 2A receptor hampers response to antidepressant drugs: A translational approach.

    PubMed

    Qesseveur, Gaël; Petit, Anne Cécile; Nguyen, Hai Thanh; Dahan, Lionel; Colle, Romain; Rotenberg, Samuel; Seif, Isabelle; Robert, Pauline; David, Denis; Guilloux, Jean-Philippe; Gardier, Alain M; Verstuyft, Céline; Becquemont, Laurent; Corruble, Emmanuelle; Guiard, Bruno P

    2016-06-01

    Pharmacological studies have yielded valuable insights into the role of the serotonin 2A (5-HT2A) receptor in major depressive disorder (MDD) and antidepressant drugs (ADs) response. However, it is still unknown whether genetic variants in the HTR2A gene affect the therapeutic outcome of ADs and the mechanism underlying the regulation of such response remains poorly described. In this context, a translational human-mouse study offers a unique opportunity to address the possibility that variations in the HTR2A gene may represent a relevant marker to predict the efficacy of ADs. In a first part of this study, we investigated in depressed patients the effect of three HTR2A single nucleotide polymorphisms (SNPs), selected for their potential functional consequences on 5-HT2A receptor (rs6313, rs6314 and rs7333412), on response and remission rates after 3 months of antidepressant treatments. We also explored the consequences of the constitutive genetic inactivation of the 5-HT2A receptor (i.e. in 5-HT2A(-/-) mice) on the activity of acute and prolonged administration of SSRIs. Our clinical data indicate that GG patients for the rs7333412 SNP were less prone to respond to ADs than AA/AG patients. In the preclinical study, we demonstrated that the 5-HT2A receptor exerts an inhibitory influence on the neuronal activity of the serotonergic system after acute administration of SSRIs. However, while the chronic administration of the SSRIs escitalopram or fluoxetine elicited a progressive increased in the firing rate of 5-HT neurons in 5-HT2A(+/+) mice, it failed to do so in 5-HT2A(-/-) mutants. These electrophysiological impairments were associated with a decreased ability of the chronic administration of fluoxetine to stimulate hippocampal plasticity and to produce antidepressant-like activities. Genetic loss of the 5-HT2A receptor compromised the activity of chronic treatment with SSRIs, making this receptor a putative marker to predict ADs response. PMID:26764241

  4. Activation of serotonin 2A receptors underlies the psilocybin-induced effects on α oscillations, N170 visual-evoked potentials, and visual hallucinations.

    PubMed

    Kometer, Michael; Schmidt, André; Jäncke, Lutz; Vollenweider, Franz X

    2013-06-19

    Visual illusions and hallucinations are hallmarks of serotonergic hallucinogen-induced altered states of consciousness. Although the serotonergic hallucinogen psilocybin activates multiple serotonin (5-HT) receptors, recent evidence suggests that activation of 5-HT2A receptors may lead to the formation of visual hallucinations by increasing cortical excitability and altering visual-evoked cortical responses. To address this hypothesis, we assessed the effects of psilocybin (215 μg/kg vs placebo) on both α oscillations that regulate cortical excitability and early visual-evoked P1 and N170 potentials in healthy human subjects. To further disentangle the specific contributions of 5-HT2A receptors, subjects were additionally pretreated with the preferential 5-HT2A receptor antagonist ketanserin (50 mg vs placebo). We found that psilocybin strongly decreased prestimulus parieto-occipital α power values, thus precluding a subsequent stimulus-induced α power decrease. Furthermore, psilocybin strongly decreased N170 potentials associated with the appearance of visual perceptual alterations, including visual hallucinations. All of these effects were blocked by pretreatment with the 5-HT2A antagonist ketanserin, indicating that activation of 5-HT2A receptors by psilocybin profoundly modulates the neurophysiological and phenomenological indices of visual processing. Specifically, activation of 5-HT2A receptors may induce a processing mode in which stimulus-driven cortical excitation is overwhelmed by spontaneous neuronal excitation through the modulation of α oscillations. Furthermore, the observed reduction of N170 visual-evoked potentials may be a key mechanism underlying 5-HT2A receptor-mediated visual hallucinations. This change in N170 potentials may be important not only for psilocybin-induced states but also for understanding acute hallucinatory states seen in psychiatric disorders, such as schizophrenia and Parkinson's disease. PMID:23785166

  5. Activation of serotonin 2A receptors underlies the psilocybin-induced effects on α oscillations, N170 visual-evoked potentials, and visual hallucinations.

    PubMed

    Kometer, Michael; Schmidt, André; Jäncke, Lutz; Vollenweider, Franz X

    2013-06-19

    Visual illusions and hallucinations are hallmarks of serotonergic hallucinogen-induced altered states of consciousness. Although the serotonergic hallucinogen psilocybin activates multiple serotonin (5-HT) receptors, recent evidence suggests that activation of 5-HT2A receptors may lead to the formation of visual hallucinations by increasing cortical excitability and altering visual-evoked cortical responses. To address this hypothesis, we assessed the effects of psilocybin (215 μg/kg vs placebo) on both α oscillations that regulate cortical excitability and early visual-evoked P1 and N170 potentials in healthy human subjects. To further disentangle the specific contributions of 5-HT2A receptors, subjects were additionally pretreated with the preferential 5-HT2A receptor antagonist ketanserin (50 mg vs placebo). We found that psilocybin strongly decreased prestimulus parieto-occipital α power values, thus precluding a subsequent stimulus-induced α power decrease. Furthermore, psilocybin strongly decreased N170 potentials associated with the appearance of visual perceptual alterations, including visual hallucinations. All of these effects were blocked by pretreatment with the 5-HT2A antagonist ketanserin, indicating that activation of 5-HT2A receptors by psilocybin profoundly modulates the neurophysiological and phenomenological indices of visual processing. Specifically, activation of 5-HT2A receptors may induce a processing mode in which stimulus-driven cortical excitation is overwhelmed by spontaneous neuronal excitation through the modulation of α oscillations. Furthermore, the observed reduction of N170 visual-evoked potentials may be a key mechanism underlying 5-HT2A receptor-mediated visual hallucinations. This change in N170 potentials may be important not only for psilocybin-induced states but also for understanding acute hallucinatory states seen in psychiatric disorders, such as schizophrenia and Parkinson's disease.

  6. Antidepressant, Antipsychotic, and Hallucinogen Drugs for the Treatment of Psychiatric Disorders: A Convergence at the Serotonin-2A Receptor.

    PubMed

    Howland, Robert H

    2016-07-01

    Antidepressant, atypical antipsychotic, and hallucinogen drugs mediate their actions in part by interactions with the serotonin-2A (5HT2A) receptor. Serotonergic hallucinogen drugs, such as psilocybin, bind most potently as agonists at the 5HT2A receptor, producing profound changes in perception, mood, and cognition. Some of these drugs have been or are currently being investigated in small Phase 2 studies for depression, alcoholism, smoking cessation, anxiety, and posttraumatic stress disorder. However, unlike the synergistic effects of combining antidepressant and atypical antipsychotic drugs, the potential therapeutic effects of hallucinogen drugs may be attenuated by the concurrent use of these medications because antidepressant and atypical antipsychotic drugs desensitize and/or down-regulate 5HT2A receptors. This finding has important implications for optimizing the potential therapeutic use of hallucinogen drugs in psychiatry. [Journal of Psychosocial Nursing and Mental Health Services, 54(7), 21-24.]. PMID:27362381

  7. Structure and function of the third intracellular loop of the 5-hydroxytryptamine2A receptor: the third intracellular loop is alpha-helical and binds purified arrestins.

    PubMed

    Gelber, E I; Kroeze, W K; Willins, D L; Gray, J A; Sinar, C A; Hyde, E G; Gurevich, V; Benovic, J; Roth, B L

    1999-05-01

    Understanding the precise structure and function of the intracellular domains of G protein-coupled receptors is essential for understanding how receptors are regulated, and how they transduce their signals from the extracellular milieu to intracellular sites. To understand better the structure and function of the intracellular domain of the 5-hydroxytryptamine2A (5-HT2A) receptor, a model G(alpha)q-coupled receptor, we overexpressed and purified to homogeneity the entire third intracellular loop (i3) of the 5-HT2A receptor, a region previously implicated in G-protein coupling. Circular dichroism spectroscopy of the purified i3 protein was consistent with alpha-helical and beta-loop, -turn, and -sheet structure. Using random peptide phage libraries, we identified several arrestin-like sequences as i3-interacting peptides. We subsequently found that all three known arrestins (beta-arrestin, arrestin-3, and visual arrestin) bound specifically to fusion proteins encoding the i3 loop of the 5-HT(2A) receptor. Competition binding studies with synthetic and recombinant peptides showed that the middle portion of the i3 loop, and not the extreme N and C termini, was likely to be involved in i3-arrestin interactions. Dual-label immunofluorescence confocal microscopic studies of rat cortex indicated that many cortical pyramidal neurons coexpressed arrestins (beta-arrestin or arrestin-3) and 5-HT2A receptors, particularly in intracellular vesicles. Our results demonstrate (a) that the i3 loop of the 5-HT2A receptor represents a structurally ordered domain composed of alpha-helical and beta-loop, -turn, and -sheet regions, (b) that this loop interacts with arrestins in vitro, and is hence active, and (c) that arrestins are colocalized with 5-HT2A receptors in vivo.

  8. Serotonin 2A and 2B receptor-induced phrenic motor facilitation: differential requirement for spinal NADPH oxidase activity

    PubMed Central

    MacFarlane, P.M.; Vinit, S.; Mitchell, G.S.

    2011-01-01

    Acute intermittent hypoxia (AIH) facilitates phrenic motor output by a mechanism that requires spinal serotonin (type 2) receptor activation, NADPH oxidase activity and formation of reactive oxygen species (ROS). Episodic spinal serotonin (5-HT) receptor activation alone, without changes in oxygenation, is sufficient to elicit NADPH oxidase-dependent phrenic motor facilitation (pMF). Here we investigated: 1) whether serotonin 2A and/or 2B (5-HT2a/b) receptors are expressed in identified phrenic motor neurons, and 2) which receptor subtype is capable of eliciting NADPH-oxidase-dependent pMF. In anesthetized, artificially ventilated adult rats, episodic C4 intrathecal injections (3 × 6µl injections, 5 min intervals) of a 5-HT2a (DOI) or 5-HT2b (BW723C86) receptor agonist elicited progressive and sustained increases in integrated phrenic nerve burst amplitude (i.e. pMF), an effect lasting at least 90 minutes post-injection for both receptor subtypes. 5-HT2a and 5-HT2b receptor agonist-induced pMF were both blocked by selective antagonists (ketanserin and SB206553, respectively), but not by antagonists to the other receptor subtype. Single injections of either agonist failed to elicit pMF, demonstrating a need for episodic receptor activation. Phrenic motor neurons retrogradely labeled with cholera toxin B fragment expressed both 5-HT2a and 5-HT2b receptors. Pre-treatment with NADPH oxidase inhibitors (apocynin and DPI) blocked 5-HT2b, but not 5-HT2a-induced pMF. Thus, multiple spinal type 2 serotonin receptors elicit pMF, but they act via distinct mechanisms that differ in their requirement for NADPH oxidase activity. PMID:21223996

  9. Dorsal prefrontal cortical serotonin 2A receptor binding indices are differentially related to individual scores on harm avoidance.

    PubMed

    Baeken, Chris; Bossuyt, Axel; De Raedt, Rudi

    2014-02-28

    Although the serotonergic system has been implicated in healthy as well as in pathological emotional states, knowledge about its involvement in personality is limited. Earlier research on this topic suggests that post-synaptic 5-HT2A receptors could be involved in particular in frontal cortical areas. In drug-naïve healthy individuals, we examined the relationship between these 5-HT2A receptors and the temperament dimension harm avoidance (HA) using 123I-5-I-R91150 single photon emission computed tomography (SPECT). HA is a personality feature closely related to stress, anxiety and depression proneness, and it is thought to be mediated by the serotonergic system. We focused on the prefrontal cortices as these regions are frequently implicated in cognitive processes related to a variety of affective disorders. We found a positive relationship between dorsal prefrontal cortical (DPFC) 5-HT2A receptor binding indices (BI) and individual HA scores. Further, our results suggest that those individuals with a tendency to worry or to ruminate are particularly prone to display significantly higher 5-HT2A receptor BI in the left DPFC. Although we only examined psychologically healthy individuals, this relationship suggests a possible vulnerability for affective disorders. PMID:24412555

  10. Inhibition of alpha oscillations through serotonin-2A receptor activation underlies the visual effects of ayahuasca in humans.

    PubMed

    Valle, Marta; Maqueda, Ana Elda; Rabella, Mireia; Rodríguez-Pujadas, Aina; Antonijoan, Rosa Maria; Romero, Sergio; Alonso, Joan Francesc; Mañanas, Miquel Àngel; Barker, Steven; Friedlander, Pablo; Feilding, Amanda; Riba, Jordi

    2016-07-01

    Ayahuasca is an Amazonian psychotropic plant tea typically obtained from two plants, Banisteriopsis caapi and Psychotria viridis. It contains the psychedelic 5-HT2A and sigma-1 agonist N,N-dimethyltryptamine (DMT) plus β-carboline alkaloids with monoamine-oxidase (MAO)-inhibiting properties. Although the psychoactive effects of ayahuasca have commonly been attributed solely to agonism at the 5-HT2A receptor, the molecular target of classical psychedelics, this has not been tested experimentally. Here we wished to study the contribution of the 5-HT2A receptor to the neurophysiological and psychological effects of ayahuasca in humans. We measured drug-induced changes in spontaneous brain oscillations and subjective effects in a double-blind randomized placebo-controlled study involving the oral administration of ayahuasca (0.75mg DMT/kg body weight) and the 5-HT2A antagonist ketanserin (40mg). Twelve healthy, experienced psychedelic users (5 females) participated in four experimental sessions in which they received the following drug combinations: placebo+placebo, placebo+ayahuasca, ketanserin+placebo and ketanserin+ayahuasca. Ayahuasca induced EEG power decreases in the delta, theta and alpha frequency bands. Current density in alpha-band oscillations in parietal and occipital cortex was inversely correlated with the intensity of visual imagery induced by ayahuasca. Pretreatment with ketanserin inhibited neurophysiological modifications, reduced the correlation between alpha and visual effects, and attenuated the intensity of the subjective experience. These findings suggest that despite the chemical complexity of ayahuasca, 5-HT2A activation plays a key role in the neurophysiological and visual effects of ayahuasca in humans. PMID:27039035

  11. Inhibition of alpha oscillations through serotonin-2A receptor activation underlies the visual effects of ayahuasca in humans.

    PubMed

    Valle, Marta; Maqueda, Ana Elda; Rabella, Mireia; Rodríguez-Pujadas, Aina; Antonijoan, Rosa Maria; Romero, Sergio; Alonso, Joan Francesc; Mañanas, Miquel Àngel; Barker, Steven; Friedlander, Pablo; Feilding, Amanda; Riba, Jordi

    2016-07-01

    Ayahuasca is an Amazonian psychotropic plant tea typically obtained from two plants, Banisteriopsis caapi and Psychotria viridis. It contains the psychedelic 5-HT2A and sigma-1 agonist N,N-dimethyltryptamine (DMT) plus β-carboline alkaloids with monoamine-oxidase (MAO)-inhibiting properties. Although the psychoactive effects of ayahuasca have commonly been attributed solely to agonism at the 5-HT2A receptor, the molecular target of classical psychedelics, this has not been tested experimentally. Here we wished to study the contribution of the 5-HT2A receptor to the neurophysiological and psychological effects of ayahuasca in humans. We measured drug-induced changes in spontaneous brain oscillations and subjective effects in a double-blind randomized placebo-controlled study involving the oral administration of ayahuasca (0.75mg DMT/kg body weight) and the 5-HT2A antagonist ketanserin (40mg). Twelve healthy, experienced psychedelic users (5 females) participated in four experimental sessions in which they received the following drug combinations: placebo+placebo, placebo+ayahuasca, ketanserin+placebo and ketanserin+ayahuasca. Ayahuasca induced EEG power decreases in the delta, theta and alpha frequency bands. Current density in alpha-band oscillations in parietal and occipital cortex was inversely correlated with the intensity of visual imagery induced by ayahuasca. Pretreatment with ketanserin inhibited neurophysiological modifications, reduced the correlation between alpha and visual effects, and attenuated the intensity of the subjective experience. These findings suggest that despite the chemical complexity of ayahuasca, 5-HT2A activation plays a key role in the neurophysiological and visual effects of ayahuasca in humans.

  12. Serotonin 2A Receptors in Obsessive-Compulsive Disorder: a Positron Emission Tomography Study with [11C]MDL 100907

    PubMed Central

    Simpson, H. Blair; Slifstein, Mark; Bender, James; Xu, Xiaoyan; Hackett, Elizabeth; Maher, Michael J.; Abi-Dargham, Anissa

    2014-01-01

    Background Serotonergic abnormalities are hypothesized to contribute to obsessive-compulsive disorder (OCD). This study used positron emission tomography (PET) with the radioligand [11C]MDL 100907 to examine whether the distribution of one of the serotonin receptors, the 5-HT2A receptor, is altered in OCD. Methods Nineteen OCD subjects, free of psychiatric medications and depression, and 19 matched healthy controls underwent PET scans following injection of [11C]MDL 100907. Total distribution volumes (VT) were derived by kinetic analysis using the arterial input function. Two measures of 5-HT2A availability were computed (BPND and BPP). Groups were compared using a region of interest (ROI) analysis and voxelwise analysis of spatially normalized parametric maps. ROIs included cortical regions (orbitofrontal, dorsolateral prefrontal, medial prefrontal, anterior cingulate, temporal, parietal, occipital, and insular cortex) and limbic regions (entorhinal cortex, parahippocampal gyrus, and medial temporal lobe). Results No significant group differences were observed in [11C]MDL 100907 BPND or BPP in the ROIs or in the voxelwise analysis of BPND maps. There was a significant correlation in the orbitofrontal cortex between [11C] MDL 100907 binding and age of onset, with earlier age of onset associated with higher binding. Conclusions In contrast to prior reports, people with OCD (free of psychiatric medications and depression) are not characterized as a group by major changes in 5-HT2A availability in cortical or limbic brain regions. Further research is warranted to examine potential differences in 5-HT2A availability between early and late onset OCD and to assess 5-HT2A function in relation to other neurotransmitter systems implicated in OCD. PMID:21855857

  13. Effects of serotonin 2A/1A receptor stimulation on social exclusion processing.

    PubMed

    Preller, Katrin H; Pokorny, Thomas; Hock, Andreas; Kraehenmann, Rainer; Stämpfli, Philipp; Seifritz, Erich; Scheidegger, Milan; Vollenweider, Franz X

    2016-05-01

    Social ties are crucial for physical and mental health. However, psychiatric patients frequently encounter social rejection. Moreover, an increased reactivity to social exclusion influences the development, progression, and treatment of various psychiatric disorders. Nevertheless, the neuromodulatory substrates of rejection experiences are largely unknown. The preferential serotonin (5-HT) 2A/1A receptor agonist, psilocybin (Psi), reduces the processing of negative stimuli, but whether 5-HT2A/1A receptor stimulation modulates the processing of negative social interactions remains unclear. Therefore, this double-blind, randomized, counterbalanced, cross-over study assessed the neural response to social exclusion after the acute administration of Psi (0.215 mg/kg) or placebo (Pla) in 21 healthy volunteers by using functional magnetic resonance imaging (fMRI) and resting-state magnetic resonance spectroscopy (MRS). Participants reported a reduced feeling of social exclusion after Psi vs. Pla administration, and the neural response to social exclusion was decreased in the dorsal anterior cingulate cortex (dACC) and the middle frontal gyrus, key regions for social pain processing. The reduced neural response in the dACC was significantly correlated with Psi-induced changes in self-processing and decreased aspartate (Asp) content. In conclusion, 5-HT2A/1A receptor stimulation with psilocybin seems to reduce social pain processing in association with changes in self-experience. These findings may be relevant to the normalization of negative social interaction processing in psychiatric disorders characterized by increased rejection sensitivity. The current results also emphasize the importance of 5-HT2A/1A receptor subtypes and the Asp system in the control of social functioning, and as prospective targets in the treatment of sociocognitive impairments in psychiatric illnesses.

  14. Effects of serotonin 2A/1A receptor stimulation on social exclusion processing.

    PubMed

    Preller, Katrin H; Pokorny, Thomas; Hock, Andreas; Kraehenmann, Rainer; Stämpfli, Philipp; Seifritz, Erich; Scheidegger, Milan; Vollenweider, Franz X

    2016-05-01

    Social ties are crucial for physical and mental health. However, psychiatric patients frequently encounter social rejection. Moreover, an increased reactivity to social exclusion influences the development, progression, and treatment of various psychiatric disorders. Nevertheless, the neuromodulatory substrates of rejection experiences are largely unknown. The preferential serotonin (5-HT) 2A/1A receptor agonist, psilocybin (Psi), reduces the processing of negative stimuli, but whether 5-HT2A/1A receptor stimulation modulates the processing of negative social interactions remains unclear. Therefore, this double-blind, randomized, counterbalanced, cross-over study assessed the neural response to social exclusion after the acute administration of Psi (0.215 mg/kg) or placebo (Pla) in 21 healthy volunteers by using functional magnetic resonance imaging (fMRI) and resting-state magnetic resonance spectroscopy (MRS). Participants reported a reduced feeling of social exclusion after Psi vs. Pla administration, and the neural response to social exclusion was decreased in the dorsal anterior cingulate cortex (dACC) and the middle frontal gyrus, key regions for social pain processing. The reduced neural response in the dACC was significantly correlated with Psi-induced changes in self-processing and decreased aspartate (Asp) content. In conclusion, 5-HT2A/1A receptor stimulation with psilocybin seems to reduce social pain processing in association with changes in self-experience. These findings may be relevant to the normalization of negative social interaction processing in psychiatric disorders characterized by increased rejection sensitivity. The current results also emphasize the importance of 5-HT2A/1A receptor subtypes and the Asp system in the control of social functioning, and as prospective targets in the treatment of sociocognitive impairments in psychiatric illnesses. PMID:27091970

  15. Effects of serotonin 2A/1A receptor stimulation on social exclusion processing

    PubMed Central

    Preller, Katrin H.; Pokorny, Thomas; Hock, Andreas; Kraehenmann, Rainer; Stämpfli, Philipp; Seifritz, Erich; Scheidegger, Milan; Vollenweider, Franz X.

    2016-01-01

    Social ties are crucial for physical and mental health. However, psychiatric patients frequently encounter social rejection. Moreover, an increased reactivity to social exclusion influences the development, progression, and treatment of various psychiatric disorders. Nevertheless, the neuromodulatory substrates of rejection experiences are largely unknown. The preferential serotonin (5-HT) 2A/1A receptor agonist, psilocybin (Psi), reduces the processing of negative stimuli, but whether 5-HT2A/1A receptor stimulation modulates the processing of negative social interactions remains unclear. Therefore, this double-blind, randomized, counterbalanced, cross-over study assessed the neural response to social exclusion after the acute administration of Psi (0.215 mg/kg) or placebo (Pla) in 21 healthy volunteers by using functional magnetic resonance imaging (fMRI) and resting-state magnetic resonance spectroscopy (MRS). Participants reported a reduced feeling of social exclusion after Psi vs. Pla administration, and the neural response to social exclusion was decreased in the dorsal anterior cingulate cortex (dACC) and the middle frontal gyrus, key regions for social pain processing. The reduced neural response in the dACC was significantly correlated with Psi-induced changes in self-processing and decreased aspartate (Asp) content. In conclusion, 5-HT2A/1A receptor stimulation with psilocybin seems to reduce social pain processing in association with changes in self-experience. These findings may be relevant to the normalization of negative social interaction processing in psychiatric disorders characterized by increased rejection sensitivity. The current results also emphasize the importance of 5-HT2A/1A receptor subtypes and the Asp system in the control of social functioning, and as prospective targets in the treatment of sociocognitive impairments in psychiatric illnesses. PMID:27091970

  16. Activation of serotonin2A receptors in the medial septum-diagonal band of Broca complex enhanced working memory in the hemiparkinsonian rats.

    PubMed

    Li, Li-Bo; Zhang, Li; Sun, Yi-Na; Han, Ling-Na; Wu, Zhong-Heng; Zhang, Qiao-Jun; Liu, Jian

    2015-04-01

    Serotonin2A (5-HT2A) receptors are highly expressed in the medial septum-diagonal band of Broca complex (MS-DB), especially in parvalbumin (PV)-positive neurons linked to hippocampal theta rhythm, which is involved in cognition. Cognitive impairments commonly occur in Parkinson's disease. Here we performed behavioral, electrophysiological, neurochemical and immunohistochemical studies in rats with complete unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB) to assess the importance of dopamine (DA) depletion and MS-DB 5-HT2A receptors for working memory. The MFB lesions resulted in working memory impairment and decreases in firing rate and density of MS-DB PV-positive neurons, peak frequency of hippocampal theta rhythm, and DA levels in septohippocampal system and medial prefrontal cortex (mPFC) compared to control rats. Intra-MS-DB injection of high affinity 5-HT2A receptor agonist TCB-2 enhanced working memory, increased firing rate of PV-positive neurons and peak frequency of hippocampal theta rhythm, elevated DA levels in the hippocampus and mPFC, and decreased 5-HT level in the hippocampus in control and lesioned rats. Compared to control rats, the duration of the excitatory effect produced by TCB-2 on the firing rate of PV-positive neurons was markedly shortened in lesioned rats, indicating dysfunction of 5-HT2A receptors. These findings suggest that unilateral lesions of the MFB in rats induced working memory deficit, and activation of MS-DB 5-HT2A receptors enhanced working memory, which may be due to changes in the activity of septohippocampal network and monoamine levels in the hippocampus and mPFC. PMID:25486618

  17. Activation of serotonin2A receptors in the medial septum-diagonal band of Broca complex enhanced working memory in the hemiparkinsonian rats.

    PubMed

    Li, Li-Bo; Zhang, Li; Sun, Yi-Na; Han, Ling-Na; Wu, Zhong-Heng; Zhang, Qiao-Jun; Liu, Jian

    2015-04-01

    Serotonin2A (5-HT2A) receptors are highly expressed in the medial septum-diagonal band of Broca complex (MS-DB), especially in parvalbumin (PV)-positive neurons linked to hippocampal theta rhythm, which is involved in cognition. Cognitive impairments commonly occur in Parkinson's disease. Here we performed behavioral, electrophysiological, neurochemical and immunohistochemical studies in rats with complete unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB) to assess the importance of dopamine (DA) depletion and MS-DB 5-HT2A receptors for working memory. The MFB lesions resulted in working memory impairment and decreases in firing rate and density of MS-DB PV-positive neurons, peak frequency of hippocampal theta rhythm, and DA levels in septohippocampal system and medial prefrontal cortex (mPFC) compared to control rats. Intra-MS-DB injection of high affinity 5-HT2A receptor agonist TCB-2 enhanced working memory, increased firing rate of PV-positive neurons and peak frequency of hippocampal theta rhythm, elevated DA levels in the hippocampus and mPFC, and decreased 5-HT level in the hippocampus in control and lesioned rats. Compared to control rats, the duration of the excitatory effect produced by TCB-2 on the firing rate of PV-positive neurons was markedly shortened in lesioned rats, indicating dysfunction of 5-HT2A receptors. These findings suggest that unilateral lesions of the MFB in rats induced working memory deficit, and activation of MS-DB 5-HT2A receptors enhanced working memory, which may be due to changes in the activity of septohippocampal network and monoamine levels in the hippocampus and mPFC.

  18. Characterisation of human 5-hydroxytryptamine2A and 5-hydroxytryptamine2C receptors expressed in the human neuroblastoma cell line SH-SY5Y: comparative stimulation by hallucinogenic drugs.

    PubMed

    Newton, R A; Phipps, S L; Flanigan, T P; Newberry, N R; Carey, J E; Kumar, C; McDonald, B; Chen, C; Elliott, J M

    1996-12-01

    Stable transfection of the human neuroblastoma cell line SH-SY5Y with the human 5-hydroxytryptamine2A (5-HT2A) or 5-HT2C receptor cDNA produced cell lines demonstrating ligand affinities that correlated closely with those for the corresponding endogenous receptors in human frontal cortex and choroid plexus, respectively. Stimulation of the recombinant receptors by 5-HT induced phosphoinositide hydrolysis with higher potency but lower efficacy at the 5-HT2C receptor (pEC50 = 7.80 +/- 0.06) compared with the 5-HT2A receptor (pEC50 = 7.30 +/- 0.08). Activation of the 5-HT2A receptor caused a transient fourfold increase in intracellular Ca2+ concentration. Whole-cell recordings of cells clamped at -50 mV demonstrated a small inward current (2 pA) in response to 10 microM 5-HT for both receptors. There were no differences in potency or efficacy of phosphoinositide hydrolysis among four hallucinogenic [d-lysergic acid diethylamide (LSD), 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane (DOI), 5-methoxy-N,N-dimethyltryptamine, and mescaline] and three nonhallucinogenic drugs (m-chlorophenylpiperazine, quipazine, and ergotamine). Comparison of equipotent doses producing 20% of the maximal response induced by 5-HT revealed selective activation of the 5-HT2A receptor by LSD and to a lesser degree by DOI, mescaline, and ergotamine. Quipazine and 5-methoxy-N,N-dimethyltryptamine were relatively nonselective, whereas m-chlorophenylpiperazine selectively activated the 5-HT2C receptor. It is unlikely therefore that hallucinosis is mediated primarily by activity at the 5-HT2C receptor, whereas activity at the 5-HT2A receptor may represent an important but not unique mechanism associated with hallucinogenic drug action.

  19. Serotonin 5-hydroxytryptamine(2A) receptor activation suppresses tumor necrosis factor-alpha-induced inflammation with extraordinary potency.

    PubMed

    Yu, Bangning; Becnel, Jaime; Zerfaoui, Mourad; Rohatgi, Rasika; Boulares, A Hamid; Nichols, Charles D

    2008-11-01

    The G protein-coupled serotonin 5-hydroxytryptamine (5-HT)(2A) receptor is primarily recognized for its role in brain neurotransmission, where it mediates a wide variety of functions, including certain aspects of cognition. However, there is significant expression of this receptor in peripheral tissues, where its importance is largely unknown. We have now discovered that activation of 5-HT(2A) receptors in primary aortic smooth muscle cells provides a previously unknown and extremely potent inhibition of tumor necrosis factor (TNF)-alpha-mediated inflammation. 5-HT(2A) receptor stimulation with the agonist (R)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(R)-DOI] rapidly inhibits a variety of TNF-alpha-mediated proinflammatory markers, including intracellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), and interleukin (IL)-6 gene expression, nitric-oxide synthase activity, and nuclear translocation of nuclear factor kappaB, with IC(50) values of only 10 to 20 pM. It is significant that proinflammatory markers can also be inhibited by (R)-DOI hours after treatment with TNF-alpha. With the exception of a few natural toxins, no current drugs or small molecule therapeutics demonstrate a comparable potency for any physiological effect. TNF-alpha-mediated inflammatory pathways have been strongly implicated in a number of diseases, including atherosclerosis, rheumatoid arthritis, psoriasis, type II diabetes, depression, schizophrenia, and Alzheimer's disease. Our results indicate that activation of 5-HT(2A) receptors represents a novel, and extraordinarily potent, potential therapeutic avenue for the treatment of disorders involving TNF-alpha-mediated inflammation. Note that because (R)-DOI can significantly inhibit the effects of TNF-alpha many hours after the administration of TNF-alpha, potential therapies could be aimed not only at preventing inflammation but also treating inflammatory injury that has already occurred or is ongoing. PMID

  20. A case of 25I-NBOMe (25-I) intoxication: a new potent 5-HT2A agonist designer drug

    PubMed Central

    Rose, S. Rutherfoord; Poklis, Justin L.; Poklis, Alphonse

    2014-01-01

    Context Abuse of synthetic stimulant compounds resulting in significant toxicity is being increasingly reported by poison centers. Toxicologic assessment is complicated by inconsistent manufacturing processes and limited laboratory testing. We describe a case of self-reported exposure to 25-I (25I-NBOMe), a novel phenethylamine derivative, with subsequent quantification in serum. Case details An 18-year-old male presented to the emergency department (ED) with severe agitation and hallucinations after jumping out of a moving car. He was tachycardiac (150–160 bpm) and hypertensive (150–170 mm Hg systolic and 110 mg Hg diastolic), and required physical restraints and treatment with intravenous lorazepam administration. His symptoms gradually improved and vital signs returned to normal over 48 h, though he continued to have episodes of aggressiveness. An assay was developed by our analytical toxicology laboratory for 25-I, and serum obtained during ED evaluation and treatment was found to contain 0.76 ng/ml of 25-I. Case discussion For 25I-NBOMe, 25-I is a common abbreviation for 25I-NBOMe, which is a (n-benzyl) phenethylamine in the 2C “family.” Initially synthesized for research, cases of self-reported use of 25-I have recently appeared in the literature, some of which contain qualitative urine conf rmation. There are no commercially available quantitative assays, and no previous reports have published serum concentrations. 25-I is a potent new synthetic drug with apparent significant behavioral toxicity that can be detected and quantified in serum. PMID:23473462

  1. Activation of mGlu2/3 metabotropic glutamate receptors negatively regulates the stimulation of inositol phospholipid hydrolysis mediated by 5-hydroxytryptamine2A serotonin receptors in the frontal cortex of living mice.

    PubMed

    Molinaro, G; Traficante, A; Riozzi, B; Di Menna, L; Curto, M; Pallottino, S; Nicoletti, F; Bruno, V; Battaglia, G

    2009-08-01

    The interaction between 5-hydroxytryptamine(2A) (5-HT(2A)) serotonin receptors and metabotropic glutamate (mGlu) 2/3 receptors underlies the antipsychotic activity of mGlu2/3 receptor agonists in experimental animals and humans. The molecular nature of this interaction is only partially known. We here report for the first time that pharmacological activation of mGlu2/3 receptors attenuates the stimulation of polyphosphoinositide (PI) hydrolysis mediated by 5-HT(2A) receptors in the frontal cortex of living mice. Mice were injected intracerebroventricularly with [myo-(3)H]inositol and treated with drugs 1 h after a pretreatment with lithium, which blocks the conversion of inositol monophosphate into free inositol. Systemic injection of the mGlu2/3 receptor agonist (-)-2-oxa-4-aminocyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY379268) inhibited the stimulation of PI hydrolysis induced by the hallucinogenic 5-HT(2A) receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) without affecting the stimulation by mGlu1/5 or muscarinic receptors. The action of LY379268 was prevented by the preferential mGlu2/3 receptor antagonist (2S,1'S,2'S)-2-(9-xanthylmethyl)-2-(2'-carboxycyclopropyl)glycine (LY341495). N-(4'-cyano-biphenyl-3-yl)-N-(3-pyridinylmethyl)-ethanesulfonamide hydrochloride (LY566332), a selective mGlu2 receptor enhancer, also reduced DOI-stimulated PI hydrolysis when combined with subthreshold doses of LY379268. Systemic LY379268 inhibited DOI-stimulated PI hydrolysis in mice lacking either mGlu2 or mGlu3 receptors but was inactive in double mGlu2/mGlu3 receptor knockout mice, suggesting that both mGlu2 and mGlu3 receptors interact with 5-HT(2A) receptors. Surprisingly, contrasting results were obtained in cortical slice preparations, where LY379268 amplified both DOI- and 3,5-dihydroxyphenylglycine-stimulated PI hydrolysis. Amplification was abrogated by the mGlu5 receptor antagonist 2-methyl-6-(phenylethynyl)pyridine, suggesting that

  2. Single cell laser dissection with molecular beacon polymerase chain reaction identifies 2A as the predominant serotonin receptor subtype in hypoglossal motoneurons.

    PubMed

    Zhan, G; Shaheen, F; Mackiewicz, M; Fenik, P; Veasey, S C

    2002-01-01

    We hypothesize that sleep state-dependent withdrawal of serotonin (5-hydroxytryptamine, 5-HT) at upper airway (UAW) dilator motoneurons contributes significantly to sleep-related suppression of dilator muscle activity in obstructive sleep apnea. Identification of 5-HT receptor subtypes involved in postsynaptic facilitation of UAW motoneuron activity may provide pharmacotherapies for this prevalent disorder. We have adapted two assays to provide semi-quantitative measurements of mRNA copy numbers for 5-HT receptor subtypes in single UAW motoneurons. Specifically, soma of 111 hypoglossal (XII) motoneurons in 10 adult male rats were captured using a laser dissection microscope, and then used individually in single round molecular beacon polymerase chain reaction (PCR) for real-time quantitation of 5-HT(2A), 5-HT(2C), 5-HT(3), 5-HT(4), 5-HT(5A), 5-HT(5B), 5-HT(6) or 5-HT(7) receptor. Receptor mRNA copy numbers from single XII motoneurons were compared to control samples from within the XII nucleus and lateral medulla. All 20 motoneuronal soma assayed for the 5-HT(2A) receptor had measurable copy numbers (7028+/-2656 copies/cell). In contrast, copy numbers for the 5-HT(2A) receptor in XII non-motoneuronal (n=17) and lateral medulla (n=15) samples were 81+/-51 copies and 83+/-35 copies, respectively, P<0.05. Seven of 13 XII motoneurons assayed had measurable 5-HT(2C) receptor copy numbers of mRNA (287+/-112 copies/cell). XII soma had minimal 5-HT(3), 5-HT(4), 5-HT(5A), 5-HT(5B), 5-HT(6) or 5-HT(7) receptor mRNA. 5-HT(2A) receptor mRNA presence within XII motoneurons was confirmed with digoxigenin-labeled in situ hybridization. In summary, combined use of laser dissection and molecular beacon PCR revealed 5-HT(2A) receptor as the predominant 5-HT receptor mRNA in XII motoneurons, and identified small quantities of 5-HT(2C) receptor. This information will allow a more complete understanding of serotonergic control of respiratory activity.

  3. The 5-hydroxytryptamine2A receptor antagonist R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl-4-piperidinemethanol (M100907) attenuates impulsivity after both drug-induced disruption (dizocilpine) and enhancement (antidepressant drugs) of differential-reinforcement-of-low-rate 72-s behavior in the rat.

    PubMed

    Ardayfio, Paul A; Benvenga, Mark J; Chaney, Stephen F; Love, Patrick L; Catlow, John; Swanson, Steven P; Marek, Gerard J

    2008-12-01

    Previous work has suggested that N-methyl-d-aspartate (NMDA) receptor antagonism and 5-hydroxytryptamine (5-HT)(2A) receptor blockade may enhance and attenuate, respectively, certain types of impulsivity mediated by corticothalamostriatal circuits. More specifically, past demonstrations of synergistic "antidepressant-like" effects of a 5-HT(2A) receptor antagonist and fluoxetine on differential-reinforcement-of-low-rate (DRL) 72-s schedule of operant reinforcement may speak to the role of 5-HT(2A) receptor blockade with respect to response inhibition as an important prefrontal cortical executive function relating to motor impulsivity. To examine the dynamic range over which 5-HT(2A) receptor blockade may exert effects on impulsivity, [R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl-4-piperidinemethanol] (M100907) was examined both alone and in combination with the psychotomimetic NMDA receptor antagonist dizocilpine [e.g., (-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate; MK-801] and two different antidepressants, the tricyclic antidepressant desmethylimipramine (DMI) and the monoamine oxidase inhibitor tranylcypromine in rats performing under a DRL 72-s schedule. MK-801 increased the response rate, decreased the number of reinforcers obtained, and exerted a leftward shift in the inter-response time (IRT) distribution as expected. A dose of M100907 that exerted minimal effect on DRL behavior by itself attenuated the psychotomimetic effects of MK-801. Extending previous M100907-fluoxetine observations, addition of a minimally active dose of M100907 to low doses of DMI and tranylcypromine enhanced the antidepressant-like effect of the antidepressants. Therefore, it may be that a tonic excitation of 5-HT(2A) receptors modulates impulsivity and function of corticothalamostriatal circuits over an extensive dynamic range. PMID:18772320

  4. Enriched Expression of Serotonin 1B and 2A Receptor Genes in Macaque Visual Cortex and their Bidirectional Modulatory Effects on Neuronal Responses

    PubMed Central

    Watakabe, Akiya; Komatsu, Yusuke; Sadakane, Osamu; Shimegi, Satoshi; Takahata, Toru; Higo, Noriyuki; Tochitani, Shiro; Hashikawa, Tsutomu; Naito, Tomoyuki; Osaki, Hironobu; Sakamoto, Hiroshi; Okamoto, Masahiro; Ishikawa, Ayako; Hara, Shin-ichiro; Akasaki, Takafumi; Sato, Hiromichi

    2009-01-01

    To study the molecular mechanism how cortical areas are specialized in adult primates, we searched for area-specific genes in macaque monkeys and found striking enrichment of serotonin (5-hydroxytryptamine, 5-HT) 1B receptor mRNA, and to a lesser extent, of 5-HT2A receptor mRNA, in the primary visual area (V1). In situ hybridization analyses revealed that both mRNA species were highly concentrated in the geniculorecipient layers IVA and IVC, where they were coexpressed in the same neurons. Monocular inactivation by tetrodotoxin injection resulted in a strong and rapid (<3 h) downregulation of these mRNAs, suggesting the retinal activity dependency of their expression. Consistent with the high expression level in V1, clear modulatory effects of 5-HT1B and 5-HT2A receptor agonists on the responses of V1 neurons were observed in in vivo electrophysiological experiments. The modulatory effect of the 5-HT1B agonist was dependent on the firing rate of the recorded neurons: The effect tended to be facilitative for neurons with a high firing rate, and suppressive for those with a low firing rate. The 5-HT2A agonist showed opposite effects. These results suggest that this serotonergic system controls the visual response in V1 for optimization of information processing toward the incoming visual inputs. PMID:19056862

  5. On the role of 5-HT(1A) receptor gene in behavioral effect of brain-derived neurotrophic factor.

    PubMed

    Naumenko, Vladimir S; Kondaurova, Elena M; Bazovkina, Daria V; Tsybko, Anton S; Il'chibaeva, Tatyana V; Popova, Nina K

    2014-08-01

    Experiments were made on a congenic AKR.CBA-D13Mit76C (76C) mouse strain created by transferring a chromosome 13 fragment containing the 5-HT1A receptor gene from a CBA strain to an AKR background. It was shown that 76C mice differed from AKR mice by decreased 5-HT1A receptor and tryptophan hydroxylase-2 (tph-2) genes expression in the midbrain. Functional activity of 5-HT2A receptors and 5-HT(2A) receptor mRNA levels in the midbrain and hippocampus of 76C mice were decreased compared with AKR mice. Central brain-derived neurotrophic factor (BDNF) administration (300 ng i.c.v.) reduced 5-HT1A and 5-HT(2A) receptor mRNA levels in the frontal cortex and tph-2 mRNA level in the midbrain of AKR mice. However, BDNF failed to produce any effect on the expression of 5-HT(1A) , 5-HT(2A) , and tph-2 genes in 76C mice but decreased functional activity of 5-HT(2A) receptors in 76C mice and increased it in AKR mice. BDNF restored social deficiency in 76C mice but produced asocial behavior (aggressive attacks towards young mice) in AKR mice. The data indicate that a small genetic variation altered the response to BDNF and show an important role of 5-HT(1A) receptor gene in the 5-HT system response to BDNF treatment and in behavioral effects of BDNF.

  6. Behavioral evidence for interactions between a hallucinogenic drug and group II metabotropic glutamate receptors.

    PubMed

    Gewirtz, J C; Marek, G J

    2000-11-01

    Recent electrophysiological studies in our laboratory have demonstrated a physiological interaction between 5-HT(2A) and metabotropic glutamate2/3 (mGlu2/3) receptors in the medial prefrontal cortex. Several behavioral studies have found that phenethylamine hallucinogens with partial agonist activity at 5-HT(2A) receptors induce head shakes when directly administered into the medial prefrontal cortex. The purpose of the present experiments was to examine whether an interaction occurs between mGlu2/3 and 5-HT(2A) receptors on a behavioral level using head shakes induced by phenethylamine hallucinogens as a model of 5-HT(2A) receptor activation. Administration of the mGlu2/3 agonist LY354740 (0.3-10 mg/kg, ip) suppressed head shakes induced by the phenethylamine hallucinogen 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Conversely, administration of the mGlu2/3 antagonist LY341495 (1 mg/kg, ip) enhanced the frequency of DOI-induced head shakes. Taken together, these results raise the possibility that the psychomimetic properties of hallucinogenic drugs may be mediated in part, via increased glutamate release following activation of 5-HT(2A) receptors.

  7. Behavioral tolerance to lysergic acid diethylamide is associated with reduced serotonin-2A receptor signaling in rat cortex.

    PubMed

    Gresch, Paul J; Smith, Randy L; Barrett, Robert J; Sanders-Bush, Elaine

    2005-09-01

    Tolerance is defined as a decrease in responsiveness to a drug after repeated administration. Tolerance to the behavioral effects of hallucinogens occurs in humans and animals. In this study, we used drug discrimination to establish a behavioral model of lysergic acid diethylamide (LSD) tolerance and examined whether tolerance to the stimulus properties of LSD is related to altered serotonin receptor signaling. Rats were trained to discriminate 60 microg/kg LSD from saline in a two-lever drug discrimination paradigm. Two groups of animals were assigned to either chronic saline treatment or chronic LSD treatment. For chronic treatment, rats from each group were injected once per day with either 130 microg/kg LSD or saline for 5 days. Rats were tested for their ability to discriminate either saline or 60 microg/kg LSD, 24 h after the last chronic injection. Rats receiving chronic LSD showed a 44% reduction in LSD lever selection, while rats receiving chronic vehicle showed no change in percent choice on the LSD lever. In another group of rats receiving the identical chronic LSD treatment, LSD-stimulated [35S]GTPgammaS binding, an index of G-protein coupling, was measured in the rat brain by autoradiography. After chronic LSD, a significant reduction in LSD-stimulated [35S]GTPgammaS binding was observed in the medial prefrontal cortex and anterior cingulate cortex. Furthermore, chronic LSD produced a significant reduction in 2,5-dimethoxy-4-iodoamphetamine-stimulated [35S]GTPgammaS binding in medial prefrontal cortex and anterior cingulate cortex, which was blocked by MDL 100907, a selective 5-HT2A receptor antagonist, but not SB206553, a 5-HT2C receptor antagonist, indicating a reduction in 5-HT2A receptor signaling. 125I-LSD binding to 5-HT2A receptors was reduced in cortical regions, demonstrating a reduction in 5-HT2A receptor density. Taken together, these results indicate that adaptive changes in LSD-stimulated serotonin receptor signaling may mediate tolerance

  8. 5-HT2 receptors mediate functional modulation of GABAa receptors and inhibitory synaptic transmissions in human iPS-derived neurons

    PubMed Central

    Wang, Haitao; Hu, Lingli; Liu, Chunhua; Su, Zhenghui; Wang, Lihui; Pan, Guangjin; Guo, Yiping; He, Jufang

    2016-01-01

    Neural progenitors differentiated from induced pluripotent stem cells (iPS) hold potentials for treating neurological diseases. Serotonin has potent effects on neuronal functions through multiple receptors, underlying a variety of neural disorders. Glutamate and GABA receptors have been proven functional in neurons differentiated from iPS, however, little is known about 5-HT receptor-mediated modulation in such neuronal networks. In the present study, human iPS were differentiated into cells possessing featured physiological properties of cortical neurons. Whole-cell patch-clamp recording was used to examine the involvement of 5-HT2 receptors in functional modulation of GABAergic synaptic transmission. We found that serotonin and DOI (a selective agonist of 5-HT2A/C receptor) reversibly reduced GABA-activated currents, and this 5-HT2A/C receptor mediated inhibition required G protein, PLC, PKC, and Ca2+ signaling. Serotonin increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs), which could be mimicked by α-methylserotonin, a 5-HT2 receptor agonist. In contrast, DOI reduced both frequency and amplitude of mIPSCs. These findings suggested that in iPS-derived human neurons serotonin postsynaptically reduced GABAa receptor function through 5-HT2A/C receptors, but presynaptically other 5-HT2 receptors counteracted the action of 5-HT2A/C receptors. Functional expression of serotonin receptors in human iPS-derived neurons provides a pre-requisite for their normal behaviors after grafting. PMID:26837719

  9. Effects of chronic fluoxetine treatment on catalepsy and the immune response in mice with a genetic predisposition to freezing reactions: the roles of types 1A and 2A serotonin receptors and the tph2 and SERT genes.

