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Egger K, Aicher HD, Cumming P, Scheidegger M. Neurobiological research on N,N-dimethyltryptamine (DMT) and its potentiation by monoamine oxidase (MAO) inhibition: from ayahuasca to synthetic combinations of DMT and MAO inhibitors. Cell Mol Life Sci 2024; 81:395. [PMID: 39254764 PMCID: PMC11387584 DOI: 10.1007/s00018-024-05353-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 06/19/2024] [Accepted: 07/04/2024] [Indexed: 09/11/2024]
Abstract
The potent hallucinogen N,N-dimethyltryptamine (DMT) has garnered significant interest in recent years due to its profound effects on consciousness and its therapeutic psychopotential. DMT is an integral (but not exclusive) psychoactive alkaloid in the Amazonian plant-based brew ayahuasca, in which admixture of several β-carboline monoamine oxidase A (MAO-A) inhibitors potentiate the activity of oral DMT, while possibly contributing in other respects to the complex psychopharmacology of ayahuasca. Irrespective of the route of administration, DMT alters perception, mood, and cognition, presumably through agonism at serotonin (5-HT) 1A/2A/2C receptors in brain, with additional actions at other receptor types possibly contributing to its overall psychoactive effects. Due to rapid first pass metabolism, DMT is nearly inactive orally, but co-administration with β-carbolines or synthetic MAO-A inhibitors (MAOIs) greatly increase its bioavailability and duration of action. The synergistic effects of DMT and MAOIs in ayahuasca or synthetic formulations may promote neuroplasticity, which presumably underlies their promising therapeutic efficacy in clinical trials for neuropsychiatric disorders, including depression, addiction, and post-traumatic stress disorder. Advances in neuroimaging techniques are elucidating the neural correlates of DMT-induced altered states of consciousness, revealing alterations in brain activity, functional connectivity, and network dynamics. In this comprehensive narrative review, we present a synthesis of current knowledge on the pharmacology and neuroscience of DMT, β-carbolines, and ayahuasca, which should inform future research aiming to harness their full therapeutic potential.
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Affiliation(s)
- Klemens Egger
- Department of Adult Psychiatry and Psychotherapy, Psychiatric University Clinic Zurich and University of Zurich, Zurich, Switzerland.
- Neuroscience Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, Zurich, Switzerland.
- Department of Nuclear Medicine, Bern University Hospital, Bern, Switzerland.
| | - Helena D Aicher
- Department of Adult Psychiatry and Psychotherapy, Psychiatric University Clinic Zurich and University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
- Department of Psychology, University of Zurich, Zurich, Switzerland
| | - Paul Cumming
- Department of Nuclear Medicine, Bern University Hospital, Bern, Switzerland
- School of Psychology and Counselling, Queensland University of Technology, Brisbane, Australia
| | - Milan Scheidegger
- Department of Adult Psychiatry and Psychotherapy, Psychiatric University Clinic Zurich and University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
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Cumming P, Scheidegger M, Dornbierer D, Palner M, Quednow BB, Martin-Soelch C. Molecular and Functional Imaging Studies of Psychedelic Drug Action in Animals and Humans. Molecules 2021; 26:2451. [PMID: 33922330 PMCID: PMC8122807 DOI: 10.3390/molecules26092451] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 04/15/2021] [Accepted: 04/19/2021] [Indexed: 12/19/2022] Open
Abstract
Hallucinogens are a loosely defined group of compounds including LSD, N,N-dimethyltryptamines, mescaline, psilocybin/psilocin, and 2,5-dimethoxy-4-methamphetamine (DOM), which can evoke intense visual and emotional experiences. We are witnessing a renaissance of research interest in hallucinogens, driven by increasing awareness of their psychotherapeutic potential. As such, we now present a narrative review of the literature on hallucinogen binding in vitro and ex vivo, and the various molecular imaging studies with positron emission tomography (PET) or single photon emission computer tomography (SPECT). In general, molecular imaging can depict the uptake and binding distribution of labelled hallucinogenic compounds or their congeners in the brain, as was shown in an early PET study with N1-([11C]-methyl)-2-bromo-LSD ([11C]-MBL); displacement with the non-radioactive competitor ketanserin confirmed that the majority of [11C]-MBL specific binding was to serotonin 5-HT2A receptors. However, interactions at serotonin 5HT1A and other classes of receptors and pleotropic effects on second messenger pathways may contribute to the particular experiential phenomenologies of LSD and other hallucinogenic compounds. Other salient aspects of hallucinogen action include permeability to the blood-brain barrier, the rates of metabolism and elimination, and the formation of active metabolites. Despite the maturation of radiochemistry and molecular imaging in recent years, there has been only a handful of PET or SPECT studies of radiolabeled hallucinogens, most recently using the 5-HT2A/2C agonist N-(2[11CH3O]-methoxybenzyl)-2,5-dimethoxy- 4-bromophenethylamine ([11C]Cimbi-36). In addition to PET studies of target engagement at neuroreceptors and transporters, there is a small number of studies on the effects of hallucinogenic compounds on cerebral perfusion ([15O]-water) or metabolism ([18F]-fluorodeoxyglucose/FDG). There remains considerable scope for basic imaging research on the sites of interaction of hallucinogens and their cerebrometabolic effects; we expect that hybrid imaging with PET in conjunction with functional magnetic resonance imaging (fMRI) should provide especially useful for the next phase of this research.