    PubMed

    Tikhonova, M A; Alperina, E L; Tolstikova, T G; Bazovkina, D V; Di, V Y; Idova, G V; Kulikov, A V; Popova, N K

    2010-06-01

    ASC (Antidepressant-Sensitive Catalepsy) mice, bred for a high predisposition to catalepsy, are characterized by depression-like behavior and decreased immune responses. Chronic administration of fluoxetine, which is a selective serotonin reuptake inhibitor antidepressant widely used in clinical practice, to mice of this strain weakened catalepsy and normalized the number of rosette-forming cells in the spleen. In mice of the parental cataleptic strain CBA/Lac, fluoxetine had no effect on the level of catalepsy or the immune response. Analysis of the effects of fluoxetine on the functional activity of 5-HT(1A) and 5-HT(2A) receptors, and the expression of 5-HT(1A) receptor genes in the frontal cortex and midbrain and 5-HT(2A) receptors in the frontal cortex, as well as the tryptophan hydroxylase-2 and the serotonin transporter genes in the midbrain showed that the antidepressant had no effect on these parameters in ASC mice, but decreased the functional activity of 5-HT(2A) receptors in CBA/Lac mice. The possibility that the actions of fluoxetine on catalepsy and the immune response in mice with depression-like states are mediated via other serotoninergic mechanisms is discussed.

  10. Differential interactions of indolealkylamines with 5-hydroxytryptamine receptor subtypes.

    PubMed

    McKenna, D J; Repke, D B; Lo, L; Peroutka, S J

    1990-03-01

    Affinities of drugs for 21 indolealkylamine derivatives, some with putative hallucinogenic activity, were determined at 5-HT1A, 5-HT2A and 5-HT2B recognition sites, using radioligand competition studies. Nearly all of the derivatives displayed greatest potency for the 5-HT2A receptor, labelled by [125I]R-(-)DOI in the cortex of the rat. Most derivatives displayed 2-10 times lower affinity at the HT2B receptor labelled by [3H]ketanserin in bovine cortex. Derivatives lacking ring substituents displayed lower affinities for all of the recognition sites, compared to derivatives substituted in the 4- or 5-position of the indole ring. The 4-hydroxylated derivatives displayed 25-380-fold selectivity for the 5-HT2A site, vs the 5-HT1A site, while the 5-substituted derivatives displayed approximately equal potency at the 5-HT1A and 5-HT2A sites. Affinity of all the compounds at the 5-HT2B site was greater than 300 nM. The 6-substituted derivatives displayed greater than micromolar affinities for all of the 5-HT recognition sites examined. The size of the N,N-dialkyl substituent was a secondary determinant of affinity, with groups larger than N,N-diisopropyl resulting in a marked reduction in affinity at both the 5-HT2A and 5-HT1A recognition sites. This study demonstrated that hallucinogenic 4-hydroxy-indolealkylamines, like psychotomimetic phenylisopropylamines, bind potently and selectively to the 5-HT2A recognition site, labelled by [125I]R-(-)DOI. This provides further evidence indicating that this recently described subtype of the 5-HT2 receptor may partially mediate the action of hallucinogenic agents.

  11. Phosphoinositide system-linked serotonin receptor subtypes and their pharmacological properties and clinical correlates.

    PubMed Central

    Pandey, S C; Davis, J M; Pandey, G N

    1995-01-01

    Serotonergic neurotransmission represents a complex mechanism involving pre- and post-synaptic events and distinct 5-HT receptor subtypes. Serotonin (5-HT) receptors have been classified into several categories, and they are termed as 5-HT1, 5-HT2, 5-HT3, 5-HT4, 5-HT5, 5-HT6 and 5-HT7 type receptors. 5-HT1 receptors have been further subdivided into 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E and 5-HT1F. 5-HT2 receptors have been divided into 5-HT2A, 5-HT2B and 5-HT2C receptors. All 5-HT2 receptor subtypes are linked to the multifunctional phosphoinositide (PI) signalling system. 5-HT3 receptors are considered ion-gated receptors and are also linked to the PI signalling system by an unknown mechanism. The 5-HT2A receptor subtype is the most widely studied of the 5-HT receptors in psychiatric disorders (for example, suicide, depression and schizophrenia) as well as in relation to the mechanism of action of antidepressant drugs. The roles of 5-HT2C and 5-HT3 receptors in psychiatric disorders are less clear. These 5-HT receptors also play an important role in alcoholism. It has been shown that 5-HT2A, 5-HT2C and 5-HT3 antagonists cause attenuation of alcohol intake in animals and humans. However, the exact mechanisms are unknown. The recent cloning of the cDNAs for 5-HT2A, 5-HT2C and 5-HT3 receptors provides the opportunity to explore the molecular mechanisms responsible for the alterations in these receptors during illness as well as pharmacotherapy. This review article will focus on the current research into the pharmacological properties, molecular biology, and clinical correlates of 5-HT2A, 5-HT2C and 5-HT3 receptors. PMID:7786883

  12. Interaction of psychoactive tryptamines with biogenic amine transporters and serotonin receptor subtypes

    PubMed Central

    Blough, Bruce E.; Landavazo, Antonio; Decker, Ann M.; Partilla, John S.; Baumann, Michael H.; Rothman, Richard B.

    2014-01-01

    Rationale Synthetic hallucinogenic tryptamines, especially those originally described by Alexander Shulgin, continue to be abused in the United States. The range of subjective experiences produced by different tryptamines suggests that multiple neurochemical mechanisms are involved in their actions, in addition to the established role of agonist activity at serotonin-2A (5-HT2A) receptors. Objectives This study evaluated the interaction of a series of synthetic tryptamines with biogenic amine neurotransmitter transporters and with serotonin (5-HT) receptor subtypes implicated in psychedelic effects. Methods Neurotransmitter transporter activity was determined in rat brain synaptosomes. Receptor activity was determined using calcium mobilization and DiscoveRx PathHunter® assays in HEK293, Gα16-CHO, and CHOk1 cells transfected with human receptors. Results Twenty-one tryptamines were analyzed in transporter uptake and release assays, and 5-HT2A, serotonin 1A (5-HT1A), and 5-HT2A β-arrestin functional assays. Eight of the compounds were found to have 5-HT-releasing activity. Thirteen compounds were found to be 5-HT uptake inhibitors or were inactive. All tryptamines were 5-HT2A agonists with a range of potencies and efficacies, but only a few compounds were 5-HT1A agonists. Most tryptamines recruited β-arrestin through 5-HT2A activation. Conclusions All psychoactive tryptamines are 5-HT2A agonists, but 5-HT transporter (SERT) activity may contribute significantly to the pharmacology of certain compounds. The in vitro transporter data confirm structure-activity trends for releasers and uptake inhibitors whereby releasers tend to be structurally smaller compounds. Interestingly, two tertiary amines were found to be selective substrates at SERT, which dispels the notion that 5-HT-releasing activity is limited only to primary or secondary amines. PMID:24800892

  13. Modulation of GABA release from the thalamic reticular nucleus by cocaine and caffeine: role of serotonin receptors.

    PubMed

    Goitia, Belén; Rivero-Echeto, María Celeste; Weisstaub, Noelia V; Gingrich, Jay A; Garcia-Rill, Edgar; Bisagno, Verónica; Urbano, Francisco J

    2016-02-01

    Serotonin receptors are targets of drug therapies for a variety of neuropsychiatric and neurodegenerative disorders. Cocaine inhibits the re-uptake of serotonin (5-HT), dopamine, and noradrenaline, whereas caffeine blocks adenosine receptors and opens ryanodine receptors in the endoplasmic reticulum. We studied how 5-HT and adenosine affected spontaneous GABAergic transmission from thalamic reticular nucleus. We combined whole-cell patch clamp recordings of miniature inhibitory post-synaptic currents (mIPSCs) in ventrobasal thalamic neurons during local (puff) application of 5-HT in wild type (WT) or knockout mice lacking 5-HT2A receptors (5-HT2A -/-). Inhibition of mIPSCs frequency by low (10 μM) and high (100 μM) 5-HT concentrations was observed in ventrobasal neurons from 5-HT2A -/- mice. In WT mice, only 100 μM 5-HT significantly reduced mIPSCs frequency. In 5-HT2A -/- mice, NAN-190, a specific 5-HT1A antagonist, prevented the 100 μM 5-HT inhibition while blocking H-currents that prolonged inhibition during post-puff periods. The inhibitory effects of 100 μM 5-HT were enhanced in cocaine binge-treated 5-HT2A -/- mice. Caffeine binge treatment did not affect 5-HT-mediated inhibition. Our findings suggest that both 5-HT1A and 5-HT2A receptors are present in pre-synaptic thalamic reticular nucleus terminals. Serotonergic-mediated inhibition of GABA release could underlie aberrant thalamocortical physiology described after repetitive consumption of cocaine. Our findings suggest that both 5-HT1A , 5-HT2A and A1 receptors are present in pre-synaptic TRN terminals. 5-HT1A and A1 receptors would down-regulate adenylate cyclase, whereas 5-HT1A would also increase the probability of the opening of G-protein-activated inwardly rectifying K(+) channels (GIRK). Sustained opening of GIRK channels would hyperpolarize pre-synaptic terminals activating H-currents, resulting in less GABA release. 5-HT2A -would activate PLC and IP3 , increasing intracellular [Ca(2+) ] and

  14. The serotonin 2C receptor potently modulates the head-twitch response in mice induced by a phenethylamine hallucinogen

    PubMed Central

    Canal, Clinton E.; Olaghere da Silva, Uade B.; Gresch, Paul J.; Watt, Erin E.; Sanders-Bush, Elaine

    2010-01-01

    Rationale Hallucinogenic serotonin 2A (5-HT2A) receptor partial agonists, such as (±)-1-(2,5-dimethoxy-4-iodo-phenyl)-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. Objectives We tested for involvement of 5-HT2C receptors in the HTR induced by DOI. Results 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. Conclusions 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. PMID:20165943

  15. Receptor interaction profiles of novel psychoactive tryptamines compared with classic hallucinogens.

    PubMed

    Rickli, Anna; Moning, Olivier D; Hoener, Marius C; Liechti, Matthias E

    2016-08-01

    The present study investigated interactions between the novel psychoactive tryptamines DiPT, 4-OH-DiPT, 4-OH-MET, 5-MeO-AMT, and 5-MeO-MiPT at monoamine receptors and transporters compared with the classic hallucinogens lysergic acid diethylamide (LSD), psilocin, N,N-dimethyltryptamine (DMT), and mescaline. We investigated binding affinities at human monoamine receptors and determined functional serotonin (5-hydroxytryptamine [5-HT]) 5-HT2A and 5-HT2B receptor activation. Binding at and the inhibition of human monoamine uptake transporters and transporter-mediated monoamine release were also determined. All of the novel tryptamines interacted with 5-HT2A receptors and were partial or full 5-HT2A agonists. Binding affinity to the 5-HT2A receptor was lower for all of the tryptamines, including psilocin and DMT, compared with LSD and correlated with the reported psychoactive doses in humans. Several tryptamines, including psilocin, DMT, DiPT, 4-OH-DiPT, and 4-OH-MET, interacted with the serotonin transporter and partially the norepinephrine transporter, similar to 3,4-methylenedioxymethamphetamine but in contrast to LSD and mescaline. LSD but not the tryptamines interacted with adrenergic and dopaminergic receptors. In conclusion, the receptor interaction profiles of the tryptamines predict hallucinogenic effects that are similar to classic serotonergic hallucinogens but also MDMA-like psychoactive properties.

  16. Receptor interaction profiles of novel psychoactive tryptamines compared with classic hallucinogens.

    PubMed

    Rickli, Anna; Moning, Olivier D; Hoener, Marius C; Liechti, Matthias E

    2016-08-01

    The present study investigated interactions between the novel psychoactive tryptamines DiPT, 4-OH-DiPT, 4-OH-MET, 5-MeO-AMT, and 5-MeO-MiPT at monoamine receptors and transporters compared with the classic hallucinogens lysergic acid diethylamide (LSD), psilocin, N,N-dimethyltryptamine (DMT), and mescaline. We investigated binding affinities at human monoamine receptors and determined functional serotonin (5-hydroxytryptamine [5-HT]) 5-HT2A and 5-HT2B receptor activation. Binding at and the inhibition of human monoamine uptake transporters and transporter-mediated monoamine release were also determined. All of the novel tryptamines interacted with 5-HT2A receptors and were partial or full 5-HT2A agonists. Binding affinity to the 5-HT2A receptor was lower for all of the tryptamines, including psilocin and DMT, compared with LSD and correlated with the reported psychoactive doses in humans. Several tryptamines, including psilocin, DMT, DiPT, 4-OH-DiPT, and 4-OH-MET, interacted with the serotonin transporter and partially the norepinephrine transporter, similar to 3,4-methylenedioxymethamphetamine but in contrast to LSD and mescaline. LSD but not the tryptamines interacted with adrenergic and dopaminergic receptors. In conclusion, the receptor interaction profiles of the tryptamines predict hallucinogenic effects that are similar to classic serotonergic hallucinogens but also MDMA-like psychoactive properties. PMID:27216487

  17. Serotonin 2A Receptors Differentially Contribute to Abuse-Related Effects of Cocaine and Cocaine-Induced Nigrostriatal and Mesolimbic Dopamine Overflow in Nonhuman Primates

    PubMed Central

    Murnane, Kevin S.; Winschel, Jake; Schmidt, Karl T.; Stewart, LaShaya M.; Rose, Samuel J.; Cheng, Kejun; Rice, Kenner C.

    2013-01-01

    Two of the most commonly used procedures to study the abuse-related effects of drugs in laboratory animals are intravenous drug self-administration and reinstatement of extinguished behavior previously maintained by drug delivery. Intravenous self-administration is widely accepted to model ongoing drug-taking behavior, whereas reinstatement procedures are accepted to model relapse to drug taking following abstinence. Previous studies indicate that 5-HT2A receptor antagonists attenuate the reinstatement of cocaine-maintained behavior but not cocaine self-administration in rodents. Although the abuse-related effects of cocaine have been closely linked to brain dopamine systems, no previous study has determined whether this dissociation is related to differential regulation of dopamine neurotransmission. To elucidate the neuropharmacological and neuroanatomical mechanisms underlying this phenomenon, we evaluated the effects of the selective 5-HT2A receptor antagonist M100907 on intravenous cocaine self-administration and drug- and cue-primed reinstatement in rhesus macaques (Macaca mulatta). In separate subjects, we evaluated the role of 5-HT2A receptors in cocaine-induced dopamine overflow in the nucleus accumbens (n = 4) and the caudate nucleus (n = 5) using in vivo microdialysis. Consistent with previous studies, M100907 (0.3 mg/kg, i.m.) significantly attenuated drug- and cue-induced reinstatement but had no significant effects on cocaine self-administration across a range of maintenance doses. Importantly, M100907 (0.3 mg/kg, i.m.) attenuated cocaine-induced (1.0 mg/kg, i.v.) dopamine overflow in the caudate nucleus but not in the nucleus accumbens. These data suggest that important abuse-related effects of cocaine are mediated by distinct striatal dopamine projection pathways. PMID:23946394

  18. Serotonin 2A receptors differentially contribute to abuse-related effects of cocaine and cocaine-induced nigrostriatal and mesolimbic dopamine overflow in nonhuman primates.

    PubMed

    Murnane, Kevin S; Winschel, Jake; Schmidt, Karl T; Stewart, LaShaya M; Rose, Samuel J; Cheng, Kejun; Rice, Kenner C; Howell, Leonard L

    2013-08-14

    Two of the most commonly used procedures to study the abuse-related effects of drugs in laboratory animals are intravenous drug self-administration and reinstatement of extinguished behavior previously maintained by drug delivery. Intravenous self-administration is widely accepted to model ongoing drug-taking behavior, whereas reinstatement procedures are accepted to model relapse to drug taking following abstinence. Previous studies indicate that 5-HT2A receptor antagonists attenuate the reinstatement of cocaine-maintained behavior but not cocaine self-administration in rodents. Although the abuse-related effects of cocaine have been closely linked to brain dopamine systems, no previous study has determined whether this dissociation is related to differential regulation of dopamine neurotransmission. To elucidate the neuropharmacological and neuroanatomical mechanisms underlying this phenomenon, we evaluated the effects of the selective 5-HT2A receptor antagonist M100907 on intravenous cocaine self-administration and drug- and cue-primed reinstatement in rhesus macaques (Macaca mulatta). In separate subjects, we evaluated the role of 5-HT2A receptors in cocaine-induced dopamine overflow in the nucleus accumbens (n = 4) and the caudate nucleus (n = 5) using in vivo microdialysis. Consistent with previous studies, M100907 (0.3 mg/kg, i.m.) significantly attenuated drug- and cue-induced reinstatement but had no significant effects on cocaine self-administration across a range of maintenance doses. Importantly, M100907 (0.3 mg/kg, i.m.) attenuated cocaine-induced (1.0 mg/kg, i.v.) dopamine overflow in the caudate nucleus but not in the nucleus accumbens. These data suggest that important abuse-related effects of cocaine are mediated by distinct striatal dopamine projection pathways. PMID:23946394

  19. 5-HT2 Receptor Regulation of Mitochondrial Genes: Unexpected Pharmacological Effects of Agonists and Antagonists.

    PubMed

    Harmon, Jennifer L; Wills, Lauren P; McOmish, Caitlin E; Demireva, Elena Y; Gingrich, Jay A; Beeson, Craig C; Schnellmann, Rick G

    2016-04-01

    In acute organ injuries, mitochondria are often dysfunctional, and recent research has revealed that recovery of mitochondrial and renal functions is accelerated by induction of mitochondrial biogenesis (MB). We previously reported that the nonselective 5-HT2 receptor agonist DOI [1-(4-iodo-2,5-dimethoxyphenyl)propan-2-amine] induced MB in renal proximal tubular cells (RPTCs). The goal of this study was to determine the role of 5-HT2 receptors in the regulation of mitochondrial genes and oxidative metabolism in the kidney. The 5-HT2C receptor agonist CP-809,101 [2-[(3-chlorophenyl)methoxy]-6-(1-piperazinyl)pyrazine] and antagonist SB-242,084 [6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride] were used to examine the induction of renal mitochondrial genes and oxidative metabolism in RPTCs and in mouse kidneys in the presence and absence of the 5-HT2C receptor. Unexpectedly, both CP-809,101 and SB-242,084 increased RPTC respiration and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) mRNA expression in RPTCs at 1-10 nM. In addition, CP-809,101 and SB-242,084 increased mRNA expression of PGC-1α and the mitochondrial proteins NADH dehydrogenase subunit 1 and NADH dehydrogenase (ubiquinone) β subcomplex 8 in mice. These compounds increased mitochondrial genes in RPTCs in which the 5-HT2C receptor was downregulated with small interfering RNA and in the renal cortex of mice lacking the 5-HT2C receptor. By contrast, the ability of these compounds to increase PGC-1α mRNA and respiration was blocked in RPTCs treated with 5-HT2A receptor small interfering RNA or the 5-HT2A receptor antagonist eplivanserin. In addition, the 5-HT2A receptor agonist NBOH-2C-CN [4-[2-[[(2-hydroxyphenyl)methyl]amino]ethyl]-2,5-dimethoxybenzonitrile] increased RPTC respiration at 1-100 nM. These results suggest that agonism of the 5-HT2A receptor induces MB and that the classic 5-HT2C receptor agonist CP

  20. Antagonism of lateral saphenous vein serotonin receptors from steers grazing endophyte-free, wild-type, or novel endophyte-infected tall fescue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pharmacologic profiling of 5-hydroxytryptamine (5HT) receptors of bovine lateral saphenous vein has shown that cattle grazing endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) have altered responses to ergovaline (ERV), 5HT, 5HT2A and 5HT7 agonists. To determine if 5HT...

  1. Aromatic interactions impact ligand binding and function at serotonin 5-HT2C G protein-coupled receptors: receptor homology modelling, ligand docking, and molecular dynamics results validated by experimental studies

    NASA Astrophysics Data System (ADS)

    Córdova-Sintjago, Tania; Villa, Nancy; Fang, Lijuan; Booth, Raymond G.

    2014-02-01

    The serotonin (5-hydroxytryptamine, 5-HT) 5-HT2 G protein-coupled receptor (GPCR) family consists of types 2A, 2B, and 2C that share ∼75% transmembrane (TM) sequence identity. Agonists for 5-HT2C receptors are under development for psychoses; whereas, at 5-HT2A receptors, antipsychotic effects are associated with antagonists - in fact, 5-HT2A agonists can cause hallucinations and 5-HT2B agonists cause cardiotoxicity. It is known that 5-HT2A TM6 residues W6.48, F6.51, and F6.52 impact ligand binding and function; however, ligand interactions with these residues at the 5-HT2C receptor have not been reported. To predict and validate molecular determinants for 5-HT2C-specific activation, results from receptor homology modelling, ligand docking, and molecular dynamics simulation studies were compared with experimental results for ligand binding and function at wild type and W6.48A, F6.51A, and F6.52A point-mutated 5-HT2C receptors.

  2. 5-Hydroxytryptamine (serotonin)2A receptors in rat anterior cingulate cortex mediate the discriminative stimulus properties of d-lysergic acid diethylamide.

    PubMed

    Gresch, Paul J; Barrett, Robert J; Sanders-Bush, Elaine; Smith, Randy L

    2007-02-01

    d-Lysergic acid diethylamide (LSD), an indoleamine hallucinogen, produces profound alterations in mood, thought, and perception in humans. The brain site(s) that mediates the effects of LSD is currently unknown. In this study, we combine the drug discrimination paradigm with intracerebral microinjections to investigate the anatomical localization of the discriminative stimulus of LSD in rats. Based on our previous findings, we targeted the anterior cingulate cortex (ACC) to test its involvement in mediating the discriminative stimulus properties of LSD. Rats were trained to discriminate systemically administered LSD (0.085 mg/kg s.c.) from saline. Following acquisition of the discrimination, bilateral cannulae were implanted into the ACC (AP, +1.2 mm; ML, +/-1.0 mm; DV, -2.0 mm relative to bregma). Rats were tested for their ability to discriminate varying doses of locally infused LSD (0.1875, 0.375, and 0.75 microg/side) or artificial cerebrospinal fluid (n = 3-7). LSD locally infused into ACC dose-dependently substituted for systemically administered LSD, with 0.75 microg/side LSD substituting completely (89% correct). Systemic administration of the selective 5-hydroxytryptamine (serotonin) (5-HT)(2A) receptor antagonist R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol (M100907; 0.4 mg/kg) blocked the discriminative cue of LSD (0.375 microg/side) infused into ACC (from 68 to 16% drug lever responding). Furthermore, M100907 (0.5 microg/microl/side) locally infused into ACC completely blocked the stimulus effects of systemic LSD (0.04 mg/kg; from 80 to 12% on the LSD lever). Taken together, these data indicate that 5-HT(2A) receptors in the ACC are a primary target mediating the discriminative stimulus properties of LSD.

  3. Modulatory effect of the 5-HT1A agonist buspirone and the mixed non-hallucinogenic 5-HT1A/2A agonist ergotamine on psilocybin-induced psychedelic experience.

    PubMed

    Pokorny, Thomas; Preller, Katrin H; Kraehenmann, Rainer; Vollenweider, Franz X

    2016-04-01

    The mixed serotonin (5-HT) 1A/2A/2B/2C/6/7 receptor agonist psilocybin dose-dependently induces an altered state of consciousness (ASC) that is characterized by changes in sensory perception, mood, thought, and the sense of self. The psychological effects of psilocybin are primarily mediated by 5-HT2A receptor activation. However, accumulating evidence suggests that 5-HT1A or an interaction between 5-HT1A and 5-HT2A receptors may contribute to the overall effects of psilocybin. Therefore, we used a double-blind, counterbalanced, within-subject design to investigate the modulatory effects of the partial 5-HT1A agonist buspirone (20mg p.o.) and the non-hallucinogenic 5-HT2A/1A agonist ergotamine (3mg p.o.) on psilocybin-induced (170 µg/kg p.o.) psychological effects in two groups (n=19, n=17) of healthy human subjects. Psychological effects were assessed using the Altered State of Consciousness (5D-ASC) rating scale. Buspirone significantly reduced the 5D-ASC main scale score for Visionary Restructuralization (VR) (p<0.001), which was mostly driven by a reduction of the VR item cluster scores for elementary and complex visual hallucinations. Further, buspirone also reduced the main scale score for Oceanic Boundlessness (OB) including derealisation and depersonalisation phenomena at a trend level (p=0.062), whereas ergotamine did not show any effects on the psilocybin-induced 5D-ASC main scale scores. The present finding demonstrates that buspirone exerts inhibitory effects on psilocybin-induced effects, presumably via 5-HT1A receptor activation, an interaction between 5-HT1A and 5-HT2A receptors, or both. The data suggest that the modulation of 5-HT1A receptor activity may be a useful target in the treatment of visual hallucinations in different psychiatric and neurological diseases. PMID:26875114

  4. Modulatory effect of the 5-HT1A agonist buspirone and the mixed non-hallucinogenic 5-HT1A/2A agonist ergotamine on psilocybin-induced psychedelic experience.

    PubMed

    Pokorny, Thomas; Preller, Katrin H; Kraehenmann, Rainer; Vollenweider, Franz X

    2016-04-01

    The mixed serotonin (5-HT) 1A/2A/2B/2C/6/7 receptor agonist psilocybin dose-dependently induces an altered state of consciousness (ASC) that is characterized by changes in sensory perception, mood, thought, and the sense of self. The psychological effects of psilocybin are primarily mediated by 5-HT2A receptor activation. However, accumulating evidence suggests that 5-HT1A or an interaction between 5-HT1A and 5-HT2A receptors may contribute to the overall effects of psilocybin. Therefore, we used a double-blind, counterbalanced, within-subject design to investigate the modulatory effects of the partial 5-HT1A agonist buspirone (20mg p.o.) and the non-hallucinogenic 5-HT2A/1A agonist ergotamine (3mg p.o.) on psilocybin-induced (170 µg/kg p.o.) psychological effects in two groups (n=19, n=17) of healthy human subjects. Psychological effects were assessed using the Altered State of Consciousness (5D-ASC) rating scale. Buspirone significantly reduced the 5D-ASC main scale score for Visionary Restructuralization (VR) (p<0.001), which was mostly driven by a reduction of the VR item cluster scores for elementary and complex visual hallucinations. Further, buspirone also reduced the main scale score for Oceanic Boundlessness (OB) including derealisation and depersonalisation phenomena at a trend level (p=0.062), whereas ergotamine did not show any effects on the psilocybin-induced 5D-ASC main scale scores. The present finding demonstrates that buspirone exerts inhibitory effects on psilocybin-induced effects, presumably via 5-HT1A receptor activation, an interaction between 5-HT1A and 5-HT2A receptors, or both. The data suggest that the modulation of 5-HT1A receptor activity may be a useful target in the treatment of visual hallucinations in different psychiatric and neurological diseases.

  5. Deletion of CB2 cannabinoid receptor induces schizophrenia-related behaviors in mice.

    PubMed

    Ortega-Alvaro, Antonio; Aracil-Fernández, Auxiliadora; García-Gutiérrez, María S; Navarrete, Francisco; Manzanares, Jorge

    2011-06-01

    The possible role of the CB(2) receptor (CB(2)r) in psychiatric disorders has been considered. Several animal models use knockout (KO) mice that display schizophrenia-like behaviors and this study evaluated the role of CB(2)r in the regulation of such behaviors. Mice lacking the CB(2)r (CB(2)KO) were challenged in open field, light-dark box, elevated plus-maze, tail suspension, step down inhibitory avoidance, and pre-pulse inhibition tests (PPI). Furthermore, the effects of treatment with cocaine and risperidone were evaluated using the OF and the PPI test. Gene expression of dopamine D(2) (D(2)r), adrenergic-α(2C) (α(2C)r), serotonergic 5-HT(2A) and 5-HT(2C) receptors (5-HT(2A)r and 5-HT(2C)r) were studied by RT-PCR in brain regions related to schizophrenia. Deletion of CB(2)r decreased motor activity in the OF test, but enhanced response to acute cocaine and produced mood-related alterations, PPI deficit, and cognitive impairment. Chronic treatment with risperidone tended to impair PPI in WT mice, whereas it 'normalized' the PPI deficit in CB(2)KO mice. CB(2)KO mice presented increased D(2)r and α(2C)r gene expressions in the prefrontal cortex (PFC) and locus coeruleus (LC), decreased 5-HT(2C)r gene expression in the dorsal raphe (DR), and 5-HT(2A)r gene expression in the PFC. Chronic risperidone treatment in WT mice left α(2C)r gene expression unchanged, decreased D(2)r gene expression (15 μg/kg), and decreased 5-HT(2C)r and 5-HT(2A)r in PFC and DR. In CB(2)KO, the gene expression of D(2)r in the PFC, of α(2C)r in the LC, and of 5-HT(2C)r and 5-HT(2A)r in PFC was reduced; 5-HT(2C)r and 5-HT(2A)r gene expressions in DR were increased after treatment with risperidone. These results suggest that deletion of CB(2)r has a relation with schizophrenia-like behaviors. Pharmacological manipulation of CB(2)r may merit further study as a potential therapeutic target for the treatment of schizophrenia-related disorders. PMID:21430651

  6. Differential contributions of serotonin receptors to the behavioral effects of indoleamine hallucinogens in mice.

    PubMed

    Halberstadt, Adam L; Koedood, Liselore; Powell, Susan B; Geyer, Mark A

    2011-11-01

    Psilocin (4-hydroxy-N,N-dimethyltryptamine) is a hallucinogen that acts as an agonist at 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptors. Psilocin is the active metabolite of psilocybin, a hallucinogen that is currently being investigated clinically as a potential therapeutic agent. In the present investigation, we used a combination of genetic and pharmacological approaches to identify the serotonin (5-HT) receptor subtypes responsible for mediating the effects of psilocin on head twitch response (HTR) and the behavioral pattern monitor (BPM) in C57BL/6J mice. We also compared the effects of psilocin with those of the putative 5-HT(2C) receptor-selective agonist 1-methylpsilocin and the hallucinogen and non-selective serotonin receptor agonist 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT). Psilocin, 1-methylpsilocin, and 5-MeO-DMT induced the HTR, effects that were absent in mice lacking the 5-HT(2A) receptor gene. When tested in the BPM, psilocin decreased locomotor activity, holepoking, and time spent in the center of the chamber, effects that were blocked by the selective 5-HT(1A) antagonist WAY-100635 but were not altered by the selective 5-HT(2C) antagonist SB 242,084 or by 5-HT(2A) receptor gene deletion. 5-MeO-DMT produced similar effects when tested in the BPM, and the action of 5-MeO-DMT was significantly attenuated by WAY-100635. Psilocin and 5-MeO-DMT also decreased the linearity of locomotor paths, effects that were mediated by 5-HT(2C) and 5-HT(1A) receptors, respectively. In contrast to psilocin and 5-MeO-DMT, 1-methylpsilocin (0.6-9.6 mg/kg) was completely inactive in the BPM. These findings confirm that psilocin acts as an agonist at 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptors in mice, whereas the behavioral effects of 1-methylpsilocin indicate that this compound is acting at 5-HT(2A) sites but is inactive at the 5-HT(1A) receptor. The fact that 1-methylpsilocin displays greater pharmacological selectivity than psilocin indicates that 1-methylpsilocin

  7. N-Benzyl-5-methoxytryptamines as Potent Serotonin 5-HT2 Receptor Family Agonists and Comparison with a Series of Phenethylamine Analogues

    PubMed Central

    2015-01-01

    A series of N-benzylated-5-methoxytryptamine analogues was prepared and investigated, with special emphasis on substituents in the meta position of the benzyl group. A parallel series of several N-benzylated analogues of 2,5-dimethoxy-4-iodophenethylamine (2C-I) also was included for comparison of the two major templates (i.e., tryptamine and phenethylamine). A broad affinity screen at serotonin receptors showed that most of the compounds had the highest affinity at the 5-HT2 family receptors. Substitution at the para position of the benzyl group resulted in reduced affinity, whereas substitution in either the ortho or the meta position enhanced affinity. In general, introduction of a large lipophilic group improved affinity, whereas functional activity often followed the opposite trend. Tests of the compounds for functional activity utilized intracellular Ca2+ mobilization. Function was measured at the human 5-HT2A, 5-HT2B, and 5-HT2C receptors, as well as at the rat 5-HT2A and 5-HT2C receptors. There was no general correlation between affinity and function. Several of the tryptamine congeners were very potent functionally (EC50 values from 7.6 to 63 nM), but most were partial agonists. Tests in the mouse head twitch assay revealed that many of the compounds induced the head twitch and that there was a significant correlation between this behavior and functional potency at the rat 5-HT2A receptor. PMID:25547199

  8. Antidepressant- and anxiolytic-like activity of 7-phenylpiperazinylalkyl-1,3-dimethyl-purine-2,6-dione derivatives with diversified 5-HT₁A receptor functional profile.

    PubMed

    Partyka, Anna; Chłoń-Rzepa, Grażyna; Wasik, Anna; Jastrzębska-Więsek, Magdalena; Bucki, Adam; Kołaczkowski, Marcin; Satała, Grzegorz; Bojarski, Andrzej J; Wesołowska, Anna

    2015-01-01

    Continuing our earlier study in a group of purine-2,6-dione derivatives of long chain arylpiperazines (LCAPs), a series of 8-unsubstituted 7-phenylpiperazin-4-yl-alkyl (4-14) and 7-tetrahydroisoquinolinyl-alkyl (15-17) analogues were synthesized and their serotonin 5-HT1A, 5-HT2A, 5-HT6, 5-HT7 and dopamine D2 receptor affinities were determined. The study allowed us to identify some potent 5-HT1A receptor ligands with additional moderate affinity for 5-HT2A, 5-HT7 and dopamine D2 receptors. Compounds 9, 12, 13 and 14, with the highest 5HT1A receptor affinity, were selected for further functional in vivo studies and behavioural evaluation of antidepressant- and antianxiety-like activity. Compounds 9, 12 and 13 showed features of agonists of pre- and/or post-synaptic 5-HT1A receptors, whereas 14 was classified as an antagonist of postsynaptic sites. Moreover, derivatives 9 and 14 acted as antagonists of 5-HT2A receptors. In behavioural studies, compounds 9 and 13 showed antidepressant-like activity in the mouse forced swim test, and their effects were similar or stronger than those of imipramine. Compounds 9, 12 and 14 displayed potential anxiolytic-like properties in the mouse four-plate test, similar or even greater than those of the reference anxiolytic drug, diazepam.

  9. Using psilocybin to investigate the relationship between attention, working memory, and the serotonin 1A and 2A receptors.

    PubMed

    Carter, Olivia L; Burr, David C; Pettigrew, John D; Wallis, Guy M; Hasler, Felix; Vollenweider, Franz X

    2005-10-01

    Increasing evidence suggests a link between attention, working memory, serotonin (5-HT), and prefrontal cortex activity. In an attempt to tease out the relationship between these elements, this study tested the effects of the hallucinogenic mixed 5-HT1A/2A receptor agonist psilocybin alone and after pretreatment with the 5-HT2A antagonist ketanserin. Eight healthy human volunteers were tested on a multiple-object tracking task and spatial working memory task under the four conditions: placebo, psilocybin (215 microg/kg), ketanserin (50 mg), and psilocybin and ketanserin. Psilocybin significantly reduced attentional tracking ability, but had no significant effect on spatial working memory, suggesting a functional dissociation between the two tasks. Pretreatment with ketanserin did not attenuate the effect of psilocybin on attentional performance, suggesting a primary involvement of the 5-HT1A receptor in the observed deficit. Based on physiological and pharmacological data, we speculate that this impaired attentional performance may reflect a reduced ability to suppress or ignore distracting stimuli rather than reduced attentional capacity. The clinical relevance of these results is also discussed.

  10. New halogenated tris-(phenylalkyl)amines as h5-HT2B receptor ligands.

    PubMed

    Kapadia, Nirav; Ahmed, Shahrear; Harding, Wayne W

    2016-07-15

    A series of compounds in which various halogen substituents were incorporated into a phenyl ring of a tris-(phenylalkyl)amine scaffold, was synthesized and evaluated for affinity to h5-HT2 receptors. In general, all compounds were found to have good affinity for the 5-HT2B receptor and were selective over 5-HT2A and 5-HT2C receptors. Compound 9i was the most selective compound in this study and is the highest affinity 5-HT2B receptor ligand bearing a tris-(phenylalkyl)amine scaffold to date. PMID:27261181

  11. Aminergic receptors in astrogliotic plaques from patients with multiple sclerosis.

    PubMed

    Zeinstra, Esther; te Riele, Paula; Langlois, Xavier; Wilczak, Nadine; Leysen, Josée; de Keyser, Jacques

    2002-10-11

    Cultured astrocytes express a spectrum of neurotransmitter receptors. However, little is known about these receptors in situ. We previously reported the absence of beta(2) adrenergic receptors on astrocytes in multiple sclerosis (MS). Here we used [(3)H]-radioligands and receptor autoradiography to screen for a variety of other aminergic receptors in six silent chronic astrogliotic plaques in brain tissue obtained from five patients with MS. Dopamine D(1) and histamine H(1) receptors were absent. We detected specific binding for cholinergic muscarinic receptors > dopamine D(2), alpha(1-) and alpha(2)-adrenergic receptors > 5-HT(1A), 5-HT(1B/D), 5-HT(2A), 5-HT(2c), 5-HT(4), and dopamine D(3) receptors. Radiotracers for these aminergic receptors might be useful for studying astrogliosis in patients with MS, and compounds acting at some of these receptors may have potential to modulate astroglial function in MS. PMID:12361847

  12. Increased brain monoaminergic tone after the NMDA receptor GluN2A subunit gene knockout is responsible for resistance to the hypnotic effect of nitrous oxide.

    PubMed

    Petrenko, Andrey B; Yamakura, Tomohiro; Kohno, Tatsuro; Sakimura, Kenji; Baba, Hiroshi

    2013-01-01

    N-methyl-d-aspartate (NMDA) receptors can be inhibited by inhalational anesthetics in vitro at clinically relevant concentrations. Here, to clarify the role of NMDA receptors in anesthetic-induced unconsciousness, we examined the hypnotic properties of isoflurane, sevoflurane and nitrous oxide in NMDA receptor GluN2A subunit knockout mice. The hypnotic properties of inhalational anesthetics were evaluated in mice in the loss of righting reflex (LORR) assay by measuring the 50% concentration for LORR (LORR ED(50)). Knockout mice displayed isoflurane and sevoflurane LORR ED(50) values similar to wild-type controls, indicating no significant contribution of these receptors to the hypnotic action of halogenated anesthetics. However, compared with wild-type controls, mutant mice displayed larger isoflurane LORR ED(50) values in the presence of nitrous oxide, indicating a resistance to this gaseous anesthetic. Knockout mice have enhanced brain monoaminergic activity which occurs secondary to NMDA receptor dysfunction, and the observed resistance to the isoflurane LORR ED(50)-sparing effect of nitrous oxide could be abolished by pretreatment with the dopamine D(2) receptor antagonist droperidol or with the serotonin 5-HT(2A) receptor antagonist ketanserin. Thus, resistance to nitrous oxide in knockout mice appears to be a secondary phenomenon of monoaminergic origin and not a direct result of impaired NMDA receptor function. Our results indicate that NMDA receptors are not critically involved in the hypnotic action of conventionally-used inhalational anesthetics. Also, they suggest that increased brain monoaminergic tone can diminish the effects of general anesthesia. Finally, they provide further evidence that changes secondary to genetic manipulation can explain the results obtained in global knockouts. PMID:23123346

  13. The role of 5-HT7 receptor antagonism in the amelioration of MK-801-induced learning and memory deficits by the novel atypical antipsychotic drug lurasidone.

    PubMed

    Horisawa, Tomoko; Nishikawa, Hiroyuki; Toma, Satoko; Ikeda, Atsushi; Horiguchi, Masakuni; Ono, Michiko; Ishiyama, Takeo; Taiji, Mutsuo

    2013-05-01

    Lurasidone is a novel atypical antipsychotic with high affinity for dopamine D2, serotonin 5-HT7 and 5-HT2A receptors. We previously reported that lurasidone and the selective 5-HT7 receptor antagonist, SB-656104-A improved learning and memory deficits induced by MK-801, an N-methyl-d-aspartate (NMDA) receptor antagonist, in the rat passive avoidance test. In this study, we first examined the role of the 5-HT7 receptor antagonistic activity of lurasidone in its pro-cognitive effect to ameliorate MK-801-induced deficits in the rat passive avoidance test. The 5-HT7 receptor agonist, AS19, (2S)-(+)-5-(1,3,5-trimethylpyrazol-4-yl)-2-(dimethylamino) tetralin, (3 mg/kg, s.c.) completely blocked the attenuating effects of lurasidone (3 mg/kg, p.o.), highlighting the importance of 5-HT7 receptor antagonism in the pro-cognitive effect of lurasidone. AS19 (3 mg/kg, s.c.) also blocked the ameliorating effect of SB-656104-A (10 mg/kg, i.p.) in the same experimental paradigm. To further extend our observation, we next tested whether 5-HT7 receptor antagonism still led to the amelioration of MK-801-induced deficits when combined with D2 and 5-HT2A receptor antagonists, and found that SB-656104-A (10 mg/kg, i.p.) significantly ameliorated MK-801-induced deficits even in the presence of the D2 receptor antagonist raclopride (0.1 mg/kg, s.c.) and 5-HT2A receptor antagonist ketanserin (1 mg/kg, s.c.). Taken together, these results suggest that the 5-HT7 receptor antagonistic activity of lurasidone plays an important role in its effectiveness against MK-801-induced deficits, and may contribute to its pharmacological actions in patients with schizophrenia.

  14. 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

    PubMed Central

    Canal, Clinton E.; Booth, Raymond G.; Morgan, Drake

    2013-01-01

    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. PMID:23353901

  15. Multiple receptor subtypes mediate the effects of serotonin on rat subfornical organ neurons

    NASA Technical Reports Server (NTRS)

    Scrogin, K. E.; Johnson, A. K.; Schmid, H. A.

    1998-01-01

    The subfornical organ (SFO) receives significant serotonergic innervation. However, few reports have examined the functional effects of serotonin on SFO neurons. This study characterized the effects of serotonin on spontaneously firing SFO neurons in the rat brain slice. Of 31 neurons tested, 80% responded to serotonin (1-100 microM) with either an increase (n = 15) or decrease (n = 10) in spontaneous activity. Responses to serotonin were dose dependent and persisted after synaptic blockade. Excitatory responses could also be mimicked by the 5-hydroxytryptamine (5-HT)2A/2C receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI; 1-10 microM) and could be blocked by the 5-HT2A/2C-receptor antagonist LY-53,857 (10 microM). LY-53,857 unmasked inhibitory responses to serotonin in 56% of serotonin-excited cells tested. Serotonin-inhibited cells were also inhibited by the 5-HT1A-receptor agonist 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT; 1-10 microM; n = 7). The data indicate that SFO neurons are responsive to serotonin via postsynaptic activation of multiple receptor subtypes. The results suggest that excitatory responses to serotonin are mediated by 5-HT2A or 5-HT2C receptors and that inhibitory responses may be mediated by 5-HT1A receptors. In addition, similar percentages of serotonin-excited and -inhibited cells were also sensitive to ANG II. As such the functional relationship between serotonin and ANG II in the SFO remains unclear.

  16. The antidepressant effects of curcumin in the forced swimming test involve 5-HT1 and 5-HT2 receptors.

    PubMed

    Wang, Rui; Xu, Ying; Wu, Hong-Li; Li, Ying-Bo; Li, Yu-Hua; Guo, Jia-Bin; Li, Xue-Jun

    2008-01-01

    Curcuma longa is a main constituent of many traditional Chinese medicines, such as Xiaoyao-san, used to manage mental disorders effectively. Curcumin is a major active component of C. longa and its antidepressant-like effect has been previously demonstrated in the forced swimming test. The purpose of this study was to explore the possible contribution of serotonin (5-HT) receptors in the behavioral effects induced by curcumin in this animal model of depression. 5-HT was depleted by the tryptophan hydroxylase inhibitor p-chlorophenylalanine (PCPA, 100 mg/kg, i.p.) prior to the administration of curcumin, and the consequent results showed that PCPA blocked the anti-immobility effect of curcumin in forced swimming test, suggesting the involvement of the serotonergic system. Moreover, pre-treatment of pindolol (10 mg/kg, i.p., a beta-adrenoceptors blocker/5-HT(1A/1B) receptor antagonist), 4-(2'-methoxy-phenyl)-1-[2'-(n-2''-pyridinyl)-p-iodobenzamino-]ethyl-piperazine (p-MPPI, 1 mg/kg, s.c., a selective 5-HT(1A) receptor antagonist), or 1-(2-(1-pyrrolyl)-phenoxy)-3-isopropylamino-2-propanol (isamoltane, 2.5 mg/kg, i.p., a 5-HT(1B) receptor antagonist) was found to prevent the effect of curcumin (10 mg/kg) in forced swimming test. On the other hand, a sub-effective dose of curcumin (2.5 mg/kg, p.o.) produced a synergistic effect when given jointly with (+)-8-hydroxy-2-(di-n-propylamino)tetralin, (8-OH-DPAT, 1 mg/kg, i.p., a 5-HT(1A) receptor agonist), anpirtoline (0.25 mg/kg, i.p., a 5-HT(1B) receptor agonist) or ritanserin (4 mg/kg, i.p., a 5-HT(2A/2C) receptor antagonist), but not with ketanserin (5 mg/kg, i.p., a 5-HT(2A/2C) receptor antagonist with higher affinity to 5-HT(2A) receptor) or R(-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI, 1 mg/kg, i.p., a 5-HT(2A) receptor agonist). Taken together, these results indicate that the antidepressant-like effect of curcumin in the forced swimming test is related to serotonergic system and may be mediated by, at least

  17. Pyrrolo[1,3]benzothiazepine-based serotonin and dopamine receptor antagonists. Molecular modeling, further structure-activity relationship studies, and identification of novel atypical antipsychotic agents.

    PubMed

    Campiani, Giuseppe; Butini, Stefania; Fattorusso, Caterina; Catalanotti, Bruno; Gemma, Sandra; Nacci, Vito; Morelli, Elena; Cagnotto, Alfredo; Mereghetti, Ilario; Mennini, Tiziana; Carli, Miriana; Minetti, Patrizia; Di Cesare, M Assunta; Mastroianni, Domenico; Scafetta, Nazzareno; Galletti, Bruno; Stasi, M Antonietta; Castorina, Massimo; Pacifici, Licia; Vertechy, Mario; Di Serio, Stefano; Ghirardi, Orlando; Tinti, Ornella; Carminati, Paolo

    2004-01-01

    Recently we reported the pharmacological characterization of the 9,10-dihydropyrrolo[1,3]benzothiazepine derivative (S)-(+)-8 as a novel atypical antipsychotic agent. This compound had an optimum pK(i) 5-HT(2A)/D(2) ratio of 1.21 (pK(i) 5-HT(2A) = 8.83; pK(i) D(2) = 7.79). The lower D(2) receptor affinity of (S)-(+)-8 compared to its enantiomer was explained by the difficulty in reaching the conformation required to optimally fulfill the D(2) pharmacophore. With the aim of finding novel atypical antipsychotics we further investigated the core structure of (S)-(+)-8, synthesizing analogues with specific substituents; the structure-activity relationship (SAR) study was also expanded with the design and synthesis of other analogues characterized by a pyrrolo[2,1-b][1,3]benzothiazepine skeleton, substituted on the benzo-fused ring or on the pyrrole system. On the 9,10-dihydro analogues the substituents introduced on the pyrrole ring were detrimental to affinity for dopamine and for 5-HT(2A) receptors, but the introduction of a double bond at C-9/10 on the structure of (S)-(+)-8 led to a potent D(2)/5-HT(2A) receptor ligand with a typical binding profile (9f, pK(i) 5-HT(2A)/D(2) ratio of 1.01, log Y = 8.43). Then, to reduce D(2) receptor affinity and restore atypicality on unsaturated analogues, we exploited the effect of specific substitutions on the tricyclic system of 9f. Through a molecular modeling approach we generated a novel series of potential atypical antipsychotic agents, with optimized 5HT(2A)/D(2) receptor affinity ratios and that were easier to synthesize and purify than the reference compound (S)-(+)-8. A number of SAR trends were identified, and among the analogues synthesized and tested in binding assays, 9d and 9m were identified as the most interesting, giving atypical log Y scores respectively 4.98 and 3.18 (pK(i) 5-HT(2A)/D(2) ratios of 1.20 and 1.30, respectively). They had a multireceptor affinity profile and could be promising atypical agents

  18. Investigation of the role of 5-HT2 receptor subtypes in the control of the bladder and the urethra in the anaesthetized female rat

    PubMed Central

    Mbaki, Y; Ramage, A G

    2008-01-01

    Background and purpose: Micturition is controlled by central 5-HT-containing pathways. 5-HT2 receptors have been implicated in this system especially in control of the urethra, which is a drug target for treating urinary incontinence. This study investigates the role of each of the three subtypes of this receptor with emphasis on sphincter regulation. Experimental approach: Recordings of urethral and bladder pressure, external urethral sphincter (EUS) EMG, as well as the micturition reflex induced by bladder distension along with blood pressure and heart rate were made in anaesthetized rats. The effects of agonists and antagonists for 5-HT2 receptor subtypes were studied on these variables. Key results: The 5-HT2C agonists Ro 60-0175, WAY 161503 and mCPP, i.v., activated the EUS, increased urethral pressure and inhibited the micturition reflex. The effects of Ro 60-0175 on the EUS were blocked by the 5-HT2C antagonist SB 242084 and the 5-HT2A antagonists, ketanserin and MDL 100907. SB 242084 also blocked the inhibitory action on the reflex, while the 5-HT2B antagonist RS 127445 only blocked the increase in urethral pressure. The 5-HT2A receptor agonist DOI given i.v. or i.t. but not i.c.v. activated the EUS. Conclusions and implications: 5-HT2A/2C receptors located in the sacral spinal cord activate the EUS, while central 5-HT2C receptors inhibit the micturition reflex and 5-HT2B receptors, probably at the level of the urethra, increase urethral smooth muscle tone. Furthermore, 5-HT2B and 5-HT2C receptors do not seem to play an important role in the physiological regulation of micturition. PMID:18604238

  19. Role of CRH in the effects of 5-HT-receptor agonists on food intake and metabolic rate.

    PubMed

    Bovetto, S; Rouillard, C; Richard, D

    1996-11-01

    Two series of experiments were conducted to investigate the role of corticotropin-releasing hormone (CRH) in the effects of 5-hydroxytryptamine (5-HT) on energy intake and energy expenditure. The first set of experiments was carried out to confirm the influence of 5-HT1A-, 5-HT1B-, 5-HT2A/2C-receptor agonists on the activation of the hypothalamic-pituitary-adrenal axis. Plasma corticosterone levels were measured, and a double-immunolabeling procedure was used to determine whether the neuronal activity marker, c-Fos protein (Fos), could be found within brain neurons containing CRH after treatments with 5-HT1A-, 5-HT1B-, 5-HT2A/2C-receptor agonists. The second series of experiments was conducted to assess the involvement of CRH in the effects of 5-HT on food intake and metabolic rate (VO2). The effects of the 5-HT1A-, 5-HT1B-, 5-HT2A/2C-receptor agonists on food intake and VO2 were measured in rats treated with the CRH antagonist, alpha-helical CRH-(9-41). In both experiments rats were intraperitoneally injected with either a vehicle (NaCl 0.9%), the 5-HT1A-receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT), the 5-HT1B-receptor agonist 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole succinate (RU-24969), or the 5-HT2A/2C-receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI). Fos immunoreactivity was detectable within the CRH-containing neurons of the paraventricular nucleus of the hypothalamus (PVH) after injection of each of the 5-HT-receptor agonists used. The CRH antagonist alpha-helical CRH-(9-41) attenuated the increases in metabolic rate induced by DOI and 8-OH-DPAT. alpha-Helical CRH did not, however, prevent the effects of RU-24969 and DOI on either nocturnal metabolic rate or food intake. The present results provide further evidence for a role of CRH in 5-HT-mediated thermogenic effect, which likely involves the 5-HT2A/2C receptor during the day and the 5-HT1A receptor during the night

  20. SSRI augmentation of antipsychotic alters expression of GABA(A) receptor and related genes in PMC of schizophrenia patients.

    PubMed

    Silver, Henry; Susser, Ehud; Danovich, Lena; Bilker, Warren; Youdim, Moussa; Goldin, Vladimir; Weinreb, Orly

    2011-06-01

    Clinical studies have shown that negative symptoms of schizophrenia unresponsive to antipsychotic given alone can improve after augmentation with SSRI antidepressant. Laboratory investigations into the mechanism of this synergism showed that co-administration of SSRI and antipsychotic produces changes in GABA(A) receptor and related systems, which differ from the effects of each drug alone. To examine the clinical relevance of these findings, the current study examined the effects of SSRI augmentation treatment on GABA(A) receptor and related systems in schizophrenia patients. Schizophrenia patients with high levels of negative symptoms unresponsive to antipsychotic treatment received add-on fluvoxamine (100 mg/d). Blood was taken before and 1, 3 and 6 wk after adding fluvoxamine and peripheral mononuclear cells (PMC) isolated. RNA encoding for GABA(A)β3, 5-HT2A, and 5-HT7 receptors, PKCβ2, and brain-derived neurotrophic factor (BDNF) was assayed with real-time RT-PCR. Plasma BDNF protein was assayed using ELISA. Clinical symptoms were assessed with validated rating scales. We found significant increase in mRNA encoding for GABA(A)β3 and 5-HT2A, 5-HT7 receptors and BDNF and a reduction in PKCβ2 mRNA. Plasma BDNF protein concentrations were increased. There were significant correlations among the genes. Clinical symptoms improved significantly. mRNA expression of PKCβ2, 5-HT2A and 5-HT7 showed significant associations with clinical symptoms. Combined SSRI+antipsychotic treatment is associated with changes in GABA(A) receptor and in related signalling systems in patients. These changes may be part of the mechanism of clinically effective drug action and may prove to be biomarkers of pharmacological response.

  1. Decreased striatal dopamine receptor binding in primary focal dystonia: a D2 or D3 defect?

    PubMed Central

    Karimi, Morvarid; Moerlein, Stephen M.; Videen, Tom O.; Luedtke, Robert R.; Taylor, Michelle; Mach, Robert H.; Perlmutter, Joel S.

    2010-01-01

    Dystonia is an involuntary movement disorder characterized by repetitive patterned or sustained muscle contractions causing twisting or abnormal postures. Several lines of evidence suggest that abnormalities of dopaminergic pathways contribute to the pathophysiology of dystonia. In particular dysfunction of D2-like receptors that mediate function of the indirect pathway in the basal ganglia may play a key role. We have demonstrated with positron emission tomography (PET) that patients with primary focal cranial or hand dystonia have reduced putamenal specific binding of [18F]spiperone a non-selective D2-like radioligand with nearly equal affinity for serotonergic 5-HT(2A) sites. We then repeated the study with [18F]N-methyl-benperidol (NMB), a more selective D2-like receptor radioligand with minimal affinity for 5-HT(2A). Surprisingly, there was no decrease in NMB binding in the putamen of subjects with dystonia. Our findings excluded reductions of putamenal uptake greater than 20% with 95% confidence intervals. Following analysis of the in vitro selectivity of NMB and spiperone demonstrated that NMB was highly selective for D2 receptors relative to D3 receptors (200-fold difference in affinity), whereas spiperone has similar affinity for all three of the D2-like receptor subtypes. These findings coupled with other literature suggest that a defect in D3, rather than D2, receptor expression may be associated with primary focal dystonia. PMID:20960437

  2. Stimulation of glutamate receptors in the ventral tegmental area is necessary for serotonin-2 receptor-induced increases in mesocortical dopamine release.

    PubMed

    Pehek, E A; Hernan, A E

    2015-04-01

    Modulation of dopamine (DA) released by serotonin-2 (5-HT2) receptors has been implicated in the mechanism of action of antipsychotic drugs. The mesocortical DA system has been implicated particularly in the cognitive deficits observed in schizophrenia. Agonism at 5-HT2A receptors in the prefrontal cortex (PFC) is associated with increases in cortical DA release. Evidence indicates that 5-HT2A receptors in the cortex regulate mesocortical DA release through stimulation of a "long-loop" feedback system from the PFC to the ventral tegmental area (VTA) and back. However, a causal role for VTA glutamate in the 5-HT2-induced increases in PFC DA has not been established. The present study does so by measuring 5-HT2 agonist-induced DA release in the cortex after infusions of glutamate antagonists into the VTA of the rat. Infusions of a combination of a N-methyl-d-aspartic acid (NMDA) (AP-5: 2-amino-5-phosphopentanoic acid) and an AMPA/kainate (CNQX: 6-cyano-7-nitroquinoxaline-2,3-dione) receptor antagonist into the VTA blocked the increases in cortical DA produced by administration of the 5-HT2 agonist DOI [(±)-2,5-dimethoxy-4-iodoamphetamine] (2.5mg/kg s.c.). These results demonstrate that stimulation of glutamate receptors in the VTA is necessary for 5-HT2 agonist-induced increases in cortical DA.

  3. Stimulation of glutamate receptors in the ventral tegmental area is necessary for serotonin-2 receptor-induced increases in mesocortical dopamine release.

    PubMed

    Pehek, E A; Hernan, A E

    2015-04-01

    Modulation of dopamine (DA) released by serotonin-2 (5-HT2) receptors has been implicated in the mechanism of action of antipsychotic drugs. The mesocortical DA system has been implicated particularly in the cognitive deficits observed in schizophrenia. Agonism at 5-HT2A receptors in the prefrontal cortex (PFC) is associated with increases in cortical DA release. Evidence indicates that 5-HT2A receptors in the cortex regulate mesocortical DA release through stimulation of a "long-loop" feedback system from the PFC to the ventral tegmental area (VTA) and back. However, a causal role for VTA glutamate in the 5-HT2-induced increases in PFC DA has not been established. The present study does so by measuring 5-HT2 agonist-induced DA release in the cortex after infusions of glutamate antagonists into the VTA of the rat. Infusions of a combination of a N-methyl-d-aspartic acid (NMDA) (AP-5: 2-amino-5-phosphopentanoic acid) and an AMPA/kainate (CNQX: 6-cyano-7-nitroquinoxaline-2,3-dione) receptor antagonist into the VTA blocked the increases in cortical DA produced by administration of the 5-HT2 agonist DOI [(±)-2,5-dimethoxy-4-iodoamphetamine] (2.5mg/kg s.c.). These results demonstrate that stimulation of glutamate receptors in the VTA is necessary for 5-HT2 agonist-induced increases in cortical DA. PMID:25637799

  4. Partial role of 5-HT2 and 5-HT3 receptors in the activity of antidepressants in the mouse forced swimming test.

    PubMed

    Redrobe, J P; Bourin, M

    1997-05-01

    The present study was designed to evaluate the roles of 5-HT2 and 5-HT3 receptors in the mouse forced swimming test, by using selective agonists and antagonists of 5-HT(2A/C) and 5-HT3 receptor sites. Agonists/antagonists and antidepressants were administered 45 min and 30 min, respectively, prior to testing. Pretreatment with (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) (4 mg/kg, i.p.) or 2-methyl-5-HT (4 mg/kg, i.p.) had no effect on the anti-immobility effects of any antidepressant tested. Prior administration of ritanserin (4 mg/kg, i.p.) or ketanserin (8 mg/kg, i.p.), on the other hand, potentiated the effects of sub-active doses of imipramine (8 mg/kg, i.p.) and desipramine (16 mg/kg, i.p.) but not of maprotiline (8 mg/kg, i.p.), fluoxetine (16 mg/kg, i.p.), citalopram (16 mg/kg, i.p.) or fluvoxamine (8 mg/kg, i.p.). Pretreatment with ondansetron (1 X 10(-5) mg/kg, i.p.) enhanced the antidepressant-like effects of sub-active doses of the selective serotonin reuptake inhibitors. The results of the present study suggested that, in the forced swimming test, the selective serotonin reuptake inhibitors act partially through 5-HT3 receptor sites, whereas the tricyclic antidepressants exert effects at 5-HT(2A/C) receptor sites. Anti-immobility effects of the selective noradrenaline reuptake inhibitor, maprotiline, do not seem to be mediated by 5-HT(2A/C) or 5-HT3 receptor function.

  5. Optimization of 2-phenylcyclopropylmethylamines as selective serotonin 2C receptor agonists and their evaluation as potential antipsychotic agents.

    PubMed

    Cheng, Jianjun; Giguère, Patrick M; Onajole, Oluseye K; Lv, Wei; Gaisin, Arsen; Gunosewoyo, Hendra; Schmerberg, Claire M; Pogorelov, Vladimir M; Rodriguiz, Ramona M; Vistoli, Giulio; Wetsel, William C; Roth, Bryan L; Kozikowski, Alan P

    2015-02-26

    The discovery of a new series of compounds that are potent, selective 5-HT2C receptor agonists is described herein as we continue our efforts to optimize the 2-phenylcyclopropylmethylamine scaffold. Modifications focused on the alkoxyl substituent present on the aromatic ring led to the identification of improved ligands with better potency at the 5-HT2C receptor and excellent selectivity against the 5-HT2A and 5-HT2B receptors. ADMET studies coupled with a behavioral test using the amphetamine-induced hyperactivity model identified four compounds possessing drug-like profiles and having antipsychotic properties. Compound (+)-16b, which displayed an EC50 of 4.2 nM at 5-HT2C, no activity at 5-HT2B, and an 89-fold selectivity against 5-HT2A, is one of the most potent and selective 5-HT2C agonists reported to date. The likely binding mode of this series of compounds to the 5-HT2C receptor was also investigated in a modeling study, using optimized models incorporating the structures of β2-adrenergic receptor and 5-HT2B receptor. PMID:25633969

  6. Dynamic alterations of serotonergic metabolism and receptors during social isolation of low- and high-active mice.

    PubMed

    Rilke, O; Freier, D; Jähkel, M; Oehler, J

    1998-04-01

    Alterations induced by social isolation (1 day to 18 weeks) in low- and high-active mice (LAM and HAM) were studied in respect to serotonin metabolism, [3H]-8-OH-DPAT binding of presynaptic (midbrain), postsynaptic (hippocampus) 5-HT1A receptors and [3H]-ketanserin binding of cortical 5-HT2A receptors. Individual housing of mice was associated with reduction of serotonin metabolism, depending on isolation time and brain structure. Whereas a transient decrease in the striatum and cortex was detected between 1 week and 6 weeks, reduction of cerebellar and hippocampal serotonin metabolism was found later (12-18 weeks). Serotonergic systems of HAM were found to be more reactive to environmental disturbances, and their serotonin metabolism was more affected by social isolation. Isolation-induced upregulation of cortical 5-HT2A receptors was measured only in HAM. Densities of postsynaptic 5-HT1A receptors in the hippocampus did differ either in grouped or isolated mice. However, there were significant differences in hippocampal 5-HT1A receptor affinity, especially between 1 day and 3 weeks. Transient downregulation of presynaptic 5-HT1A receptors in the midbrain was found in isolated mice between 3 and 6 weeks. These results are discussed in terms of interactions between serotonergic alterations and isolation-induced aggression.

  7. Association of Polymorphisms within the Serotonin Receptor Genes 5-HTR1A, 5-HTR1B, 5-HTR2A and 5-HTR2C and Migraine Susceptibility in a Turkish Population

    PubMed Central

    Yücel, Yavuz; Coşkun, Salih; Cengiz, Beyhan; Özdemir, Hasan H.; Uzar, Ertuğrul; Çim, Abdullah; Camkurt, M. Akif; Aluclu, M. Ufuk

    2016-01-01

    Objective Migraine, a highly prevelant headache disorder, is regarded as a polygenic multifactorial disease. Serotonin (5-HT) and their respective receptors have been implicated in the patogenesis. Methods We investigated the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptor gene polymorphisms and their association with migraine in Turkish patients. The rs6295, rs1300060, rs1228814, rs6311, rs6313, rs6314, rs6318, rs3813929 (−759C/T) and rs518147 polymorphisms were analyzed in 135 patients with migraine and 139 healthy subjects, using a BioMark 96.96 dynamic array system. Results We found no difference in the frequency of the analyzed eight out of nine polymorpisms between migraine and control groups. However, a significant association was found between the rs3813929 polymorphism in the promoter region of 5-HTR2C gene and migraine. Also, the allele of rs3813929 was more common in the migraine group. Conclusion This result suggests that the 5-HTR2C rs3813929 polymorphism can be a genetic risk factor for migraine in a Turkish population. PMID:27489378

  8. Multiple microvascular and astroglial 5-hydroxytryptamine receptor subtypes in human brain: molecular and pharmacologic characterization.

    PubMed

    Cohen, Z; Bouchelet, I; Olivier, A; Villemure, J G; Ball, R; Stanimirovic, D B; Hamel, E

    1999-08-01

    Physiologic and anatomic evidence suggest that 5-hydroxytryptamine (5-HT) neurons regulate local cerebral blood flow and blood-brain barrier permeability. To evaluate the possibility that some of these effects occur directly on the blood vessels, molecular and/or pharmacologic approaches were used to assess the presence of 5-HT receptors in human brain microvascular fractions, endothelial and smooth muscle cell cultures, as well as in astroglial cells which intimately associate with intraparenchymal blood vessels. Isolated microvessels and capillaries consistently expressed messages for the h5-HT1B, h5-HT1D, 5-HT1F, 5-HT2A but not 5-HT7 receptors. When their distribution within the vessel wall was studied in more detail, it was found that capillary endothelial cells exhibited mRNA for the h5-HT1D and for the 5-HT7 receptors whereas microvascular smooth muscle cells, in addition to h5-HT1D and 5-HT7, also showed polymerase chain reaction products for h5-HT1B receptors. Expression of 5-HT1F and 5-HT2A receptor mRNAs was never detected in any of the microvascular cell cultures. In contrast, messages for all 5-HT receptors tested were detected in human brain astrocytes with a predominance of the 5-HT2A and 5-HT7 subtypes. In all cultures, sumatriptan inhibited (35-58%, P < .05) the forskolin-stimulated production of cyclic AMP, an effect blocked by the 5-HT1B/1D receptor antagonists GR127935 and GR55562. In contrast, 5-carboxamidotryptamine induced strong increases (> or = 400%, P < .005) in basal cyclic AMP levels that were abolished by mesulergine, a nonselective 5-HT7 receptor antagonist. Only astroglial cells showed a ketanserin-sensitive increase (177%, P < .05) in IP3 formation when exposed to 5-HT. These results show that specific populations of functional 5-HT receptors are differentially distributed within the various cellular compartments of the human cortical microvascular bed, and that human brain astroglial cells are endowed with multiple 5-HT receptors

  9. Increased numbers of motor activity peaks during light cycle are associated with reductions in adrenergic alpha(2)-receptor levels in a transgenic Huntington's disease rat model.

    PubMed

    Bode, Felix J; Stephan, Michael; Wiehager, Sara; Nguyen, Huu Phuc; Björkqvist, Maria; von Hörsten, Stephan; Bauer, Andreas; Petersén, Asa

    2009-12-14

    Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the HD gene. Besides psychiatric, motor and cognitive symptoms, HD patients suffer from sleep disturbances. In order to screen a rat model transgenic for HD (tgHD rats) for sleep-wake cycle dysregulation, we monitored their circadian activity peaks in the present study. TgHD rats of both sexes showed hyperactivity during the dark cycle and more frequent light cycle activity peaks indicative for a disturbed sleep-wake cycle. Focusing on males at the age of 4 and 14 months, analyses of receptor levels in the hypothalamus and the basal forebrain revealed that 5-HT(2A)- and adrenergic alpha(2)-receptor densities in these regions were significantly altered in tgHD rats compared to their wild-type littermates. Adrenergic receptor densities correlated negatively with the light cycle hyperactivity peaks at later stages of the disease in male tgHD rats. Furthermore, reduced leptin levels, a feature associated with circadian misalignment, were present. Our study demonstrates that the male tgHD rat is a suitable model to investigate HD associated sleep alterations. Further studies are warranted to elucidate the role of adrenergic- and 5-HT(2A)-receptors as therapeutic targets for dysregulation of the circadian activity in HD.

  10. Up-regulation of 5-HT2B receptor density and receptor-mediated glycogenolysis in mouse astrocytes by long-term fluoxetine administration.

    PubMed

    Kong, Ebenezer K C; Peng, Liang; Chen, Ye; Yu, Albert C H; Hertz, Leif

    2002-02-01

    The effects were studied of short-term (1 week) versus long-term (2-3 weeks) fluoxetine treatment of primary cultures of mouse astrocytes, differentiated by treatment with dibutyryl cyclic AMP. From previous experiments it is known that acute treatment with fluoxetine stimulates glycogenolysis and increases free cytosolic Ca2+ concentration ([Ca2+]i]) in these cultures, whereas short-term (one week) treatment with 10 microM down-regulates the effects on glycogen and [Ca2+]i, when fluoxetine administration is renewed (or when serotonin is administered). Moreover, antagonist studies have shown that these responses are evoked by activation of a 5-HT2, receptor that is different from the 5-HT2A receptor and therefore at that time tentatively were interpreted as being exerted on 5-HT2C receptors. In the present study the cultures were found by RT-PCR to express mRNA for 5-HT2A and 5-HT2B receptors, but not for the 5-HT2C receptor, identifying the 5-HT2 receptor activated by fluoxetine as the 5-HT2B receptor, the most recently cloned 5-Ht2 receptor and a 5-HT receptor known to be more abundant in human, than in rodent, brain. Both short-term and long-term treatment with fluoxetine increased the specific binding of [3H]mesulergine, a ligand for alL three 5-HT2 receptors. Long-term treatment with fluoxetine caused an agonist-induced up-regulation of the glycogenolytic response to renewed administration of fluoxetine, whereas short-term treatment abolished the fluoxetine-induced hydrolysis of glycogen. Thus, during a treatment period similar to that required for fluoxetine's clinical response to occur, 5-HT2B-mediated effects are initially down-regulated and subsequently up-regulated. PMID:11930908

  11. The effect of the sigma-1 receptor selective compound LS-1-137 on the DOI-induced head twitch response in mice.

    PubMed

    Malik, Maninder; Rangel-Barajas, Claudia; Mach, Robert H; Luedtke, Robert R

    2016-09-01

    Several receptor mediated pathways have been shown to modulate the murine head twitch response (HTR). However, the role of sigma receptors in the murine (±)-2,5-dimethoxy-4-iodoamphetamine (DOI)-induced HTR has not been previously investigated. We examined the ability of LS-1-137, a novel sigma-1 vs. sigma-2 receptor selective phenylacetamide, to modulate the DOI-induced HTR in DBA/2J mice. We also assessed the in vivo efficacy of reference sigma-1 receptor antagonists and agonists PRE-084 and PPCC. The effect of the sigma-2 receptor selective antagonist RHM-1-86 was also examined. Rotarod analysis was performed to monitor motor coordination after LS-1-137 administration. Radioligand binding techniques were used to determine the affinity of LS-1-137 at 5-HT2A and 5-HT2C receptors. LS-1-137 and the sigma-1 receptor antagonists haloperidol and BD 1047 were able to attenuate a DOI-induced HTR, indicating that LS-1-137 was acting in vivo as a sigma-1 receptor antagonist. LS-1-137 did not compromise rotarod performance within a dose range capable of attenuating the effects of DOI. Radioligand binding studies indicate that LS-1-137 exhibits low affinity binding at both 5-HT2A and 5-HT2C receptors. Based upon the results from these and our previous studies, LS-1-137 is a neuroprotective agent that attenuates the murine DOI-induced HTR independent of activity at 5-HT2 receptor subtypes, D2-like dopamine receptors, sigma-2 receptors and NMDA receptors. LS-1-137 appears to act as a sigma-1 receptor antagonist to inhibit the DOI-induced HTR. Therefore, the DOI-induced HTR can be used to assess the in vivo efficacy of sigma-1 receptor selective compounds. PMID:27397487

  12. The effect of the sigma-1 receptor selective compound LS-1-137 on the DOI-induced head twitch response in mice.

    PubMed

    Malik, Maninder; Rangel-Barajas, Claudia; Mach, Robert H; Luedtke, Robert R

    2016-09-01

    Several receptor mediated pathways have been shown to modulate the murine head twitch response (HTR). However, the role of sigma receptors in the murine (±)-2,5-dimethoxy-4-iodoamphetamine (DOI)-induced HTR has not been previously investigated. We examined the ability of LS-1-137, a novel sigma-1 vs. sigma-2 receptor selective phenylacetamide, to modulate the DOI-induced HTR in DBA/2J mice. We also assessed the in vivo efficacy of reference sigma-1 receptor antagonists and agonists PRE-084 and PPCC. The effect of the sigma-2 receptor selective antagonist RHM-1-86 was also examined. Rotarod analysis was performed to monitor motor coordination after LS-1-137 administration. Radioligand binding techniques were used to determine the affinity of LS-1-137 at 5-HT2A and 5-HT2C receptors. LS-1-137 and the sigma-1 receptor antagonists haloperidol and BD 1047 were able to attenuate a DOI-induced HTR, indicating that LS-1-137 was acting in vivo as a sigma-1 receptor antagonist. LS-1-137 did not compromise rotarod performance within a dose range capable of attenuating the effects of DOI. Radioligand binding studies indicate that LS-1-137 exhibits low affinity binding at both 5-HT2A and 5-HT2C receptors. Based upon the results from these and our previous studies, LS-1-137 is a neuroprotective agent that attenuates the murine DOI-induced HTR independent of activity at 5-HT2 receptor subtypes, D2-like dopamine receptors, sigma-2 receptors and NMDA receptors. LS-1-137 appears to act as a sigma-1 receptor antagonist to inhibit the DOI-induced HTR. Therefore, the DOI-induced HTR can be used to assess the in vivo efficacy of sigma-1 receptor selective compounds.

  13. The antidepressant activity of inositol in the forced swim test involves 5-HT(2) receptors.

    PubMed

    Einat, H; Clenet, F; Shaldubina, A; Belmaker, R H; Bourin, M

    2001-01-01

    The effect of inositol as an antidepressant was previously demonstrated in both animal models of depression-like behavior and in clinical trials. Unlike most antidepressant drugs, inositol does not have a clear target in the synapse and was not demonstrated to alter monoamine levels in the brain. The present study attempted to draw a psychopharmacological profile of inositol's behavioral effects by exploring the interactions between the drug and specific receptor agonists and antagonists in the forced swim test. Rats received inositol treatment (or control) in combination with the serotonergic metabolism inhibitor PCPA or with the noradrenergic neurotoxin DSP-4. Results indicated that PCPA but not DSP-4 abolished the ability of inositol to cause a reduction in immobility time in the forced swim test. In mice, the specific 5-HT(2A)/5-HT(2C) antagonist ritanserin, but not the 5-HT(1A)/5-HT(1B)/beta adrenergic antagonist pindolol, abolished inositol's effect in the forced swim test. The 5-HT(2A)/5-HT(2C) agonist DOI and the 5-HT(1A) agonist 8-OH-DPAT did not have any significant effects on inositol's activity. The present data indicates that the antidepressant effect of inositol may involve 5-HT(2) receptors. It is thus possible that the effects of reuptake antidepressant drugs and the effects of inositol may have a common final pathway.

  14. Serotonin1A receptors in the pathophysiology of schizophrenia: development of novel cognition-enhancing therapeutics.

    PubMed

    Sumiyoshi, Tomiki; Bubenikova-Valesova, Vera; Horacek, Jiri; Bert, Bettina

    2008-10-01

    Serotonin (5-HT) receptors have been suggested to play key roles in psychosis, cognition, and mood via influence on neurotransmitters, synaptic integrity, and neural plasticity. Specifically, genetic evidence indicates that 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor single-nucleotide polymorphisms (SNPs) are related to psychotic symptoms, cognitive disturbances, and treatment response in schizophrenia. Data from animal research suggest the role of 5-HT in cognition via its influence on dopaminergic, cholinergic, glutamatergic, and GABAergic function. This article provides up-to-date findings on the role of 5-HT receptors in endophenotypic variations in schizophrenia and the development of newer cognition-enhancing medications, based on basic science and clinical evidence. Imaging genetics studies on associations of polymorphisms of several 5-HT receptor subtypes with brain structure, function, and metabolism suggest a role for the prefrontal cortex and the parahippocampal gyrus in cognitive impairments of schizophrenia. Data from animal experiments to determine the effect of agonists/antagonists at 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptors on behavioral performance in animal models of schizophrenia based on the glutamatergic hypothesis provide useful information. For this purpose, standard as well as novel cognitive tasks provide a measure of memory/information processing and social interaction. In order to scrutinize mixed evidence for the ability of 5-HT(1A) agonists/antagonists to improve cognition, behavioral data in various paradigms from transgenic mice overexpressing 5-HT(1A) receptors provide valuable insights. Clinical trials reporting the advantage of 5-HT(1A) partial agonists add to efforts to shape pharmacologic perspectives concerning cognitive enhancement in schizophrenia by developing novel compounds acting on 5-HT receptors. Overall, these lines of evidence from translational research will facilitate the development of newer pharmacologic strategies

  15. A systematic investigation of the differential roles for ventral tegmentum serotonin 1- and 2-type receptors on food intake in the rat.

    PubMed

    Pratt, Wayne E; Clissold, Kara A; Lin, Peagan; Cain, Amanda E; Ciesinski, Alexa F; Hopkins, Thomas R; Ilesanmi, Adeolu O; Kelly, Erin A; Pierce-Messick, Zachary; Powell, Daniel S; Rosner, Ian A

    2016-10-01

    Central serotonin (5-HT) pathways are known to influence feeding and other ingestive behaviors. Although the ventral tegmentum is important for promoting the seeking and consumption of food and drugs of abuse, the roles of 5-HT receptor subtypes in this region on food intake have yet to be comprehensively examined. In these experiments, food restricted rats were given 2-h access to rat chow; separate groups of non-restricted animals had similar access to a sweetened fat diet. Feeding and locomotor activity were monitored following ventral tegmentum stimulation or blockade of 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, or 5-HT2C receptors. 5-HT1A receptor stimulation transiently inhibited rearing behavior and chow intake in food-restricted rats, and had a biphasic effect on non-restricted rats offered the palatable diet. 5-HT1B receptor agonism transiently inhibited feeding in restricted animals, but did not affect intake of non-restricted rats. In contrast, 5-HT1B receptor antagonism decreased palatable feeding. Although stimulation of ventral tegmental 5-HT2B receptors with BW723C86 did not affect hunger-driven food intake, it significantly affected palatable feeding, with a trend for an increasing intake at 2.0µg/side but not at 5.0µg/side. Antagonism of the same receptor modestly but significantly inhibited feeding of the palatable diet at 5.0µg/side ketanserin. Neither stimulation nor blockade of 5-HT2A or 5-HT2C receptors caused prolonged effects on intake or locomotion. These data suggest that serotonin's effects on feeding within the ventral tegmentum depend upon the specific receptor targeted, as well as whether intake is motivated by food restriction or the palatable nature of the offered diet. PMID:27431937

  16. A systematic investigation of the differential roles for ventral tegmentum serotonin 1- and 2-type receptors on food intake in the rat.

    PubMed

    Pratt, Wayne E; Clissold, Kara A; Lin, Peagan; Cain, Amanda E; Ciesinski, Alexa F; Hopkins, Thomas R; Ilesanmi, Adeolu O; Kelly, Erin A; Pierce-Messick, Zachary; Powell, Daniel S; Rosner, Ian A

    2016-10-01

    Central serotonin (5-HT) pathways are known to influence feeding and other ingestive behaviors. Although the ventral tegmentum is important for promoting the seeking and consumption of food and drugs of abuse, the roles of 5-HT receptor subtypes in this region on food intake have yet to be comprehensively examined. In these experiments, food restricted rats were given 2-h access to rat chow; separate groups of non-restricted animals had similar access to a sweetened fat diet. Feeding and locomotor activity were monitored following ventral tegmentum stimulation or blockade of 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, or 5-HT2C receptors. 5-HT1A receptor stimulation transiently inhibited rearing behavior and chow intake in food-restricted rats, and had a biphasic effect on non-restricted rats offered the palatable diet. 5-HT1B receptor agonism transiently inhibited feeding in restricted animals, but did not affect intake of non-restricted rats. In contrast, 5-HT1B receptor antagonism decreased palatable feeding. Although stimulation of ventral tegmental 5-HT2B receptors with BW723C86 did not affect hunger-driven food intake, it significantly affected palatable feeding, with a trend for an increasing intake at 2.0µg/side but not at 5.0µg/side. Antagonism of the same receptor modestly but significantly inhibited feeding of the palatable diet at 5.0µg/side ketanserin. Neither stimulation nor blockade of 5-HT2A or 5-HT2C receptors caused prolonged effects on intake or locomotion. These data suggest that serotonin's effects on feeding within the ventral tegmentum depend upon the specific receptor targeted, as well as whether intake is motivated by food restriction or the palatable nature of the offered diet.

  17. Polymorphisms of Serotonin Receptor 2A and 2C Genes and COMT in Relation to Obesity and Type 2 Diabetes

    PubMed Central

    Kring, Sofia I. I.; Werge, Thomas; Holst, Claus; Toubro, Søren; Astrup, Arne; Hansen, Torben; Pedersen, Oluf; Sørensen, Thorkild I. A.

    2009-01-01

    Background Candidate genes of psychological importance include 5HT2A, 5HT2C, and COMT, implicated in the serotonin, noradrenaline and dopamine pathways, which also may be involved in regulation of energy balance. We investigated the associations of single nucleotide polymorphisms (SNPs) of these genes with obesity and metabolic traits. Methodology/Principal Findings In a population of 166 200 young men examined at the draft boards, obese men (n = 726, BMI≥31.0 kg/m2) and a randomly selected group (n = 831) were re-examined at two surveys at mean ages 46 and 49 years (S-46, S-49). Anthropometric, physiological and biochemical measures were available. Logistic regression analyses were used to assess age-adjusted odds ratios. No significant associations were observed of 5HT2A rs6311, 5HT2C rs3813929 and COMT rs4680 with obesity, except that COMT rs4680 GG-genotype was associated with fat-BMI (OR = 1.08, CI = 1.01–1.16). The SNPs were associated with a number of physiological variables; most importantly 5HT2C rs3813929 T-allele was associated with glucose (OR = 4.56, CI = 1.13–18.4) and acute insulin response (OR = 0.65, CI = 0.44–0.94) in S-49. COMT rs4680 GG-genotype was associated with glucose (OR = 1.04, CI = 1.00–1.09). Except for an association between 5HT2A rs6311 and total-cholesterol at both surveys, significant in S-46 (OR = 2.66, CI = 1.11–6.40), no significant associations were observed for the other phenotypes. Significant associations were obtained when combined genotype of 5HT2C rs3813929 and COMT rs4680 were examined in relation to BMI (OR = 1.12, CI = 1.03–1.21), fat-BMI (OR = 1.22, CI = 1.08–1.38), waist (OR = 1.13, CI = 1.04–1.22), and cholesterol (OR = 5.60, CI = 0.99–31.4). Analyses of impaired glucose tolerance (IGT) and type 2 diabetes (T2D) revealed, a 12.3% increased frequency of 5HT2C rs3813929 T-allele and an 11.6% increased frequency of COMT

  18. Discriminative stimulus properties of 1.25mg/kg clozapine in rats: Mediation by serotonin 5-HT2 and dopamine D4 receptors.

    PubMed

    Prus, Adam J; Wise, Laura E; Pehrson, Alan L; Philibin, Scott D; Bang-Andersen, Benny; Arnt, Jørn; Porter, Joseph H

    2016-10-01

    The atypical antipsychotic drug clozapine remains one of most effective treatments for schizophrenia, given a lack of extrapyramidal side effects, improvements in negative symptoms, cognitive impairment, and in symptoms in treatment-resistant schizophrenia. The adverse effects of clozapine, including agranulocytosis, make finding a safe clozapine-like a drug a goal for drug developers. The drug discrimination paradigm is a model of interoceptive stimulus that has been used in an effort to screen experimental drugs for clozapine-like atypical antipsychotic effects. The present study was conducted to elucidate the receptor-mediated stimulus properties that form this clozapine discriminative cue by testing selective receptor ligands in rats trained to discriminate a 1.25mg/kg dose of clozapine from vehicle in a two choice drug discrimination task. Full substitution occurred with the 5-HT2A inverse agonist M100907 and the two preferential D4/5-HT2/α1 receptor antagonists Lu 37-114 ((S)-1-(3-(2-(4-(1H-indol-5-yl)piperazin-1-yl)ethyl)indolin-1-yl)ethan-1-one) and Lu 37-254 (1-(3-(4-(1H-indol-5-yl)piperazin-1-yl)propyl)-3,4-dihydroquinolin-2(1H)-one). Partial substitution occurred with the D4 receptor antagonist Lu 38-012 and the α1 adrenoceptor antagonist prazosin. Drugs selective for 5-HT2C, 5-HT6 muscarinic, histamine H1, and benzodiazepine receptors did not substitute for clozapine. The present findings suggest that 5-HT2A inverse agonism and D4 receptor antagonism mediate the discriminative stimulus properties of 1.25mg/kg clozapine in rats, and further confirm that clozapine produces a complex compound discriminative stimulus. PMID:27502027

  19. Human Serotonin 5-HT2C G Protein-Coupled Receptor Homology Model from the β2 Adrenoceptor Structure: Ligand Docking and Mutagenesis Studies

    PubMed Central

    RDOVA-SINTJAGO, TANIA CÓ; VILLA, NANCY; CANAL, CLINTON; BOOTH, RAYMOND

    2013-01-01

    Activation of the serotonin (5-hydroxytryptamine, 5-HT) 5HT2C G protein-coupled receptor (GPCR) is proposed as novel pharmacotherapy for obesity and neuropsychiatric disorders. In contrast, activation of the 5-HT2A and 5-HT2B GPCRs is associated with untoward hallucinogenic and cardiopulmonary effects, respectively. There is no crystal structure available to guide design of 5-HT2C receptor-specific ligands. For this reason, a homology model of the 5-HT2C receptor was built based on the crystal structure of the human β2 adrenoceptor GPCR to delineate molecular determinants of ligand–receptor interactions for drug design purposes. Computational and experimental studies were carried out to validate the model. Binding of N(CH3)2-PAT [(1R, 3S)-(−)-trans-1-phenyl-3-N,N-dimethylamino-1,2,3,4-tetrahydronaphthalene], a novel 5-HT2C agonist/5-HT2A/2B inverse agonist, and its secondary [NH(CH3)-PAT] and primary (NH2-PAT) amine analogs were studied at the 5-HT2C wild type (WT) and D3.32A, S3.36A, and Y7.43A 5-HT2C point-mutated receptors. Reference ligands included the tertiary amines lisuride and mesulergine and the primary amine 5-HT. Modeling results indicated that 5-HT2C residues D3.32, S3.36, and Y7.43 play a role in ligand binding. Experimental ligand binding results with WT and point-mutated receptors confirmed the impact of D3.32, S3.36, and Y7.43 on ligand affinity. PMID:24244046

  20. Translational neurophysiological markers for activity of the metabotropic glutamate receptor (mGluR2) modulator JNJ-40411813: Sleep EEG correlates in rodents and healthy men.

    PubMed

    Ahnaou, A; de Boer, P; Lavreysen, H; Huysmans, H; Sinha, V; Raeymaekers, L; Van De Casteele, T; Cid, J M; Van Nueten, L; Macdonald, G J; Kemp, J A; Drinkenburg, W H I M

    2016-04-01

    Alterations in rapid eye movement sleep (REM) have been suggested as valid translational efficacy markers: activation of the metabotropic glutamate receptor 2 (mGluR2) was shown to increase REM latency and to decrease REM duration. The present paper addresses the effects on vigilance states of the mGluR2 positive allosteric modulator (PAM) JNJ-40411813 at different circadian times in rats and after afternoon dosing in humans. Due to its dual mGluR2 PAM/serotonin 2A (5-HT2A) receptor antagonism in rodents, mGlu2R specificity of effects was studied in wild-type (WT) and mGluR2 (-/-) mice. 5-HT2A receptor occupancy was determined in humans using positron emission tomography (PET). Tolerance development was examined in rats after chronic dosing. EEG oscillations and network connectivity were assessed using multi-channel EEG. In rats, JNJ-40411813 increased deep sleep time and latency of REM onset but reduced REM time when administered 2 h after 'lights on' (CT2): this was sustained after chronic dosing. At CT5 similar effects were elicited, at CT10 only deep sleep was enhanced. Withdrawal resulted in baseline values, while re-administration reinstated drug effects. Parieto-occipital cortical slow theta and gamma oscillations were correlated with low locomotion. The specificity of functional response was confirmed in WT but not mGluR2 (-/-) mice. A double-blind, placebo-controlled polysomnographic study in healthy, elderly subjects showed that 500 mg of JNJ-40411813 consistently increased deep sleep time, but had no effect on REM parameters. This deep sleep effect was not explained by 5-HT2A receptor binding, as in the PET study even 700 mg only marginally displaced the tracer. JNJ-40411813 elicited comparable functional responses in rodents and men if circadian time of dosing was taken into account. These findings underscore the translational potential of sleep mechanisms in evaluating mGluR2 therapeutics when administered at the appropriate circadian time.

  1. Antagonism of lateral saphenous vein serotonin receptors from steers grazing endophyte-free, wild-type, or novel endophyte-infected tall fescue.

    PubMed

    Klotz, J L; Aiken, G E; Johnson, J M; Brown, K R; Bush, L P; Strickland, J R

    2013-09-01

    Pharmacologic profiling of serotonin (5HT) receptors of bovine lateral saphenous vein has shown that cattle grazing endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) have altered responses to ergovaline, 5HT, 5HT2A, and 5HT7 agonists. To determine if 5HT receptor activity of tall fescue alkaloids is affected by grazing endophyte-free (EF), wild-type [Kentucky-31 (KY31)], novel endophyte AR542-infected (MAXQ), or novel endophyte AR584-infected (AR584) tall fescue, contractile responses of lateral saphenous veins biopsied from cattle grazing these different fescue-endophyte combinations were evaluated in presence or absence of antagonists for 5HT2A (ketanserin) or 5HT7 (SB-269970) receptors. Biopsies were conducted over 2 yr on 35 mixed-breed steers (361.5 ± 6.3 kg) grazing EF (n = 12), KY31 (n = 12), MAXQ (n = 6), or AR584 (n = 5) pasture treatments (3 ha) between 84 and 98 d (Yr 1) or 108 to 124 d (Yr 2). Segments (2 to 3 cm) of vein were surgically biopsied, sliced into 2- to 3-mm cross-sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O2/5% CO2; pH = 7.4; 37°C). Veins were exposed to increasing concentrations of 5HT, ergovaline, and ergovaline + 1 × 10(-5) M ketanserin or + 1 × 10(-6) M SB-269970 in Yr 1. In Yr 2, ergotamine and ergocornine were evaluated in presence or absence of 1 × 10(-5) M ketanserin. Contractile response data were normalized to a reference addition of 1 × 10(-4) M norepinephrine. In Yr 1, contractile response to 5HT and ergovaline were least (P < 0.05) in KY31 pastures and the presence of ketanserin greatly reduced (P < 0.05) the response to ergovaline in all pastures. However, presence of SB-269970 did not (P = 0.91) alter contractile response to ergovaline. In Yr 2, there was no difference in contractile response to ergotamine (P = 0.13) or ergocornine (P = 0.99) across pasture treatments, but ketanserin reduced (P < 0.05) the contractile response to

  2. Agonist Derived Molecular Probes for A2A Adenosine Receptors

    PubMed Central

    Jacobson, Kenneth A.; Pannell, Lewis K.; Ji, Xiao-duo; Jarvis, Michael F.; Williams, Michael; Hutchison, Alan J.; Barrington, William W.; Stiles, Gary L.

    2011-01-01

    The adenosine agonist 2-(4-(2-carboxyethyl)phenylethylamino)-5′-N-ethylcarboxamidoadenosine (CGS21680) was recently reported to be selective for the A2A adenosine receptor subtype, which mediates its hypotensive action. To investigate structurelactivity relationships at a distal site, CGS21680 was derivatized using a functionalized congener approach. The carboxylic group of CGS21680 has been esterified to form a methyl ester, which was then treated with ethylenediamine to produce an amine congener. The amine congener was an intermediate for acylation reactions, in which the reactive acyl species contained a reported group, or the precursor for such. For radioiodination, derivatives of p-hydroxyphenylpropionic, 2-thiophenylacetic, and p-aminophenylacetic acids were prepared. The latter derivative (PAPA-APEC) was iodinated electrophilically using [125I]iodide resulting in a radioligand which was used for studies of competition of binding to striatal A, adenosine receptors in bovine brain. A biotin conjugate and an aryl sulfonate were at least 350-fold selective for A, receptors. For spectroscopic detection, a derivative of the stable free radical tetramethyl-1-piperidinyloxy (TEMPO) was prepared. For irreversible inhibition of receptors, meta- and para-phenylenediisothiocyanate groups were incorporated in the analogs. We have demonstrated that binding at A2A receptors is relatively insensitive to distal structural changes at the 2-position, and we report high affinity molecular probes for receptor characterization by radioactive, spectroscopic and affinity labelling methodology. PMID:2561548

  3. Combined unilateral blockade of cholinergic, peptidergic, and serotonergic receptors in the ventral respiratory column does not affect breathing in awake or sleeping goats

    PubMed Central

    Muere, Clarissa; Neumueller, Suzanne; Olesiak, Samantha; Miller, Justin; Langer, Thomas; Hodges, Matthew R.; Pan, Lawrence

    2015-01-01

    Previous work in intact awake and sleeping goats has found that unilateral blockade of excitatory inputs in the ventral respiratory column (VRC) elicits changes in the concentrations of multiple neurochemicals, including serotonin (5-HT), substance P, glycine, and GABA, while increasing or having no effect on breathing. These findings are consistent with the concept of interdependence between neuromodulators, whereby attenuation of one modulator elicits compensatory changes in other modulators to maintain breathing. Because there is a large degree of redundancy and multiplicity of excitatory inputs to the VRC, we herein tested the hypothesis that combined unilateral blockade of muscarinic acetylcholine (mACh), neurokinin-1 (NK1, the receptor for substance P), and 5-HT2A receptors would elicit changes in multiple neurochemicals, but would not change breathing. We unilaterally reverse-dialyzed a cocktail of antagonists targeting these receptors into the VRC of intact adult goats. Breathing was continuously monitored while effluent fluid from dialysis was collected for quantification of neurochemicals. We found that neither double blockade of mACh and NK1 receptors, nor triple blockade of mACh, NK1, and 5-HT2A receptors significantly affected breathing (P ≥ 0.05) in goats that were awake or in non-rapid eye movement (NREM) sleep. However, both double and triple blockade increased the effluent concentration of substance P (P < 0.001) and decreased GABA concentrations. These findings support our hypothesis and, together with past data, suggest that both in wakefulness and NREM sleep, multiple neuromodulator systems collaborate to stabilize breathing when a deficit in one or multiple excitatory neuromodulators exists. PMID:26023224

  4. Serotonin acts through 5-HT1 and 5-HT2 receptors to exert biphasic actions on GnRH neuron excitability in the mouse.

    PubMed

    Bhattarai, Janardhan P; Roa, Juan; Herbison, Allan E; Han, Seong Kyu

    2014-02-01

    The effect of serotonin (5-HT) on the electrical excitability of GnRH neurons was examined using gramicidin perforated-patch electrophysiology in transgenic GnRH-green fluorescent protein mice. In diestrous female, the predominant effect of 5-HT was inhibition (70%) with 50% of these cells also exhibiting a late-onset excitation. Responses were dose dependent (EC(50) = 1.2μM) and persisted in the presence of amino acid receptor antagonists and tetrodotoxin, indicating a predominant postsynaptic action of 5-HT. Studies in neonatal, juvenile, peripubertal, and adult mice revealed that 5-HT exerted less potent responses from GnRH neurons with advancing postnatal age in both sexes. In adult male mice, 5-HT exerted less potent hyperpolarizing responses with more excitations compared with females. In addition, adult proestrous female GnRH neurons exhibited reduced inhibition and a complete absence of biphasic hyperpolarization-excitation responses. Studies using 5-HT receptor antagonists demonstrated that the activation of 5-HT(1A) receptors mediated the inhibitory responses, whereas the excitation was mediated by the activation of 5-HT(2A) receptors. The 5-HT-mediated hyperpolarization involved both potassium channels and adenylate cyclase activation, whereas the 5-HT excitation was dependent on protein kinase C. The effects of exogenous 5-HT were replicated using fluoxetine, which enhances endogenous 5-HT levels. These studies demonstrate that 5-HT exerts a biphasic action on most GnRH neurons whereby a fast 5HT(1A)-mediated inhibition occurs alongside a slow 5-HT(2A) excitation. The balance of 5-HT-evoked inhibition vs excitation is developmentally regulated, sexually differentiated, and variable across the estrous cycle and may play a role in regulation of hypothalamic-pituitary-gonadal axis throughout postnatal development.

  5. Serotonin aggravates exercise-induced cardiac ischemia in the dog: effect of serotonin receptor antagonists.

    PubMed

    Guilbert, Frédérique; Lainée, Pierre; Dubreuil, Brigitte; McCort, Gary; O'Connor, Stephen E; Janiak, Philip; Herbert, Jean-Marc

    2004-08-16

    We investigated the effects of serotonin (5-HT), SL65.0472 (7-fluoro-2-oxo-4-[2-[4-thieno[3,2-c]pyridine-4-yl)piperazin-1-yl]ethyl]-1,2-dihydroquinoline-1-acetamide, a 5-HT(1B)/5-HT(2A) receptor antagonist) and ketanserin (a 5-HT(2A) receptor antagonist) during exercise-induced cardiac ischemia in conscious dogs. Dogs were administered a hypercholesterolemic diet and an inhibitor of nitric oxide synthetase to produce chronic endothelial dysfunction. Myocardial ischemia was induced by a treadmill exercise test associated with limitation of left anterior descending coronary blood flow. Infusion of serotonin during exercise produced dose-related cardiovascular changes (after 10 microg/kg/min; heart rate +27+/-6 bpm, systolic blood pressure +18+/-3 mm Hg, left circumflex coronary blood flow +64+/-8 ml/min, myocardial segment length shortening in the ischemic zone -5.9+/-1.9%, P<0.05). SL65.0472 blocked serotonin-induced increases in blood pressure, rate pressure product and circumflex coronary artery flow (100 microg/kg i.v., P<0.05) and reduced serotonin-induced ischemic myocardial segment length shortening (300 microg/kg i.v., P<0.05). Ketanserin (30-300 microg/kg i.v.) had no significant effect on any serotonin-induced changes during exercise. Thus, SL65.0472 opposes serotonin-induced myocardial dysfunction in a dog model of exercise-induced ischemia.