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Affiliation(s)
- Paul Cumming
- Department of Nuclear Medicine, Bern University Hospital, CH-3010 Bern, Switzerland
- School of Psychology and Counselling, Queensland University of Technology, Brisbane 4059, Australia
| | - Milan Scheidegger
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital of the University of Zurich, CH-8032 Zurich, Switzerland; (M.S.); (D.D.); (B.B.Q.)
| | - Dario Dornbierer
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital of the University of Zurich, CH-8032 Zurich, Switzerland; (M.S.); (D.D.); (B.B.Q.)
| | - Mikael Palner
- Odense Department of Clinical Research, University of Southern Denmark, DK-5000 Odense, Denmark;
- Department of Nuclear Medicine, Odense University Hospital, DK-5000 Odense, Denmark
- Neurobiology Research Unit, Copenhagen University Hospital, DK-2100 Copenhagen, Denmark
| | - Boris B. Quednow
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital of the University of Zurich, CH-8032 Zurich, Switzerland; (M.S.); (D.D.); (B.B.Q.)
- Neuroscience Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, CH-8058 Zurich, Switzerland
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Subburaju S, Sromek AW, Seeman P, Neumeyer JL. The High Affinity Dopamine D 2 Receptor Agonist MCL-536: A New Tool for Studying Dopaminergic Contribution to Neurological Disorders. ACS Chem Neurosci 2021; 12:1428-1437. [PMID: 33844498 DOI: 10.1021/acschemneuro.1c00094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The dopamine D2 receptor exists in two different states, D2high and D2low; the former is the functional form of the D2 receptor and associates with intracellular G-proteins. The D2 agonist [3H]MCL-536 has high affinity for the D2 receptor (Kd 0.8 nM) and potently displaces the binding of (R-(-)-N-n-propylnorapomorphine (NPA; Ki 0.16 nM) and raclopride (Ki 0.9 nM) in competition binding assays. Here, we further characterize [3H]MCL-536. [3H]MCL-536 was metabolically stable, with about 75% of the compound remaining intact after 1 h incubation with human liver microsomes. Blood-brain barrier penetration in rats was good, attaining at 15 min a % injected dose per gram of wet tissue (%ID/g) of 0.28 in males versus 0.42 in females in the striatum. Specific uptake ratios ([%ID/g striatum]/[%ID/g cerebellum]) were stable in males during the first 60 min and in females up to 15-30 min. The D2-rich striatum exhibited the highest uptake and slowest washout compared to D2-poor cortex or cerebellum. In peripheral organs, uptake peaked at 15 min but declined to baseline at 60 min, indicating good clearance from the body. In vitro autoradiography on transaxial and coronal brain sections showed specific binding of [3H]MCL-536, which was abolished by preincubation with D2/D3 ligands sulpiride, NPA, and raclopride and in the presence of the stable GTP analogue guanylylimidodiphosphate. In amphetamine-sensitized animals, striatal binding was higher than in controls, indicating specificity for the D2high receptor state. [3H]MCL-536's unique properties make it a valuable tool for research on neurological disorders involving the dopaminergic system like Parkinson's disease or schizophrenia.