  6. The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A

    SciTech Connect

    Sato, Shoko; Shirakawa, Hitoshi; Tomita, Shuhei; Tohkin, Masahiro; Gonzalez, Frank J.; Komai, Michio

    2013-11-15

    Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction.

  7. 5-Hydroxytryptamine Receptor Subtypes and their Modulators with Therapeutic Potentials

    PubMed Central

    Pithadia, Anand B.; Jain, Sunita M.

    2009-01-01

    5-hydroxytryptamine (5-HT) has become one of the most investigated and complex biogenic amines. The main receptors and their subtypes, e.g., 5-HTI (5-HT1A, 5-HT1B, 5-HTID, 5-HTIE and 5-HT1F), 5-HT2 (5-HT2A, 5-HT2B and 5-HT2C), 5-HT3, 5-HT4, 5-HT5 (5-HT5A, 5-HT5B), 5-HT6 and 5-HT7 have been identified. Specific drugs which are capable of either selectively stimulating or inhibiting these receptor subtypes are being designed. This has generated therapeutic potentials of 5-HT receptor modulators in a variety of disease conditions. Conditions where 5-HT receptor modulators have established their use with distinct efficacy and advantages include migraine, anxiety, psychosis, obesity and cancer therapy-induced vomiting by cytotoxic drugs and radiation. Discovery of 5-HT, its biosynthesis, metabolism, physiological role and the potential of 5-HT receptor modulators in various nervous, cardiovascular and gastrointestinal tract disorders, bone growth and micturition have been discussed in this article. Keywords 5-hydroxytryptamine (5-HT) receptors; Modulators; Biogenic amines PMID:22505971

  8. Biophysical Mapping of the Adenosine A2A Receptor

    PubMed Central

    2011-01-01

    A new approach to generating information on ligand receptor interactions within the binding pocket of G protein-coupled receptors has been developed, called Biophysical Mapping (BPM). Starting from a stabilized receptor (StaR), minimally engineered for thermostability, additional single mutations are then added at positions that could be involved in small molecule interactions. The StaR and a panel of binding site mutants are captured onto Biacore chips to enable characterization of the binding of small molecule ligands using surface plasmon resonance (SPR) measurement. A matrix of binding data for a set of ligands versus each active site mutation is then generated, providing specific affinity and kinetic information (KD, kon, and koff) of receptor–ligand interactions. This data set, in combination with molecular modeling and docking, is used to map the small molecule binding site for each class of compounds. Taken together, the many constraints provided by these data identify key protein–ligand interactions and allow the shape of the site to be refined to produce a high quality three-dimensional picture of ligand binding, thereby facilitating structure based drug design. Results of biophysical mapping of the adenosine A2A receptor are presented. PMID:21661720

  9. Functional Selectivity and Antidepressant Activity of Serotonin 1A Receptor Ligands

    PubMed Central

    Chilmonczyk, Zdzisław; Bojarski, Andrzej Jacek; Pilc, Andrzej; Sylte, Ingebrigt

    2015-01-01

    Serotonin (5-HT) is a monoamine neurotransmitter that plays an important role in physiological functions. 5-HT has been implicated in sleep, feeding, sexual behavior, temperature regulation, pain, and cognition as well as in pathological states including disorders connected to mood, anxiety, psychosis and pain. 5-HT1A receptors have for a long time been considered as an interesting target for the action of antidepressant drugs. It was postulated that postsynaptic 5-HT1A agonists could form a new class of antidepressant drugs, and mixed 5-HT1A receptor ligands/serotonin transporter (SERT) inhibitors seem to possess an interesting pharmacological profile. It should, however, be noted that 5-HT1A receptors can activate several different biochemical pathways and signal through both G protein-dependent and G protein-independent pathways. The variables that affect the multiplicity of 5-HT1A receptor signaling pathways would thus result from the summation of effects specific to the host cell milieu. Moreover, receptor trafficking appears different at pre- and postsynaptic sites. It should also be noted that the 5-HT1A receptor cooperates with other signal transduction systems (like the 5-HT1B or 5-HT2A/2B/2C receptors, the GABAergic and the glutaminergic systems), which also contribute to its antidepressant and/or anxiolytic activity. Thus identifying brain specific molecular targets for 5-HT1A receptor ligands may result in a better targeting, raising a hope for more effective medicines for various pathologies. PMID:26262615

  10. Functional Selectivity and Antidepressant Activity of Serotonin 1A Receptor Ligands.

    PubMed

    Chilmonczyk, Zdzisław; Bojarski, Andrzej Jacek; Pilc, Andrzej; Sylte, Ingebrigt

    2015-01-01

    Serotonin (5-HT) is a monoamine neurotransmitter that plays an important role in physiological functions. 5-HT has been implicated in sleep, feeding, sexual behavior, temperature regulation, pain, and cognition as well as in pathological states including disorders connected to mood, anxiety, psychosis and pain. 5-HT1A receptors have for a long time been considered as an interesting target for the action of antidepressant drugs. It was postulated that postsynaptic 5-HT1A agonists could form a new class of antidepressant drugs, and mixed 5-HT1A receptor ligands/serotonin transporter (SERT) inhibitors seem to possess an interesting pharmacological profile. It should, however, be noted that 5-HT1A receptors can activate several different biochemical pathways and signal through both G protein-dependent and G protein-independent pathways. The variables that affect the multiplicity of 5-HT1A receptor signaling pathways would thus result from the summation of effects specific to the host cell milieu. Moreover, receptor trafficking appears different at pre- and postsynaptic sites. It should also be noted that the 5-HT1A receptor cooperates with other signal transduction systems (like the 5-HT1B or 5-HT2A/2B/2C receptors, the GABAergic and the glutaminergic systems), which also contribute to its antidepressant and/or anxiolytic activity. Thus identifying brain specific molecular targets for 5-HT1A receptor ligands may result in a better targeting, raising a hope for more effective medicines for various pathologies. PMID:26262615

  11. Characterization of the 5-hydroxytryptamine receptors mediating contraction in the pig isolated intravesical ureter

    PubMed Central

    Hernández, Medardo; Barahona, María Victoria; Simonsen, Ulf; Recio, Paz; Rivera, Luis; Martínez, Ana Cristina; García-Sacristán, Albino; Orensanz, Luis M; Prieto, Dolores

    2003-01-01

    This study was designed to investigate the effect of 5-hydroxytryptamine (5-HT) and to characterize the 5-HT receptors involved in 5-HT responses in the pig intravesical ureter. 5-HT (0.01–10 μM) concentration-dependently increased the tone of intravesical ureteral strips, whereas the increases in phasic contractions were concentration-independent. The 5-HT2 receptor agonist α-methyl 5-HT, mimicked the effect on tone whereas weak or no response was obtained with 5-CT, 8-OH-DPAT, m-chlorophenylbiguanide and RS 67333, 5-HT1, 5-HT1A, 5-HT3 and 5-HT4 receptor agonists, respectively. 5-HT did not induce relaxation of U46619-contracted ureteral preparations. Pargyline (100 μM), a monoaminooxidase A/B activity inhibitor, produced leftward displacements of the concentration-response curves for 5-HT. 5-HT-induced tone was reduced by the 5-HT2 and 5-HT2A receptor antagonists ritanserine (0.1 μM) and spiperone (0.2 μM), respectively. However, 5-HT contraction was not antagonized by cyanopindolol (2 μM), SDZ–SER 082 (1 μM), Y-25130 (1 μM) and GR 113808 (0.1 μM), which are respectively, 5-HT1A/1B, 5-HT2B/2C, 5-HT3, and 5-HT4 selective receptor antagonists. Removal of the urothelium did not modify 5-HT-induced contractions. Blockade of neuronal voltage-activated sodium channels, α-adrenergic receptors and adrenergic neurotransmission with tetrodotoxin (1 μM), phentolamine (0.3 μM) and guanethidine (10 μM), respectively, reduced the contractions to 5-HT. However, physostigmine (1 μM), atropine (0.1 μM) and suramin (30 μM), inhibitors of cholinesterase activity, muscarinic- and purinergic P2-receptors, respectively, failed to modify the contractions to 5-HT. These results suggest that 5-HT increases the tone of the pig intravesical ureter through 5-HT2A receptors located at the smooth muscle. Part of the 5-HT contraction is indirectly mediated via noradrenaline release from sympathetic nerves. PMID:12522083

  12. Phosphaturic mesenchymal tumors show positive staining for somatostatin receptor 2A (SSTR2A).

    PubMed

    Houang, Michelle; Clarkson, Adele; Sioson, Loretta; Elston, Marianne S; Clifton-Bligh, Roderick J; Dray, Michael; Ranchere-Vince, Dominique; Decouvelaere, Anne-Valerie; de la Fouchardiere, Arnaud; Gill, Anthony J

    2013-12-01

    Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome associated with tumors that secrete phosphaturic hormones, most notably fibroblast growth factor 23 (FGF23). The majority of tumors associated with this syndrome show stereotypical histological features and are now known as phosphaturic mesenchymal tumors (PMTs). We postulated that immunohistochemistry for somatostatin receptor 2A (SSTR2A) could be used to definitively identify PMTs or other tumors that cause TIO. Immunohistochemistry for FGF23 and SSTR2A was performed on 15 tumors from 14 patients with a definite diagnosis of TIO. All showed positive staining for both markers. While FGF23 staining was quite focal in some tumors, SSTR2A showed diffuse strong expression. In 40 control tumors not known to be associated with the clinical or biochemical features of TIO, FGF23 expression was found in 2 cases (one aneurysmal bone cyst and one osteosarcoma). SSTR2A expression was found in 9 control tumors (4 synovial sarcomas, 2 hemangiomas, 2 aneurysmal bone cysts and one osteosarcoma). Only one tumor (an aneurysmal bone cyst) showed positive staining for both FGF23 and SSTR2A. SSTR2A also commonly stained neoplastic and non-neoplastic endothelial cells. We conclude that neither FGF23 nor SSTR2A expression are specific for the diagnosis of PMT. However both stains are highly sensitive. Because of its diffuse strong expression and widespread availability, immunohistochemistry for SSTR2A is useful to confirm the diagnosis of PMT in an appropriate setting particularly if material is limited. Negative staining can serve as an excellent rule out test for this diagnosis. PMID:24060005

  13. The developmental basis of epigenetic regulation of HTR2A and psychiatric outcomes.

    PubMed

    Paquette, Alison G; Marsit, Carmen J

    2014-12-01

    The serotonin receptor 5-HT2A (encoded by HTR2A) is an important regulator of fetal brain development and adult cognitive function. Environmental signals that induce epigenetic changes of serotonin response genes, including HTR2A, have been implicated in adverse mental health outcomes. The objective of this perspective article is to address the medical implications of HTR2A epigenetic regulation, which has been associated with both infant neurobehavioral outcomes and adult mental health. Ongoing research has identified a region of the HTR2A promoter that has been associated with a number of medical outcomes in adults and infants, including bipolar disorder, schizophrenia, chronic fatigue syndrome, borderline personality disorder, suicidality, and neurobehavioral outcomes. Epigenetic regulation of HTR2A has been studied in several different types of tissues, including the placenta. The placenta is an important source of serotonin during fetal neurodevelopment, and placental epigenetic variation of HTR2A has been associated with infant neurobehavioral outcomes, which may represent the basis of adult mental health disorders. Further analysis is needed to identify intrinsic and extrinsic factors that modulate HTR2A methylation, and the mechanism by which this epigenetic variation influences fetal growth and leads to altered brain development, manifesting in psychiatric disorders.

  14. The Developmental Basis of Epigenetic Regulation of HTR2A and Psychiatric Outcomes

    PubMed Central

    Paquette, Alison G.; Marsit, Carmen J.

    2014-01-01

    The serotonin receptor 5-HT2A (encoded by HTR2A) is an important regulator of fetal brain development and adult cognitive function. Environmental signals that induce epigenetic changes of serotonin response genes, including HTR2A, have been implicated in adverse mental health outcomes. The objective of this perspective article is to address the medical implications of HTR2A epigenetic regulation, which has been associated with both infant neurobehavioral outcomes and adult mental health. Ongoing research has identified a region of the HTR2A promoter that has been associated with a number of medical outcomes in adults and infants, including bipolar disorder, schizophrenia, chronic fatigue syndrome, borderline personality disorder, suicidality, and neurobehavioral outcomes. Epigenetic regulation of HTR2A has been studied in several different types of tissues, including the placenta. The placenta is an important source of serotonin during fetal neurodevelopment, and placental epigenetic variation of HTR2A has been associated with infant neurobehavioral outcomes, which may represent the basis of adult mental health disorders. Further analysis is needed to identify intrinsic and extrinsic factors modulate HTR2A methylation, and the mechanism by which this epigenetic variation influences fetal growth and leads to altered brain development, manifesting in psychiatric disorders. PMID:25043477

  15. Pharmacological and pharmacokinetic properties of JNJ-40411813, a positive allosteric modulator of the mGlu2 receptor

    PubMed Central

    Lavreysen, Hilde; Ahnaou, Abdellah; Drinkenburg, Wilhelmus; Langlois, Xavier; Mackie, Claire; Pype, Stefan; Lütjens, Robert; Le Poul, Emmanuel; Trabanco, Andrés A; Nuñez, José María Cid

    2015-01-01

    Compounds modulating metabotropic glutamate type 2 (mGlu2) receptor activity may have therapeutic benefits in treating psychiatric disorders like schizophrenia and anxiety. The pharmacological and pharmacokinetic properties of a novel mGlu2 receptor-positive allosteric modulator (PAM), 1-butyl-3-chloro-4-(4-phenyl-1-piperidinyl)-2(1H)-pyridinone (JNJ-40411813/ADX71149) are described here. JNJ-40411813 acts as a PAM at the cloned mGlu2 receptor: EC50 = 147 ± 42 nmol/L in a [35S]GTPγS binding assay with human metabotropic glutamate type 2 (hmGlu2) CHO cells and EC50 = 64 ± 29 nmol/L in a Ca2+ mobilization assay with hmGlu2 Gα16 cotransfected HEK293 cells. [35S]GTPγS autoradiography on rat brain slices confirmed PAM activity of JNJ-40411813 on native mGlu2 receptor. JNJ-40411813 displaced [3H]JNJ-40068782 and [3H]JNJ-46281222 (mGlu2 receptor PAMs), while it failed to displace [3H]LY341495 (a competitive mGlu2/3 receptor antagonist). In rats, JNJ-40411813 showed ex vivo mGlu2 receptor occupancy using [3H]JNJ-46281222 with ED50 of 16 mg/kg (p.o.). PK-PD modeling using the same radioligand resulted in an EC50 of 1032 ng/mL. While JNJ-40411813 demonstrated moderate affinity for human 5HT2A receptor in vitro (Kb = 1.1 μmol/L), higher than expected 5HT2A occupancy was observed in vivo (in rats, ED50 = 17 mg/kg p.o.) due to a metabolite. JNJ-40411813 dose dependently suppressed REM sleep (LAD, 3 mg/kg p.o.), and promoted and consolidated deep sleep. In fed rats, JNJ-40411813 (10 mg/kg p.o.) was rapidly absorbed (Cmax 938 ng/mL at 0.5 h) with an absolute oral bioavailability of 31%. Collectively, our data show that JNJ-40411813 is an interesting candidate to explore the therapeutic potential of mGlu2 PAMs, in in vivo rodents experiments as well as in clinical studies. PMID:25692015

  16. Exploration of synthetic approaches and pharmacological evaluation of PNU-69176E and its stereoisomer as 5-HT2C receptor allosteric modulators.

    PubMed

    Ding, Chunyong; Bremer, Nicole M; Smith, Thressa D; Seitz, Patricia K; Anastasio, Noelle C; Cunningham, Kathryn A; Zhou, Jia

    2012-07-18

    Allosteric modulators of the serotonin (5-HT) 5-HT(2C) receptor (5-HT(2C)R) present a unique drug design strategy to augment the response to endogenous 5-HT in a site- and event-specific manner with great potential as novel central nervous system probes and therapeutics. To date, PNU-69176E is the only reported selective positive allosteric modulator for the 5-HT(2C)R. For the first time, an optimized synthetic route to readily access PNU-69176E (1) and its diastereomer 2 has been established in moderate to good overall yields over 10 steps starting from commercially available picolinic acid. This synthetic approach not only enables a feasible preparation of a sufficient amount of 1 for use as a reference compound for secondary pharmacological studies, but also provides an efficient synthesis of key intermediates to develop novel and simplified 5-HT(2C)R allosteric modulators. Compound 1 and its diastereomer 2 were functionally characterized in Chinese hamster ovary (CHO) cells stably transfected with the 5-HT(2C)R using an intracellular calcium (Ca(i) (2+)) release assay. Compound 1 demonstrated efficacy and potency as an allosteric modulator for the 5-HT(2C)R with no intrinsic agonist activity. Compound 1 did not alter 5-HT-evoked Ca(i) (2+) in CHO cells stably transfected with the highly homologous 5-HT(2A)R. In contrast, the diastereomer 2 did not alter 5-HT-evoked Ca(i) (2+) release in 5-HT(2A)R-CHO or 5-HT(2C)R-CHO cells or exhibit intrinsic agonist activity.

  17. Dopamine D2/3 receptor antagonism reduces activity-based anorexia

    PubMed Central

    Klenotich, S J; Ho, E V; McMurray, M S; Server, C H; Dulawa, S C

    2015-01-01

    Anorexia nervosa (AN) is an eating disorder characterized by severe hypophagia and weight loss, and an intense fear of weight gain. Activity-based anorexia (ABA) refers to the weight loss, hypophagia and paradoxical hyperactivity that develops in rodents exposed to running wheels and restricted food access, and provides a model for aspects of AN. The atypical antipsychotic olanzapine was recently shown to reduce both AN symptoms and ABA. We examined which component of the complex pharmacological profile of olanzapine reduces ABA. Mice received 5-HT2A/2C, 5-HT3, dopamine D1-like, D2, D3 or D2/3 antagonist treatment, and were assessed for food intake, body weight, wheel running and survival in ABA. D2/3 receptor antagonists eticlopride and amisulpride reduced weight loss and hypophagia, and increased survival during ABA. Furthermore, amisulpride produced larger reductions in weight loss and hypophagia than olanzapine. Treatment with either D3 receptor antagonist SB277011A or D2 receptor antagonist L-741,626 also increased survival. All the other treatments either had no effect or worsened ABA. Overall, selective antagonism of D2 and/or D3 receptors robustly reduces ABA. Studies investigating the mechanisms by which D2 and/or D3 receptors regulate ABA, and the efficacy for D2/3 and/or D3 antagonists to treat AN, are warranted. PMID:26241351

  18. Dopamine D2/3 receptor antagonism reduces activity-based anorexia.

    PubMed

    Klenotich, S J; Ho, E V; McMurray, M S; Server, C H; Dulawa, S C

    2015-08-04

    Anorexia nervosa (AN) is an eating disorder characterized by severe hypophagia and weight loss, and an intense fear of weight gain. Activity-based anorexia (ABA) refers to the weight loss, hypophagia and paradoxical hyperactivity that develops in rodents exposed to running wheels and restricted food access, and provides a model for aspects of AN. The atypical antipsychotic olanzapine was recently shown to reduce both AN symptoms and ABA. We examined which component of the complex pharmacological profile of olanzapine reduces ABA. Mice received 5-HT(2A/2C), 5-HT3, dopamine D1-like, D2, D3 or D2/3 antagonist treatment, and were assessed for food intake, body weight, wheel running and survival in ABA. D2/3 receptor antagonists eticlopride and amisulpride reduced weight loss and hypophagia, and increased survival during ABA. Furthermore, amisulpride produced larger reductions in weight loss and hypophagia than olanzapine. Treatment with either D3 receptor antagonist SB277011A or D2 receptor antagonist L-741,626 also increased survival. All the other treatments either had no effect or worsened ABA. Overall, selective antagonism of D2 and/or D3 receptors robustly reduces ABA. Studies investigating the mechanisms by which D2 and/or D3 receptors regulate ABA, and the efficacy for D2/3 and/or D3 antagonists to treat AN, are warranted.

  19. Differential effects of three 5-HT receptor antagonists on the performance of rats in attentional and working memory tasks.

    PubMed

    Ruotsalainen, S; Sirviö, J; Jäkälä, P; Puumala, T; MacDonald, E; Riekkinen, P

    1997-05-01

    The effects of three different serotonin (5-HT) receptor antagonists (ketanserin, methysegide, methiothepin) in the modulation of attention, working memory and behavioural activity were investigated in this study by assessing the performance of rats in two separate cognitive models; the 5-choice serial reaction time (5-CSRT) task, which measures attention, and the delayed non-matching to position (DNMTP) task, which measures working memory. Methysergide and methiothepin bind at the 5-HT1 and 5-HT2 as well as the 5-HT5-7 receptors, with varying degrees of selectivity, and ketanserin binds at the 5-HT2A receptors rather selectively. None of these agents bind to any significant extent to 5-HT3 or 5-HT4 receptors. In the 5-CSRT task, neither methiothepin (0.15 mg/kg) nor ketanserin (1.0 and 3.0 mg/kg) impaired the choice accuracy of rats, although they induced sedation. The low doses of methysergide (1.5 and 3.0 mg/kg) slightly increased the behavioural activity of rats, whereas the high dose of methysergide (15.0 mg/kg) reduced behavioural activity and slightly reduced choice accuracy of the rats in the attentional task (monitoring of visual stimuli) under the baseline conditions or curtailed stimulus duration. This effect was not augmented at the reduced stimulus intensity. These findings suggest that the high dose of methysergide did not interfere with the visual discrimination of rats. Furthermore, methysergide did not reduce motivation for this task, since it did not increase food collection latencies. In the DNMTP task, methiothepin (0.15 mg/kg) induced a delay non-dependent deficit in choice accuracy. This could be due to an impaired alternation ability or akinesia, which increases an actual delay between sample and choice. Methiothepin (0.15 mg/kg) also interfered with behavioural activity of rats. Interestingly, ketanserin (1.0 mg/kg and 3.0 mg/kg) and methysergide (3.0-15.0 mg/kg) neither impaired the choice accuracy nor reduced the behavioural activity of

  20. Spinal 5-HT-receptors and tonic modulation of transmission through a withdrawal reflex pathway in the decerebrated rabbit.

    PubMed Central

    Clarke, R. W.; Harris, J.; Houghton, A. K.

    1996-01-01

    1. In decerebrated, non-spinalized rabbits, intrathecal administration of either of the selective 5-HT1A-receptor antagonists (S)WAY-100135 or WAY-100635 resulted in dose-dependent enhancement of the reflex responses of gastrocnemius motoneurones evoked by electrical stimulation of all myelinated afferents of the sural nerve. The approximate ED50 for WAY-100635 was 0.9 nmol and that for (S)WAY-100135 13 nmol. Intrathecal doses of the antagonists which caused maximal facilitation of reflexes in non-spinalized rabbits had no effect in spinalized preparations. 2. In non-spinalized animals, intravenous administration of (S)WAY-100135 was significantly less effective in enhancing reflexes than when it was given by the intrathecal route. 3. When given intrathecally, the selective 5-HT 2A/2C-receptor antagonist, ICI 170,809, produced a bellshaped dose-effect curve, augmenting reflexes at low doses (< or = 44 nmol), but reducing them at higher doses (982 nmol). Idazoxan, the selective alpha 2-adrenoceptor antagonist, was less effective in enhancing reflex responses when given intrathecally after ICI 170,809 compared to when it was given alone. Intravenous ICI 170,809 resulted only in enhancement of reflexes and the facilitatory effects of subsequent intrathecal administration of idazoxan were not compromised. 4. The selective 5-HT3-receptor blocker ondansetron faciliated gastrocnemius medialis reflex responses in a dose-related manner when given by either intrathecal or intravenous routes. This drug was slightly more potent when given i.v. and it did not alter the efficacy of subsequent intrathecal administration of idazoxan. 5. None of the antagonists had any consistent effects on arterial blood pressure or heart rate. 6. These data are consistent with the idea that, in the decrebrated rabbit, 5-HT released from descending axons has multiple roles in controlling transmission through the sural-gastrocnemius medialis reflex pathway. Thus, it appears 5-HT tonically inhibits

  1. Involvement of spinal muscarinic and serotonergic receptors in the anti-allodynic effect of electroacupuncture in rats with oxaliplatin-induced neuropathic pain

    PubMed Central

    Lee, Ji Hwan; Go, Donghyun; Kim, Woojin; Lee, Giseog; Bae, Hyojeong; Quan, Fu Shi

    2016-01-01

    This study was performed to investigate whether the spinal cholinergic and serotonergic analgesic systems mediate the relieving effect of electroacupuncture (EA) on oxaliplatin-induced neuropathic cold allodynia in rats. The cold allodynia induced by an oxaliplatin injection (6 mg/kg, i.p.) was evaluated by immersing the rat's tail into cold water (4℃) and measuring the withdrawal latency. EA stimulation (2 Hz, 0.3-ms pulse duration, 0.2~0.3 mA) at the acupoint ST36, GV3, or LI11 all showed a significant anti-allodynic effect, which was stronger at ST36. The analgesic effect of EA at ST36 was blocked by intraperitoneal injection of muscarinic acetylcholine receptor antagonist (atropine, 1 mg/kg), but not by nicotinic (mecamylamine, 2 mg/kg) receptor antagonist. Furthermore, intrathecal administration of M2 (methoctramine, 10 µg) and M3 (4-DAMP, 10 µg) receptor antagonist, but not M1 (pirenzepine, 10 µg) receptor antagonist, blocked the effect. Also, spinal administration of 5-HT3 (MDL-72222, 12 µg) receptor antagonist, but not 5-HT1A (NAN-190, 15 µg) or 5-HT2A (ketanserin, 30 µg) receptor antagonist, prevented the anti-allodynic effect of EA. These results suggest that EA may have a signifi cant analgesic action against oxaliplatin-induced neuropathic pain, which is mediated by spinal cholinergic (M2, M3) and serotonergic (5-HT3) receptors. PMID:27382357

  2. Interaction between two HTR2A polymorphisms and gender is associated with treatment response in MDD.

    PubMed

    Viikki, Merja; Huuhka, Kaija; Leinonen, Esa; Illi, Ari; Setälä-Soikkeli, Eija; Huuhka, Martti; Mononen, Nina; Lehtimäki, Terho; Kampman, Olli

    2011-08-21

    The 5HT2A receptor gene (HTR2A) polymorphisms rs7997012 and rs6311 have in some earlier studies been associated with serotonin selective reuptake inhibitor (SSRI) treatment response in major depressive disorder (MDD), but the findings are inconsistent. The aim of the present study was to test for an association between two HTR2A polymorphisms (rs7997012 and rs6311), their interaction and the Montgomery and Åsberg Depression Rating Scale (MADRS) score change after ECT or SSRI treatment. The total number of patients was 218. All were treated in outpatient care. Of these, 119 subjects had treatment-resistant MDD and were treated with ECT and 99 were depressive patients treated with SSRI. Treatment response was assessed by MADRS. Patients scoring <8 on post-treatment MADRS were considered remitters. Neither rs7997012 nor rs6311 HTR2A polymorphism was significantly associated with MADRS score change alone, but the interaction between them and gender explained 14% of the variance in MADRS score change. The finding suggests an association between MADRS score change and interaction of HTR2A polymorphisms, rs7997012 and rs6311 and gender.

  3. Glycine Potentiates AMPA Receptor Function through Metabotropic Activation of GluN2A-Containing NMDA Receptors

    PubMed Central

    Li, Li-Jun; Hu, Rong; Lujan, Brendan; Chen, Juan; Zhang, Jian-Jian; Nakano, Yasuko; Cui, Tian-Yuan; Liao, Ming-Xia; Chen, Jin-Cao; Man, Heng-Ye; Feng, Hua; Wan, Qi

    2016-01-01

    NMDA receptors are Ca2+-permeable ion channels. The activation of NMDA receptors requires agonist glutamate and co-agonist glycine. Recent evidence indicates that NMDA receptor also has metabotropic function. Here we report that in cultured mouse hippocampal neurons, glycine increases AMPA receptor-mediated currents independent of the channel activity of NMDA receptors and the activation of glycine receptors. The potentiation of AMPA receptor function by glycine is antagonized by the inhibition of ERK1/2. In the hippocampal neurons and in the HEK293 cells transfected with different combinations of NMDA receptors, glycine preferentially acts on GluN2A-containing NMDA receptors (GluN2ARs), but not GluN2B-containing NMDA receptors (GluN2BRs), to enhance ERK1/2 phosphorylation independent of the channel activity of GluN2ARs. Without requiring the channel activity of GluN2ARs, glycine increases AMPA receptor-mediated currents through GluN2ARs. Thus, these results reveal a metabotropic function of GluN2ARs in mediating glycine-induced potentiation of AMPA receptor function via ERK1/2 activation. PMID:27807405

  4. Substituted methcathinones differ in transporter and receptor interactions

    PubMed Central

    Eshleman, Amy J; Wolfrum, Katherine M; Hatfield, Meagan G; Johnson, Robert A; Murphy, Kevin V; Janowsky, Aaron

    2013-01-01

    The use of synthetic methcathinones, components of “bath salts,” is a world-wide health concern. These compounds, structurally similar to methamphetamine (METH) and 3,4-methylendioxymethamphetamine (MDMA), cause tachycardia, hallucinations and psychosis. We hypothesized that these potentially neurotoxic and abused compounds display differences in their transporter and receptor interactions as compared to amphetamine counterparts. 3,4-Methylenedioxypyrovalerone and naphyrone had high affinity for radioligand binding sites on recombinant human dopamine (hDAT), serotonin (hSERT) and norepinephrine (hNET) transporters, potently inhibited [3H]neurotransmitter uptake, and, like cocaine, did not induce transporter-mediated release. Butylone was a lower affinity uptake inhibitor. In contrast, 4-fluoromethcathinone, mephedrone and methylone had higher inhibitory potency at uptake compared to binding and generally induced release of preloaded [3H]neurotransmitter from hDAT, hSERT and hNET (highest potency at hNET), and thus are transporter substrates, similar to METH and MDMA. At hNET, 4-fluoromethcathinone was a more efficacious releaser than METH. These substituted methcathinones had low uptake inhibitory potency and low efficacy at inducing release via human vesicular monoamine transporters (hVMAT2). These compounds were low potency 1) h5-HT1A receptor partial agonists, 2) h5-HT2A receptor antagonists, 3) weak h5-HT2C receptor antagonists. This is the first report on aspects of substituted methcathinone efficacies at serotonin (5-HT) receptors and in superfusion release assays. Additionally, the drugs had no affinity for dopamine receptors, and high- mid-micromolar affinity for hSigma1 receptors. Thus, direct interactions with hVMAT2 and serotonin, dopamine, and hSigma1 receptors may not explain psychoactive effects. The primary mechanisms of action may be as inhibitors or substrates of DAT, SERT and NET. PMID:23583454

  5. Recruitment of a Cytoplasmic Chaperone Relay by the A2A Adenosine Receptor*

    PubMed Central

    Bergmayr, Christian; Thurner, Patrick; Keuerleber, Simon; Kudlacek, Oliver; Nanoff, Christian; Freissmuth, Michael; Gruber, Christian W.

    2013-01-01

    The adenosine A2A receptor is a prototypical rhodopsin-like G protein-coupled receptor but has several unique structural features, in particular a long C terminus (of >120 residues) devoid of a palmitoylation site. It is known to interact with several accessory proteins other than those canonically involved in signaling. However, it is evident that many more proteins must interact with the A2A receptor, if the trafficking trajectory of the receptor is taken into account from its site of synthesis in the endoplasmic reticulum (ER) to its disposal by the lysosome. Affinity-tagged versions of the A2A receptor were expressed in HEK293 cells to identify interacting partners residing in the ER by a proteomics approach based on tandem affinity purification. The receptor-protein complexes were purified in quantities sufficient for analysis by mass spectrometry. We identified molecular chaperones (heat-shock proteins HSP90α and HSP70-1A) that interact with and retain partially folded A2A receptor prior to ER exit. Complex formation between the A2A receptor and HSP90α (but not HSP90β) and HSP70-1A was confirmed by co-affinity precipitation. HSP90 inhibitors also enhanced surface expression of the receptor in PC12 cells, which endogenously express the A2A receptor. Finally, proteins of the HSP relay machinery (e.g. HOP/HSC70-HSP90 organizing protein and P23/HSP90 co-chaperone) were recovered in complexes with the A2A receptor. These observations are consistent with the proposed chaperone/coat protein complex II exchange model. This posits that cytosolic HSP proteins are sequentially recruited to folding intermediates of the A2A receptor. Release of HSP90 is required prior to recruitment of coat protein complex II components. This prevents premature ER export of partially folded receptors. PMID:23965991

  6. Interaction between μ-opioid and 5-HT1A receptors in the regulation of panic-related defensive responses in the rat dorsal periaqueductal grey.

    PubMed

    Rangel, Marcel P; Zangrossi, Hélio; Roncon, Camila M; Graeff, Frederico G; Audi, Elisabeth A

    2014-12-01

    A wealth of evidence indicates that the activation of 5-HT1A and 5-HT2A receptors in the dorsal periaqueductal grey matter (dPAG) inhibits escape, a panic-related defensive behaviour. Results that were previously obtained with the elevated T-maze test of anxiety/panic suggest that 5-HT1A and μ-opioid receptors in this midbrain area work together to regulate this response. To investigate the generality of this finding, we assessed whether the same cooperative mechanism is engaged when escape is evoked by a different aversive stimulus electrical stimulation of the dPAG. Administration of the μ-receptor blocker CTOP into the dPAG did not change the escape threshold, but microinjection of the μ-receptor agonist DAMGO (0.3 and 0.5 nmol) or the 5-HT1A receptor agonist 8-OHDPAT (1.6 nmol) increased this index, indicating a panicolytic-like effect. Pretreatment with CTOP antagonised the anti-escape effect of 8-OHDPAT. Additionally, combined administration of subeffective doses of DAMGO and 8-OHDPAT increased the escape threshold, indicating drug synergism. Therefore, regardless of the aversive nature of the stimulus, μ-opioid and 5-HT1A receptors cooperatively act to regulate escape behaviour. A better comprehension of this mechanism might allow for new therapeutic strategies for panic disorder.

  7. Gene expression and function of adenosine A(2A) receptor in the rat carotid body.

    PubMed

    Kobayashi, S; Conforti, L; Millhorn, D E

    2000-08-01

    The present study was undertaken to determine whether rat carotid bodies express adenosine (Ado) A(2A) receptors and whether this receptor is involved in the cellular response to hypoxia. Our results demonstrate that rat carotid bodies express the A(2A) and A(2B) Ado receptor mRNAs but not the A(1) or A(3) receptor mRNAs as determined by reverse transcriptase-polymerase chain reaction. In situ hybridization confirmed the expression of the A(2A) receptor mRNA. Immunohistochemical studies further showed that the A(2A) receptor is expressed in the carotid body and that it is colocalized with tyrosine hydroxylase in type I cells. Whole cell voltage-clamp studies using isolated type I cells showed that Ado inhibited the voltage-dependent Ca(2+) currents and that this inhibition was abolished by the selective A(2A) receptor antagonist ZM-241385. Ca(2+) imaging studies using fura 2 revealed that exposure to severe hypoxia induced elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) in type I cells and that extracellularly applied Ado significantly attenuated the hypoxia-induced elevation of [Ca(2+)](i). Taken together, our findings indicate that A(2A) receptors are present in type I cells and that activation of A(2A) receptors modulates Ca(2+) accumulation during hypoxia. This mechanism may play a role in regulating intracellular Ca(2+) homeostasis and cellular excitability during hypoxia. PMID:10926550

  8. Discriminative stimulus effects of the imidazoline I2 receptor ligands BU224 and phenyzoline in rats

    PubMed Central

    Qiu, Yanyan; Zhang, Yanan; Li, Jun-Xu

    2015-01-01

    Although imidazoline I2 receptor ligands have been used as discriminative stimuli, the role of efficacy of I2 receptor ligands as a critical determinant in drug discrimination has not been explored. This study characterized the discriminative stimulus effects of selective imidazoline I2 receptor ligands BU224 (a low-efficacy I2 receptor ligand) and phenyzoline (a higher efficacy I2 receptor ligand) in rats. Two groups of male Sprague-Dawley rats were trained to discriminate 5.6 mg/kg BU224 or 32 mg/kg phenyzoline (i.p.) from their vehicle in a two-lever food-reinforced drug discrimination procedure, respectively. All rats acquired the discriminations after an average of 18 (BU224) and 56 (phenyzoline) training sessions, respectively. BU224 and phenyzoline completely substituted for one another symmetrically. Several I2 receptor ligands (tracizoline, CR4056, RS45041, and idazoxan) all occasioned > 80% drug-associated lever responding in both discriminations. The I2 receptor ligand 2-BFI and a monoamine oxidase inhibitor harmane occasioned > 80% drug-associated lever responding in rats discriminating BU224. Other drugs that occasioned partial or less substitution to BU224 cue included clonidine, methamphetamine, ketamine, morphine, methadone and agmatine. Clonidine, methamphetamine and morphine also only produced partial substitution to phenyzoline cue. Naltrexone, dopamine D2 receptor antagonist haloperidol and serotonin (5-HT) 2A receptor antagonist MDL100907 failed to alter the discriminative stimulus effects of BU224 or phenyzoline. Combined, these results are the first to demonstrate that BU224 and phenyzoline can serve as discriminative stimuli and that the low-efficacy I2 receptor ligand BU224 shares similar discriminative stimulus effects with higher-efficacy I2 receptor ligands such as phenyzoline and 2-BFI. PMID:25617792

  9. The involvement of medial septum 5-HT1 and 5-HT2 receptors on ACPA-induced memory consolidation deficit: possible role of TRPC3, TRPC6 and TRPV2.

    PubMed

    Najar, Farzaneh; Nasehi, Mohammad; Haeri-Rohani, Seyed-Ali; Zarrindast, Mohammad-Reza

    2015-11-01

    The present study evaluates the roles of serotonergic receptors of the medial septum on amnesia induced by arachidonylcyclopropylamide (ACPA; as selective cannabinoid CB1 receptor agonist) in adult male Wistar rats. Cannulae were implanted in the medial septum of the brain of the rats. The animals were trained in a passive avoidance learning apparatus, and were tested 24 hours after training for step-through latency. Results indicated that post-training medial septum administration of CP94253 (5-HT1B/1D receptor agonist) and cinancerine (as 5-HT2 receptor antagonist) reduced the step-through latency showing an amnesic response, while GR127935 (5-HT1B/1D receptor antagonist) and αm5htm (as 5-HT2A/2B/2D receptor agonist) did not alter memory consolidation by themselves. On continuing the test, the results showed that CP94253 increased and GR127935 did not alter ACPA (0.02 µg/rat)-induced memory impairment, respectively. Other data indicated that αm5htm induced a modulatory effect, while cinancerine restored ACPA-induced amnesia. Using SKF-96365 (inhibitor of transient receptor potential TRPC3/6 and TRPV2 channels) demonstrated that TRPC3, TRPC3 and TRPV2 channels have a significant role, according to our results. PMID:26464456

  10. Nucleus tractus solitarii A(2a) adenosine receptors inhibit cardiopulmonary chemoreflex control of sympathetic outputs.

    PubMed

    Minic, Zeljka; O'Leary, Donal S; Scislo, Tadeusz J

    2014-02-01

    Previously we have shown that stimulation of inhibitory A1 adenosine receptors located in the nucleus tractus solitarii (NTS) attenuates cardiopulmonary chemoreflex (CCR) evoked inhibition of renal, adrenal and lumbar sympathetic nerve activity and reflex decreases in arterial pressure and heart rate. Activation of facilitatory A2a adenosine receptors, which dominate over A1 receptors in the NTS, contrastingly alters baseline activity of regional sympathetic outputs: it decreases renal, increases adrenal and does not change lumbar nerve activity. Considering that NTS A2a receptors may facilitate release of inhibitory transmitters we hypothesized that A2a receptors will act in concert with A1 receptors differentially inhibiting regional sympathetic CCR responses (adrenal>lumbar>renal). In urethane/chloralose anesthetized rats (n=38) we compared regional sympathetic responses evoked by stimulation of the CCR with right atrial injections of serotonin 5HT3 receptor agonist, phenylbiguanide, (1-8μg/kg) before and after selective stimulation, blockade or combined blockade and stimulation of NTS A2a adenosine receptors (microinjections into the NTS of CGS-21680 0.2-20pmol/50nl, ZM-241385 40pmol/100nl or ZM-241385+CGS-21680, respectively). We found that stimulation of A2a adenosine receptors uniformly inhibited the regional sympathetic and hemodynamic reflex responses and this effect was abolished by the selective blockade of NTS A2a receptors. This indicates that A2a receptor triggered inhibition of CCR responses and the contrasting shifts in baseline sympathetic activity are mediated via different mechanisms. These data implicate that stimulation of NTS A2a receptors triggers unknown inhibitory mechanism(s) which in turn inhibit transmission in the CCR pathway when adenosine is released into the NTS during severe hypotension. PMID:24216055

  11. The role of dorsal raphe nucleus serotonergic and non-serotonergic neurons, and of their receptors, in regulating waking and rapid eye movement (REM) sleep.

    PubMed

    Monti, Jaime M

    2010-10-01

    Based on electrophysiological, neurochemical, genetic and neuropharmacological approaches it is currently accepted that serotonin (5-HT) functions to promote waking (W) and to inhibit rapid-eye movement sleep (REMS). The serotonin-containing neurons of the dorsal raphe nucleus (DRN) provide part of the serotonergic innervation of the telencephalon, diencephalon, mesencephalon and rhombencephalon of laboratory animals and man. The DRN has been subdivided into several clusters on the basis of differences in cellular morphology, expression of other neurotransmitters and afferent and efferent connections. These differences among subpopulations of 5-HT neurons may have important implications for neural mechanisms underlying 5-HT modulation of sleep and waking. The DRN contains 5-HT and non-5-HT neurons. The latter express a variety of substances including dopamine, γ-aminobutyric acid (GABA) and glutamate. In addition, nitric oxide and a number of neuropeptides have been characterized in the DRN. Available evidence tends to indicate that non-5-HT cells contribute to the regulation of the activity of 5-HT neurons during the sleep-wake cycle through local circuits and/or their mediation of the effects of afferent inputs. Mutant mice that do not express 5-HT(1A) or 5-HT(1B) receptor exhibit greater amounts of REMS than their wild-type couterparts. 5-HT(2A) and 5-HT(2C) receptor knockout mice show a significant increase of W and a reduction of slow wave sleep that is related, at least in part, to the increased release of norepinephrine and dopamine. A normal circadian sleep pattern is observed in 5-HT(7) receptor knockout mice; however, the mutants spend less time in REMS. Local microinjection of 5-HT(1B), 5-HT(2A/2C), 5-HT(3) and 5-HT(7) receptor agonists into the DRN selectively suppresses REMS in the rat. In contrast, microinjection of 5-HT(1A) receptor agonists promotes REMS. Similarly, local administration of the melanin-concentrating hormone or the GABA(A) receptor

  12. Activation of 5-HT(2C) receptors in the dorsal periaqueductal gray increases antinociception in mice exposed to the elevated plus-maze.

    PubMed

    Baptista, Daniela; Nunes-de-Souza, Ricardo Luiz; Canto-de-Souza, Azair

    2012-11-01

    Several findings have pointed to the role of the dorsal periaqueductal gray (dPAG) serotonin 5-HT(1A) and 5-HT(2A-C) receptor subtypes in the modulation of defensive behavior in animals exposed to the elevated plus-maze (EPM). Besides displaying anxiety-like behavior, rodents also exhibit antinociception in the EPM. This study investigated the effects of intra-dPAG injections of 5-HT(1A) and 5-HT(2B/2C) receptor ligands on EPM-induced antinociception in mice. Male Swiss mice received 0.1 μl intra-dPAG injections of vehicle, 5.6 and 10 nmol of 8-OHDPAT, a 5-HT(1A) receptor agonist (Experiment 1), or 0.01, 0.03 and 0.1 nmol of mCPP, a 5-HT(2B/2C) receptor agonist (Experiment 2). Five minutes later, each mouse received an intraperitoneal injection of 0.6% acetic acid (0.1 ml/10 g body weight; nociceptive stimulus) and was individually confined in the open (OA) or enclosed (EA) arms of the EPM for 5 min, during which the number of abdominal writhes induced by the acetic acid was recorded. While intra-dPAG injection of 8-OHDPAT did not change open-arm antinociception (OAA), mCPP (0.01 nmol) enhanced it. Combined injections of ketanserin (10 nmol/0.1 μl), a 5-HT(2A/2C) receptor antagonist, and 0.01 nmol of mCPP (Experiment 3), selectively and completely blocked the OAA enhancement induced by mCPP. Although intra-dPAG injection of mCPP (0.01 nmol) also produced antinociception in EA-confined mice (Experiment 2), this effect was not confirmed in Experiment 3. Moreover, no other compound changed the nociceptive response in EA-confined animals. These results suggest that the 5-HT(2C) receptors located within the PAG play a role in this type of environmentally induced pain inhibition in mice.

  13. Adenosine A2a receptors and O2 sensing in development

    PubMed Central

    2011-01-01

    Reduced mitochondrial oxidative phosphorylation, via activation of adenylate kinase and the resulting exponential rise in the cellular AMP/ATP ratio, appears to be a critical factor underlying O2 sensing in many chemoreceptive tissues in mammals. The elevated AMP/ATP ratio, in turn, activates key enzymes that are involved in physiologic adjustments that tend to balance ATP supply and demand. An example is the conversion of AMP to adenosine via 5′-nucleotidase and the resulting activation of adenosine A2A receptors, which are involved in acute oxygen sensing by both carotid bodies and the brain. In fetal sheep, A2A receptors associated with carotid bodies trigger hypoxic cardiovascular chemoreflexes, while central A2A receptors mediate hypoxic inhibition of breathing and rapid eye movements. A2A receptors are also involved in hypoxic regulation of fetal endocrine systems, metabolism, and vascular tone. In developing lambs, A2A receptors play virtually no role in O2 sensing by the carotid bodies, but brain A2A receptors remain critically involved in the roll-off ventilatory response to hypoxia. In adult mammals, A2A receptors have been implicated in O2 sensing by carotid glomus cells, while central A2A receptors likely blunt hypoxic hyperventilation. In conclusion, A2A receptors are crucially involved in the transduction mechanisms of O2 sensing in fetal carotid bodies and brains. Postnatally, central A2A receptors remain key mediators of hypoxic respiratory depression, but they are less critical for O2 sensing in carotid chemoreceptors, particularly in developing lambs. PMID:21677265

  14. 5-HT3 receptors as important mediators of nausea and vomiting due to chemotherapy.

    PubMed

    Navari, Rudolph M

    2015-10-01

    Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. The use of a combination of a 5-hydroxytryptamine-3 (5-HT3) receptor antagonist, dexamethasone, and a neurokinin-1 (NK-1) receptor antagonist has significantly improved the control of acute and delayed emesis in single-day chemotherapy. The first generation 5-HT3 receptor antagonists have been very effective in the control of chemotherapy induced emesis in the first 24 h postchemotherapy (acute emesis), but have not been as effective against delayed emesis (24-120 h postchemotherapy). Palonosetron, a second generation 5-HT3 receptor antagonist with a different half-life, a different binding capacity, and a different mechanism of action than the first generation 5-HT3 receptor antagonists appears to be the most effective agent in its class. Despite the control of emesis, nausea has not been well controlled by current agents. Olanzapine, a FDA approved antipsychotic that blocks multiple neurotransmitters: dopamine at D1, D2, D3, D4 brain receptors, serotonin at 5-HT2a, 5-HT2c, 5-HT3, 5-HT6 receptors, catecholamines at alpha1 adrenergic receptors, acetylcholine at muscarinic receptors, and histamine at H1 receptors, has emerged in recent trials as an effective preventative agent for chemotherapy-induced emesis and nausea, as well as a very effective agent for the treatment of breakthrough emesis and nausea. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

  15. The role of serotonin receptor subtypes in treating depression: a review of animal studies

    PubMed Central

    Carr, Gregory V.

    2012-01-01

    Rationale Serotonin reuptake inhibitors (SSRIs) are effective in treating depression. Given the existence of different families and subtypes of 5-HT receptors, multiple 5-HT receptors may be involved in the antidepressant-like behavioral effects of SSRIs. Objective Behavioral pharmacology studies investigating the role of 5-HT receptor subtypes in producing or blocking the effects of SSRIs were reviewed. Results Few animal behavior tests were available to support the original development of SSRIs. Since their development, a number of behavioral tests and models of depression have been developed that are sensitive to the effects of SSRIs, as well as to other types of antidepressant treatments. The rationale for the development and use of these tests is reviewed. Behavioral effects similar to those of SSRIs (antidepressant-like) have been produced by agonists at 5-HT1A, 5-HT1B, 5-HT2C, 5-HT4, and 5-HT6 receptors. Also, antagonists at 5-HT2A, 5-HT2C, 5-HT3, 5- HT6, and 5-HT7 receptors have been reported to produce antidepressant-like responses. Although it seems paradoxical that both agonists and antagonists at particular 5-HT receptors can produce antidepressant-like effects, they probably involve diverse neurochemical mechanisms. The behavioral effects of SSRIs and other antidepressants may also be augmented when 5-HT receptor agonists or antagonists are given in combination. Conclusions The involvement of 5-HT receptors in the antidepressant-like effects of SSRIs is complex and involves the orchestration of stimulation and blockade at different 5-HT receptor subtypes. Individual 5-HT receptors provide opportunities for the development of a newer generation of antidepressants that may be more beneficial and effective than SSRIs. PMID:21107537

  16. New functional activity of aripiprazole revealed: Robust antagonism of D2 dopamine receptor-stimulated Gβγ signaling.

    PubMed

    Brust, Tarsis F; Hayes, Michael P; Roman, David L; Watts, Val J

    2015-01-01

    The dopamine D2 receptor (DRD2) is a G protein-coupled receptor (GPCR) that is generally considered to be a primary target in the treatment of schizophrenia. First generation antipsychotic drugs (e.g. haloperidol) are antagonists of the DRD2, while second generation antipsychotic drugs (e.g. olanzapine) antagonize DRD2 and 5HT2A receptors. Notably, both these classes of drugs may cause side effects associated with D2 receptor antagonism (e.g. hyperprolactemia and extrapyramidal symptoms). The novel, "third generation" antipsychotic drug, aripiprazole is also used to treat schizophrenia, with the remarkable advantage that its tendency to cause extrapyramidal symptoms is minimal. Aripiprazole is considered a partial agonist of the DRD2, but it also has partial agonist/antagonist activity for other GPCRs. Further, aripiprazole has been reported to have a unique activity profile in functional assays with the DRD2. In the present study the molecular pharmacology of aripiprazole was further examined in HEK cell models stably expressing the DRD2 and specific isoforms of adenylyl cyclase to assess functional responses of Gα and Gβγ subunits. Additional studies examined the activity of aripiprazole in DRD2-mediated heterologous sensitization of adenylyl cyclase and cell-based dynamic mass redistribution (DMR). Aripiprazole displayed a unique functional profile for modulation of G proteins, being a partial agonist for Gαi/o and a robust antagonist for Gβγ signaling. Additionally, aripiprazole was a weak partial agonist for both heterologous sensitization and dynamic mass redistribution.

  17. Serotonin 5-HT2 Receptor Interactions with Dopamine Function: Implications for Therapeutics in Cocaine Use Disorder

    PubMed Central

    Cunningham, Kathryn A.

    2015-01-01

    Cocaine exhibits prominent abuse liability, and chronic abuse can result in cocaine use disorder with significant morbidity. Major advances have been made in delineating neurobiological mechanisms of cocaine abuse; however, effective medications to treat cocaine use disorder remain to be discovered. The present review will focus on the role of serotonin (5-HT; 5-hydroxytryptamine) neurotransmission in the neuropharmacology of cocaine and related abused stimulants. Extensive research suggests that the primary contribution of 5-HT to cocaine addiction is a consequence of interactions with dopamine (DA) neurotransmission. The literature on the neurobiological and behavioral effects of cocaine is well developed, so the focus of the review will be on cocaine with inferences made about other monoamine uptake inhibitors and releasers based on mechanistic considerations. 5-HT receptors are widely expressed throughout the brain, and several different 5-HT receptor subtypes have been implicated in mediating the effects of endogenous 5-HT on DA. However, the 5-HT2A and 5-HT2C receptors in particular have been implicated as likely candidates for mediating the influence of 5-HT in cocaine abuse as well as to traits (e.g., impulsivity) that contribute to the development of cocaine use disorder and relapse in humans. Lastly, new approaches are proposed to guide targeted development of serotonergic ligands for the treatment of cocaine use disorder. PMID:25505168

  18. Serotonin 5-HT2 receptor interactions with dopamine function: implications for therapeutics in cocaine use disorder.

    PubMed

    Howell, Leonard L; Cunningham, Kathryn A

    2015-01-01

    Cocaine exhibits prominent abuse liability, and chronic abuse can result in cocaine use disorder with significant morbidity. Major advances have been made in delineating neurobiological mechanisms of cocaine abuse; however, effective medications to treat cocaine use disorder remain to be discovered. The present review will focus on the role of serotonin (5-HT; 5-hydroxytryptamine) neurotransmission in the neuropharmacology of cocaine and related abused stimulants. Extensive research suggests that the primary contribution of 5-HT to cocaine addiction is a consequence of interactions with dopamine (DA) neurotransmission. The literature on the neurobiological and behavioral effects of cocaine is well developed, so the focus of the review will be on cocaine with inferences made about other monoamine uptake inhibitors and releasers based on mechanistic considerations. 5-HT receptors are widely expressed throughout the brain, and several different 5-HT receptor subtypes have been implicated in mediating the effects of endogenous 5-HT on DA. However, the 5-HT2A and 5-HT2C receptors in particular have been implicated as likely candidates for mediating the influence of 5-HT in cocaine abuse as well as to traits (e.g., impulsivity) that contribute to the development of cocaine use disorder and relapse in humans. Lastly, new approaches are proposed to guide targeted development of serotonergic ligands for the treatment of cocaine use disorder. PMID:25505168

  19. Prenatal nicotine exposure enhances the trigeminocardiac reflex via serotonin receptor facilitation in brainstem pathways

    PubMed Central

    Gorini, C.; Jameson, H.; Woerman, A. L.; Perry, D. C.

    2013-01-01

    In this study we used a rat model for prenatal nicotine exposure to test whether clinically relevant concentrations of brain nicotine and cotinine are passed from dams exposed to nicotine to her pups, whether this changes the trigeminocardiac reflex (TCR), and whether serotonergic function in the TCR brainstem circuitry is altered. Pregnant Sprague-Dawley dams were exposed to 6 mg·kg−1·day−1 of nicotine via osmotic minipumps for the duration of pregnancy. Following birth dams and pups were killed, blood was collected, and brain nicotine and cotinine levels were measured. A separate group of prenatal nicotine-exposed pups was used for electrophysiological recordings. A horizontal brainstem slice was obtained by carefully preserving the trigeminal nerve with fluorescent identification of cardiac vagal neurons (CVNs) in the nucleus ambiguus. Stimulation of the trigeminal nerve evoked excitatory postsynaptic current in CVNs. Our data demonstrate that prenatal nicotine exposure significantly exaggerates both the TCR-evoked changes in heart rate in conscious unrestrained pups, and the excitatory neurotransmission to CVNs upon trigeminal afferent nerve stimulation within this brainstem reflex circuit. Application of the 5-HT1A receptor antagonist WAY 100635 (100 μM) and 5-HT2A/C receptor antagonist ketanserin (10 μM)significantly decreased neurotransmission, indicating an increased facilitation of 5-HT function in prenatal nicotine-exposed animals. Prenatal nicotine exposure enhances activation of 5-HT receptors and exaggerates the trigeminocardiac reflex. PMID:23766497

  20. The CC genotype in HTR2A T102C polymorphism is associated with behavioral impulsivity in alcohol-dependent patients

    PubMed Central

    Jakubczyk, Andrzej; Wrzosek, Małgorzata; Łukaszkiewicz, Jacek; Sadowska-Mazuryk, Joanna; Matsumoto, Halina; Śliwerska, Elżbieta; Glass, Jennifer; Burmeister, Margit; Brower, Kirk J.; Wojnar, Marcin

    2011-01-01

    High levels of impulsivity can increase the vulnerability for development of alcohol dependence. Moreover, impulsivity is considered to be a predictor of poor treatment outcomes. Few studies, however, have directly examined the genetics of impulsivity in alcohol-dependent patients. We analyzed the relationships between a well-recognized genetic marker of serotonin activity and levels of impulsivity as measured by both the Barratt Impulsiveness Scale (BIS-11) and the stop-signal task among 304 alcohol-dependent patients. The stop-signal task was used as an independent, objective method of estimating the level of behavioral impulsivity, and the BIS-11 as a self-report measure of global impulsivity. Blood was collected and analyzed for the T102C (rs6313) polymorphism in the serotonin type 2A receptor gene (HTR2A). Our results indicate a significant association between high levels of behavioral impulsivity and the C/C genotype of rs6313 in alcohol-dependent patients. The CC genotype has been previously found to be associated with a reduction in 5HT2A receptors in the central nervous system. These results support the hypothesis that genetic factors are important determinants of behavioral impulsivity in alcohol-dependent patients, and that the serotonin system plays an important role in establishing its level. PMID:21930285

  1. The CC genotype in HTR2A T102C polymorphism is associated with behavioral impulsivity in alcohol-dependent patients.

    PubMed

    Jakubczyk, Andrzej; Wrzosek, Małgorzata; Lukaszkiewicz, Jacek; Sadowska-Mazuryk, Joanna; Matsumoto, Halina; Sliwerska, Elżbieta; Glass, Jennifer; Burmeister, Margit; Brower, Kirk J; Wojnar, Marcin

    2012-01-01

    High levels of impulsivity can increase the vulnerability for development of alcohol dependence. Moreover, impulsivity is considered to be a predictor of poor treatment outcomes. Few studies, however, have directly examined the genetics of impulsivity in alcohol-dependent patients. We analyzed the relationships between a well-recognized genetic marker of serotonin activity and levels of impulsivity as measured by both the Barratt Impulsiveness Scale (BIS-11) and the stop-signal task among 304 alcohol-dependent patients. The stop-signal task was used as an independent, objective method of estimating the level of behavioral impulsivity, and the BIS-11 as a self-report measure of global impulsivity. Blood was collected and analyzed for the T102C (rs6313) polymorphism in the serotonin type 2A receptor gene (HTR2A). Our results indicate a significant association between high levels of behavioral impulsivity and the C/C genotype of rs6313 in alcohol-dependent patients. The CC genotype has been previously found to be associated with a reduction in 5HT2A receptors in the central nervous system. These results support the hypothesis that genetic factors are important determinants of behavioral impulsivity in alcohol-dependent patients, and that the serotonin system plays an important role in establishing its level.

  2. Positive association between a DNA sequence variant in the serotonin 2A receptor gene and schizophrenia

    SciTech Connect

    Inayama, Y.; Yoneda, H.; Sakai, T.

    1996-02-16

    Sixty-two patients with schizophrenia and 96 normal controls were investigated for genetic association with restriction fragment length polymorphisms (RFLPs) in the serotonin receptor genes. A positive association between the serotonin 2A receptor gene (HTR2A) and schizophrenia was found, but not between schizophrenia and the serotonin 1A receptor gene. The positive association we report here would suggest that the DNA region with susceptibility to schizophrenia lies in the HTR2A on the long arm of chromosome 13. 15 refs., 2 tabs.

  3. Effect of prenatal exposure of lindane on alterations in the expression of cerebral cytochrome P450s and neurotransmitter receptors in brain regions.

    PubMed

    Srivastava, Shikha; Singh, Anshuman; Shukla, Rajendra K; Khanna, Vinay K; Parmar, Devendra

    2015-03-01

    Prenatal exposure to low doses (0.0625- or 0.125- or 0.25 mg/kg b. wt., orally) of lindane, an organochlorine insecticide, from gestation day (GD) 5-21 was found to produce a dose-dependent increase in the mRNA expression of cytochrome P450s (CYPs) and associated transcription factors in frontal cortex, cerebellum and corpus striatum isolated from the offsprings. Though the increase in the expression persisted up to postnatal day 60, the increase was significant at postnatal days 21-, and 45- in the offsprings exposed prenatally to relatively higher doses (0.125- or 0.25 mg/kg) of lindane and even up to postnatal day 60 in the offsprings exposed prenatally to the highest dose of lindane. A similar increase in the expression of dopamine D2, 5HT2A and GABAA receptors and associated neurotransmitter receptor binding was observed in the brain regions of the exposed offsprings. Scatchard analysis also suggested an increase in the levels of these neurotransmitter receptors in offsprings prenatally exposed to lindane. The data indicating similarities in the alterations of neurotransmitter receptors and CYPs in brain regions in prenatally exposed offsprings have suggested that neurotransmission processes and CYPs are closely linked that will eventually help in understanding the developmental neurotoxicity of lindane. PMID:25572523

  4. Astrocytic adenosine receptor A2A and Gs-coupled signaling regulate memory

    PubMed Central

    Orr, Anna G.; Hsiao, Edward C.; Wang, Max M.; Ho, Kaitlyn; Kim, Daniel H.; Wang, Xin; Guo, Weikun; Kang, Jing; Yu, Gui-Qiu; Adame, Anthony; Devidze, Nino; Dubal, Dena B.; Masliah, Eliezer; Conklin, Bruce R.; Mucke, Lennart

    2014-01-01

    Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory. However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known. We found that humans with Alzheimer’s disease (AD) had increased levels of the Gs-coupled adenosine receptor A2A in astrocytes. Conditional genetic removal of these receptors enhanced long-term memory in young and aging mice, and increased the levels of Arc/Arg3.1, an immediate-early gene required for long-term memory. Chemogenetic activation of astrocytic Gs-coupled signaling reduced long-term memory in mice without affecting learning. Similar to humans with AD, aging mice expressing human amyloid precursor protein (hAPP) showed increased levels of astrocytic A2A receptors. Conditional genetic removal of these receptors enhanced memory in aging hAPP mice. Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss. PMID:25622143

  5. Astrocytic adenosine receptor A2A and Gs-coupled signaling regulate memory.

    PubMed

    Orr, Anna G; Hsiao, Edward C; Wang, Max M; Ho, Kaitlyn; Kim, Daniel H; Wang, Xin; Guo, Weikun; Kang, Jing; Yu, Gui-Qiu; Adame, Anthony; Devidze, Nino; Dubal, Dena B; Masliah, Eliezer; Conklin, Bruce R; Mucke, Lennart

    2015-03-01

    Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory. However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known. We found that humans with Alzheimer's disease (AD) had increased levels of the Gs-coupled adenosine receptor A2A in astrocytes. Conditional genetic removal of these receptors enhanced long-term memory in young and aging mice and increased the levels of Arc (also known as Arg3.1), an immediate-early gene that is required for long-term memory. Chemogenetic activation of astrocytic Gs-coupled signaling reduced long-term memory in mice without affecting learning. Like humans with AD, aging mice expressing human amyloid precursor protein (hAPP) showed increased levels of astrocytic A2A receptors. Conditional genetic removal of these receptors enhanced memory in aging hAPP mice. Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss. PMID:25622143

  6. Lack of tolerance to motor stimulant effects of a selective adenosine A(2A) receptor antagonist.

    PubMed

    Halldner, L; Lozza, G; Lindström, K; Fredholm, B B

    2000-10-20

    It is well known that tolerance develops to the actions of caffeine, which acts as an antagonist on adenosine A(1) and A(2A) receptors. Since selective adenosine A(2A) antagonists have been proposed as adjuncts to 3,4-dihydroxyphenylalanine (L-DOPA) therapy in Parkinson's disease we wanted to examine if tolerance also develops to the selective A(2A) receptor antagonist 5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo-[4,3-e]-1,2, 4-triazolo [1,5-c]pyrimidine (SCH 58261). SCH 58261 (0.1 and 7.5 mg/kg) increased basal locomotion and the motor stimulation afforded by apomorphine. Neither effect was subject to tolerance following long-term treatment with the same doses given intraperitoneally twice daily. There were no adaptive changes in A(1) and A(2A) adenosine receptors or their corresponding messenger RNA or in dopamine D(1) or D(2) receptors. These results demonstrate that the tolerance that develops to caffeine is not secondary to its inhibition of adenosine A(2A) receptors. The results also offer hope that long-term treatment with an adenosine A(2A) receptor antagonist may be possible in man.

  7. Adenosine A2A Receptors Modulate Acute Injury and Neuroinflammation in Brain Ischemia

    PubMed Central

    Pedata, Felicita; Pugliese, Anna Maria; Coppi, Elisabetta; Dettori, Ilaria; Maraula, Giovanna; Cellai, Lucrezia; Melani, Alessia

    2014-01-01

    The extracellular concentration of adenosine in the brain increases dramatically during ischemia. Adenosine A2A receptor is expressed in neurons and glial cells and in inflammatory cells (lymphocytes and granulocytes). Recently, adenosine A2A receptor emerged as a potential therapeutic attractive target in ischemia. Ischemia is a multifactorial pathology characterized by different events evolving in the time. After ischemia the early massive increase of extracellular glutamate is followed by activation of resident immune cells, that is, microglia, and production or activation of inflammation mediators. Proinflammatory cytokines, which upregulate cell adhesion molecules, exert an important role in promoting recruitment of leukocytes that in turn promote expansion of the inflammatory response in ischemic tissue. Protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. A2A receptors present on central cells and on blood cells account for important effects depending on the time-related evolution of the pathological condition. Evidence suggests that A2A receptor antagonists provide early protection via centrally mediated control of excessive excitotoxicity, while A2A receptor agonists provide protracted protection by controlling massive blood cell infiltration in the hours and days after ischemia. Focus on inflammatory responses provides for adenosine A2A receptor agonists a wide therapeutic time-window of hours and even days after stroke. PMID:25165414

  8. Preclinical pharmacology of mGlu2/3 receptor agonists: novel agents for schizophrenia?

    PubMed

    DD, Darryle D Schoepp; Marek, Gerard J

    2002-04-01

    Agonists for mGlu2/3 receptors decrease the evoked release of glutamate at certain (ie. forebrain / limbic) glutamatergic synapses, indicating that the functional role of mGlu2 and/or mGlu3 receptors is to suppress glutamate excitations. This offers a mechanism for dampening glutamate excitation under pathological states resulting from excessive glutamate release. Based, in part, on the psychotomimetic actions of phencyclidine (PCP)- like drugs, excessive or pathological glutamate release has been implicated in a number of clinical conditions including psychosis. With this in mind, the pharmacology of multiple mGlu2/3 receptor agonists have been investigated in PCP treated rats. Agonists for mGlu2/3 receptors such as LY354740 and LY379268 have been shown to block certain behavioral responses to PCP in rats. The effects of mGlu2/3 agonists on PCP-induced behaviors are blocked by a low doses of a selective mGlu2/3 receptor antagonist, indicating that these actions are mediated via mGlu2/3 receptors. In addition, mGlu2/3 agonists potently suppress glutamate release in rat prefrontal cortex, as reflected by excitatory post-synaptic potentials (EPSPs) induced by serotonin (5-HT) acting on 5HT(2A) receptors. These actions of LY354740 and LY379268 are also blocked by a selective mGlu2/3 antagonist. Atypical antipsychotic drugs such as clozapine also suppress 5-HT-induced EPSPs in this brain region, thus suggesting a common pathway for the actions of atypical antipsychotic drugs and mGlu2/3 receptor agonists. As glutamatergic dysfunction has been implicated in psychotic states and possibly in the etiology of schizophrenia, clinical studies with mGlu2/3 agonists may be warranted to further explore the validity of the glutamatergic hypothesis of schizophrenia. PMID:12769628

  9. Group II Metabotropic Glutamate Receptors as Targets for Novel Antipsychotic Drugs

    PubMed Central

    Muguruza, Carolina; Meana, J. Javier; Callado, Luis F.

    2016-01-01

    Schizophrenia is a chronic psychiatric disorder which substantially impairs patients’ quality of life. Despite the extensive research in this field, the pathophysiology and etiology of schizophrenia remain unknown. Different neurotransmitter systems and functional networks have been found to be affected in the brain of patients with schizophrenia. In this context, postmortem brain studies as well as genetic assays have suggested alterations in Group II metabotropic glutamate receptors (mGluRs) in schizophrenia. Despite many years of drug research, several needs in the treatment of schizophrenia have not been addressed sufficiently. In fact, only 5–10% of patients with schizophrenia successfully achieve a full recovery after treatment. In recent years mGluRs have turned up as novel targets for the design of new antipsychotic medications for schizophrenia. Concretely, Group II mGluRs are of particular interest due to their regulatory role in neurotransmission modulating glutamatergic activity in brain synapses. Preclinical studies have demonstrated that orthosteric Group II mGluR agonists exhibit antipsychotic-like properties in animal models of schizophrenia. However, when these compounds have been tested in human clinical studies with schizophrenic patients results have been inconclusive. Nevertheless, it has been recently suggested that this apparent lack of efficacy in schizophrenic patients may be related to previous exposure to atypical antipsychotics. Moreover, the role of the functional heterocomplex formed by 5-HT2A and mGlu2 receptors in the clinical response to Group II mGluR agonists is currently under study. PMID:27242534

  10. α(2A) adrenergic receptor promotes amyloidogenesis through disrupting APP-SorLA interaction.

    PubMed

    Chen, Yunjia; Peng, Yin; Che, Pulin; Gannon, Mary; Liu, Yin; Li, Ling; Bu, Guojun; van Groen, Thomas; Jiao, Kai; Wang, Qin

    2014-12-01

    Accumulation of amyloid β (Aβ) peptides in the brain is the key pathogenic factor driving Alzheimer's disease (AD). Endocytic sorting of amyloid precursor protein (APP) mediated by the vacuolar protein sorting (Vps10) family of receptors plays a decisive role in controlling the outcome of APP proteolytic processing and Aβ generation. Here we report for the first time to our knowledge that this process is regulated by a G protein-coupled receptor, the α(2A) adrenergic receptor (α(2A)AR). Genetic deficiency of the α(2A)AR significantly reduces, whereas stimulation of this receptor enhances, Aβ generation and AD-related pathology. Activation of α(2A)AR signaling disrupts APP interaction with a Vps10 family receptor, sorting-related receptor with A repeat (SorLA), in cells and in the mouse brain. As a consequence, activation of α(2A)AR reduces Golgi localization of APP and concurrently promotes APP distribution in endosomes and cleavage by β secretase. The α(2A)AR is a key component of the brain noradrenergic system. Profound noradrenergic dysfunction occurs consistently in patients at the early stages of AD. α(2A)AR-promoted Aβ generation provides a novel mechanism underlying the connection between noradrenergic dysfunction and AD. Our study also suggests α(2A)AR as a previously unappreciated therapeutic target for AD. Significantly, pharmacological blockade of the α(2A)AR by a clinically used antagonist reduces AD-related pathology and ameliorates cognitive deficits in an AD transgenic model, suggesting that repurposing clinical α(2A)R antagonists would be an effective therapeutic strategy for AD.

  11. Impaired Discrimination Learning in Mice Lacking the NMDA Receptor NR2A Subunit

    ERIC Educational Resources Information Center

    Brigman, Jonathan L.; Feyder, Michael; Saksida, Lisa M.; Bussey, Timothy J.; Mishina, Masayoshi; Holmes, Andrew

    2008-01-01

    N-Methyl-D-aspartate receptors (NMDARs) mediate certain forms of synaptic plasticity and learning. We used a touchscreen system to assess NR2A subunit knockout mice (KO) for (1) pairwise visual discrimination and reversal learning and (2) acquisition and extinction of an instrumental response requiring no pairwise discrimination. NR2A KO mice…

  12. Adenosine A2A receptors are necessary and sufficient to trigger memory impairment in adult mice

    PubMed Central

    Pagnussat, N; Almeida, A S; Marques, D M; Nunes, F; Chenet, G C; Botton, P H S; Mioranzza, S; Loss, C M; Cunha, R A; Porciúncula, L O

    2015-01-01

    Background and Purpose Caffeine (a non-selective adenosine receptor antagonist) prevents memory deficits in aging and Alzheimer’s disease, an effect mimicked by adenosine A2A receptor, but not A1 receptor, antagonists. Hence, we investigated the effects of adenosine receptor agonists and antagonists on memory performance and scopolamine-induced memory impairment in mice. Experimental Approach We determined whether A2A receptors are necessary for the emergence of memory impairments induced by scopolamine and whether A2A receptor activation triggers memory deficits in naïve mice, using three tests to assess short-term memory, namely the object recognition task, inhibitory avoidance and modified Y-maze. Key Results Scopolamine (1.0 mg·kg−1, i.p.) impaired short-term memory performance in all three tests and this scopolamine-induced amnesia was prevented by the A2A receptor antagonist (SCH 58261, 0.1–1.0 mg·kg−1, i.p.) and by the A1 receptor antagonist (DPCPX, 0.2–5.0 mg·kg−1, i.p.), except in the modified Y-maze where only SCH58261 was effective. Both antagonists were devoid of effects on memory or locomotion in naïve rats. Notably, the activation of A2A receptors with CGS 21680 (0.1–0.5 mg·kg−1, i.p.) before the training session was sufficient to trigger memory impairment in the three tests in naïve mice, and this effect was prevented by SCH 58261 (1.0 mg·kg−1, i.p.). Furthermore, i.c.v. administration of CGS 21680 (50 nmol) also impaired recognition memory in the object recognition task. Conclusions and Implications These results show that A2A receptors are necessary and sufficient to trigger memory impairment and further suggest that A1 receptors might also be selectively engaged to control the cholinergic-driven memory impairment. PMID:25939452

  13. Linoleic acid derivative DCP-LA ameliorates stress-induced depression-related behavior by promoting cell surface 5-HT1A receptor translocation, stimulating serotonin release, and inactivating GSK-3β.

    PubMed

    Kanno, Takeshi; Tanaka, Akito; Nishizaki, Tomoyuki

    2015-04-01

    Impairment of serotonergic neurotransmission is the major factor responsible for depression and glycogen synthase kinase 3β (GSK-3β) participates in serotonergic transmission-mediated signaling networks relevant to mental illnesses. In the forced-swim test to assess depression-like behavior, the immobility time for mice with restraint stress was significantly longer than that for nonstressed control mice. Postsynaptic cell surface localization of 5-HT1A receptor, but not 5-HT2A receptor, in the hypothalamus for mice with restraint stress was significantly reduced as compared with that for control mice, which highly correlated to prolonged immobility time, i.e., depression-like behavior. The linoleic acid derivative 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) restored restraint stress-induced reduction of cell surface 5-HT1A receptor and improved depression-like behavior in mice with restraint stress. Moreover, DCP-LA stimulated serotonin release from hypothalamic slices and cancelled restraint stress-induced reduction of GSK-3β phosphorylation at Ser9. Taken together, the results of the present study indicate that DCP-LA could ameliorate depression-like behavior by promoting translocation of 5-HT1A receptor to the plasma membrane on postsynaptic cells, stimulating serotonin release, and inactivating GSK-3β.

  14. Relation of exploratory behavior of rats in elevated plus-maze to brain receptor binding properties and serum growth hormone levels.

    PubMed

    Kõks, S; Vasar, E; Soosaar, A; Lang, A; Volke, V; Võikar, V; Bourin, M; Männistö, P T

    1997-11-01

    Forty-five male Wistar rats were selected according to their behavior in the elevated plus-maze. They were separated as follows: animals with low exploratory activity ('anxious'), an 'intermediate' group and animals having high exploratory activity ('non-anxious'). Various receptor binding studies and hormonal assays were also performed in these selected rats. The affinity of 5-hydroxytryptamine 5-HT2A receptors in the frontal cortex was lower in the 'anxious' rats compared to home-cage controls and 'non-anxious' animals. Moreover, the number of cholecystokinin (CCK) receptors in the hippocampus was significantly elevated in the 'anxious' group compared to home-cage control animals. The blood levels of growth hormone (GH) were significantly lower in the 'non-anxious' rats compared to 'anxious' counterparts. In conclusion, it seems likely that the decreased exploratory activity of rats is related to the increased 5-hydroxytryptamine (5-HT) and CCK mediated neurotransmission in the brain. The different serum levels of GH in the selected rats probably reflect alterations in the activity of 5-HT and CCK.

  15. Increased desensitization of dopamine D₂ receptor-mediated response in the ventral tegmental area in the absence of adenosine A(2A) receptors.

    PubMed

    Al-Hasani, R; Foster, J D; Metaxas, A; Ledent, C; Hourani, S M O; Kitchen, I; Chen, Y

    2011-09-01

    G-protein coupled receptors interact to provide additional regulatory mechanisms for neurotransmitter signaling. Adenosine A(2A) receptors are expressed at a high density in striatal neurons, where they closely interact with dopamine D₂ receptors and modulate effects of dopamine and responses to psychostimulants. A(2A) receptors are expressed at much lower densities in other forebrain neurons but play a more prominent yet opposing role to striatal receptors in response to psychostimulants in mice. It is, therefore, possible that A(2A) receptors expressed at low levels elsewhere in the brain may also regulate neurotransmitter systems and modulate neuronal functions. Dopamine D₂ receptors play an important role in autoinhibition of neuronal firing in dopamine neurons of the ventral tegmental area (VTA) and dopamine release in other brain areas. Here, we examined the effect of A(2A) receptor deletion on D₂ receptor-mediated inhibition of neuronal firing in dopamine neurons in the VTA. Spontaneous activity of dopamine neurons was recorded in midbrain slices, and concentration-dependent effects of the dopamine D₂ receptor agonist, quinpirole, was compared between wild-type and A(2A) knockout mice. The potency of quinpirole applied in single concentrations and the expression of D₂ receptors were not altered in the VTA of the knockout mice. However, quinpirole applied in stepwise escalating concentrations caused significantly reduced maximal inhibition in A(2A) knockout mice, indicating an enhanced agonist-induced desensitization of D₂ receptors in the absence of A(2A) receptors. The A(2A) receptor agonist, CGS21680, did not exert any effect on dopamine neuron firing or response to quinpirole, revealing a novel non-pharmacological interaction between adenosine A(2A) receptors and dopaminergic neurotransmission in midbrain dopamine neurons. Altered D₂ receptor desensitization may result in changes in dopamine neuron firing rate and pattern and dopamine

  16. Protein phosphatase 2A mediates resensitization of the neurokinin 1 receptor

    PubMed Central

    Murphy, Jane E.; Roosterman, Dirk; Cottrell, Graeme S.; Padilla, Benjamin E.; Feld, Micha; Brand, Eva; Cedron, Wendy J.; Steinhoff, Martin

    2011-01-01

    Activated G protein-coupled receptors (GPCRs) are phosphorylated and interact with β-arrestins, which mediate desensitization and endocytosis. Endothelin-converting enzyme-1 (ECE-1) degrades neuropeptides in endosomes and can promote recycling. Although endocytosis, dephosphorylation, and recycling are accepted mechanisms of receptor resensitization, a large proportion of desensitized receptors can remain at the cell surface. We investigated whether reactivation of noninternalized, desensitized (phosphorylated) receptors mediates resensitization of the substance P (SP) neurokinin 1 receptor (NK1R). Herein, we report a novel mechanism of resensitization by which protein phosphatase 2A (PP2A) is recruited to dephosphorylate noninternalized NK1R. A desensitizing concentration of SP reduced cell-surface SP binding sites by only 25%, and SP-induced Ca2+ signals were fully resensitized before cell-surface binding sites started to recover, suggesting resensitization of cell-surface-retained NK1R. SP induced association of β-arrestin1 and PP2A with noninternalized NK1R. β-Arrestin1 small interfering RNA knockdown prevented SP-induced association of cell-surface NK1R with PP2A, indicating that β-arrestin1 mediates this interaction. ECE-1 inhibition, by trapping β-arrestin1 in endosomes, also impeded SP-induced association of cell-surface NK1R with PP2A. Resensitization of NK1R signaling required both PP2A and ECE-1 activity. Thus, after stimulation with SP, PP2A interacts with noninternalized NK1R and mediates resensitization. PP2A interaction with NK1R requires β-arrestin1. ECE-1 promotes this process by releasing β-arrestin1 from NK1R in endosomes. These findings represent a novel mechanism of PP2A- and ECE-1-dependent resensitization of GPCRs. PMID:21795521

  17. Protein phosphatase 2A mediates resensitization of the neurokinin 1 receptor.

    PubMed

    Murphy, Jane E; Roosterman, Dirk; Cottrell, Graeme S; Padilla, Benjamin E; Feld, Micha; Brand, Eva; Cedron, Wendy J; Bunnett, Nigel W; Steinhoff, Martin

    2011-10-01

    Activated G protein-coupled receptors (GPCRs) are phosphorylated and interact with β-arrestins, which mediate desensitization and endocytosis. Endothelin-converting enzyme-1 (ECE-1) degrades neuropeptides in endosomes and can promote recycling. Although endocytosis, dephosphorylation, and recycling are accepted mechanisms of receptor resensitization, a large proportion of desensitized receptors can remain at the cell surface. We investigated whether reactivation of noninternalized, desensitized (phosphorylated) receptors mediates resensitization of the substance P (SP) neurokinin 1 receptor (NK(1)R). Herein, we report a novel mechanism of resensitization by which protein phosphatase 2A (PP2A) is recruited to dephosphorylate noninternalized NK(1)R. A desensitizing concentration of SP reduced cell-surface SP binding sites by only 25%, and SP-induced Ca(2+) signals were fully resensitized before cell-surface binding sites started to recover, suggesting resensitization of cell-surface-retained NK(1)R. SP induced association of β-arrestin1 and PP2A with noninternalized NK(1)R. β-Arrestin1 small interfering RNA knockdown prevented SP-induced association of cell-surface NK(1)R with PP2A, indicating that β-arrestin1 mediates this interaction. ECE-1 inhibition, by trapping β-arrestin1 in endosomes, also impeded SP-induced association of cell-surface NK(1)R with PP2A. Resensitization of NK(1)R signaling required both PP2A and ECE-1 activity. Thus, after stimulation with SP, PP2A interacts with noninternalized NK(1)R and mediates resensitization. PP2A interaction with NK(1)R requires β-arrestin1. ECE-1 promotes this process by releasing β-arrestin1 from NK(1)R in endosomes. These findings represent a novel mechanism of PP2A- and ECE-1-dependent resensitization of GPCRs.

  18. Adenosine A2a receptors form distinct oligomers in protein detergent complexes.

    PubMed

    Schonenbach, Nicole S; Rieth, Monica D; Han, Songi; O'Malley, Michelle A

    2016-09-01

    The human adenosine A2a receptor (A2aR) tunes its function by forming homo-oligomers and hetero-oligomers with other G protein-coupled receptors, but the biophysical characterization of these oligomeric species is limited. Here, we show that upon reconstitution into an optimized mixed micelle system, and purification via an antagonist affinity column, full-length A2aR exists as a distribution of oligomers. We isolated the dimer population from the other oligomers via size exclusion chromatography and showed that it is stable upon dilution, thus supporting the hypotheses that the A2aR dimer has a defined structure and function. This study presents a crucial enabling step to a detailed biophysical characterization of A2aR homodimers. PMID:27543907

  19. Desensitization of human CRF2(a) receptor signaling governed by agonist potency and βarrestin2 recruitment.

    PubMed

    Hauger, Richard L; Olivares-Reyes, J Alberto; Braun, Sandra; Hernandez-Aranda, Judith; Hudson, Christine C; Gutknecht, Eric; Dautzenberg, Frank M; Oakley, Robert H

    2013-09-10

    The primary goal was to determine agonist-specific regulation of CRF2(a) receptor function. Exposure of human retinoblastoma Y79 cells to selective (UCN2, UCN3 or stresscopins) and non-selective (UCN1 or sauvagine) agonists prominently desensitized CRF2(a) receptors in a rapid, concentration-dependent manner. A considerably slower rate and smaller magnitude of desensitization developed in response to the weak agonist CRF. CRF1 receptor desensitization stimulated by CRF, cortagine or stressin1-A had no effect on CRF2(a) receptor cyclic AMP signaling. Conversely, desensitization of CRF2(a) receptors by UCN2 or UCN3 did not cross-desensitize Gs-coupled CRF1 receptor signaling. In transfected HEK293 cells, activation of CRF2(a) receptors by UCN2, UCN3 or CRF resulted in receptor phosphorylation and internalization proportional to agonist potency. Neither protein kinase A nor casein kinases mediated CRF2(a) receptor phosphorylation or desensitization. Exposure of HEK293 or U2OS cells to UCN2 or UCN3 (100nM) produced strong βarrestin2 translocation and colocalization with membrane CRF2(a) receptors while CRF (1μM) generated only weak βarrestin2 recruitment. βarrestin2 did not internalize with the receptor, however, indicating that transient CRF2(a) receptor-arrestin complexes dissociate at or near the cell membrane. Since deletion of the βarrestin2 gene upregulated Gs-coupled CRF2(a) receptor signaling in MEF cells, a βarrestin2 mechanism restrains Gs-coupled CRF2(a) receptor signaling activated by urocortins. We further conclude that the rate and extent of homologous CRF2(a) receptor desensitization are governed by agonist-specific mechanisms affecting GRK phosphorylation, βarrestin2 recruitment, and internalization thereby producing unique signal transduction profiles that differentially affect the stress response. PMID:23820308

  20. Structural Basis for Negative Allosteric Modulation of GluN2A-Containing NMDA Receptors.

    PubMed

    Yi, Feng; Mou, Tung-Chung; Dorsett, Katherine N; Volkmann, Robert A; Menniti, Frank S; Sprang, Stephen R; Hansen, Kasper B

    2016-09-21

    NMDA receptors mediate excitatory synaptic transmission and regulate synaptic plasticity in the central nervous system, but their dysregulation is also implicated in numerous brain disorders. Here, we describe GluN2A-selective negative allosteric modulators (NAMs) that inhibit NMDA receptors by stabilizing the apo state of the GluN1 ligand-binding domain (LBD), which is incapable of triggering channel gating. We describe structural determinants of NAM binding in crystal structures of the GluN1/2A LBD heterodimer, and analyses of NAM-bound LBD structures corresponding to active and inhibited receptor states reveal a molecular switch in the modulatory binding site that mediate the allosteric inhibition. NAM binding causes displacement of a valine in GluN2A and the resulting steric effects can be mitigated by the transition from glycine bound to apo state of the GluN1 LBD. This work provides mechanistic insight to allosteric NMDA receptor inhibition, thereby facilitating the development of novel classes NMDA receptor modulators as therapeutic agents. PMID:27618671

  1. Possible involvement of serotonin 5-HT2 receptor in the regulation of feeding behavior through the histaminergic system.

    PubMed

    Murotani, Tomotaka; Ishizuka, Tomoko; Isogawa, Yuka; Karashima, Michitaka; Yamatodani, Atsushi

    2011-01-01

    The central histaminergic system has been proven to be involved in several physiological functions including feeding behavior. Some atypical antipsychotics like risperidone and aripiprazole are known to affect feeding behavior and to antagonize the serotonin (5-HT) receptor subtypes. To examine the possible neural relationship between the serotonergic and histaminergic systems in the anorectic effect of the antipsychotics, we studied the effect of a single administration of these drugs on food intake and hypothalamic histamine release in mice using in vivo microdialysis. Single injection of risperidone (0.5mg/kg, i.p.) or aripiprazole (1mg/kg, i.p.), which have binding affinities to 5-HT(1A, 2A, 2B) and (2C) receptors decreased food intake in C57BL/6N mice with concomitant increase of hypothalamic histamine release. However, a selective D(2)-antagonist, haloperidol (0.5mg/kg, i.p.), did not have effects on food intake or histamine release. Furthermore, in histamine H(1) receptor-deficient mice, there was no reduction of food intake induced by atypical antipsychotics, although histamine release was increased. Moreover, selective 5-HT(2A)-antagonists, volinanserin (0.5, 1mg/kg, i.p.) and ketanserin (5, 10mg/kg, i.p.), significantly increased histamine release and 5-HT(2B/2C) -antagonist, SB206553 (2.5, 5mg/kg, i.p.), slightly increased it. On the contrary, 5-HT(1A) -selective antagonist, WAY100635 (1, 2mg/kg), did not affect the histaminergic tone. These findings suggest that serotonin tonically inhibits histamine release via 5-HT(2) receptors and that antipsychotics enhance the release of hypothalamic histamine by blockade of 5-HT(2) receptors resulting in anorexia via the H(1) receptor.

  2. NTS adenosine A2a receptors inhibit the cardiopulmonary chemoreflex control of regional sympathetic outputs via a GABAergic mechanism.

    PubMed

    Minic, Zeljka; O'Leary, Donal S; Scislo, Tadeusz J

    2015-07-01

    Adenosine is a powerful central neuromodulator acting via opposing A1 (inhibitor) and A2a (activator) receptors. However, in the nucleus of the solitary tract (NTS), both adenosine receptor subtypes attenuate cardiopulmonary chemoreflex (CCR) sympathoinhibition of renal, adrenal, and lumbar sympathetic nerve activity and attenuate reflex decreases in arterial pressure and heart rate. Adenosine A1 receptors inhibit glutamatergic transmission in the CCR pathway, whereas adenosine A2a receptors most likely facilitate release of an unknown inhibitory neurotransmitter, which, in turn, inhibits the CCR. We hypothesized that adenosine A2a receptors inhibit the CCR via facilitation of GABA release in the NTS. In urethane-chloralose-anesthetized rats (n = 51), we compared regional sympathetic responses evoked by stimulation of the CCR with right atrial injections of the 5-HT3 receptor agonist phenylbiguanide (1-8 μg/kg) before and after selective stimulation of NTS adenosine A2a receptors [microinjections into the NTS of CGS-21680 (20 pmol/50 nl)] preceded by blockade of GABAA or GABAB receptors in the NTS [bicuculline (10 pmol/100 nl) or SCH-50911 (1 nmol/100 nl)]. Blockade of GABAA receptors virtually abolished adenosine A2a receptor-mediated inhibition of the CCR. GABAB receptors had much weaker but significant effects. These effects were similar for the different sympathetic outputs. We conclude that stimulation of NTS adenosine A2a receptors inhibits CCR-evoked hemodynamic and regional sympathetic reflex responses via a GABA-ergic mechanism.

  3. NTS adenosine A2a receptors inhibit the cardiopulmonary chemoreflex control of regional sympathetic outputs via a GABAergic mechanism.

    PubMed

    Minic, Zeljka; O'Leary, Donal S; Scislo, Tadeusz J

    2015-07-01

    Adenosine is a powerful central neuromodulator acting via opposing A1 (inhibitor) and A2a (activator) receptors. However, in the nucleus of the solitary tract (NTS), both adenosine receptor subtypes attenuate cardiopulmonary chemoreflex (CCR) sympathoinhibition of renal, adrenal, and lumbar sympathetic nerve activity and attenuate reflex decreases in arterial pressure and heart rate. Adenosine A1 receptors inhibit glutamatergic transmission in the CCR pathway, whereas adenosine A2a receptors most likely facilitate release of an unknown inhibitory neurotransmitter, which, in turn, inhibits the CCR. We hypothesized that adenosine A2a receptors inhibit the CCR via facilitation of GABA release in the NTS. In urethane-chloralose-anesthetized rats (n = 51), we compared regional sympathetic responses evoked by stimulation of the CCR with right atrial injections of the 5-HT3 receptor agonist phenylbiguanide (1-8 μg/kg) before and after selective stimulation of NTS adenosine A2a receptors [microinjections into the NTS of CGS-21680 (20 pmol/50 nl)] preceded by blockade of GABAA or GABAB receptors in the NTS [bicuculline (10 pmol/100 nl) or SCH-50911 (1 nmol/100 nl)]. Blockade of GABAA receptors virtually abolished adenosine A2a receptor-mediated inhibition of the CCR. GABAB receptors had much weaker but significant effects. These effects were similar for the different sympathetic outputs. We conclude that stimulation of NTS adenosine A2a receptors inhibits CCR-evoked hemodynamic and regional sympathetic reflex responses via a GABA-ergic mechanism. PMID:25910812

  4. ( sup 3 H)-DOB(4-bromo-2,5-dimethoxyphenylisopropylamine) and ( sup 3 H) ketanserin label two affinity states of the cloned human 5-hydroxytryptamine2 receptor

    SciTech Connect

    Branchek, T.; Adham, N.; Macchi, M.; Kao, H.T.; Hartig, P.R. )

    1990-11-01

    The binding properties of the 5-hydroxytryptamine2 (5-HT2) receptor have been the subject of much interest and debate in recent years. The hallucinogenic amphetamine derivative 4-bromo-2,5-dimethoxyphenylisopropylamine (DOB) has been shown to bind to a small number of binding sites with properties very similar to (3H)ketanserin-labeled 5-HT2 receptors, but with much higher agonist affinities. Some researchers have interpreted this as evidence for the existence of a new subtype of 5-HT2 receptor (termed 5-HT2A), whereas others have interpreted these data as indicative of agonist high affinity and agonist low affinity states for the 5-HT2 receptor. In this investigation, a cDNA clone encoding the serotonin 5-HT2 receptor was transiently transfected into monkey kidney Cos-7 cells and stably transfected into mouse fibroblast L-M(TK-) cells. In both systems, expression of this single serotonin receptor cDNA led to the appearance of both (3H)DOB and (3H)ketanserin binding sites with properties that matched their binding characteristics in mammalian brain homogenates. Addition of guanosine 5'-(beta, gamma-imido) triphosphate (Gpp(NH)p) to this system caused a rightward shift and steepening of agonist competition curves for (3H) ketanserin binding, converting a two-site binding curve to a single low affinity binding state. Gpp(NH)p addition also caused a 50% decrease in the number of high affinity (3H)DOB binding sites, with no change in the dissociation constant of the remaining high affinity states. These data on a single human 5-HT2 receptor cDNA expressed in two different transfection host cells indicate that (3H)DOB and (3H)ketanserin binding reside on the same gene product, apparently interacting with agonist and antagonist conformations of a single human 5-HT2 receptor protein.

  5. HSV-Mediated Transgene Expression of Chimeric Constructs to Study Behavioral Function of GPCR Heteromers in Mice.

    PubMed

    Holloway, Terrell; Moreno, Jose L; González-Maeso, Javier

    2016-01-01

    The heteromeric receptor complex between 5-HT2A and mGlu2 has been implicated in some of the behavioral phenotypes in mouse models of psychosis(1,2). Consequently, investigation of structural details of the interaction between 5-HT2A and mGlu2 affecting schizophrenia-related behaviors represents a powerful translational tool. As previously shown, the head-twitch response (HTR) in mice is elicited by hallucinogenic drugs and this behavioral response is absent in 5-HT2A knockout (KO) mice(3,4). Additionally, by conditionally expressing the 5-HT2A receptor only in cortex, it was demonstrated that 5-HT2A receptor-dependent signaling pathways on cortical pyramidal neurons are sufficient to elicit head-twitch behavior in response to hallucinogenic drugs(3). Finally, it has been shown that the head-twitch behavioral response induced by the hallucinogens DOI and lysergic acid diethylamide (LSD) is significantly decreased in mGlu2-KO mice(5). These findings suggest that mGlu2 is at least in part necessary for the 5-HT2A receptor-dependent psychosis-like behavioral effects induced by LSD-like drugs. However, this does not provide evidence as to whether the 5-HT2A-mGlu2 receptor complex is necessary for this behavioral phenotype. To address this question, herpes simplex virus (HSV) constructs to express either mGlu2 or mGlu2ΔTM4N (mGlu2/mGlu3 chimeric construct that does not form the 5-HT2A-mGlu2 receptor complex) in the frontal cortex of mGlu2-KO mice were used to examine whether this GPCR heteromeric complex is needed for the behavioral effects induced by LSD-like drugs(6). PMID:27501227

  6. Receptor mechanisms of antipsychotic drug action in bipolar disorder - focus on asenapine.

    PubMed

    Reynolds, Gavin P

    2011-12-01

    The atypical antipsychotic drugs are considered a first-line treatment for mania in bipolar disorder with many having a proven superiority to the classical mood stabilisers. This review addresses the pharmacological mechanisms underlying this therapeutic efficacy, as well as those mechanisms considered responsible for the adverse effects of antipsychotic drugs, with a particular focus on the recently introduced asenapine. The high efficacy in bipolar mania of haloperidol, a relatively selective dopamine D2-like receptor antagonist, indicates that the one common receptor mechanism underlying antipsychotic effects on mania is antagonism at the D2 receptor. Serotonin receptors are implicated in antidepressant response, and relief of depressed mood in mixed states is likely to involve drug effects at one, or more likely several interacting, serotonin receptors. Asenapine shows a unique breadth of action at these sites, with potential effects at clinical doses at 5HT1A, 1B, 2A, 2C, 6 and 7 receptors. Antagonism at alpha2 adrenoceptors may also be involved. Adverse effects include those classically associated with dopamine D2 receptor blockade, the extrapyramidal side effects (EPS), and which are relatively diminished in the atypical (in comparison with the conventional) antipsychotics. A variety of protective mechanisms against EPS associated with different drugs include low D2 affinity, D2 partial agonism, high 5-HT2A and 2C antagonism. Similar effects at the D2 and 5-HT2C receptors may underlie the low propensity for hyperprolactinaemia of the atypicals, although the strong prolactin-elevating effect of risperidone reflects its relatively high blood/brain concentration ratio, a consequence of it being a substrate for the p-glycoprotein pump. Weight gain is a further concern of antipsychotic treatment of bipolar disorder which is particularly severe with olanzapine. Histamine H1, alpha1 adrenergic and particularly 5-HT2C receptors are implicated in this effect

  7. Brain Serotonin Receptors and Transporters: Initiation vs. Termination of Escalated Aggression

    PubMed Central

    Takahashi, Aki; Quadros, Isabel M.; de Almeida, Rosa M. M.; Miczek, Klaus A.

    2013-01-01

    Rationale Recent findings have shown a complexly regulated 5-HT system as it is linked to different kinds of aggression. Objective We focus on (1) phasic and tonic changes of 5-HT and (2) state and trait of aggression, and emphasize the different receptor subtypes, their role in specific brain regions, feed-back regulation and modulation by other amines, acids and peptides. Results New pharmacological tools differentiate the first three 5-HT receptor families and their modulation by GABA, glutamate and CRF. Activation of 5-HT1A, 5-HT1B and 5-HT2A/2C receptors in mesocorticolimbic areas, reduce species-typical and other aggressive behaviors. In contrast, agonists at 5-HT1A and 5-HT1B receptors in the medial prefrontal cortex or septal area can increase aggressive behavior under specific conditions. Activation of serotonin transporters reduce mainly pathological aggression. Genetic analyses of aggressive individuals have identified several molecules that affect the 5-HT system directly (e.g., Tph2, 5-HT1B, 5-HT transporter, Pet1, MAOA) or indirectly (e.g., Neuropeptide Y, αCaMKII, NOS, BDNF). Dysfunction in genes for MAOA escalates pathological aggression in rodents and humans, particularly in interaction with specific experiences. Conclusions Feedback to autoreceptors of the 5-HT1 family and modulation via heteroreceptors are important in the expression of aggressive behavior. Tonic increase of the 5-HT2 family expression may cause escalated aggression, whereas the phasic increase of 5-HT2 receptors inhibits aggressive behaviors. Polymorphisms in the genes of 5-HT transporters or rate-limiting synthetic and metabolic enzymes of 5-HT modulate aggression, often requiring interaction with the rearing environment. PMID:20938650

  8. Ligand Binding and Subtype Selectivity of the Human A2A Adenosine Receptor

    PubMed Central

    Jaakola, Veli-Pekka; Lane, J. Robert; Lin, Judy Y.; Katritch, Vsevolod; IJzerman, Adriaan P.; Stevens, Raymond C.

    2010-01-01

    The crystal structure of the human A2A adenosine receptor bound to the A2A receptor-specific antagonist, ZM241385, was recently determined at 2.6-Å resolution. Surprisingly, the antagonist binds in an extended conformation, perpendicular to the plane of the membrane, and indicates a number of interactions unidentified before in ZM241385 recognition. To further understand the selectivity of ZM241385 for the human A2A adenosine receptor, we examined the effect of mutating amino acid residues within the binding cavity likely to have key interactions and that have not been previously examined. Mutation of Phe-168 to Ala abolishes both agonist and antagonist binding as well as receptor activity, whereas mutation of this residue to Trp or Tyr had only moderate effects. The Met-177 → Ala mutation impeded antagonist but not agonist binding. Finally, the Leu-249 → Ala mutant showed neither agonist nor antagonist binding affinity. From our results and previously published mutagenesis data, we conclude that conserved residues Phe-168(5.29), Glu-169(5.30), Asn-253(6.55), and Leu-249(6.51) play a central role in coordinating the bicyclic core present in both agonists and antagonists. By combining the analysis of the mutagenesis data with a comparison of the sequences of different adenosine receptor subtypes from different species, we predict that the interactions that determine subtype selectivity reside in the more divergent “upper” region of the binding cavity while the “lower” part of the binding cavity is conserved across adenosine receptor subtypes. PMID:20147292

  9. Antagonists of the human A(2A) receptor. Part 6: Further optimization of pyrimidine-4-carboxamides.

    PubMed

    Gillespie, Roger J; Bamford, Samantha J; Clay, Alex; Gaur, Suneel; Haymes, Tim; Jackson, Philip S; Jordan, Allan M; Klenke, Burkhard; Leonardi, Stefania; Liu, Jeanette; Mansell, Howard L; Ng, Sean; Saadi, Mona; Simmonite, Heather; Stratton, Gemma C; Todd, Richard S; Williamson, Douglas S; Yule, Ian A

    2009-09-15

    Antagonists of the human A(2A) receptor have been reported to have potential therapeutic benefit in the alleviation of the symptoms associated with neurodegenerative movement disorders such as Parkinson's disease. As part of our efforts to discover potent and selective antagonists of this receptor, we herein describe the detailed optimization and structure-activity relationships of a series of pyrimidine-4-carboxamides. These optimized derivatives display desirable physiochemical and pharmacokinetic profiles, which have led to promising oral activity in clinically relevant models of Parkinson's disease.

  10. Effects of serotonin on expression of the LDL receptor family member LR11 and 7-ketocholesterol-induced apoptosis in human vascular smooth muscle cells

    SciTech Connect

    Nagayama, Daiji; Ishihara, Noriko; Bujo, Hideaki; Shirai, Kohji; Tatsuno, Ichiro

    2014-04-18

    Highlights: • The dedifferentiation of VSMCs in arterial intima is involved in atherosclerosis. • 5-HT showed proliferative effect on VSMCs which was abolished by sarpogrelate. • 5-HT enhanced expression of LR11 mRNA in VSMCs which was abolished by sarpogrelate. • 5-HT suppressed 7KCHO-induced apoptosis of VSMCs via caspase-3/7-dependent pathway. • The mechanisms explain the 5-HT-induced remodeling of arterial structure. - Abstract: Serotonin (5-HT) is a known mitogen for vascular smooth muscle cells (VSMCs). The dedifferentiation and proliferation/apoptosis of VSMCs in the arterial intima represent one of the atherosclerotic changes. LR11, a member of low-density lipoprotein receptor family, may contribute to the proliferation of VSMCs in neointimal hyperplasia. We conducted an in vitro study to investigate whether 5-HT is involved in LR11 expression in human VSMCs and apoptosis of VSMCs induced by 7-ketocholesterol (7KCHO), an oxysterol that destabilizes plaque. 5-HT enhanced the proliferation of VSMCs, and this effect was abolished by sarpogrelate, a selective 5-HT2A receptor antagonist. Sarpogrelate also inhibited the 5-HT-enhanced LR11 mRNA expression in VSMCs. Furthermore, 5-HT suppressed the 7KCHO-induced apoptosis of VSMCs via caspase-3/7-dependent pathway. These findings provide new insights on the changes in the differentiation stage of VSMCs mediated by 5-HT.

  11. Test-retest paradigm of the forced swimming test in female mice is not valid for predicting antidepressant-like activity: participation of acetylcholine and sigma-1 receptors.

    PubMed

    Su, Jing; Hato-Yamada, Noriko; Araki, Hiroaki; Yoshimura, Hiroyuki

    2013-01-01

    The forced swimming test (FST) in mice is widely used to predict the antidepressant activity of a drug, but information describing the immobility of female mice is limited. We investigated whether a prior swimming experience affects the immobility duration in a second FST in female mice and whether the test-retest paradigm is a valid screening tool for antidepressants. Female ICR mice were exposed to the FST using two experimental paradigms: a single FST and a double FST in which mice had experienced FST once 24 h prior to the second trail. The initial FST experience reliably prolonged immobility duration in the second FST. The antidepressants imipramine and paroxetine significantly reduced immobility duration in the single FST, but not in the double FST. Scopolamine and the sigma-1 (σ1) antagonist NE-100 administered before the second trial significantly prevented the prolongation of immobility. Neither a 5-HT1A nor a 5-HT2A receptor agonist affected immobility duration. We suggest that the test-retest paradigm in female mice is not adequate for predicting antidepressant-like activity of a drug; the prolongation of immobility in the double FST is modulated through acetylcholine and σ1 receptors.

  12. Serotonin receptor 2A (HTR2A) gene polymorphism predicts treatment response to venlafaxine XR in generalized anxiety disorder.

    PubMed

    Lohoff, F W; Aquino, T D; Narasimhan, S; Multani, P K; Etemad, B; Rickels, K

    2013-02-01

    Generalized anxiety disorder (GAD) is a chronic psychiatric disorder with significant morbidity and mortality. Antidepressant drugs are the preferred choice for treatment; however, treatment response is often variable. Several studies in major depression have implicated a role of the serotonin receptor gene (HTR2A) in treatment response to antidepressants. We tested the hypothesis that the genetic polymorphism rs7997012 in the HTR2A gene predicts treatment outcome in GAD patients treated with venlafaxine XR. Treatment response was assessed in 156 patients that participated in a 6-month open-label clinical trial of venlafaxine XR for GAD. Primary analysis included Hamilton Anxiety Scale (HAM-A) reduction at 6 months. Secondary outcome measure was the Clinical Global Impression of Improvement (CGI-I) score at 6 months. Genotype and allele frequencies were compared between groups using χ(2) contingency analysis. The frequency of the G-allele differed significantly between responders (70%) and nonresponders (56%) at 6 months (P=0.05) using the HAM-A scale as outcome measure. Similarly, using the CGI-I as outcome, the G-allele was significantly associated with improvement (P=0.01). Assuming a dominant effect of the G-allele, improvement differed significantly between groups (P=0.001, odds ratio=4.72). Similar trends were observed for remission although not statistically significant. We show for the first time a pharmacogenetic effect of the HTR2A rs7997012 variant in anxiety disorders, suggesting that pharmacogenetic effects cross diagnostic categories. Our data document that individuals with the HTR2A rs7997012 single nucleotide polymorphism G-allele have better treatment outcome over time. Future studies with larger sample sizes are necessary to further characterize this effect in treatment response to antidepressants in GAD. PMID:22006095

  13. Therapeutic Opportunities for Caffeine and A2A Receptor Antagonists in Retinal Diseases.

    PubMed

    Boia, Raquel; Ambrósio, António Francisco; Santiago, Ana Raquel

    2016-01-01

    Caffeine, the major component of coffee, is the most consumed psychostimulant in the world. Caffeine is an adenosine analog and acts as a nonselective adenosine receptor antagonist. The majority of the effects of caffeine are mainly mediated by the blockade of adenosine receptors, and the proved neuroprotective effects of caffeine in brain disorders have been mimicked by the blockade of adenosine A2A receptor (A2AR). A growing body of evidence demonstrates that microglia-mediated neuroinflammation plays a key role in the pathophysiology of brain and retinal diseases. Moreover, the control of microglia reactivity by blocking A2AR has been proposed to be the mechanism underlying the observed protective effects of caffeine. Hence, it is conceivable that caffeine and A2AR antagonists offer therapeutic value for the treatment of retinal diseases, mainly those involving microglia-mediated neuroinflammation.

  14. Therapeutic Opportunities for Caffeine and A2A Receptor Antagonists in Retinal Diseases.

    PubMed

    Boia, Raquel; Ambrósio, António Francisco; Santiago, Ana Raquel

    2016-01-01

    Caffeine, the major component of coffee, is the most consumed psychostimulant in the world. Caffeine is an adenosine analog and acts as a nonselective adenosine receptor antagonist. The majority of the effects of caffeine are mainly mediated by the blockade of adenosine receptors, and the proved neuroprotective effects of caffeine in brain disorders have been mimicked by the blockade of adenosine A2A receptor (A2AR). A growing body of evidence demonstrates that microglia-mediated neuroinflammation plays a key role in the pathophysiology of brain and retinal diseases. Moreover, the control of microglia reactivity by blocking A2AR has been proposed to be the mechanism underlying the observed protective effects of caffeine. Hence, it is conceivable that caffeine and A2AR antagonists offer therapeutic value for the treatment of retinal diseases, mainly those involving microglia-mediated neuroinflammation. PMID:26959995

  15. The CC genotype in the T102C HTR2A polymorphism predicts relapse in individuals after alcohol treatment

    PubMed Central

    Jakubczyk, Andrzej; Klimkiewicz, Anna; Kopera, Maciej; Krasowska, Aleksandra; Wrzosek, Małgorzata; Matsumoto, Halina; Burmeister, Margit; Brower, Kirk J.; Wojnar, Marcin

    2013-01-01

    The serotonin system is hypothesized to contribute to predisposition and course of alcohol dependence. However, the potential association between the T102C polymorphism (rs6313) in the type 2A serotonin receptor (HTR2A) gene and treatment outcomes in alcohol dependence has not been investigated. The aim of the study was to assess the contribution of this genetic polymorphism as a predictor of relapse in relation to other previously identified predictors. A sample of 254 alcohol dependent subjects, were recruited in alcohol treatment centers in Warsaw, Poland and prospectively assessed at baseline and follow-up after 12 months. At baseline, information about demographics, psychopathological symptoms and alcohol problems was obtained. The stop-signal task was performed and blood samples for genetic analysis of HTR2A T102C (rs6313) were collected. Relapse was defined as any drinking during the follow-up period. The statistical analysis showed that the CC genotype was significantly associated with increased relapse. Other significant factors were baseline depressive symptoms, number of drinking days during the 3 months prior to the baseline assessment, severity of alcohol-related problems, and a lifetime history of impulsive suicide attempts. Logistic regression analysis with and without the genetic factor revealed that adding the genetic factor increased the R square value by about 4%, with the CC genotype in the T102C polymorphism being the strongest predictor of relapse (OR=2.32). The significant influence on relapse of the CC genotype, which is associated with fewer 5-HT2A receptors in the central nervous system, suggests the possibility that this genetic polymorphism could influence response to serotonergic medications. PMID:23321485

  16. The CC genotype in the T102C HTR2A polymorphism predicts relapse in individuals after alcohol treatment.

    PubMed

    Jakubczyk, Andrzej; Klimkiewicz, Anna; Kopera, Maciej; Krasowska, Aleksandra; Wrzosek, Małgorzata; Matsumoto, Halina; Burmeister, Margit; Brower, Kirk J; Wojnar, Marcin

    2013-04-01

    The serotonin system is hypothesized to contribute to predisposition and course of alcohol dependence. However, the potential association between the T102C polymorphism (rs6313) in the type 2A serotonin receptor (HTR2A) gene and treatment outcomes in alcohol dependence has not been investigated. The aim of the study was to assess the contribution of this genetic polymorphism as a predictor of relapse in relation to other previously identified predictors. A sample of 254 alcohol dependent subjects, were recruited in alcohol treatment centers in Warsaw, Poland and prospectively assessed at baseline and follow-up after 12 months. At baseline, information about demographics, psychopathological symptoms and alcohol problems was obtained. The stop-signal task was performed and blood samples for genetic analysis of HTR2A T102C (rs6313) were collected. Relapse was defined as any drinking during the follow-up period. The statistical analysis showed that the CC genotype was significantly associated with increased relapse. Other significant factors were baseline depressive symptoms, number of drinking days during the 3 months prior to the baseline assessment, severity of alcohol-related problems, and a lifetime history of impulsive suicide attempts. Logistic regression analysis with and without the genetic factor revealed that adding the genetic factor increased the R square value by about 4%, with the CC genotype in the T102C polymorphism being the strongest predictor of relapse (OR = 2.32). The significant influence on relapse of the CC genotype, which is associated with fewer 5-HT2A receptors in the central nervous system, suggests the possibility that this genetic polymorphism could influence response to serotonergic medications.

  17. NMDA receptor surface mobility depends on NR2A-2B subunits

    PubMed Central

    Groc, Laurent; Heine, Martin; Cousins, Sarah L.; Stephenson, F. Anne; Lounis, Brahim; Cognet, Laurent; Choquet, Daniel

    2006-01-01

    The NR2 subunit composition of NMDA receptors (NMDARs) varies during development, and this change is important in NMDAR-dependent signaling. In particular, synaptic NMDAR switch from containing mostly NR2B subunit to a mixture of NR2B and NR2A subunits. The pathways by which neurons differentially traffic NR2A- and NR2B-containing NMDARs are poorly understood. Using single-particle and -molecule approaches and specific antibodies directed against NR2A and NR2B extracellular epitopes, we investigated the surface mobility of native NR2A and NR2B subunits at the surface of cultured neurons. The surface mobility of NMDARs depends on the NR2 subunit subtype, with NR2A-containing NMDARs being more stable than NR2B-containing ones, and NR2A subunit overexpression stabilizes surface NR2B-containing NMDARs. The developmental change in the synaptic surface content of NR2A and NR2B subunits was correlated with a developmental change in the time spent by the subunits within synapses. This suggests that the switch in synaptic NMDAR subtypes depends on the regulation of the receptor surface trafficking. PMID:17124177

  18. Communication over the Network of Binary Switches Regulates the Activation of A2A Adenosine Receptor

    PubMed Central

    Lee, Yoonji; Choi, Sun; Hyeon, Changbong

    2015-01-01

    Dynamics and functions of G-protein coupled receptors (GPCRs) are accurately regulated by the type of ligands that bind to the orthosteric or allosteric binding sites. To glean the structural and dynamical origin of ligand-dependent modulation of GPCR activity, we performed total ~ 5 μsec molecular dynamics simulations of A2A adenosine receptor (A2AAR) in its apo, antagonist-bound, and agonist-bound forms in an explicit water and membrane environment, and examined the corresponding dynamics and correlation between the 10 key structural motifs that serve as the allosteric hotspots in intramolecular signaling network. We dubbed these 10 structural motifs “binary switches” as they display molecular interactions that switch between two distinct states. By projecting the receptor dynamics on these binary switches that yield 210 microstates, we show that (i) the receptors in apo, antagonist-bound, and agonist-bound states explore vastly different conformational space; (ii) among the three receptor states the apo state explores the broadest range of microstates; (iii) in the presence of the agonist, the active conformation is maintained through coherent couplings among the binary switches; and (iv) to be most specific, our analysis shows that W246, located deep inside the binding cleft, can serve as both an agonist sensor and actuator of ensuing intramolecular signaling for the receptor activation. Finally, our analysis of multiple trajectories generated by inserting an agonist to the apo state underscores that the transition of the receptor from inactive to active form requires the disruption of ionic-lock in the DRY motif. PMID:25664580

  19. The NMDA receptor NR2A subunit regulates proliferation of MKN45 human gastric cancer cells

    SciTech Connect

    Watanabe, Kanako; Kanno, Takeshi; Oshima, Tadayuki; Miwa, Hiroto; Tashiro, Chikara; Nishizaki, Tomoyuki

    2008-03-07

    The present study investigated proliferation of MKN28 and MKN45 human gastric cancer cells regulated by the N-methyl-D-aspartate (NMDA) receptor subunit. The NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (AP5) inhibited proliferation of MKN45 cells, but not MKN28 cells. Of the NMDA subunits such as NR1, NR2 (2A, 2B, 2C, and 2D), and NR3 (3A and 3B), all the NMDA subunit mRNAs except for the NR2B subunit mRNA were expressed in both MKN28 and MKN45 cells. MKN45 cells were characterized by higher expression of the NR2A subunit mRNA and lower expression of the NR1 subunit mRNA, but MKN28 otherwise by higher expression of the NR1 subunit mRNA and lower expression of the NR2A subunit mRNA. MKN45 cell proliferation was also inhibited by silencing the NR2A subunit-targeted gene. For MKN45 cells, AP5 or knocking-down the NR2A subunit increased the proportion of cells in the G{sub 1} phase of cell cycling and decreased the proportion in the S/G{sub 2} phase. The results of the present study, thus, suggest that blockage of NMDA receptors including the NR2A subunit suppresses MKN45 cell proliferation due to cell cycle arrest at the G{sub 1} phase; in other words, the NR2A subunit promotes MKN45 cell proliferation by accelerating cell cycling.

  20. Signal Transduction Mechanism for Serotonin 5-HT2B Receptor-Mediated DNA Synthesis and Proliferation in Primary Cultures of Adult Rat Hepatocytes.

    PubMed

    Naito, Kota; Tanaka, Chizuru; Mitsuhashi, Manami; Moteki, Hajime; Kimura, Mitsutoshi; Natsume, Hideshi; Ogihara, Masahiko

    2016-01-01

    The involvement of serotonin (5-hydroxytryptamine; 5-HT) and the 5-HT2 receptor subtypes in the induction of DNA synthesis and proliferation was investigated in primary cultures of adult rat hepatocytes to elucidate the intracellular signal transduction mechanisms. Hepatocyte parenchymal cells maintained in a serum-free, defined medium, synthesized DNA and proliferated in the presence of 5-HT or a selective 5-HT2B receptor agonist, BW723C86, but not in the presence of 5-HT2A, or 5-HT2C receptor agonists (TCB-2 and CP809101, respectively), in a time- and dose-dependent manner. A selective 5-HT2B receptor antagonist, LY272015 (10(-7) M), and a specific phospholipase C (PLC) inhibitor, U-73122 (10(-6) M), as well as specific inhibitors of growth-related signal transducers-including AG1478, LY294002, PD98059, and rapamycin-completely inhibited 5-HT (10(-6) M)- or BW723C86 (10(-6) M)-induced hepatocyte DNA synthesis and proliferation. Both 5-HT and BW723C86 were shown to significantly stimulate the phosphorylation of epidermal growth factor (EGF)/transforming growth factor (TGF)-α receptor tyrosine kinase (p175 kDa) and extracellular signal-regulated kinase (ERK) 2 on Western blot analysis. These results suggest that the proliferative mechanism of activating 5-HT is mediated mainly through 5-HT2B receptor-stimulated Gq/PLC and EGF/TGF-α-receptor/phosphatidylinositol 3-kinase (PI3K)/ERK2/mammalian target of rapamycin (mTOR) signaling pathways in primary cultured hepatocytes.

  1. An Update on Adenosine A2A-Dopamine D2 receptor interactions. Implications for the Function of G Protein-Coupled Receptors

    PubMed Central

    Ferré, S.; Quiroz, C.; Woods, A. S.; Cunha, R.; Popoli, P.; Ciruela, F.; Lluis, C.; Franco, R.; Azdad, K.; Schiffmann, S. N.

    2008-01-01

    Adenosine A2A-dopamine D2 receptor interactions play a very important role in striatal function. A2A-D2 receptor interactions provide an example of the capabilities of information processing by just two different G protein-coupled receptors. Thus, there is evidence for the coexistence of two reciprocal antagonistic interactions between A2A and D2 receptors in the same neurons, the GABAergic enkephalinergic nens. An antagonistic A2A-D2 intramembrane receptor interaction, which depends on A2A-D2 receptor heteromerization and Gq/11-PLC signaling, modulates neuronal excitability and neurotransmitter release. On the other hand, an antagonistic A2A-D2 receptor interaction at the adenylyl-cyclase level, which depends on Gs/olf- and Gi/o- type V adenylyl-cyclase signaling, modulates protein phosphorylation and gene expression. Finally, under conditions of upregulation of an activator of G protein signaling (AGS3), such as during chronic treatment with addictive drugs, a synergistic A2A-D2 receptor interaction can also be demonstrated. AGS3 facilitates a synergistic interaction between Gs/olf- and Gi/o- coupled receptors on the activation of types II/IV adenylyl cyclase, leading to a paradoxical increase in protein phosphorylation and gene expression upon co-activation of A2A and D2 receptors. The analysis of A2-D2 receptor interactions will have implications for the pathophysiology and treatment of basal ganglia disorders and drug addiction. PMID:18537670

  2. An efficient route to xanthine based A(2A) adenosine receptor antagonists and functional derivatives.

    PubMed

    Labeaume, Paul; Dong, Ma; Sitkovsky, Michail; Jones, Elizabeth V; Thomas, Rhiannon; Sadler, Sara; Kallmerten, Amy E; Jones, Graham B

    2010-09-21

    A one-pot route to 8-substituted xanthines has been developed from 5,6-diaminouracils and carboxaldehydes. Yields are good and the process applicable to a range of substrates including a family of A(2A) adenosine receptor antagonists. A new route to the KW-6002 family of antagonists is presented including a pro-drug variant, and application to related image contrast agents developed.

  3. Key modulatory role of presynaptic adenosine A2A receptors in cortical neurotransmission to the striatal direct pathway.

    PubMed

    Quiroz, César; Luján, Rafael; Uchigashima, Motokazu; Simoes, Ana Patrícia; Lerner, Talia N; Borycz, Janusz; Kachroo, Anil; Canas, Paula M; Orru, Marco; Schwarzschild, Michael A; Rosin, Diane L; Kreitzer, Anatol C; Cunha, Rodrigo A; Watanabe, Masahiko; Ferré, Sergi

    2009-11-18

    Basal ganglia processing results from a balanced activation of direct and indirect striatal efferent pathways, which are controlled by dopamine D1 and D2 receptors, respectively. Adenosine A2A receptors are considered novel antiparkinsonian targets, based on their selective postsynaptic localization in the indirect pathway, where they modulate D2 receptor function. The present study provides evidence for the existence of an additional, functionally significant, segregation of A2A receptors at the presynaptic level. Using integrated anatomical, electrophysiological, and biochemical approaches, we demonstrate that presynaptic A2A receptors are preferentially localized in cortical glutamatergic terminals that contact striatal neurons of the direct pathway, where they exert a selective modulation of corticostriatal neurotransmission. Presynaptic striatal A2A receptors could provide a new target for the treatment of neuropsychiatric disorders.

  4. 3-iodothyronamine differentially modulates α-2A-adrenergic receptor-mediated signaling.

    PubMed

    Dinter, Juliane; Mühlhaus, Jessica; Jacobi, Simon Friedrich; Wienchol, Carolin Leonie; Cöster, Maxi; Meister, Jaroslawna; Hoefig, Carolin Stephanie; Müller, Anne; Köhrle, Josef; Grüters, Annette; Krude, Heiko; Mittag, Jens; Schöneberg, Torsten; Kleinau, Gunnar; Biebermann, Heike

    2015-06-01

    Most in vivo effects of 3-iodothyronamine (3-T1AM) have been thus far thought to be mediated by binding at the trace amine-associated receptor 1 (TAAR1). Inconsistently, the 3-T1AM-induced hypothermic effect still persists in Taar1 knockout mice, which suggests additional receptor targets. In support of this general assumption, it has previously been reported that 3-T1AM also binds to the α-2A-adrenergic receptor (ADRA2A), which modulates insulin secretion. However, the mechanism of this effect remains unclear. We tested two different scenarios that may explain the effect: the sole action of 3-T1AM at ADRA2A and a combined action of 3-T1AM at ADRA2A and TAAR1, which is also expressed in pancreatic islets. We first investigated a potential general signaling modification using the label-free EPIC technology and then specified changes in signaling by cAMP inhibition and MAPKs (ERK1/2) determination. We found that 3-T1AM induced Gi/o activation at ADRA2A and reduced the norepinephrine (NorEpi)-induced MAPK activation. Interestingly, in ADRA2A/TAAR1 hetero-oligomers, application of NorEpi resulted in uncoupling of the Gi/o signaling pathway, but it did not affect MAPK activation. However, 3-T1AM application in mice over a period of 6 days at a daily dose of 5 mg/kg had no significant effects on glucose homeostasis. In summary, we report an agonistic effect of 3-T1AM on the ADRA2A-mediated Gi/o pathway but an antagonistic effect on MAPK induced by NorEpi. Moreover, in ADRA2A/TAAR1 hetero-oligomers, the capacity of NorEpi to stimulate Gi/o signaling is reduced by co-stimulation with 3-T1AM. The present study therefore points to a complex spectrum of signaling modification mediated by 3-T1AM at different G protein-coupled receptors.

  5. Early and transient alteration of adenosine A2A receptor signaling in a mouse model of Huntington disease.

    PubMed

    Tarditi, Alessia; Camurri, Alessandra; Varani, Katia; Borea, Pier Andrea; Woodman, Ben; Bates, Gillian; Cattaneo, Elena; Abbracchio, Maria P

    2006-07-01

    Huntington Disease (HD) is characterized by choreic involuntary movements and striatal vulnerability. A2A receptors expressed on GABAergic striatal neurons have been suggested to play a pathogenetic role. Previous data demonstrated the presence of an aberrant alteration of A2A receptor-dependent adenylyl cyclase in an in vitro model of the disease (striatal cells expressing mutant huntingtin) and in peripheral circulating cells of HD patients. Here, we investigated whether this dysfunction is present in the R6/2 HD transgenic mouse model, by analyzing striatal A2A receptor-binding and adenylyl cyclase activity at different developmental stages in comparison with age-matched wild type animals. A transient increase in A2A receptor density (Bmax) and A2A receptor-dependent cAMP production at early presymptomatic ages (7-14 postnatal days) was found. Both alterations normalized to control values starting from postnatal day 21. In contrast, A2A receptor mRNA, as detected by real time PCR, dramatically decreased starting from PND21 until late symptomatic stages (12 weeks of age). The discrepancy between A2A receptor expression and density suggests compensatory mechanisms. These data, reproducing ex vivo the previous observations in vitro, support the hypothesis that an alteration of A2A receptor signaling is present in HD and might represent an interesting target for neuroprotective therapies.

  6. Striatal pre- and postsynaptic profile of adenosine A(2A) receptor antagonists.

    PubMed

    Orru, Marco; Bakešová, Jana; Brugarolas, Marc; Quiroz, César; Beaumont, Vahri; Goldberg, Steven R; Lluís, Carme; Cortés, Antoni; Franco, Rafael; Casadó, Vicent; Canela, Enric I; Ferré, Sergi

    2011-01-11

    Striatal adenosine A(2A) receptors (A(2A)Rs) are highly expressed in medium spiny neurons (MSNs) of the indirect efferent pathway, where they heteromerize with dopamine D(2) receptors (D(2)Rs). A(2A)Rs are also localized presynaptically in cortico-striatal glutamatergic terminals contacting MSNs of the direct efferent pathway, where they heteromerize with adenosine A(1) receptors (A(1)Rs). It has been hypothesized that postsynaptic A(2A)R antagonists should be useful in Parkinson's disease, while presynaptic A(2A)R antagonists could be beneficial in dyskinetic disorders, such as Huntington's disease, obsessive-compulsive disorders and drug addiction. The aim or this work was to determine whether selective A(2A)R antagonists may be subdivided according to a preferential pre- versus postsynaptic mechanism of action. The potency at blocking the motor output and striatal glutamate release induced by cortical electrical stimulation and the potency at inducing locomotor activation were used as in vivo measures of pre- and postsynaptic activities, respectively. SCH-442416 and KW-6002 showed a significant preferential pre- and postsynaptic profile, respectively, while the other tested compounds (MSX-2, SCH-420814, ZM-241385 and SCH-58261) showed no clear preference. Radioligand-binding experiments were performed in cells expressing A(2A)R-D(2)R and A(1)R-A(2A)R heteromers to determine possible differences in the affinity of these compounds for different A(2A)R heteromers. Heteromerization played a key role in the presynaptic profile of SCH-442416, since it bound with much less affinity to A(2A)R when co-expressed with D(2)R than with A(1)R. KW-6002 showed the best relative affinity for A(2A)R co-expressed with D(2)R than co-expressed with A(1)R, which can at least partially explain the postsynaptic profile of this compound. Also, the in vitro pharmacological profile of MSX-2, SCH-420814, ZM-241385 and SCH-58261 was is in accordance with their mixed pre- and postsynaptic

  7. Control of sensory neuron excitability by serotonin involves 5HT2C receptors and Ca(2+)-activated chloride channels.

    PubMed

    Salzer, Isabella; Gantumur, Enkhbileg; Yousuf, Arsalan; Boehm, Stefan

    2016-11-01

    Serotonin (5HT) is a constituent of the so-called "inflammatory soup" that sensitizes nociceptors during inflammation. Nevertheless, receptors and signaling mechanisms that mediate an excitation of dorsal root ganglion (DRG) neurons by 5HT remained controversial. Therefore, capsaicin-sensitive nociceptive neurons dissociated from rat DRGs were used to investigate effects of 5HT on membrane excitability and currents through ligand- as well as voltage-gated ion channels. In 58% of the neurons tested, 5HT increased action potential firing, an effect that was abolished by the 5HT2 receptor antagonist ritanserin, but not by the 5HT3 antagonist tropisetron. Unlike other algogenic mediators, such as PGE2 and bradykinin, 5HT did not affect currents through TTX-resistant Na(+) channels or Kv7 K(+) channels. In all neurons investigated, 5HT potentiated capsaicin-evoked currents through TRPV1 channels, an effect that was attenuated by antagonists at 5HT2A (4 F 4 PP), 5HT2B (SB 204741), as well as 5HT2C (RS 102221) receptors. 5HT triggered slowly arising inward Cl(-) currents in 53% of the neurons. This effect was antagonized by the 5HT2C receptor blocker only, and the current was prevented by an inhibitor of Ca(2+)-activated chloride channels (CaCC). The 5HT-induced increase in action potential firing was also abolished by this CaCC blocker and by the TRPV1 inhibitor capsazepine. Amongst the subtype selective 5HT2 antagonists, only RS 102221 (5HT2C-selectively) counteracted the rise in action potential firing elicited by 5HT. These results show that 5HT excites DRG neurons mainly via 5HT2C receptors which concomitantly mediate a sensitization of TRPV1 channels and an opening of CaCCs.

  8. Polymorphism in the Serotonin Receptor 2a (HTR2A) Gene as Possible Predisposal Factor for Aggressive Traits

    PubMed Central

    Banlaki, Zsofia; Elek, Zsuzsanna; Nanasi, Tibor; Szekely, Anna; Nemoda, Zsofia; Sasvari-Szekely, Maria; Ronai, Zsolt

    2015-01-01

    Aggressive manifestations and their consequences are a major issue of mankind, highlighting the need for understanding the contributory factors. Still, aggression-related genetic analyses have so far mainly been conducted on small population subsets such as individuals suffering from a certain psychiatric disorder or a narrow-range age cohort, but no data on the general population is yet available. In the present study, our aim was to identify polymorphisms in genes affecting neurobiological processes that might explain some of the inter-individual variation between aggression levels in the non-clinical Caucasian adult population. 55 single nucleotide polymorphisms (SNP) were simultaneously determined in 887 subjects who also filled out the self-report Buss-Perry Aggression Questionnaire (BPAQ). Single marker association analyses between genotypes and aggression scores indicated a significant role of rs7322347 located in the HTR2A gene encoding serotonin receptor 2a following Bonferroni correction for multiple testing (p = 0.0007) both for males and females. Taking the four BPAQ subscales individually, scores for Hostility, Anger and Physical Aggression showed significant association with rs7322347 T allele in themselves, while no association was found with Verbal Aggression. Of the subscales, relationship with rs7322347 was strongest in the case of Hostility, where statistical significance virtually equaled that observed with the whole BPAQ. In conclusion, this is the first study to our knowledge analyzing SNPs in a wide variety of genes in terms of aggression in a large sample-size non-clinical adult population, also describing a novel candidate polymorphism as predisposal to aggressive traits. PMID:25658328

  9. Photoperiod regulates genes encoding melanocortin 3 and serotonin receptors and secretogranins in the dorsomedial posterior arcuate of the Siberian hamster.

    PubMed

    Nilaweera, K N; Archer, Z A; Campbell, G; Mayer, C-D; Balik, A; Ross, A W; Mercer, J G; Ebling, F J P; Morgan, P J; Barrett, P

    2009-02-01

    The mechanism(s) involved in the regulation of the seasonal-appropriate body weight of the Siberian hamster are currently unknown. We have identified photoperiodically regulated genes including VGF in a sub-region of the arcuate nucleus termed the dorsomedial posterior arcuate (dmpARC). Gene expression changes in this nucleus so far account for a significant number of those reported as photoperiodically regulated and are therefore likely to contribute to seasonal physiological responses of the hamsters. The present study aimed to identify additional genes expressed in the dmpARC regulated by photoperiod that could be involved in regulating the activity of this nucleus with respect to seasonal physiology of the Siberian hamster. Using laser capture microdissection coupled with a microarray analysis and a candidate gene approach, we have identified several photoperiodically regulated genes in the dmpARC that are known to have roles in secretory and intracellular signalling pathways. These include secretogranin (sg) III and SgVI (secretory pathway), melanocortin 3 receptor (MC3-R) and serotonin (5-HT) receptors 2A and 7 (signalling pathway), all of which increase in expression under a short photoperiod. The spatial relationship between receptor signalling and potential secretory pathways was investigated by dual in situ hybridisation, which revealed that 5-HT2A and 5-HT7 receptors are expressed in neurones expressing VGF mRNA and that a sub-population (approximately 40%) of these neurones express MC3-R. These gene expression changes in dmpARC neurones may reflect the functional requirement of these neurones for seasonal physiological responses of the hamster.

  10. Ultraslow Water-Mediated Transmembrane Interactions Regulate the Activation of A2A Adenosine Receptor.

    PubMed

    Lee, Yoonji; Kim, Songmi; Choi, Sun; Hyeon, Changbong

    2016-09-20

    Water molecules inside a G-protein coupled receptor (GPCR) have recently been spotlighted in a series of crystal structures. To decipher the dynamics and functional roles of internal water molecules in GPCR activity, we studied the A2A adenosine receptor using microsecond molecular-dynamics simulations. Our study finds that the amount of water flux across the transmembrane (TM) domain varies depending on the receptor state, and that the water molecules of the TM channel in the active state flow three times more slowly than those in the inactive state. Depending on the location in solvent-protein interface as well as the receptor state, the average residence time of water in each residue varies from ∼O(10(2)) ps to ∼O(10(2)) ns. Especially, water molecules, exhibiting ultraslow relaxation (∼O(10(2)) ns) in the active state, are found around the microswitch residues that are considered activity hotspots for GPCR function. A continuous allosteric network spanning the TM domain, arising from water-mediated contacts, is unique in the active state, underscoring the importance of slow water molecules in the activation of GPCRs. PMID:27653477

  11. Activation of NTS A2a adenosine receptors differentially resets baroreflex control of renal vs. adrenal sympathetic nerve activity.

    PubMed

    Ichinose, Tomoko K; O'Leary, Donal S; Scislo, Tadeusz J

    2009-04-01

    The role of nucleus of solitary tract (NTS) A(2a) adenosine receptors in baroreflex mechanisms is controversial. Stimulation of these receptors releases glutamate within the NTS and elicits baroreflex-like decreases in mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA), whereas inhibition of these receptors attenuates HR baroreflex responses. In contrast, stimulation of NTS A(2a) adenosine receptors increases preganglionic adrenal sympathetic nerve activity (pre-ASNA), and the depressor and sympathoinhibitory responses are not markedly affected by sinoaortic denervation and blockade of NTS glutamatergic transmission. To elucidate the role of NTS A(2a) adenosine receptors in baroreflex function, we compared full baroreflex stimulus-response curves for HR, RSNA, and pre-ASNA (intravenous nitroprusside/phenylephrine) before and after bilateral NTS microinjections of selective adenosine A(2a) receptor agonist (CGS-21680; 2.0, 20 pmol/50 nl), selective A(2a) receptor antagonist (ZM-241385; 40 pmol/100 nl), and nonselective A(1) + A(2a) receptor antagonist (8-SPT; 1 nmol/100 nl) in urethane/alpha-chloralose anesthetized rats. Activation of A(2a) receptors decreased the range, upper plateau, and gain of baroreflex-response curves for RSNA, whereas these parameters all increased for pre-ASNA, consistent with direct effects of the agonist on regional sympathetic activity. However, no resetting of baroreflex-response curves along the MAP axis occurred despite the marked decreases in baseline MAP. The antagonists had no marked effects on baseline variables or baroreflex-response functions. We conclude that the activation of NTS A(2a) adenosine receptors differentially alters baroreflex control of HR, RSNA, and pre-ASNA mostly via non-baroreflex mechanism(s), and these receptors have virtually no tonic action on baroreflex control of these sympathetic outputs.

  12. Adenosine A2A receptors modulate glutamate uptake in cultured astrocytes and gliosomes.

    PubMed

    Matos, Marco; Augusto, Elisabete; Santos-Rodrigues, Alexandre Dos; Schwarzschild, Michael A; Chen, Jiang-Fan; Cunha, Rodrigo A; Agostinho, Paula

    2012-05-01

    Glutamate is the primary excitatory neurotransmitter in the central nervous system, where its toxic build-up leads to synaptic dysfunction and excitotoxic cell death that underlies many neurodegenerative diseases. Therefore, efforts have been made to understand the regulation of glutamate transporters, which are responsible for the clearance of extracellular glutamate. We now report that adenosine A(2A) receptors (A(2A) R) control the uptake of D-aspartate in primary cultured astrocytes as well as in an ex vivo preparation enriched in glial plasmalemmal vesicles (gliosomes) from adult rats, whereas A(1) R and A(3) R were devoid of effects. Thus, the acute exposure to the A(2A) R agonist, CGS 21680, inhibited glutamate uptake, an effect prevented by the A(2A) R antagonist, SCH 58261, and abbrogated in cultured astrocytes from A(2A) R knockout mice. Furthermore, the prolonged activation of A(2A) R lead to a cAMP/protein kinase A-dependent reduction of GLT-I and GLAST mRNA and protein levels, which leads to a sustained decrease of glutamate uptake. This dual mechanism of inhibition of glutamate transporters by astrocytic A(2A) R provides a novel candidate mechanism to understand the ability of A(2) (A) R to control synaptic plasticity and neurodegeneration, two conditions tightly associated with the control of extracellular glutamate levels by glutamate transporters.

  13. Modulation of antigen-induced responses by serotonin and prostaglandin E2 via EP1 and EP4 receptors in the peripheral rat lung.

    PubMed

    Larsson-Callerfelt, Anna-Karin; Dahlén, Sven-Erik; Kühl, Anna-Rebekka; Lex, Dennis; Uhlig, Stefan; Martin, Christian

    2013-01-15

    The cyclooxygenase (COX) pathway and prostanoids may critically contribute to the early allergic airway response. In the rat lung, serotonin (5-HT) is a major mediator of antigen-induced contractions. The aim of this study was therefore to examine the relative role of the COX pathway and serotonin for antigen-induced contractions in the rat lung. Airway responses were studied in rat precision-cut lung slices (PCLS). Lung slices were stimulated with ovalbumin or serotonin after pretreatment with COX inhibitors or specific TP or EP receptor antagonists. Changes in airway size (contractions/relaxations) were measured by a digital video camera. The supernatants were analysed for changes in prostaglandin and serotonin release. Airway contractions to ovalbumin were attenuated by the unselective COX inhibitor indomethacin, the selective COX-1 inhibitor FR-122047 and COX-2 inhibitor celecoxib. The EP(1) receptor antagonist ONO-8713 reduced the contractions, whereas the EP(4) receptor antagonist L-161,982 significantly increased the contractile response to ovalbumin. The 5-HT(2A) receptor antagonist ketanserin completely inhibited the ovalbumin-induced contractions. The different COX inhibitors decreased the production of prostaglandins but did not affect the synthesis of serotonin. The serotonin-induced bronchoconstriction was attenuated by celecoxib and ONO-8713, but not by methacholine. Taken together, our data indicate that PGE(2) is the main prostanoid involved in the early allergic airway response in the rat lung. PGE(2) appears to act both as a primary mediator of antigen-induced airway contraction via the EP(4) receptor and as a downstream modulator of serotonin-induced bronchoconstriction via the EP(1) receptor.

  14. The hypolipidemic drug metabolites nafenopin-CoA and ciprofibroyl-CoA are competitive P2Y1 receptor antagonists.

    PubMed

    Coddou, Claudio; Loyola, Gloria; Boyer, José Luis; Bronfman, Miguel; Huidobro-Toro, J Pablo

    2003-02-11

    Coenzyme A (CoA-SH), endogenous and drug-derived CoA-derivatives were tested as putative antagonists of P2Y receptors expressed in Xenopus laevis oocytes, a method used to determine calcium-activated chloride current, an indicator of the activation of these receptors. CoA-SH antagonized reversibly and in a concentration-dependent manner the ATP-gated currents evoked by the human P2Y(1) but not the P2Y(2) receptor. Palmitoyl-CoA was four-fold more potent than CoA-SH as an antagonist while palmitoyl-carnitine was inactive, highlighting the role of the CoA-SH moiety in the antagonism. The CoA derivatives of nafenopin and ciprofibrate, two clinically relevant hypolipidemic drugs, increased 13 and three-fold the potency of CoA-SH, respectively. The K(B)s of nafenopin-CoA and ciprofibroyl-CoA were 58 and 148 nM, respectively; the slopes of the Schild plots were unitary. Neither 100 microM nafenopin nor ciprofibrate alone altered the P2Y(1) receptor activity. Neither CoA-SH nor ciprofibroyl-CoA antagonized the rat P2X(2) or the P2X(4) nucleotide receptors nor interacted with the 5-HT(2A/C) receptors. The bulky drug CoA-SH derivatives identify a hydrophobic pocket, which may serve as a potential target for novel selective P2Y(1) antagonists.

  15. Allosteric interactions between agonists and antagonists within the adenosine A2A receptor-dopamine D2 receptor heterotetramer

    PubMed Central

    Bonaventura, Jordi; Navarro, Gemma; Casadó-Anguera, Verònica; Azdad, Karima; Rea, William; Moreno, Estefanía; Brugarolas, Marc; Mallol, Josefa; Canela, Enric I.; Lluís, Carme; Cortés, Antoni; Volkow, Nora D.; Schiffmann, Serge N.; Ferré, Sergi; Casadó, Vicent

    2015-01-01

    Adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromers are key modulators of striatal neuronal function. It has been suggested that the psychostimulant effects of caffeine depend on its ability to block an allosteric modulation within the A2AR-D2R heteromer, by which adenosine decreases the affinity and intrinsic efficacy of dopamine at the D2R. We describe novel unsuspected allosteric mechanisms within the heteromer by which not only A2AR agonists, but also A2AR antagonists, decrease the affinity and intrinsic efficacy of D2R agonists and the affinity of D2R antagonists. Strikingly, these allosteric modulations disappear on agonist and antagonist coadministration. This can be explained by a model that considers A2AR-D2R heteromers as heterotetramers, constituted by A2AR and D2R homodimers, as demonstrated by experiments with bioluminescence resonance energy transfer and bimolecular fluorescence and bioluminescence complementation. As predicted by the model, high concentrations of A2AR antagonists behaved as A2AR agonists and decreased D2R function in the brain. PMID:26100888

  16. Tricyclic antidepressants exhibit variable pharmacological profiles at the α(2A) adrenergic receptor.

    PubMed

    Cottingham, Christopher; Percival, Stefanie; Birky, Tana; Wang, Qin

    2014-08-29

    Antidepressant mechanisms of action remain shrouded in mystery, greatly hindering our ability to develop therapeutics which can fully treat patients suffering from depressive disorders. In an attempt to shed new light on this topic, we have undertaken a series of studies investigating actions of tricyclic antidepressant drugs (TCAs) at the α2A adrenergic receptor (AR), a centrally important receptor, dysregulation of which has been linked to depression. Our previous work established a particular TCA, desipramine, as an arrestin-biased α2AAR ligand driving receptor endocytosis and downregulation but not canonical heterotrimeric G protein-mediated signaling. The present work is aimed at broadening our understanding of how members of the TCA drug class act at the α2AAR, as we have selected the closely related but subtly different TCAs imipramine and amitriptyline for evaluation. Our data demonstrate that these drugs do also function as direct arrestin-biased α2AAR ligands. However, these data reveal differences in receptor affinity and in the extent/nature of arrestin recruitment to and endocytosis of α2AARs. Specifically, amitriptyline exhibits an approximately 14-fold stronger interaction with the receptor, is a weaker driver of arrestin recruitment, and preferentially recruits a different arrestin subtype. Extent of endocytosis is similar for all TCAs studied so far, and occurs in an arrestin-dependent manner, although imipramine uniquely retains a slight ability to drive α2AAR endocytosis in arrestin-null cells. These findings signify an important expansion of our mechanistic understanding of antidepressant pharmacology, and provide useful insights for future medicinal chemistry efforts.

  17. C5L2: a controversial receptor of complement anaphylatoxin, C5a.

    PubMed

    Li, Rui; Coulthard, Liam G; Wu, M C L; Taylor, Stephen M; Woodruff, Trent M

    2013-03-01

    C5a is the paramount proinflammatory mediator of the complement cascade, and has been previously thought to act only through a single, G-protein-coupled, C5a receptor (C5aR; also termed CD88). In 2000, a second C5a receptor, C5L2 (previously known as GPR77), was discovered; yet, despite 12 yr of intensive research, its biological, or pathophysiological, function is both enigmatic and controversial. Unlike C5aR, this receptor does not couple to G proteins, and early studies promoted the hypothesis that C5L2 functions as a decoy receptor. However, recent data have provided other evidence for more complicated and conflicting interactions between C5L2 and other inflammatory mediators. C5L2 has been recently demonstrated to physically interact with both C5aR and β-arrestin to negatively regulate C5aR signaling toward an anti-inflammatory manner, and to reduce pathology, in several disease models in vivo. In direct contrast, other groups have demonstrated that C5L2 stimulation caused release of HMGB1 both in vitro and in vivo, and enhanced pathology in sepsis models, suggesting a clear proinflammatory signaling role. These astoundingly contradictory data challenge our precepts and complicate the foundational bases for the possible targeting of C5L2 as a therapeutic option in inflammatory disease. C5L2 may be the great masquerader in complement biology; its function dependent on the cell type, species, and disease context. Because of these unusual and unforeseen complexities, we present the current state of knowledge on C5L2 structure, expression and, most controversially, its putative functions.-Li, R., Coulthard, L.G., Wu, M. C. L., Taylor, S. M., Woodruff, T. M. C5L2: a controversial receptor of complement anaphylatoxin, C5a. PMID:23239822

  18. Cariprazine (RGH-188), a dopamine D(3) receptor-preferring, D(3)/D(2) dopamine receptor antagonist-partial agonist antipsychotic candidate: in vitro and neurochemical profile.

    PubMed

    Kiss, Béla; Horváth, Attila; Némethy, Zsolt; Schmidt, Eva; Laszlovszky, István; Bugovics, Gyula; Fazekas, Károly; Hornok, Katalin; Orosz, Szabolcs; Gyertyán, István; Agai-Csongor, Eva; Domány, György; Tihanyi, Károly; Adham, Nika; Szombathelyi, Zsolt

    2010-04-01

    Cariprazine {RGH-188; trans-N-[4-[2-[4-(2,3-dichlorophenyl)piperazin-1-yl]ethyl]cyclohexyl]-N',N'-dimethylurea hydrochloride}, a novel candidate antipsychotic, demonstrated approximately 10-fold higher affinity for human D(3) versus human D(2L) and human D(2S) receptors (pKi 10.07, 9.16, and 9.31, respectively). It displayed high affinity at human serotonin (5-HT) type 2B receptors (pK(i) 9.24) with pure antagonism. Cariprazine had lower affinity at human and rat hippocampal 5-HT(1A) receptors (pK(i) 8.59 and 8.34, respectively) and demonstrated low intrinsic efficacy. Cariprazine displayed low affinity at human 5-HT(2A) receptors (pK(i) 7.73). Moderate or low affinity for histamine H(1) and 5-HT(2C) receptors (pK(i) 7.63 and 6.87, respectively) suggest cariprazine's reduced propensity for adverse events related to these receptors. Cariprazine demonstrated different functional profiles at dopamine receptors depending on the assay system. It displayed D(2) and D(3) antagonism in [(35)S]GTPgammaS binding assays, but stimulated inositol phosphate (IP) production (pEC(50) 8.50, E(max) 30%) and antagonized (+/-)-quinpirole-induced IP accumulation (pK(b) 9.22) in murine cells expressing human D(2L) receptors. It had partial agonist activity (pEC(50) 8.58, E(max) 71%) by inhibiting cAMP accumulation in Chinese hamster ovary cells expressing human D(3) receptors and potently antagonized R(+)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphtalene HBr (7-OH-DPAT)-induced suppression of cAMP formation (pK(b) 9.57). In these functional assays, cariprazine showed similar (D(2)) or higher (D(3)) antagonist-partial agonist affinity and greater (3- to 10-fold) D(3) versus D(2) selectivity compared with aripiprazole. In in vivo turnover and biosynthesis experiments, cariprazine demonstrated D(2)-related partial agonist and antagonist properties, depending on actual dopaminergic tone. The antagonist-partial agonist properties of cariprazine at D(3) and D(2) receptors, with very high

  19. Adenosine A2A Receptor Antagonists and Parkinson’s Disease

    PubMed Central

    2011-01-01

    This Review summarizes and updates the work on adenosine A2A receptor antagonists for Parkinson’s disease from 2006 to the present. There have been numerous publications, patent applications, and press releases within this time frame that highlight new medicinal chemistry approaches to this attractive and promising target to treat Parkinson’s disease. The Review is broken down by scaffold type and will discuss the efforts to optimize particular scaffolds for activity, pharmacokinetics, and other drug discovery parameters. The majority of approaches focus on preparing selective A2A antagonists, but a few approaches to dual A2A/A1 antagonists will also be highlighted. The in vivo profiles of compounds will be highlighted and discussed to compare activities across different chemical series. A clinical report and update will be given on compounds that have entered clinical trials. PMID:22860156

  20. Physical origins of remarkable thermostabilization by an octuple mutation for the adenosine A2a receptor

    NASA Astrophysics Data System (ADS)

    Kajiwara, Yuta; Ogino, Takahiro; Yasuda, Satoshi; Takamuku, Yuuki; Murata, Takeshi; Kinoshita, Masahiro

    2016-07-01

    It was experimentally showed that the thermal stability of a membrane protein, the adenosine A2a receptor, was remarkably enhanced by an octuple mutation. Here we theoretically prove that the energy decrease arising from the formation of protein intramolecular hydrogen bonds and the solvent-entropy gain upon protein folding are made substantially larger by the mutation, leading to the remarkable enhancement. The solvent is formed by hydrocarbon groups constituting nonpolar chains of the lipid bilayer within a membrane. The mutation modifies geometric characteristics of the structure so that the solvent crowding can be reduced to a larger extent when the protein folds.

  1. Mass spectrometry-based ligand binding assays on adenosine A1 and A2A receptors.

    PubMed

    Massink, A; Holzheimer, M; Hölscher, A; Louvel, J; Guo, D; Spijksma, G; Hankemeier, T; IJzerman, A P

    2015-12-01

    Conventional methods to measure ligand-receptor binding parameters typically require radiolabeled ligands as probes. Despite the robustness of radioligand binding assays, they carry inherent disadvantages in terms of safety precautions, expensive synthesis, special lab requirements, and waste disposal. Mass spectrometry (MS) is a method that can selectively detect ligands without the need of a label. The sensitivity of MS equipment increases progressively, and currently, it is possible to detect low ligand quantities that are usually found in ligand binding assays. We developed a label-free MS ligand binding (MS binding) assay on the adenosine A(1) and A(2A) receptors (A(1)AR and A(2A)AR), which are well-characterized members of the class A G protein-coupled receptor (GPCR) family. Radioligand binding assays for both receptors are well established, and ample data is available to compare and evaluate the performance of an MS binding assay. 1,3-Dipropyl-8-cyclopentyl-xanthine (DPCPX) and 4-(2-((7-amino-2-(furan-2-yl)-[1,2,4]triazolo[1,5-a]-[1,3,5]triazin-5-yl)amino)ethyl)phenol (ZM-241,385) are high-affinity ligands selective for the A(1)AR and A(2A)AR, respectively. To proof the feasibility of MS binding on the A(1)AR and A(2A)AR, we first developed an MS detection method for unlabeled DPCPX and ZM-241,385. To serve as internal standards, both compounds were also deuterium-labeled. Subsequently, we investigated whether the two unlabeled compounds could substitute for their radiolabeled counterparts as marker ligands in binding experiments, including saturation, displacement, dissociation, and competition association assays. Furthermore, we investigated the accuracy of these assays if the use of internal standards was excluded. The results demonstrate the feasibility of the MS binding assay, even in the absence of a deuterium-labeled internal standard, and provide great promise for the further development of label-free assays based on MS for other GPCRs. PMID

  2. CRTH2, a prostaglandin D2 receptor, mediates depression-related behavior in mice.

    PubMed

    Onaka, Yusuke; Shintani, Norihito; Nakazawa, Takanobu; Haba, Ryota; Ago, Yukio; Wang, Hyper; Kanoh, Takuya; Hayata-Takano, Atsuko; Hirai, Hiroyuki; Nagata, Kin-Ya; Nakamura, Masataka; Hashimoto, Ryota; Matsuda, Toshio; Waschek, James A; Kasai, Atsushi; Nagayasu, Kazuki; Baba, Akemichi; Hashimoto, Hitoshi

    2015-05-01

    Depression is a complex neuropsychiatric disorder with an unclear molecular etiology. Inflammatory cytokines and molecular intermediates (including prostaglandins) are suggested to be involved in depression; however, the roles of prostaglandins and their respective receptors are largely unknown in depression. Using genetic and pharmacological approaches, we show here that chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2), a second receptor for prostaglandin D2 (PGD2), mediates depression-related behavior in mice. CRTH2-deficient (CRTH2(-/-)) mice showed antidepressant-like activity in a chronic corticosterone treatment-induced depression. Consistent with this observation, the pharmacological inhibition of CRTH2 via the clinically available drug ramatroban also rescued abnormal social interaction and depression-related behavior in well-established models, including chronic corticosterone-, lipopolysaccharide-, and tumor-induced pathologically relevant depression models. Importantly, chronic stress via corticosterone treatment increased mRNA levels in PGD2-producing enzymes, such as cyclooxygenase-2 and lipocalin-type PGD2 synthase, in the brain. Furthermore, the activity of the hippocampal noradrenergic system but not the dopaminergic or serotonergic systems was increased in CRTH2(-/-) mice. Together with the observation that untreated CRTH2(-/-) mice showed antidepressant-like activity in the forced swim test, these results provide evidence that central CRTH2-mediated signaling is critically involved in depression-related behavior. PMID:25698598

  3. Expression, binding, and signaling properties of CRF2(a) receptors endogenously expressed in human retinoblastoma Y79 cells: passage-dependent regulation of functional receptors.

    PubMed

    Gutknecht, Eric; Hauger, Richard L; Van der Linden, Ilse; Vauquelin, Georges; Dautzenberg, Frank M

    2008-02-01

    Endogenous expression of the corticotropin-releasing factor type 2a receptor [CRF2(a)] but not CRF2(b) and CRF2(c) was observed in higher passage cultures of human Y79 retinoblastoma cells. Functional studies further demonstrated an increase in CRF2(a) mRNA and protein levels with higher passage numbers (> 20 passages). Although the CRF1 receptor was expressed at higher levels than the CRF2(a) receptor, both receptors were easily distinguishable from one another by selective receptor ligands. CRF(1)-preferring or non-selective agonists such as CRF, urocortin 1 (UCN1), and sauvagine stimulated cAMP production in Y79 to maximal responses of approximately 100 pmoles/10(5) cells, whereas the exclusive CRF2 receptor-selective agonists UCN2 and 3 stimulated cAMP production to maximal responses of approximately 25-30 pmoles/10(5) cells. UCN2 and 3-mediated cAMP stimulation was potently blocked by the approximately 300-fold selective CRF2 antagonist antisauvagine (IC50 = 6.5 +/- 1.6 nmol/L), whereas the CRF(1)-selective antagonist NBI27914 only blocked cAMP responses at concentrations > 10 microL. When the CRF(1)-preferring agonist ovine CRF was used to activate cAMP signaling, NBI27914 (IC50 = 38.4 +/- 3.6 nmol/L) was a more potent inhibitor than antisauvagine (IC50 = 2.04 +/- 0.2 microL). Finally, UCN2 and 3 treatment potently and rapidly desensitized the CRF2 receptor responses in Y79 cells. These data demonstrate that Y79 cells express functional CRF1 and CRF2a receptors and that the CRF2(a) receptor protein is up-regulated during prolonged culture. PMID:17976162

  4. Blockade of adenosine A2A receptors prevents protein phosphorylation in the striatum induced by cortical stimulation.

    PubMed

    Quiroz, César; Gomes, Catarina; Pak, Arlene C; Ribeiro, Joaquim A; Goldberg, Steven R; Hope, Bruce T; Ferré, Sergi

    2006-10-18

    Previous studies have shown that cortical stimulation selectively activates extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and immediate early gene expression in striatal GABAergic enkephalinergic neurons. In the present study, we demonstrate that blockade of adenosine A2A receptors with caffeine or a selective A2A receptor antagonist counteracts the striatal activation of cAMP-protein kinase A cascade (phosphorylation of the Ser845 residue of the glutamate receptor 1 subunit of the AMPA receptor) and mitogen-activated protein kinase (ERK1/2 phosphorylation) induced by the in vivo stimulation of corticostriatal afferents. The results indicate that A2A receptors strongly modulate the efficacy of glutamatergic synapses on striatal enkephalinergic neurons.

  5. Postsynaptic Adenosine A2A Receptors Modulate Intrinsic Excitability of Pyramidal Cells in the Rat Basolateral Amygdala

    PubMed Central

    Rau, Andrew R.; Ariwodola, Olusegun J.

    2015-01-01

    Background: The basolateral amygdala plays a critical role in the etiology of anxiety disorders and addiction. Pyramidal neurons, the primary output cells of this region, display increased firing following exposure to stressors, and it is thought that this increase in excitability contributes to stress responsivity and the expression of anxiety-like behaviors. However, much remains unknown about the underlying mechanisms that regulate the intrinsic excitability of basolateral amygdala pyramidal neurons. Methods: Ex vivo gramicidin perforated patch recordings were conducted in current clamp mode where hyper- and depolarizing current steps were applied to basolateral amygdala pyramidal neurons to assess the effects of adenosine A2A receptor modulation on intrinsic excitability. Results: Activation of adenosine A2A receptors with the selective A2A receptor agonist CGS-21680 significantly increased the firing rate of basolateral amygdala pyramidal neurons in rat amygdala brain slices, likely via inhibition of the slow afterhyperpolarization potential. Both of these A2A receptor-mediated effects were blocked by preapplication of a selective A2A receptor antagonist (ZM-241385) or by intra-pipette infusion of a protein kinase A inhibitor, suggesting a postsynaptic locus of A2A receptors on basolateral amygdala pyramidal neurons. Interestingly, bath application of the A2A receptor antagonist alone significantly attenuated basolateral amygdala pyramidal cell firing, consistent with a role for tonic adenosine in the regulation of the intrinsic excitability of these neurons. Conclusions: Collectively, these data suggest that adenosine, via activation of A2A receptors, may directly facilitate basolateral amygdala pyramidal cell output, providing a possible balance for the recently described inhibitory effects of adenosine A1 receptor activation on glutamatergic excitation of basolateral amygdala pyramidal cells. PMID:25716780

  6. Reduced striatal adenosine A2A receptor levels define a molecular subgroup in schizophrenia.

    PubMed

    Villar-Menéndez, Izaskun; Díaz-Sánchez, Sara; Blanch, Marta; Albasanz, José Luis; Pereira-Veiga, Thais; Monje, Alfonso; Planchat, Luis Maria; Ferrer, Isidre; Martín, Mairena; Barrachina, Marta

    2014-04-01

    Schizophrenia (SZ) is a mental disorder of unknown origin. Some scientific evidence seems to indicate that SZ is not a single disease entity, since there are patient groups with clear symptomatic, course and biomarker differences. SZ is characterized by a hyperdopaminergic state related to high dopamine D2 receptor activity. It has also been proposed that there is a hypoadenosynergic state. Adenosine is a nucleoside widely distributed in the organism with neuromodulative and neuroprotective activity in the central nervous system. In the brain, the most abundant adenosine receptors are A1R and A2AR. In the present report, we characterize the presence of both receptors in human postmortem putamens of patients suffering SZ with real time TaqMan PCR, western blotting and radioligand binding assay. We show that A1R levels remain unchanged with respect to age-matched controls, whereas nearly fifty percent of patients have reduced A2AR, at the transcriptional and translational levels. Moreover, we describe how DNA methylation plays a role in the pathological A2AR levels with the bisulfite-sequencing technique. In fact, an increase in 5-methylcytosine percentage in the 5' UTR region of ADORA2A was found in those SZ patients with reduced A2AR levels. Interestingly, there was a relationship between the A2A/β-actin ratio and motor disturbances as assessed with some items of the PANSS, AIMS and SAS scales. Therefore, there may be a subgroup of SZ patients with reduced striatal A2AR levels accompanied by an altered motor phenotype. PMID:24433848

  7. Effects of α-2A adrenergic receptor agonist on time and risk preference in primates

    PubMed Central

    Kim, Soyoun; Bobeica, Irina; Gamo, Nao J.; Arnsten, Amy F. T.; Lee, Daeyeol

    2012-01-01

    Rationale Subjective values of actions are influenced by the uncertainty and immediacy of expected rewards. Multiple brain areas, including the prefrontal cortex and basal ganglia, are implicated in selecting actions according to their subjective values. Alterations in these neural circuits therefore might contribute to symptoms of impulsive choice behaviors in disorders such as substance abuse and attention-deficit hyperactivity disorder (ADHD). In particular, the α-2A noradrenergic system is known to have a key influence on prefrontal cortical circuits, and medications that stimulate this receptor are currently in use for the treatment of ADHD. Objective We tested whether the preference of rhesus monkeys for delayed and uncertain reward is influenced by the α-2A adrenergic receptor agonist, guanfacine. Methods In each trial, the animal chose between a small, certain and immediate reward and another larger, more delayed reward. In half of the trials, the larger reward was certain, whereas in the remaining trials, the larger reward was uncertain. Results Guanfacine increased the tendency for the animal to choose the larger and more delayed reward only when it was certain. By applying an econometric model to the animal’s choice behavior, we found that guanfacine selectively reduced the animal’s time preference, increasing their choice of delayed, larger rewards, without significantly affecting their risk preference. Conclusions In combination with previous findings that guanfacine improves the efficiency of working memory and other prefrontal functions, these results suggest that impulsive choice behaviors may also be ameliorated by strengthening prefrontal functions. PMID:21979441

  8. Vasopressin V1 receptors contribute to hemodynamic and sympathoinhibitory responses evoked by stimulation of adenosine A2a receptors in NTS.

    PubMed

    Scislo, Tadeusz J; O'Leary, Donal S

    2006-05-01

    Activation of adenosine A2a receptors in the nucleus of the solitary tract (NTS) decreases mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA), whereas increases in preganglionic adrenal sympathetic nerve activity (pre-ASNA) occur, a pattern similar to that observed during hypotensive hemorrhage. Central vasopressin V1 receptors may contribute to posthemorrhagic hypotension and bradycardia. Both V1 and A2a receptors are densely expressed in the NTS, and both of these receptors are involved in cardiovascular control; thus they may interact. The responses elicited by NTS A2a receptors are mediated mostly via nonglutamatergic mechanisms, possibly via release of vasopressin. Therefore, we investigated whether blockade of NTS V1 receptors alters the autonomic response patterns evoked by stimulation of NTS A2a receptors (CGS-21680, 20 pmol/50 nl) in alpha-chloralose-urethane anesthetized male Sprague-Dawley rats. In addition, we compared the regional sympathetic responses to microinjections of vasopressin (0.1-100 ng/50 nl) into the NTS. Blockade of V1 receptors reversed the normal decreases in MAP into increases (-95.6 +/- 28.3 vs. 51.4 +/- 15.7 integralDelta%), virtually abolished the decreases in HR (-258.3 +/- 54.0 vs. 18.9 +/- 57.8 integralDeltabeats/min) and RSNA (-239.3 +/- 47.4 vs. 15.9 +/- 36.1 integralDelta%), and did not affect the increases in pre-ASNA (279.7 +/- 48.3 vs. 233.1 +/- 54.1 integralDelta%) evoked by A2a receptor stimulation. The responses partially returned toward normal values approximately 90 min after the blockade. Microinjections of vasopressin into the NTS evoked dose-dependent decreases in HR and RSNA and variable MAP and pre-ASNA responses with a tendency toward increases. We conclude that the decreases in MAP, HR, and RSNA in response to NTS A2a receptor stimulation may be mediated via release of vasopressin from neural terminals in the NTS. The differential effects of NTS V1 and A2a receptors on

  9. Characterization of the NR1, NR2A, and NR2C receptor proteins.

    PubMed Central

    Köpke, A. K.; Bonk, I.; Sydow, S.; Menke, H.; Spiess, J.

    1993-01-01

    N-Methyl-D-aspartate (NMDA) receptor subunits were characterized with seven polyclonal antibodies. The antibodies were directed against NR1-A, NR2A-N1, and NR2C-N1, representing N-terminal sequences of the NR1, NR2A, and NR2C subunits, and against NR1-E, NR2A-C1, and NR2C-C1, derived from C-terminal sequences of these subunits. The anti-NR1-D antibody was raised against the putative internal loop of NR1. A size of 118 kDa was found in sodium dodecyl sulfate-polyacrylamide gel electrophoresis for NR1 (from rat brain) detected by anti-NR1-D and -NR1-E, but not anti-NR1-A. With the anti-NR1-A antibody, a 125-kDa protein was discovered that may represent a glutamate receptor not yet characterized. NR2A and NR2C were identified as proteins with sizes of 175 and 140 kDa, respectively. Enzymatic N-deglycosylation generated a 97-kDa protein from NR1, a 105-kDa protein from the 125-kDa protein, a 162-kDa protein from NR2A, and a 127-kDa protein from NR2C. In contrast to the deglycosylation product of the NR2A, the 97- and 127-kDa proteins derived from NR1 and NR2C, respectively, were found significantly smaller than the molecular masses of 103 and 141 kDa, respectively, predicted on the basis of DNA data. These products may represent truncated proteins. The tissue content of the NR1 and NR2A was high in bovine hippocampus and cortex but lower in the cerebellum. In contrast, NR2C was solely found in the cerebellum. The 125-kDa protein was highest in the cerebellum and cortex. PMID:8298456

  10. A1 and A2a receptors mediate inhibitory effects of adenosine on the motor activity of human colon.

    PubMed

    Fornai, M; Antonioli, L; Colucci, R; Ghisu, N; Buccianti, P; Marioni, A; Chiarugi, M; Tuccori, M; Blandizzi, C; Del Tacca, M

    2009-04-01

    Experimental evidence in animal models suggests that adenosine is involved in the regulation of digestive functions. This study examines the influence of adenosine on the contractile activity of human colon. Reverse transcription-polymerase chain reaction revealed A(1) and A(2a) receptor expression in colonic neuromuscular layers. Circular muscle preparations were connected to isotonic transducers to determine the effects of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; A(1) receptor antagonist), ZM 241385 (A(2a) receptor antagonist), CCPA (A(1) receptor agonist) and 2-[(p-2-carboxyethyl)-phenethylamino]-5'-N-ethyl-carboxamide-adenosine (CGS 21680; A(2a) receptor agonist) on motor responses evoked by electrical stimulation or carbachol. Electrically evoked contractions were enhanced by DPCPX and ZM 241385, and reduced by CCPA and CGS 21680. Similar effects were observed when colonic preparations were incubated with guanethidine (noradrenergic blocker), L-732,138, GR-159897 and SB-218795 (NK receptor antagonists). However, in the presence of guanethidine, NK receptor antagonists and N(omega)-propyl-L-arginine (NPA; neuronal nitric oxide synthase inhibitor), the effects of DPCPX and CCPA were still evident, while those of ZM 241385 and CGS 21680 no longer occurred. Carbachol-induced contractions were unaffected by A(2a) receptor ligands, but they were enhanced or reduced by DPCPX and CCPA, respectively. When colonic preparations were incubated with guanethidine, NK antagonists and atropine, electrically induced relaxations were partly reduced by ZM 241385 or NPA, but unaffected by DPCPX. Dipyridamole or application of exogenous adenosine reduced electrically and carbachol-evoked contractions, whereas adenosine deaminase enhanced such motor responses. In conclusion, adenosine exerts an inhibitory control on human colonic motility. A(1) receptors mediate direct modulating actions on smooth muscle, whereas A(2a) receptors operate through inhibitory nitrergic nerve pathways.

  11. Serotonin via 5-HT7 receptors activates p38 mitogen-activated protein kinase and protein kinase C epsilon resulting in interleukin-6 synthesis in human U373 MG astrocytoma cells.

    PubMed

    Lieb, Klaus; Biersack, Lisa; Waschbisch, Anne; Orlikowski, Sonja; Akundi, Ravi Shankar; Candelario-Jalil, Eduardo; Hüll, Michael; Fiebich, Bernd L

    2005-05-01

    Serotonin [5-hydroxytryptamine (5-HT)] is a widely distributed neurotransmitter which is involved in neuroimmunomodulatory processes. Previously, it has been demonstrated that 5-HT may induce interleukin (IL)-6 expression in primary rat hippocampal astrocytes. The present study was undertaken to investigate the molecular pathways underlying this induction of IL-6 synthesis. As a model system, we used the human astrocytoma cell line U373 MG, which synthesizes IL-6 upon stimulation with various inducers. 5-HT dose- and time-dependently induced IL-6 protein synthesis. We identified several 5-HT receptors to be expressed on U373 MG cells, including the 5-HT1D, 5-HT2A, 5-HT3 and 5-HT7 receptors. In this report, we show that the 5-HT-induced IL-6 release is mediated by the 5-HT7 receptor based on several agonist/antagonists that were used. 5-HT-induced IL-6 synthesis is inhibited by the partially selective 5-HT7 receptor antagonist, pimozide, and the selective antagonist SB269970. Furthermore, IL-6 synthesis was induced by the 5-HT7 receptor agonist carboxamidotryptamin. In addition, we found p38 MAPKs and protein kinase C (PKC) epsilon to be involved in 5-HT-induced IL-6 synthesis as specific inhibitors of these enzymes (SB202190 and RO-31-8425, respectively) blocked 5-HT-induced IL-6 synthesis. Furthermore, 5-HT mediated the phosphorylation of both p38 MAPK as well as the PKC epsilon isoform. The p42/44 MAPKs, however, were not involved in 5-HT-induced IL-6 synthesis. This study shows, for the first time, a central role of 5-HT7 receptor linked to p38 MAPK and PKC epsilon for the induction of cytokine synthesis in astrocytic cells. PMID:15836614

  12. Past, present and future of A2A adenosine receptor antagonists in the therapy of Parkinson’s disease

    PubMed Central

    Armentero, Marie Therese; Pinna, Annalisa; Ferré, Sergi; Lanciego, José Luis; Müller, Christa E.; Franco, Rafael

    2011-01-01

    Several selective antagonists for adenosine A2A receptors (A2AR) are currently under evaluation in clinical trials (phases I to III) to treat Parkinson’s disease, and they will probably soon reach the market. The usefulness of these antagonists has been deduced from studies demonstrating functional interactions between dopamine D2 and adenosine A2A receptors in the basal ganglia. At present it is believed that A2AR antagonists can be used in combination with the dopamine precursor L-DOPA to minimize the motor symptoms of Parkinson’s patients. However, a considerable body of data indicates that in addition to ameliorating motor symptoms, adenosine A2AR antagonists may also prevent neurodegeneration. Despite these promising indications, one further issue must be considered in order to develop fully optimized anti-parkinsonian drug therapy, namely the existence of receptor (hetero)dimers/oligomers of G protein-coupled receptors, a topic currently the focus of intense debate within the scientific community. Dopamine D2 receptors (D2Rs) expressed in the striatum are known to form heteromers with A2A adenosine receptors. Thus, the development of heteromer-specific A2A receptor antagonists represents a promising strategy for the identification of more selective and safer drugs. PMID:21810444

  13. Serotonin excites hippocampal CA1 GABAergic interneurons at the stratum radiatum-stratum lacunosum moleculare border.

    PubMed

    Wyskiel, Daniel R; Andrade, Rodrigo

    2016-09-01

    The hippocampus receives robust serotonergic innervation that is thought to control the excitability of both pyramidal cells and GABAergic interneurons. Previous work has addressed serotonergic regulation of pyramidal cells but considerable gaps remain in our understanding of how serotonin regulates different interneuron subclasses. 5-HT2A receptors (5-HT2A Rs) appear to localize predominantly, if not solely, on interneurons in the hippocampus and have been implicated in the regulation of hippocampal function including mnemonic and novelty recognition processes. Interneurons are functionally diverse. Therefore in the current work, we have used a BAC transgenic mouse line expressing EGFP under the control of the 5-HT2A R promoter to identify the interneuron subtype(s) regulated by serotonin via 5-HT2A Rs. We find that EGFP expression in this mouse identifies a group of interneurons that resides predominantly along the border of the stratum radiatum (SR) and stratum lacunosum moleculare (SLM) of the CA1 region. We then show that these cells are depolarized and excited by serotonin acting through 5-HT2A Rs and appear to belong predominantly to the perforant pathway-associated and Schaffer collateral/commissural pathway-associated subtypes. These results indicate that serotonin interneurons expressing 5-HT2A Rs are localized primarily along the SR-SLM border of the CA1 region and represent a newly identified target for serotonin regulation in the hippocampus. © 2016 Wiley Periodicals, Inc.

  14. Serotonin excites hippocampal CA1 GABAergic interneurons at the stratum radiatum-stratum lacunosum moleculare border.

    PubMed

    Wyskiel, Daniel R; Andrade, Rodrigo

    2016-09-01

    The hippocampus receives robust serotonergic innervation that is thought to control the excitability of both pyramidal cells and GABAergic interneurons. Previous work has addressed serotonergic regulation of pyramidal cells but considerable gaps remain in our understanding of how serotonin regulates different interneuron subclasses. 5-HT2A receptors (5-HT2A Rs) appear to localize predominantly, if not solely, on interneurons in the hippocampus and have been implicated in the regulation of hippocampal function including mnemonic and novelty recognition processes. Interneurons are functionally diverse. Therefore in the current work, we have used a BAC transgenic mouse line expressing EGFP under the control of the 5-HT2A R promoter to identify the interneuron subtype(s) regulated by serotonin via 5-HT2A Rs. We find that EGFP expression in this mouse identifies a group of interneurons that resides predominantly along the border of the stratum radiatum (SR) and stratum lacunosum moleculare (SLM) of the CA1 region. We then show that these cells are depolarized and excited by serotonin acting through 5-HT2A Rs and appear to belong predominantly to the perforant pathway-associated and Schaffer collateral/commissural pathway-associated subtypes. These results indicate that serotonin interneurons expressing 5-HT2A Rs are localized primarily along the SR-SLM border of the CA1 region and represent a newly identified target for serotonin regulation in the hippocampus. © 2016 Wiley Periodicals, Inc. PMID:27328460

  15. Evaluation of neuronal phosphoproteins as effectors of caffeine and mediators of striatal adenosine A2A receptor signaling

    PubMed Central

    Sahin, Bogachan; Galdi, Stacey; Hendrick, Joseph; Greene, Robert W.; Snyder, Gretchen L.; Bibb, James A.

    2007-01-01

    Adenosine A2A receptors are predominantly expressed in the dendrites of enkephalin-positive γ-aminobutyric acidergic medium spiny neurons in the striatum. Evidence indicates that these receptors modulate striatal dopaminergic neurotransmission and regulate motor control, vigilance, alertness, and arousal. Although the physiological and behavioral correlates of adenosine A2A receptor signaling have been extensively studied using a combination of pharmacological and genetic tools, relatively little is known about the signal transduction pathways that mediate the diverse biological functions attributed to this adenosine receptor subtype. Using a candidate approach based on the coupling of these receptors to adenylate cyclase-activating G proteins, a number of membranal, cytosolic, and nuclear phosphoproteins regulated by PKA were evaluated as potential mediators of adenosine A2A receptor signaling in the striatum. Specifically, the adenosine A2A receptor agonist, CGS 21680, was used to determine whether the phosphorylation state of each of the following PKA targets is responsive to adenosine A2A receptor stimulation in this tissue: Ser40 of tyrosine hydroxylase, Ser9 of synapsin, Ser897 of the NR1 subunit of the N-methyl-D-aspartate-type glutamate receptor, Ser845 of the GluR1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate receptor, Ser94 of spinophilin, Thr34 of the dopamine- and cAMP-regulated phosphoprotein, Mr32,000, Ser133 of the cAMP-response element-binding protein, Thr286 of Ca2+/calmodulin-dependent protein kinase II, and Thr202/Tyr204 and Thr183/Tyr185 of the p44 and p42 isoforms, respectively, of mitogen-activated protein kinase. Although the substrates studied differed considerably in their responsiveness to selective adenosine A2A receptor activation, the phosphorylation state of all postsynaptic PKA targets was up-regulated in a time- and dose-dependent manner by treatment with CGS 21680, whereas presynaptic PKA

  16. Evaluation of neuronal phosphoproteins as effectors of caffeine and mediators of striatal adenosine A2A receptor signaling.

    PubMed

    Sahin, Bogachan; Galdi, Stacey; Hendrick, Joseph; Greene, Robert W; Snyder, Gretchen L; Bibb, James A

    2007-01-19

    Adenosine A(2A) receptors are predominantly expressed in the dendrites of enkephalin-positive gamma-aminobutyric acidergic medium spiny neurons in the striatum. Evidence indicates that these receptors modulate striatal dopaminergic neurotransmission and regulate motor control, vigilance, alertness, and arousal. Although the physiological and behavioral correlates of adenosine A(2A) receptor signaling have been extensively studied using a combination of pharmacological and genetic tools, relatively little is known about the signal transduction pathways that mediate the diverse biological functions attributed to this adenosine receptor subtype. Using a candidate approach based on the coupling of these receptors to adenylate cyclase-activating G proteins, a number of membranal, cytosolic, and nuclear phosphoproteins regulated by PKA were evaluated as potential mediators of adenosine A(2A) receptor signaling in the striatum. Specifically, the adenosine A(2A) receptor agonist, CGS 21680, was used to determine whether the phosphorylation state of each of the following PKA targets is responsive to adenosine A(2A) receptor stimulation in this tissue: Ser40 of tyrosine hydroxylase, Ser9 of synapsin, Ser897 of the NR1 subunit of the N-methyl-d-aspartate-type glutamate receptor, Ser845 of the GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate receptor, Ser94 of spinophilin, Thr34 of the dopamine- and cAMP-regulated phosphoprotein, M(r) 32,000, Ser133 of the cAMP-response element-binding protein, Thr286 of Ca(2+)/calmodulin-dependent protein kinase II, and Thr202/Tyr204 and Thr183/Tyr185 of the p44 and p42 isoforms, respectively, of mitogen-activated protein kinase. Although the substrates studied differed considerably in their responsiveness to selective adenosine A(2A) receptor activation, the phosphorylation state of all postsynaptic PKA targets was up-regulated in a time- and dose-dependent manner by treatment with CGS 21680

  17. Pharmacological Preconditioning by Adenosine A2a Receptor Stimulation: Features of the Protected Liver Cell Phenotype

    PubMed Central

    Alchera, Elisa; Imarisio, Chiara; Mandili, Giorgia; Merlin, Simone; Chandrashekar, Bangalore R.; Novelli, Francesco; Follenzi, Antonia; Carini, Rita

    2015-01-01

    Ischemic preconditioning (IP) of the liver by a brief interruption of the blood flow protects the damage induced by a subsequent ischemia/reperfusion (I/R) preventing parenchymal and nonparenchymal liver cell damage. The discovery of IP has shown the existence of intrinsic systems of cytoprotection whose activation can stave off the progression of irreversible tissue damage. Deciphering the molecular mediators that underlie the cytoprotective effects of preconditioning can pave the way to important therapeutic possibilities. Pharmacological activation of critical mediators of IP would be expected to emulate or even to intensify its salubrious effects. In vitro and in vivo studies have demonstrated the role of the adenosine A2a receptor (A2aR) as a trigger of liver IP. This review will provide insight into the phenotypic changes that underline the resistance to death of liver cells preconditioned by pharmacological activation of A2aR and their implications to develop innovative strategies against liver IR damage. PMID:26539478

  18. Additive antidepressant-like effects of fasting with imipramine via modulation of 5-HT2 receptors in the mice.

    PubMed

    Li, Bingjin; Zhao, Jing; Lv, Jiayin; Tang, Fang; Liu, Lei; Sun, Zhihui; Wang, Liang; Siwela, Sibongile P; Wang, Yinuo; Song, Yunong; Manchishi, Stephen M; Cui, Ranji

    2014-01-01

    Recently, studies show that intermittent fasting and caloric restriction may improve symptoms of depression. However, there is little scientific evidence regarding the literature on the antidepressant-like effects of acute fasting. The present study aims to investigate the antidepressant-like effects and its influence on brain levels of the transcription factor cAMP response element-binding protein (CREB) and its phosphorylated form (p-CREB) in different time periods of fasting mice. Furthermore, the additive antidepressant-like effects of fasting with imipramine and the possible involvement of the 5-HT2 receptors were examined. In the present study 9h, but not 3h and 18h of fasting significantly reduced immobility time in the forced swimming test (FST) without alteration in locomotor activity in the open field test. 9h fasting also enhanced the ratio of p-CREB/CREB in the frontal cortex and hippocampus. Co-administration of 9h of fasting and imipramine (30mg/kg, i.p) produced the additive antidepressant-like effects in the FST and increased the ratio of p-CREB/CREB. Meanwhile, the additive effects were partially reversed by treatment with a 5-HT2A/2C receptor agonist, (±)-1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI) (5mg/kg, s.c). Furthermore, the antidepressant-like effects of 9h fasting was also blocked by DOI compared to the non-fasting control group. Serum corticosterone level, but not 5-HT and noradrenaline, was significantly increased in a time-dependent manner following different time periods of fasting. Taken together, these results suggest that acute fasting produces antidepressant-like effects via enhancement of the p-CREB/CREB ratio, and additive antidepressant-like effects of fasting with imipramine may be related to modulating 5-HT2 receptors. PMID:24036107

  19. Molecular Determinants of CGS21680 Binding to the Human Adenosine A2A Receptor

    PubMed Central

    Edwards, Patricia C.; Leslie, Andrew G. W.

    2015-01-01

    The adenosine A2A receptor (A2AR) plays a key role in transmembrane signaling mediated by the endogenous agonist adenosine. Here, we describe the crystal structure of human A2AR thermostabilized in an active-like conformation bound to the selective agonist 2-[p-(2-carboxyethyl)phenylethyl-amino]-5′-N-ethylcarboxamido adenosine (CGS21680) at a resolution of 2.6 Å. Comparison of A2AR structures bound to either CGS21680, 5′-N-ethylcarboxamido adenosine (NECA), UK432097 [6-(2,2-diphenylethylamino)-9-[(2R,3R,4S,5S)-5-(ethylcarbamoyl)-3,4-dihydroxy-tetrahydrofuran-2-yl]-N-[2-[[1-(2-pyridyl)-4-piperidyl]carbamoylamino]ethyl]purine-2-carboxamide], or adenosine shows that the adenosine moiety of the ligands binds to the receptor in an identical fashion. However, an extension in CGS21680 compared with adenosine, the (2-carboxyethyl)phenylethylamino group, binds in an extended vestibule formed from transmembrane regions 2 and 7 (TM2 and TM7) and extracellular loops 2 and 3 (EL2 and EL3). The (2-carboxyethyl)phenylethylamino group makes van der Waals contacts with side chains of amino acid residues Glu169EL2, His264EL3, Leu2677.32, and Ile2747.39, and the amine group forms a hydrogen bond with the side chain of Ser672.65. Of these residues, only Ile2747.39 is absolutely conserved across the human adenosine receptor subfamily. The major difference between the structures of A2AR bound to either adenosine or CGS21680 is that the binding pocket narrows at the extracellular surface when CGS21680 is bound, due to an inward tilt of TM2 in that region. This conformation is stabilized by hydrogen bonds formed by the side chain of Ser672.65 to CGS21680, either directly or via an ordered water molecule. Mutation of amino acid residues Ser672.65, Glu169EL2, and His264EL3, and analysis of receptor activation either in the presence or absence of ligands implicates this region in modulating the level of basal activity of A2AR. PMID:25762024

  20. Caffeine interaction with glutamate receptor gene GRIN2A: Parkinson's disease in Swedish population.

    PubMed

    Yamada-Fowler, Naomi; Fredrikson, Mats; Söderkvist, Peter

    2014-01-01

    A complex interplay between genetic and environmental factors is thought to be involved in the etiology of Parkinson's disease (PD). A recent genome-wide association and interaction study (GWAIS) identified GRIN2A, which encodes an NMDA-glutamate-receptor subunit involved in brain's excitatory neurotransmission, as a PD genetic modifier in inverse association with caffeine intake. Here in, we attempted to replicate the reported association of a single nucleotide polymorphism, GRIN2A_rs4998386, and its interaction with caffeine intake with PD in patient-control study in an ethnically homogenous population in southeastern Sweden, as consistent and independent genetic association studies are the gold standard for the validation of genome-wide association studies. All the subjects (193 sporadic PD patients and 377 controls) were genotyped, and the caffeine intake data was obtained by questionnaire. We observed an association between rs4998386 and PD with odds ratio (OR) of 0.61, 95% confidence intervals (CI) of 0.39-0.96, p = 0.03, under a model excluding rare TT allele. There was also a strong significance in joint effects of gene and caffeine on PD risk (TC heavy caffeine vs. CC light caffeine: OR = 0.38, 95%CI = [0.20-0.70], p = 0.002) and gene-caffeine interaction (OR = 0.998, 95%CI = [0.991-0.999], p<0.001). Overall, our results are in support of the findings of the GWAIS and provided additional evidence indicating PD protective effects of coffee drinking/caffeine intake as well as the interaction with glutamate receptor genotypes.

  1. Pharmacological evaluation of novel 5-HT3 receptor antagonist, QCM-13 (N-cyclohexyl-3-methoxyquinoxalin-2-carboxamide) as anti-anxiety agent in behavioral test battery

    PubMed Central

    Gupta, Deepali; Radhakrishnan, Mahesh; Thangaraj, Devadoss; Kurhe, Yeshwant

    2015-01-01

    Objective: In the last few decades, serotonin type-3 (5-HT3) receptor antagonists have been identified as potential targets for anxiety disorders. In preclinical studies, 5-HT3 antagonists have shown promising antianxiety effects. In this study, a novel 5-HT3 receptor antagonist, QCM-13(N-cyclohexyl-3-methoxyquinoxalin-2-carboxamide) was evaluated for anxiolytic-like activity in rodent behavioral test battery. Materials and Methods: Mice were given QCM-13 (2 and 4 mg/kg, intraperitoneally [i.p.]) or diazepam (2 mg/kg, i.p.) or vehicle and after 30 min, mice were subjected to four validated behavioral test batteries viz. elevated plus maze, hole board, light-dark and open field tests. Interaction study of QCM-13 with m-chlorophenyl piperazine (mCPP) (mCPP, a 5-HT2A/2C receptor agonist, 1 mg/kg, i.p.) and buspirone (BUS, a partial 5-HT1A agonist, 10 mg/kg, i.p.) were performed to assess the pharmacological mechanism of the drug. Results: QCM-13 expressed potential anxiolytic effect with significant (P < 0.05) increase in behavioral parameters measured in aforementioned preliminary models. Besides, QCM-13 was unable to reverse the anxiogenic effect of mCPP, but potentiated anxiolytic affect of BUS. Conclusion: The results suggest that QCM-13 can be a potential therapeutic candidate for the management of anxiety-like disorders and combination doses of novel 5-HT3 receptor antagonist with standard anxiolytics may improve therapeutic efficacy. PMID:25883513

  2. Adenosine A(1), A(2a), A(2b), and A(3) receptors in hematopoiesis. 1. Expression of receptor mRNA in four mouse hematopoietic precursor cells.

    PubMed

    Streitová, D; Sefc, L; Savvulidi, F; Pospísil, M; Holá, J; Hofer, M

    2010-01-01

    Four mouse bone marrow or thymus cell populations, namely granulopoietic/monocytopoietic, erythropoietic, B-lymphopoietic, and T-lymphopoietic precursor cells have been assayed by RT-PCR technique for the presence and relative amounts of adenosine A(1), A(2a), A(2b), and A(3) receptor mRNA. It has been found that (i) all four populations studied express all four adenosine receptor subtypes, (ii) the A(1), receptor is the least expressed in all populations studied, (iii) the A(3) receptor is markedly expressed in the populations of granulopoietic/monocytopoietic and erythropoietic cells, (iv) the A(2a) receptor is markedly expressed in the populations of B-lymphopoietic and T-lymphopoietic cells, and v) the A(2b) receptor does not predominate in any of the precursor cells studied. Our data offer a new possibility for the assessment of the readiness of these cells to respond, by receptor-mediated mechanisms, to adenosine or its analogs present in the tissues as a result of endogenous processes and/or following their administration.

  3. Structure-Activity Relationships of Constrained Phenylethylamine Ligands for the Serotonin 5-HT2 Receptors

    PubMed Central

    Isberg, Vignir; Paine, James; Leth-Petersen, Sebastian; Kristensen, Jesper L.; Gloriam, David E.

    2013-01-01

    Serotonergic ligands have proven effective drugs in the treatment of migraine, pain, obesity, and a wide range of psychiatric and neurological disorders. There is a clinical need for more highly 5-HT2 receptor subtype-selective ligands and the most attention has been given to the phenethylamine class. Conformationally constrained phenethylamine analogs have demonstrated that for optimal activity the free lone pair electrons of the 2-oxygen must be oriented syn and the 5-oxygen lone pairs anti relative to the ethylamine moiety. Also the ethyl linker has been constrained providing information about the bioactive conformation of the amine functionality. However, combined 1,2-constriction by cyclization has only been tested with one compound. Here, we present three new 1,2-cyclized phenylethylamines, 9–11, and describe their synthetic routes. Ligand docking in the 5-HT2B crystal structure showed that the 1,2-heterocyclized compounds can be accommodated in the binding site. Conformational analysis showed that 11 can only bind in a higher-energy conformation, which would explain its absent or low affinity. The amine and 2-oxygen interactions with D3.32 and S3.36, respectively, can form but shift the placement of the core scaffold. The constraints in 9–11 resulted in docking poses with the 4-bromine in closer vicinity to 5.46, which is polar only in the human 5-HT2A subtype, for which 9–11 have the lowest affinity. The new ligands, conformational analysis and docking expand the structure-activity relationships of constrained phenethylamines and contributes towards the development of 5-HT2 receptor subtype-selective ligands. PMID:24244317

  4. A selective positive allosteric modulator of metabotropic glutamate receptor subtype 2 blocks a hallucinogenic drug model of psychosis.

    PubMed

    Benneyworth, Michael A; Xiang, Zixiu; Smith, Randy L; Garcia, Efrain E; Conn, P Jeffrey; Sanders-Bush, Elaine

    2007-08-01

    Recent clinical studies reveal that selective agonists of group II metabotropic glutamate (mGlu) receptors have robust efficacy in treating positive and negative symptoms in patients with schizophrenia. Group II mGlu receptor agonists also modulate the in vivo activity of psychotomimetic drugs and reduce the ability of psychotomimetic hallucinogens to increase glutamatergic transmission. Because increased excitation of the medial prefrontal cortex (mPFC) has been implicated in pathophysiology of schizophrenia, the ability of group II mGlu receptor agonists to reduce hallucinogenic drug action in this region is believed to be directly related to their antipsychotic efficacy. A novel class of ligands, termed positive allosteric modulators, has recently been identified, displaying exceptional mGlu2 receptor selectivity. These compounds do not activate mGlu2 receptors directly but potentiate the ability of glutamate and other agonists to activate this receptor. We now report that the mGlu2 receptor-selective positive allosteric modulator biphenyl-indanone A (BINA) modulates excitatory neurotransmission in the mPFC and attenuates the in vivo actions of the hallucinogenic 5-HT(2A/2C) receptor agonist (-)2,5-dimethoxy-4-bromoamphetamine [(-)DOB]. BINA attenuates serotonin-induced increases in spontaneous excitatory postsynaptic currents in the mPFC, mimicking the effect of the mGlu2/3 receptor agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV). In addition, BINA reduced (-)DOB-induced head twitch behavior and Fos expression in mPFC, effects reversed by pretreatment with the mGlu2/3 receptor antagonist 2S-2-amino-2-(1S,2S-2-carboxycyclopropan-1-yl) -3 - (xanth-9-yl-)propionic acid (LY341495). These data confirm the relevance of excitatory signaling in the mPFC to the behavioral actions of hallucinogens and further support the targeting of mGlu2 receptors as a novel strategy for treating glutamatergic dysfunction in schizophrenia.

  5. [3H]-SCH 58261 labelling of functional A2A adenosine receptors in human neutrophil membranes

    PubMed Central

    Varani, Katia; Gessi, Stefania; Dionisotti, Silvio; Ongini, Ennio; Andrea Borea, Pier

    1998-01-01

    The present study describes the direct labelling of A2A adenosine receptors in human neutrophil membranes with the potent and selective antagonist radioligand, [3H]-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4 triazolo[1,5-c]pyrimidine, ([3H]-SCH 58261). In addition, both receptor affinity and potency of a number of adenosine receptor agonists and antagonists were determined in binding, adenylyl cyclase and superoxide anion production assays.Saturation experiments revealed a single class of binding sites with Kd and Bmax values of 1.34 nM and 75 fmol mg−1 protein, respectively. Adenosine receptor ligands competed for the binding of 1 nM [3H]-SCH 58261 to human neutrophil membranes, with a rank order of potency consistent with that typically found for interactions with the A2A adenosine receptors. In the adenylyl cyclase and in the superoxide anion production assays the same compounds exhibited a rank order of potency identical to that observed in binding experiments.Thermodynamic data indicated that [3H]-SCH 58261 binding to human neutrophils is entropy and enthalpy-driven. This finding is in agreement with the thermodynamic behaviour of antagonists binding to rat striatal A2A adenosine receptors.It was concluded that in human neutrophil membranes, [3H]-SCH 58261 directly labels binding sites with pharmacological properties similar to those of A2A adenosine receptors of other tissues. The receptors labelled by [3H]-SCH 58261 mediated the effects of adenosine and adenosine receptor agonists to stimulate cyclic AMP accumulation and inhibition of superoxide anion production in human neutrophils. PMID:9605581

  6. Characterization of A2A adenosine receptors in human lymphocyte membranes by [3H]-SCH 58261 binding

    PubMed Central

    Varani, Katia; Gessi, Stefania; Dalpiaz, Alessandro; Ongini, Ennio; Andrea Borea, Pier

    1997-01-01

    The present study describes for the first time the characterization of the adenosine A2A receptor in human lymphocyte membranes with the new potent and selective antagonist radioligand, [3H]-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo [4,3-e]-1,2,4 triazolo [1,5-c] pyrimidine, ([3H]-SCH 58261). In addition, both receptor affinity and potency of reference adenosine receptor agonists and antagonists were determined in binding and adenylyl cyclase studies. Saturation experiments revealed a single class of binding sites with Kd and Bmax values of 0.85 nM and 35 fmol mg−1 protein, respectively. A series of adenosine receptor ligands were found to compete for the binding of 0.8 nM [3H]-SCH 58261 to human lymphocyte membranes with a rank order of potency consistent with that typically found for interactions with the A2A-adenosine receptor. In the adenylyl cyclase assay the same compounds exhibited a rank order of potency similar to that observed in binding experiments. Thermodynamic data indicate that [3H]-SCH 58261 binding to human lymphocytes is entropy and enthalpy-driven, a finding in agreement with the thermodynamic behaviour of antagonists for rat striatal A2A-adenosine receptors. It is concluded that in human lymphocyte membranes [3H]-SCH 58261 directly labels binding sites showing the characteristic properties of the adenosine A2A-receptor. The presence of A2A-receptors in peripheral tissue such as human lymphocytes strongly suggests an important role for adenosine in modulating immune and inflammatory responses. PMID:9313951

  7. The influence of 5-HT2 and 5-HT4 receptor antagonists to modify drug induced disinhibitory effects in the mouse light/dark test

    PubMed Central

    Costall, Brenda; Naylor, Robert J

    1997-01-01

    The ability of 5-HT2 and 5-HT4 receptor antagonists to modify the disinhibitory profile of diazepam and other agents was investigated in male BKW mice in the light/dark test box. The 5-HT2A/2B/2C receptor antagonists ritanserin, MDL11939 and RP62203 and also methysergide, which failed to modify mouse behaviour when administered alone, caused dose-related enhancements (4 to 8 fold) in the potency of diazepam to disinhibit behavioural responding to the aversive situation of the test box. Ritanserin was shown to enhance the disinhibitory potency of other benzodiazepines, chlordiazepoxide (4 fold), temazepam (10 fold) and lorazepam (10 fold), the 5-HT1A receptor ligands, 8-OH-DPAT (25 fold), buspirone (100 fold) and lesopitron (500 fold), the 5-HT3 receptor antagonists, ondansetron (100 fold) R(+)-zacopride (100 fold) and S(−)-zacopride (greater than a 1000 fold), the substituted benzamides, sulpiride (10 fold) and tiapride (5 to 10 fold) and the cholecystokinin (CCK)A receptor antagonist, devazepide (100 fold). It also reduced the onset of action of disinhibition following treatment with the 5-HT synthesis inhibitor parachlorophenylalanine. Ritanserin failed to enhance the disinhibitory effects of the CCKB receptor antagonist CI-988, the angiotensin AT1 receptor antagonist losarten or the angiotensin converting enzyme inhibitor ceranapril. The 5-HT4 receptor antagonists SDZ205-557, GR113808 and SB204070 caused dose-related reductions in the disinhibitory effect of diazepam, returning values to those shown in vehicle treated controls. The antagonists failed to modify mouse behaviour when administered alone. GR113808 was also shown to cause a dose-related antagonism of the disinhibitory effects of chlordiazepoxide, lorazepam, 8-OH-DPAT, buspirone, lesopitron, ondansetron, R(+)-zacopride, sulpiride, tiapride, devazepide, CI-988, losarten, ceranapril and parachlorophenylalanine. It was concluded that in BKW mice (a) the failure of 5-HT2 and 5-HT4 receptor antagonists

  8. Lipopolysaccharide rapidly modifies adenosine receptor transcripts in murine and human macrophages: role of NF-kappaB in A(2A) adenosine receptor induction.

    PubMed

    Murphree, Lauren J; Sullivan, Gail W; Marshall, Melissa A; Linden, Joel

    2005-11-01

    The A(2A) adenosine receptor (A(2A)AR) mediates anti-inflammatory actions of adenosine in a variety of cell types. LPS (lipopolysaccharide) was reported to induce a small (<2-fold) increase in the expression of A(2A)AR mRNA in human monocytes and monocytic cell lines. We investigated the effects of LPS on the expression of adenosine receptor mRNAs in primary mouse IPMPhi (intraperitoneal macrophages), human macrophages and Wehi-3 cells. Treatment with 10 ng/ml LPS for 4 h produced a >100-fold increase in A(2A)AR mRNA. LPS-induced increases in mRNA for A(2A)AR and TNFalpha (tumour necrosis factor alpha) are reduced by 90% in IPMPhi pretreated with the NF-kappaB (nuclear factor kappaB) inhibitor, BAY 11-7082 {(E)3-[(4-methylphenyl)sulphonyl]-2-propenenitrile; 10 microM}. In Wehi-3 cells exposed to LPS, A(2A)AR and A(2B)AR transcripts are elevated by 290- and 10-fold respectively, the A(1)AR transcript is unchanged and the A(3)AR transcript is decreased by 67%. The induction of A(2A)AR mRNA by LPS is detectable after 1 h, reaches a peak at 6 h at 600 times control and remains elevated beyond 24 h. The ED50 (effective dose) of LPS is 2.3 ng/ml. A(2A)AR receptor number, measured by 125I-ZM241385 binding to whole cells, is undetectable in naïve cells and increases linearly at a rate of 23 receptors x cell(-1) x min(-1) to a B(max) of 348 fmol/mg (28000 receptors/cell) in 20 h. The increase in receptor number is correlated with an increase in the potency of an A(2A) agonist (4-{3-[6-amino-9-(5-ethylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl)-9H-purin-2-yl]-prop-2-ynyl}-cyclohexanecarboxylic acid methyl ester; referred to as ATL146e) to stimulate cAMP in these cells. After LPS pretreatment, the potency of the A(2A) agonist, ATL146e, to reduce TNFalpha release from IPMPhi was increased by 200-fold. The results support the hypothesis that regulation of adenosine receptor expression, especially up-regulation of the A(2A)AR, is part of a delayed feedback mechanism

  9. The antidepressant desipramine is an arrestin-biased ligand at the α(2A)-adrenergic receptor driving receptor down-regulation in vitro and in vivo.

    PubMed

    Cottingham, Christopher; Chen, Yunjia; Jiao, Kai; Wang, Qin

    2011-10-14

    The neurobiological mechanisms of action underlying antidepressant drugs remain poorly understood. Desipramine (DMI) is an antidepressant classically characterized as an inhibitor of norepinephrine reuptake. Available evidence, however, suggests a mechanism more complex than simple reuptake inhibition. In the present study, we have characterized the direct interaction between DMI and the α(2A)-adrenergic receptor (α(2A)AR), a key regulator of noradrenergic neurotransmission with altered expression and function in depression. DMI alone was found to be sufficient to drive receptor internalization acutely and a robust down-regulation of α(2A)AR expression and signaling following prolonged stimulation in vitro. These effects are achieved through arrestin-biased regulation of the receptor, as DMI selectively induces recruitment of arrestin but not activation of heterotrimeric G proteins. Meanwhile, a physiologically relevant concentration of endogenous agonist (norepinephrine) was unable to sustain a down-regulation response. Prolonged in vivo administration of DMI resulted in significant down-regulation of synaptic α(2A)AR expression, a response that was lost in arrestin3-null animals. We contend that direct DMI-driven arrestin-mediated α(2A)AR down-regulation accounts for the therapeutically desirable but mechanistically unexplained adaptive alterations in receptor expression associated with this antidepressant. Our results provide novel insight into both the pharmacology of this antidepressant drug and the targeting of the α(2A)AR in depression.

  10. Mutagenesis Reveals Structure–Activity Parallels between Human A2A Adenosine Receptors and Biogenic Amine G Protein-Coupled Receptors

    PubMed Central

    Jiang, Qiaoling; Lee, Brian X.; Glashofer, Marc; van Rhee, A. Michiel; Jacobson, Kenneth A.

    2012-01-01

    Structure–affinity relationships for ligand binding at the human A2A adenosine receptor have been probed using site-directed mutagenesis in the transmembrane helical domains (TMs). The mutant receptors were expressed in COS-7 cells and characterized by binding of the radioligands [3H]CGS21680, [3H]NECA, and [3H]XAC. Three residues, at positions essential for ligand binding in other G protein-coupled receptors, were individually mutated. The residue V(3.32) in the A2A receptor that is homologous to the essential aspartate residue of TM3 in the biogenic amine receptors, i.e., V84(3.32), may be substituted with L (present in the A3 receptor) but not with D (in biogenic amine receptors) or A. H250(6.52), homologous to the critical N507 of rat m3 muscarinic acetylcholine receptors, may be substituted with other aromatic residues or with N but not with A (Kim et al. J. Biol. Chem. 1995, 270, 13987–13997). H278(7.43), homologous to the covalent ligand anchor site in rhodopsin, may not be substituted with either A, K, or N. Both V84L(3.32) and H250N(6.52) mutant receptors were highly variable in their effect on ligand competition depending on the structural class of the ligand. Adenosine-5′-uronamide derivatives were more potent at the H250N(6.52) mutant receptor than at wild type receptors. Xanthines tended to be close in potency (H250N(6.52)) or less potent (V84L-(3.32)) than at wild type receptors. The affinity of CGS21680 increased as the pH was lowered to 5.5 in both the wild type and H250N(6.52) mutant receptors. Thus, protonation of H250-(6.52) is not involved in this pH dependence. These data are consistent with a molecular model predicting the proximity of bound agonist ligands to TM3, TM5, TM6, and TM7. PMID:9258366

  11. A2A adenosine receptor regulates the human blood brain barrier permeability

    PubMed Central

    Kim, Do-Geun; Bynoe, Margaret S.

    2015-01-01

    The blood brain barrier (BBB) symbolically represents the gateway to the central nervous system. It is a single layer of specialized endothelial cells that coats the central nervous system (CNS) vasculature and physically separates the brain environment from the blood constituents, to maintain the homeostasis of the CNS. However, this protective measure is a hindrance to the delivery of therapeutics to treat neurological diseases. Here, we show that activation of A2A adenosine receptor (AR) with an FDA-approved agonist potently permeabilizes an in vitro primary human brain endothelial barrier (hBBB) to the passage of chemotherapeutic drugs and T cells. T cell migration under AR signaling occurs primarily by paracellular transendothelial route. Permeabilization of the hBBB is rapid, time-dependent and reversible and is mediated by morphological changes in actin-cytoskeletal reorganization induced by RhoA signaling and a potent down-regulation of Claudin-5 and VE-Cadherin. Moreover, the kinetics of BBB permeability in mice closely overlaps with the permeability kinetics of the hBBB. These data suggest that activation of A2A AR is an endogenous mechanism that may be used for CNS drug delivery in human. PMID:25262373

  12. Age-dependent effects on social interaction of NMDA GluN2A receptor subtype-selective antagonism.

    PubMed

    Green, Torrian L; Burket, Jessica A; Deutsch, Stephen I

    2016-07-01

    NMDA receptor-mediated neurotransmission is implicated in the regulation of normal sociability in mice. The heterotetrameric NMDA receptor is composed of two obligatory GluN1 and either two "modulatory" GluN2A or GluN2B receptor subunits. GluN2A and GluN2B-containing receptors differ in terms of their developmental expression, distribution between synaptic and extrasynaptic locations, and channel kinetic properties, among other differences. Because age-dependent differences in disruptive effects of GluN2A and GluN2B subtype-selective antagonists on sociability and locomotor activity have been reported in rats, the current investigation explored age-dependent effects of PEAQX, a GluN2A subtype-selective antagonist, on sociability, stereotypic behaviors emerging during social interaction, and spatial working memory in 4- and 8-week old male Swiss Webster mice. The data implicate an age-dependent contribution of GluN2A-containing NMDA receptors to the regulation of normal social interaction in mice. Specifically, at a dose of PEAQX devoid of any effect on locomotor activity and mouse rotarod performance, the social interaction of 8-week old mice was disrupted without any effect on the social salience of a stimulus mouse. Moreover, PEAQX attenuated stereotypic behavior emerging during social interaction in 4- and 8-week old mice. However, PEAQX had no effect on spontaneous alternations, a measure of spatial working memory, suggesting that neural circuits mediating sociability and spatial working memory may be discrete and dissociable from each other. Also, the data suggest that the regulation of stereotypic behaviors and sociability may occur independently of each other. Because expression of GluN2A-containing NMDA receptors occurs at a later developmental stage, they may be more involved in mediating the pathogenesis of ASDs in patients with histories of "regression" after a period of normal development than GluN2B receptors.

  13. Perikaryal and synaptic localization of alpha 2A-adrenergic receptor-like immunoreactivity.

    PubMed

    Aoki, C; Go, C G; Venkatesan, C; Kurose, H

    1994-07-11

    Through molecular cloning, the existence of three distinct subtypes of alpha 2-adrenergic receptors (alpha 2AR)--A, B and C--has been established and are referred to as alpha 2A AR, alpha 2B AR and alpha 2CAR. Due to limitations in pharmacological tools, it has been difficult to ascribe the role of each subtype to the central functions of alpha 2AR. In situ hybridization studies have provided valuable information regarding their distribution within brain. However, little is known about their subcellular distribution, and in particular, their pre- versus postsynaptic localization or their relation to noradrenergic neurons in the CNS. We used an antiserum that selectively recognizes the A-subtype of alpha 2AR to determine: (1) the regional distribution of the receptor within brains of rat and monkey; (2) the subcellular distribution of the receptor in locus coeruleus (LC) of rats and prefrontal cortex of monkeys; and (3) the ultrastructural relation of the receptor to noradrenergic processes in LC. Light microscopic immunocytochemistry revealed prominent immunoreactivity in LC, the brainstem regions modulating the baroreflex, the granule cell layer of the cerebellar cortex, the paraventricular and supraoptic nuclei of the hypothalamus (PVN, SON), the basal ganglia, all thalamic nuclei, the hippocampal formation and throughout cerebral cortical areas. Comparison of results obtained from rat and monkey brains revealed no apparent interspecies-differences in the regional distribution of immunoreactivity. Immunoreactivity occurred as small puncta, less than 1 micron in diameter, that cluster over neuronal perikarya. Besides these puncta, cell bodies, proximal dendrites and fine varicose processes--most likely to be axonal--of the PVN and SON and the hippocampal granule cells also exhibited homogeneously intense distribution of immunoreactivity. Subcellularly, alpha 2AAR-ir in LC and prefrontal cortex were associated with synaptic and non-synaptic plasma membrane of

  14. Differential expression of adenosine A3 receptors controls adenosine A2A receptor-mediated inhibition of TLR responses in microglia.

    PubMed

    van der Putten, Céline; Zuiderwijk-Sick, Ella A; van Straalen, Linda; de Geus, Eveline D; Boven, Leonie A; Kondova, Ivanela; IJzerman, Ad P; Bajramovic, Jeffrey J

    2009-06-15

    Microglia activation is a prominent feature in many neuroinflammatory disorders. Unrestrained activation can generate a chronic inflammatory environment that might lead to neurodegeneration and autoimmunity. Extracellular adenosine modulates cellular activation through adenosine receptor (ADORA)-mediated signaling. There are four ADORA subtypes that can either increase (A(2A) and A(2B) receptors) or decrease (A(1) and A(3) receptors) intracellular cyclic AMP levels. The expression pattern of the subtypes thus orchestrates the cellular response to extracellular adenosine. We have investigated the expression of ADORA subtypes in unstimulated and TLR-activated primary rhesus monkey microglia. Activation induced an up-regulation of A(2A) and a down-regulation of A(3) receptor (A(3)R) levels. The altered ADORA-expression pattern sensitized microglia to A(2A) receptor (A(2A)R)-mediated inhibition of subsequent TLR-induced cytokine responses. By using combinations of subtype-specific agonists and antagonists, we revealed that in unstimulated microglia, A(2A)R-mediated inhibitory signaling was effectively counteracted by A(3)R-mediated signaling. In activated microglia, the decrease in A(3)R-mediated signaling sensitized them to A(2A)R-mediated inhibitory signaling. We report a differential, activation state-specific expression of ADORA in microglia and uncover a role for A(3)R as dynamically regulated suppressors of A(2A)R-mediated inhibition of TLR-induced responses. This would suggest exploration of combinations of A(2A)R agonists and A(3)R antagonists to dampen microglial activation during chronic neuroinflammatory conditions.

  15. Hyperactivation of D1 and A2A receptors contributes to cognitive dysfunction in Huntington's disease.

    PubMed

    Tyebji, Shiraz; Saavedra, Ana; Canas, Paula M; Pliassova, Anna; Delgado-García, José M; Alberch, Jordi; Cunha, Rodrigo A; Gruart, Agnès; Pérez-Navarro, Esther

    2015-02-01

    Stimulation of dopamine D1 receptor (D1R) and adenosine A2A receptor (A2AR) increases cAMP-dependent protein kinase (PKA) activity in the brain. In Huntington's disease, by essentially unknown mechanisms, PKA activity is increased in the hippocampus of mouse models and patients and contributes to hippocampal-dependent cognitive impairment in R6 mice. Here, we show for the first time that D1R and A2AR density and functional efficiency are increased in hippocampal nerve terminals from R6/1 mice, which accounts for increased cAMP levels and PKA signaling. In contrast, PKA signaling was not altered in the hippocampus of Hdh(Q7/Q111) mice, a full-length HD model. In line with these findings, chronic (but not acute) combined treatment with D1R plus A2AR antagonists (SCH23390 and SCH58261, respectively) normalizes PKA activity in the hippocampus, facilitates long-term potentiation in behaving R6/1 mice, and ameliorates cognitive dysfunction. By contrast, chronic treatment with either D1R or A2AR antagonist alone does not modify PKA activity or improve cognitive dysfunction in R6/1 mice. Hyperactivation of both D1R and A2AR occurs in HD striatum and chronic treatment with D1R plus A2AR antagonists normalizes striatal PKA activity but it does not affect motor dysfunction in R6/1 mice. In conclusion, we show that parallel alterations in dopaminergic and adenosinergic signaling in the hippocampus contribute to increase PKA activity, which in turn selectively participates in hippocampal-dependent learning and memory deficits in HD. In addition, our results point to the chronic inhibition of both D1R and A2AR as a novel therapeutic strategy to manage early cognitive impairment in this neurodegenerative disease. PMID:25449908

  16. Striatal Pre- and Postsynaptic Profile of Adenosine A2A Receptor Antagonists

    PubMed Central

    Quiroz, César; Beaumont, Vahri; Goldberg, Steven R.; Lluís, Carme; Cortés, Antoni; Franco, Rafael; Casadó, Vicent; Canela, Enric I.; Ferré, Sergi

    2011-01-01

    Striatal adenosine A2A receptors (A2ARs) are highly expressed in medium spiny neurons (MSNs) of the indirect efferent pathway, where they heteromerize with dopamine D2 receptors (D2Rs). A2ARs are also localized presynaptically in cortico-striatal glutamatergic terminals contacting MSNs of the direct efferent pathway, where they heteromerize with adenosine A1 receptors (A1Rs). It has been hypothesized that postsynaptic A2AR antagonists should be useful in Parkinson's disease, while presynaptic A2AR antagonists could be beneficial in dyskinetic disorders, such as Huntington's disease, obsessive-compulsive disorders and drug addiction. The aim or this work was to determine whether selective A2AR antagonists may be subdivided according to a preferential pre- versus postsynaptic mechanism of action. The potency at blocking the motor output and striatal glutamate release induced by cortical electrical stimulation and the potency at inducing locomotor activation were used as in vivo measures of pre- and postsynaptic activities, respectively. SCH-442416 and KW-6002 showed a significant preferential pre- and postsynaptic profile, respectively, while the other tested compounds (MSX-2, SCH-420814, ZM-241385 and SCH-58261) showed no clear preference. Radioligand-binding experiments were performed in cells expressing A2AR-D2R and A1R-A2AR heteromers to determine possible differences in the affinity of these compounds for different A2AR heteromers. Heteromerization played a key role in the presynaptic profile of SCH-442416, since it bound with much less affinity to A2AR when co-expressed with D2R than with A1R. KW-6002 showed the best relative affinity for A2AR co-expressed with D2R than co-expressed with A1R, which can at least partially explain the postsynaptic profile of this compound. Also, the in vitro pharmacological profile of MSX-2, SCH-420814, ZM-241385 and SCH-58261 was is in accordance with their mixed pre- and postsynaptic profile. On the basis of their preferential

  17. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    PubMed Central

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease. PMID:26796668

  18. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    NASA Astrophysics Data System (ADS)

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease.

  19. Blockage of A2A and A3 adenosine receptors decreases the desensitization of human GABAA receptors microtransplanted to Xenopus oocytes

    PubMed Central

    Roseti, Cristina; Palma, Eleonora; Martinello, Katiuscia; Fucile, Sergio; Morace, Roberta; Esposito, Vincenzo; Cantore, Gianpaolo; Arcella, Antonietta; Giangaspero, Felice; Aronica, Eleonora; Mascia, Addolorata; Di Gennaro, Giancarlo; Quarato, Pier Paolo; Manfredi, Mario; Cristalli, Gloria; Lambertucci, Catia; Marucci, Gabriella; Volpini, Rosaria; Limatola, Cristina; Eusebi, Fabrizio

    2009-01-01

    We previously found that the endogenous anticonvulsant adenosine, acting through A2A and A3 adenosine receptors (ARs), alters the stability of currents (IGABA) generated by GABAA receptors expressed in the epileptic human mesial temporal lobe (MTLE). Here we examined whether ARs alter the stability (desensitization) of IGABA expressed in focal cortical dysplasia (FCD) and in periglioma epileptic tissues. The experiments were performed with tissues from 23 patients, using voltage-clamp recordings in Xenopus oocytes microinjected with membranes isolated from human MTLE and FCD tissues or using patch-clamp recordings of pyramidal neurons in epileptic tissue slices. On repetitive activation, the epileptic GABAA receptors revealed instability, manifested by a large IGABA rundown, which in most of the oocytes (≈70%) was obviously impaired by the new A2A antagonists ANR82, ANR94, and ANR152. In most MTLE tissue-microtransplanted oocytes, a new A3 receptor antagonist (ANR235) significantly improved IGABA stability. Moreover, patch-clamped pyramidal neurons from human neocortical slices of periglioma epileptic tissues exhibited altered IGABA rundown on ANR94 treatment. Our findings indicate that antagonizing A2A and A3 receptors increases the IGABA stability in different epileptic tissues and suggest that adenosine derivatives may offer therapeutic opportunities in various forms of human epilepsy. PMID:19721003

  20. Modulation of GluK2a subunit-containing kainate receptors by 14-3-3 proteins.

    PubMed

    Sun, Changcheng; Qiao, Haifa; Zhou, Qin; Wang, Yan; Wu, Yuying; Zhou, Yi; Li, Yong

    2013-08-23

    Kainate receptors (KARs) are one of the ionotropic glutamate receptors that mediate excitatory postsynaptic currents (EPSCs) with characteristically slow kinetics. Although mechanisms for the slow kinetics of KAR-EPSCs are not totally understood, recent evidence has implicated a regulatory role of KAR-associated proteins. Here, we report that decay kinetics of GluK2a-containing receptors is modulated by closely associated 14-3-3 proteins. 14-3-3 binding requires PKC-dependent phosphorylation of serine residues localized in the carboxyl tail of the GluK2a subunit. In transfected cells, 14-3-3 binding to GluK2a slows desensitization kinetics of both homomeric GluK2a and heteromeric GluK2a/GluK5 receptors. Moreover, KAR-EPSCs at mossy fiber-CA3 synapses decay significantly faster in the 14-3-3 functional knock-out mice. Collectively, these results demonstrate that 14-3-3 proteins are an important regulator of GluK2a-containing KARs and may contribute to the slow decay kinetics of native KAR-EPSCs. PMID:23861400

  1. Adenosine A(2A) receptor stimulation reduces inflammation and neointimal growth in a murine carotid ligation model.

    PubMed

    McPherson, J A; Barringhaus, K G; Bishop, G G; Sanders, J M; Rieger, J M; Hesselbacher, S E; Gimple, L W; Powers, E R; Macdonald, T; Sullivan, G; Linden, J; Sarembock, I J

    2001-05-01

    Endothelial activation and leukocyte recruitment are early events in atherosclerosis and the vascular response to injury. Adenosine has anti-inflammatory effects on leukocytes and endothelial cells mediated through its A(2A) receptor. We tested the hypothesis that A(2A) activation would reduce inflammation and neointimal formation in a murine carotid ligation model. Before injury, mice were randomized to a 7-day subcutaneous infusion of a specific A(2A) receptor agonist (ATL-146e, 0.004 microg/kg per minute), vehicle control, ATL-146e plus ZM241385 (a selective A(2A) antagonist), or ZM241385 alone. Leukocyte recruitment and adhesion molecule expression were assessed at early time points, and the neointimal area was measured at 14 and 28 days after injury. Compared with control mice, ATL-146e-treated mice had significantly less neutrophil and macrophage recruitment and vascular cell adhesion molecule-1, intercellular adhesion molecule-1, and P-selectin expression in the first 7 days after injury. Neointimal area was markedly and persistently reduced by 80% at 14 and 28 days, despite termination of ATL infusion at 7 days. ATL-146e+ZM241385-treated and ZM241385-treated animals had neointimal areas similar to those of control animals, confirming that the observed effects of ATL-146e were mediated specifically by the A(2A) receptor. These data demonstrate that novel stimulation of adenosine A(2A) receptors can inhibit early inflammatory processes that are important in neointimal formation after vascular injury.

  2. Homology modelling of the human adenosine A2B receptor based on X-ray structures of bovine rhodopsin, the beta2-adrenergic receptor and the human adenosine A2A receptor.

    PubMed

    Sherbiny, Farag F; Schiedel, Anke C; Maass, Astrid; Müller, Christa E

    2009-11-01

    A three-dimensional model of the human adenosine A2B receptor was generated by means of homology modelling, using the crystal structures of bovine rhodopsin, the beta2-adrenergic receptor, and the human adenosine A2A receptor as templates. In order to compare the three resulting models, the binding modes of the adenosine A2B receptor antagonists theophylline, ZM241385, MRS1706, and PSB601 were investigated. The A2A-based model was much better able to stabilize the ligands in the binding site than the other models reflecting the high degree of similarity between A2A and A2B receptors: while the A2B receptor shares about 21% of the residues with rhodopsin, and 31% with the beta2-adrenergic receptor, it is 56% identical to the adenosine A2A receptor. The A2A-based model was used for further studies. The model included the transmembrane domains, the extracellular and the intracellular hydrophilic loops as well as the terminal domains. In order to validate the usefulness of this model, a docking analysis of several selective and nonselective agonists and antagonists was carried out including a study of binding affinities and selectivities of these ligands with respect to the adenosine A2A and A2B receptors. A common binding site is proposed for antagonists and agonists based on homology modelling combined with site-directed mutagenesis and a comparison between experimental and calculated affinity data. The new, validated A2B receptor model may serve as a basis for developing more potent and selective drugs.

  3. Adenosine A2A receptor antagonists: blockade of adenosinergic effects and T regulatory cells

    PubMed Central

    Sitkovsky, M; Lukashev, D; Deaglio, S; Dwyer, K; Robson, S C; Ohta, A

    2008-01-01

    The intensity and duration of host responses are determined by protective mechanisms that control tissue injury by dampening down inflammation. Adenosine generation and consequent effects, mediated via A2A adenosine receptors (A2AR) on effector cells, play a critical role in the pathophysiological modulation of these responses in vivo. Adenosine is both released by hypoxic cells/tissues and is also generated from extracellular nucleotides by ecto-enzymes e.g. CD39 (ENTPD1) and CD73 that are expressed by the vasculature and immune cells, in particular by T regulatory cell. In general, these adenosinergic mechanisms minimize the extent of collateral damage to host tissues during the course of inflammatory reactions. However, induction of suppressive pathways might also cause escape of pathogens and permit dissemination. In addition, adenosinergic responses may inhibit immune responses while enhancing vascular angiogenic responses to malignant cells that promote tumor growth. Novel drugs that block A2AR-adenosinergic effects and/or adenosine generation have the potential to boost pathogen destruction and to selectively destroy malignant tissues. In the latter instance, future treatment modalities might include novel ‘anti-adenosinergic' approaches that augment immune clearance of malignant cells and block permissive angiogenesis. This review addresses several possible pharmacological modalities to block adenosinergic pathways and speculates on their future application together with impacts on human disease. PMID:18311159

  4. Macrophage A2A Adenosine Receptors Are Essential to Protect from Progressive Kidney Injury.

    PubMed

    Truong, Luan D; Trostel, Jessica; McMahan, Rachel; Chen, Jiang-Fan; Garcia, Gabriela E

    2016-10-01

    A2A adenosine receptors (A2ARs) are endogenous inhibitor of inflammation. Macrophages that are key effectors of kidney disease progression express A2ARs. We investigated the role of A2ARs in kidney inflammation in a macrophage-mediated anti-glomerular basement membrane reactive serum-induced immune nephritis in A2AR-deficient mice. Sub-threshold doses of glomerular basement membrane-reactive serum induced more severe and prolonged kidney damage with higher levels of proinflammatory cytokines and greater accumulation of inflammatory cells in A2AR(-/-) mice than wild-type (WT) mice. To investigate the role of macrophage A2AR in progressive kidney injury, glomerulonephritis was induced in CD11b-DTR transgenic mice. Macrophages were selectively depleted in the established phase of the disease and reconstituted with macrophages from WT or A2AR-deficient mice and then treated with an A2AR agonist. In mice receiving WT macrophages and treated with an A2AR agonist, the glomerular cellularity, crescent formation, sclerotic glomeruli, and tubulointerstitial injury were significantly reduced compared with the control group. In contrast, in mice reconstituted with A2AR-deficient macrophages and treated with an A2AR agonist, the kidney injury was more severe with increased deposition of collagen I, III, and IV. These findings suggest that disruption of the protective A2AR amplifies inflammation to accelerate glomerular damage and endogenous macrophage A2ARs are essential to protect from progressive kidney fibrosis.

  5. Continuous adenosine A2A receptor antagonism after focal cerebral ischemia in spontaneously hypertensive rats.

    PubMed

    Fronz, Ulrike; Deten, Alexander; Baumann, Frank; Kranz, Alexander; Weidlich, Sarah; Härtig, Wolfgang; Nieber, Karen; Boltze, Johannes; Wagner, Daniel-Christoph

    2014-02-01

    Antagonism of the adenosine A2A receptor (A2AR) has been shown to elicit substantial neuroprotective properties when given immediately after cerebral ischemia. We asked whether the continuous application of a selective A2AR antagonist within a clinically relevant time window will be a feasible and effective approach to treat focal cerebral ischemia. To answer this question, we subjected 20 male spontaneously hypertensive rats to permanent middle cerebral artery occlusion and randomized them equally to a verum and a control group. Two hours after stroke onset, the animals received a subcutaneous implantation of an osmotic minipump filled with 5 mg kg(-1) day(-1) 8-(3-chlorostyryl) caffeine (CSC) or vehicle solution. The serum level of CSC was measured twice a day for three consecutive days. The infarct volume was determined at days 1 and 3 using magnetic resonance imaging. We found the serum level of CSC showing a bell-shaped curve with its maximum at 36 h. The infarct volume was not affected by continuous CSC treatment. These results suggest that delayed and continuous CSC application was not sufficient to treat acute ischemic stroke, potentially due to unfavorable hepatic elimination and metabolization of the pharmaceutical. PMID:24170241

  6. [Beta]-Adrenergic Receptor Activation Rescues Theta Frequency Stimulation-Induced LTP Deficits in Mice Expressing C-Terminally Truncated NMDA Receptor GluN2A Subunits

    ERIC Educational Resources Information Center

    Moody, Teena D.; Watabe, Ayako M.; Indersmitten, Tim; Komiyama, Noboru H.; Grant, Seth G. N.; O'Dell, Thomas J.

    2011-01-01

    Through protein interactions mediated by their cytoplasmic C termini the GluN2A and GluN2B subunits of NMDA receptors (NMDARs) have a key role in the formation of NMDAR signaling complexes at excitatory synapses. Although these signaling complexes are thought to have a crucial role in NMDAR-dependent forms of synaptic plasticity such as long-term…

  7. HBK-7 - A new xanthone derivative and a 5-HT1A receptor antagonist with antidepressant-like properties.

    PubMed

    Pytka, Karolina; Kazek, Grzegorz; Siwek, Agata; Mordyl, Barbara; Głuch-Lutwin, Monika; Rapacz, Anna; Olczyk, Adrian; Gałuszka, Adam; Waszkielewicz, Anna; Marona, Henryk; Sapa, Jacek; Filipek, Barbara; Zygmunt, Małgorzata

    2016-01-01

    Xanthone derivatives possess many biological properties, including neuroprotective, antioxidant or antidepressant-like. In this study we aimed to investigate antidepressant- and anxiolytic-like properties of a new xanthone derivative - 6-methoxy-4-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-7), as well as its possible mechanism of action, and the influence on cognitive and motor function. HBK-7 in our earlier studies showed high affinity for serotonergic 5-HT1A receptor. We determined the affinity of HBK-7 for CNS receptors and transporters using radioligand assays and examined its intrinsic activity towards 5-HT1A receptor. We evaluated antidepressant- and anxiolytic-like activity of HBK-7 in the mouse forced swim test, and four-plate test, respectively. We examined the influence on locomotor activity in mice to determine if the effect observed in the forced swim test was specific. We used step-through passive avoidance and rotarod tests to evaluate the influence of HBK-7 on cognitive and motor function, respectively. HBK-7 showed moderate affinity for dopaminergic D2 receptor and very low for serotonergic 5-HT2A, adrenergic α2 receptors, as well as serotonin transporter. Functional studies revealed that HBK-7 was a 5-HT1A receptor antagonist. HBK-7 (10mg/kg) decreased immobility time in the forced swim test. Combined treatment with sub-effective doses of HBK-7 and fluoxetine reduced immobility of mice in the forced swim test. Pretreatment with p-chlorophenylalanine and WAY-100,635 antagonized the antidepressant-like effect of HBK-7. Neither of the treatments influenced locomotor activity of mice. HBK-7 at antidepressant-like dose did not impair memory or motor coordination in mice. We demonstrated that HBK-7 was a 5-HT1A receptor antagonist with potent, comparable to mianserin, antidepressant-like activity. HBK-7 mediated its effect through serotonergic system and its antidepressant-like action required the activation of 5-HT1A receptors. At active

  8. HBK-7 - A new xanthone derivative and a 5-HT1A receptor antagonist with antidepressant-like properties.

    PubMed

    Pytka, Karolina; Kazek, Grzegorz; Siwek, Agata; Mordyl, Barbara; Głuch-Lutwin, Monika; Rapacz, Anna; Olczyk, Adrian; Gałuszka, Adam; Waszkielewicz, Anna; Marona, Henryk; Sapa, Jacek; Filipek, Barbara; Zygmunt, Małgorzata

    2016-01-01

    Xanthone derivatives possess many biological properties, including neuroprotective, antioxidant or antidepressant-like. In this study we aimed to investigate antidepressant- and anxiolytic-like properties of a new xanthone derivative - 6-methoxy-4-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-7), as well as its possible mechanism of action, and the influence on cognitive and motor function. HBK-7 in our earlier studies showed high affinity for serotonergic 5-HT1A receptor. We determined the affinity of HBK-7 for CNS receptors and transporters using radioligand assays and examined its intrinsic activity towards 5-HT1A receptor. We evaluated antidepressant- and anxiolytic-like activity of HBK-7 in the mouse forced swim test, and four-plate test, respectively. We examined the influence on locomotor activity in mice to determine if the effect observed in the forced swim test was specific. We used step-through passive avoidance and rotarod tests to evaluate the influence of HBK-7 on cognitive and motor function, respectively. HBK-7 showed moderate affinity for dopaminergic D2 receptor and very low for serotonergic 5-HT2A, adrenergic α2 receptors, as well as serotonin transporter. Functional studies revealed that HBK-7 was a 5-HT1A receptor antagonist. HBK-7 (10mg/kg) decreased immobility time in the forced swim test. Combined treatment with sub-effective doses of HBK-7 and fluoxetine reduced immobility of mice in the forced swim test. Pretreatment with p-chlorophenylalanine and WAY-100,635 antagonized the antidepressant-like effect of HBK-7. Neither of the treatments influenced locomotor activity of mice. HBK-7 at antidepressant-like dose did not impair memory or motor coordination in mice. We demonstrated that HBK-7 was a 5-HT1A receptor antagonist with potent, comparable to mianserin, antidepressant-like activity. HBK-7 mediated its effect through serotonergic system and its antidepressant-like action required the activation of 5-HT1A receptors. At active

  9. Phencyclidine-induced disruption of oscillatory activity in prefrontal cortex: Effects of antipsychotic drugs and receptor ligands.

    PubMed

    Lladó-Pelfort, L; Troyano-Rodriguez, E; van den Munkhof, H E; Cervera-Ferri, A; Jurado, N; Núñez-Calvet, M; Artigas, F; Celada, P

    2016-03-01

    The non-competitive NMDA receptor (NMDA-R) antagonist phencyclidine (PCP) markedly disrupts thalamocortical activity, increasing excitatory neuron discharge and reducing low frequency oscillations (LFO, <4Hz) that temporarily group neuronal discharge. These actions are mainly driven by PCP interaction with NMDA-R in GABAergic neurons of the thalamic reticular nucleus and likely underlie PCP psychotomimetic activity. Here we report that classical (haloperidol, chlorpromazine, perphenazine) and atypical (clozapine, olanzapine, quetiapine, risperidone, ziprasidone, aripripazole) antipsychotic drugs--but not the antidepressant citalopram--countered PCP-evoked fall of LFO in the medial prefrontal cortex (mPFC) of anesthetized rats. PCP reduces LFO by breaking the physiological balance between excitatory and inhibitory transmission. Next, we examined the role of different neurotransmitter receptors to reverse PCP actions. D2-R and D1-R blockade may account for classical antipsychotic action since raclopride and SCH-23390 partially reversed PCP effects. Atypical antipsychotic reversal may additionally involve 5-HT1A-R activation (but not 5-HT2A-R blockade) since 8-OH-DPAT and BAYx3702 (but not M100907) fully countered PCP effects. Blockade of histamine H1-R (pyrilamine) and α1-adrenoceptors (prazosin) was without effect. However, the enhancement of GABAA-R-mediated neurotransmission (using muscimol, diazepam or valproate) and the reduction of excitatory neurotransmission (using the mGluR2/3 agonist LY379268 and the preferential kainite/AMPA antagonist CNQX--but not the preferential AMPA/kainate antagonist NBQX) partially or totally countered PCP effects. Overall, these results shed new light on the neurobiological mechanisms used by antipsychotic drugs to reverse NMDA-R antagonist actions and suggest that agents restoring the physiological excitatory/inhibitory balance altered by PCP may be new targets in antipsychotic drug development.

  10. SB 242084, a selective and brain penetrant 5-HT2C receptor antagonist.

    PubMed

    Kennett, G A; Wood, M D; Bright, F; Trail, B; Riley, G; Holland, V; Avenell, K Y; Stean, T; Upton, N; Bromidge, S; Forbes, I T; Brown, A M; Middlemiss, D N; Blackburn, T P

    1997-01-01

    SB 242084 has a high affinity (pKi 9.0) for the cloned human 5-HT2C receptor and 100- and 158-fold selectivity over the closely related cloned human 5-HT2B and 5-HT2A subtypes respectively. SB 242084 had over 100-fold selectivity over a range of other 5-HT, dopamine and adrenergic receptors. In studies of 5-HT-stimulated phosphatidylinositol hydrolysis using SH-SY5Y cells stably expressing the cloned human 5-HT2C receptor, SB 242084 acted as an antagonist with a pKb of 9.3, which closely resembled its corresponding receptor binding affinity. SB 242084 potently inhibited m-chlorophenylpiperazine (mCPP, 7 mgkg i.p. 20 min pre-test)-induced hypolocomotion in rats, a model of in vivo central 5-HT2C receptor function, with an ID50 of 0.11 mg/kg i.p., and 2.0 mg/kg p.o. SB 242084 (0.1-1 mg/kg i.p.) exhibited an anxiolytic-like profile in the rat social interaction test, increasing time spent in social interaction, but having no effect on locomotion. SB 242084 (0.1-1 mg/kg i.p.) also markedly increased punished responding in a rat Geller-Seifter conflict test of anxiety, but had no consistent effect on unpunished responding. A large acute dose of SB 242084 (30 mg/kg p.o.) had no effect on seizure susceptibility in the rat maximal electroshock seizure threshold test. Also, while SB 242084 (2 and 6 mg/kg p.o. 1 hr pre-test) antagonized the hypophagic response to mCPP, neither acute nor subchronic administration of the drug, for 5 days at 2 or 6 mg/kg p.o. twice daily, affected food intake or weight gain. The results suggest that SB 242084 is the first reported selective potent and brain penetrant 5-HT2C receptor antagonist and has anxiolytic-like activity, but does not possess either proconvulsant or hyperphagic properties which are characteristic of mutant mice lacking the 5-HT2C receptor. PMID:9225286

  11. Adenosine A2(A) receptor modulates the oxidative stress response of primed polymorphonuclear leukocytes after parabolic flight.

    PubMed

    Kaufmann, Ines; Feuerecker, Matthias; Salam, Alex; Schelling, Gustav; Thiel, Manfred; Choukèr, Alexander

    2011-07-01

    Space flight and gravitational stress can alter innate immune function. Parabolic flights (PFs) as a model for short-term gravitational changes prime the cytotoxic capability of polymorphonuclear leukocytes (PMNs). In view of the emerging role of adenosine in the regulation of innate immune responses, we examined the potency of adenosine to control the release of cytotoxic H(2)O(2) by primed PMNs via the adenosine receptor system. During PFs, microgravity conditions (<10(-2) G) are generated for approximately 22 seconds, followed by a hypergravity (1.8 G) phase resulting in gravitational stress. We studied the ex vivo effects of adenosine on the production of H(2)O(2) by stimulated PMNs and determined adenosine plasma levels and adenosine A2(A) receptor transcripts of leukocytes of PF participants (n = 15). Increasing concentrations of adenosine dose dependently reduced tissue-toxic H(2)O(2) production by PMNs with a half-maximal inhibitory concentration (IC(50)) of 19.5 nM before takeoff and 7.6 nM at 48 hours after PF. This increase in the adenosine-mediated inhibition of PMNs' H(2)O(2) production was completely reversed by addition of the A2(A) receptor antagonist ZM241385. PF induced a nonsignificant elevation in adenosine plasma levels; A2(A) receptor mRNA from leukocytes remained almost unchanged. Adenosine limits the oxidative stress response of PMNs after PFs through an upregulation of the adenosine A2(A) receptor function. This stop signal on inflammation is stronger than that under normal physiologic states and may limit further cytotoxic damage. Pharmacologic manipulation of the adenosine A2(A) receptor pathway could be a potential target for control of unwanted exacerbations of cytotoxic PMN functions.

  12. Alpha2A adrenergic receptor activation inhibits epileptiform activity in the rat hippocampal CA3 region.

    PubMed

    Jurgens, Chris W D; Hammad, Hana M; Lichter, Jessica A; Boese, Sarah J; Nelson, Brian W; Goldenstein, Brianna L; Davis, Kylie L; Xu, Ke; Hillman, Kristin L; Porter, James E; Doze, Van A

    2007-06-01

    Norepinephrine has potent antiepileptic properties, the pharmacology of which is unclear. Under conditions in which GABAergic inhibition is blocked, norepinephrine reduces hippocampal cornu ammonis 3 (CA3) epileptiform activity through alpha(2) adrenergic receptor (AR) activation on pyramidal cells. In this study, we investigated which alpha(2)AR subtype(s) mediates this effect. First, alpha(2)AR genomic expression patterns of 25 rat CA3 pyramidal cells were determined using real-time single-cell reverse transcription-polymerase chain reaction, demonstrating that 12 cells expressed alpha(2A)AR transcript; 3 of the 12 cells additionally expressed mRNA for alpha(2C)AR subtype and no cells possessing alpha(2B)AR mRNA. Hippocampal CA3 epileptiform activity was then examined using field potential recordings in brain slices. The selective alphaAR agonist 6-fluoronorepinephrine caused a reduction of CA3 epileptiform activity, as measured by decreased frequency of spontaneous epileptiform bursts. In the presence of betaAR blockade, concentration-response curves for AR agonists suggest that an alpha(2)AR mediates this response, as the rank order of potency was 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK-14304) >or= epinephrine >6-fluoronorepinephrine > norepinephrine > phenylephrine. Finally, equilibrium dissociation constants (K(b)) of selective alphaAR antagonists were functionally determined to confirm the specific alpha(2)AR subtype inhibiting CA3 epileptiform activity. Apparent K(b) values calculated for atipamezole (1.7 nM), MK-912 (4.8 nM), BRL-44408 (15 nM), yohimbine (63 nM), ARC-239 (540 nM), prazosin (4900 nM), and terazosin (5000 nM) correlated best with affinities previously determined for the alpha(2A)AR subtype (r = 0.99, slope = 1.0). These results suggest that, under conditions of impaired GABAergic inhibition, activation of alpha(2A)ARs is primarily responsible for the antiepileptic actions of norepinephrine in the rat hippocampal CA3

  13. Sustained Suppression of Hyperalgesia during Latent Sensitization by μ-, δ-, and κ-opioid receptors and α2A Adrenergic Receptors: Role of Constitutive Activity

    PubMed Central

    Walwyn, Wendy M.; Chen, Wenling; Kim, Hyeyoung; Minasyan, Ani; Ennes, Helena S.; McRoberts, James A.

    2016-01-01

    Many chronic pain disorders alternate between bouts of pain and periods of remission. The latent sensitization model reproduces this in rodents by showing that the apparent recovery (“remission”) from inflammatory or neuropathic pain can be reversed by opioid antagonists. Therefore, this remission represents an opioid receptor-mediated suppression of a sustained hyperalgesic state. To identify the receptors involved, we induced latent sensitization in mice and rats by injecting complete Freund's adjuvant (CFA) in the hindpaw. In WT mice, responses to mechanical stimulation returned to baseline 3 weeks after CFA. In μ-opioid receptor (MOR) knock-out (KO) mice, responses did not return to baseline but partially recovered from peak hyperalgesia. Antagonists of α2A-adrenergic and δ-opioid receptors reinstated hyperalgesia in WT mice and abolished the partial recovery from hyperalgesia in MOR KO mice. In rats, antagonists of α2A adrenergic and μ-, δ-, and κ-opioid receptors reinstated hyperalgesia during remission from CFA-induced hyperalgesia. Therefore, these four receptors suppress hyperalgesia in latent sensitization. We further demonstrated that suppression of hyperalgesia by MORs was due to their constitutive activity because of the following: (1) CFA-induced hyperalgesia was reinstated by the MOR inverse agonist naltrexone (NTX), but not by its neutral antagonist 6β-naltrexol; (2) pro-enkephalin, pro-opiomelanocortin, and pro-dynorphin KO mice showed recovery from hyperalgesia and reinstatement by NTX; (3) there was no MOR internalization during remission; (4) MORs immunoprecipitated from the spinal cord during remission had increased Ser375 phosphorylation; and (5) electrophysiology recordings from dorsal root ganglion neurons collected during remission showed constitutive MOR inhibition of calcium channels. SIGNIFICANCE STATEMENT Chronic pain causes extreme suffering to millions of people, but its mechanisms remain to be unraveled. Latent

  14. Differential role of nitric oxide in regional sympathetic responses to stimulation of NTS A2a adenosine receptors.

    PubMed

    Scislo, Tadeusz J; Tan, Nobusuke; O'Leary, Donal S

    2005-02-01

    Our previous studies showed that preganglionic adrenal (pre-ASNA), renal (RSNA), lumbar, and postganglionic adrenal sympathetic nerve activities (post-ASNA) are inhibited after stimulation of arterial baroreceptors, nucleus of the solitary tract (NTS), and glutamatergic and P2x receptors and are activated after stimulation of adenosine A1 receptors. However, stimulation of adenosine A2a receptors inhibited RSNA and post-ASNA, whereas it activated pre-ASNA. Because the effects evoked by NTS A