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Affiliation(s)
- Sivan Subburaju
- Division of Basic Neuroscience, Medicinal Chemistry Laboratory, McLean Hospital, Belmont, Massachusetts 02478, United States
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Anna W. Sromek
- Division of Basic Neuroscience, Medicinal Chemistry Laboratory, McLean Hospital, Belmont, Massachusetts 02478, United States
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Philip Seeman
- Departments of Pharmacology and Psychiatry, University of Toronto, 260 Heath St. West, unit 605, Toronto, Ontario M5P 3L6, Canada
| | - John L. Neumeyer
- Division of Basic Neuroscience, Medicinal Chemistry Laboratory, McLean Hospital, Belmont, Massachusetts 02478, United States
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115, United States
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Colom M, Vidal B, Zimmer L. Is There a Role for GPCR Agonist Radiotracers in PET Neuroimaging? Front Mol Neurosci 2019; 12:255. [PMID: 31680859 PMCID: PMC6813225 DOI: 10.3389/fnmol.2019.00255] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/02/2019] [Indexed: 12/30/2022] Open
Abstract
Positron emission tomography (PET) is a molecular imaging modality that enables in vivo exploration of metabolic processes and especially the pharmacology of neuroreceptors. G protein-coupled receptors (GPCRs) play an important role in numerous pathophysiologic disorders of the central nervous system. Thus, they are targets of choice in PET imaging to bring proof concept of change in density in pathological conditions or in pharmacological challenge. At present, most radiotracers are antagonist ligands. In vitro data suggest that properties differ between GPCR agonists and antagonists: antagonists bind to receptors with a single affinity, whereas agonists are characterized by two different affinities: high affinity for receptors that undergo functional coupling to G-proteins, and low affinity for those that are not coupled. In this context, agonist radiotracers may be useful tools to give functional images of GPCRs in the brain, with high sensitivity to neurotransmitter release. Here, we review all existing PET radiotracers used from animals to humans and their role for understanding the ligand-receptor paradigm of GPCR in comparison with corresponding antagonist radiotracers.
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Affiliation(s)
- Matthieu Colom
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France
| | - Benjamin Vidal
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France
| | - Luc Zimmer
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France.,Institut National des Sciences et Techniques Nucléaires, CEA Saclay, Gif-sur-Yvette, France
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Park J, Wakabayashi KT, Szalkowski C, Bhimani RV. Heterogeneous extracellular dopamine regulation in the subregions of the olfactory tubercle. J Neurochem 2017; 142:365-377. [PMID: 28498499 DOI: 10.1111/jnc.14069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 04/04/2017] [Accepted: 04/26/2017] [Indexed: 12/01/2022]
Abstract
Recent studies show that dense dopamine (DA) innervation from the ventral tegmental area to the olfactory tubercle (OT) may play an important role in processing multisensory information pertaining to arousal and reward, yet little is known about DA regulation in the OT. This is mainly due to the anatomical limitations of conventional methods of determining DA dynamics in small heterogeneous OT subregions located in the ventral most part of the brain. Additionally, there is increasing awareness that anteromedial and anterolateral subregions of the OT have distinct functional roles in natural and psychostimulant drug reinforcement as well as in regulating other types of behavioral responses, such as aversion. Here, we compared extracellular DA regulation (release and clearance) in three subregions (anteromedial, anterolateral, and posterior) of the OT of urethane-anesthetized rats, using in vivo fast-scan cyclic voltammetry following electrical stimulation of ventral tegmental area dopaminergic cell bodies. The neurochemical, anatomical, and pharmacological evidence confirmed that the major electrically evoked catecholamine in the OT was DA across both its anteroposterior and mediolateral extent. While both D2 autoreceptors and DA transporters play important roles in regulating DA evoked in OT subregions, DA in the anterolateral OT was regulated less by the D2 receptors when compared to other OT subregions. Comparing previous data from other DA rich ventral striatum regions, the slow DA clearance across the OT subregions may lead to a high extracellular DA concentration and contribute towards volume transmission. These differences in DA regulation in the terminals of OT subregions and other limbic structures will help us understand the neural regulatory mechanisms of DA in the OT, which may elucidate its distinct functional contribution in the ventral striatum towards mediating aversion, reward and addiction processes.
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Affiliation(s)
- Jinwoo Park
- Department of Biotechnical and Clinical Laboratory Sciences, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA.,Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA.,Neuroscience Program, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA
| | - Ken T Wakabayashi
- Department of Biotechnical and Clinical Laboratory Sciences, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA.,Research Institute on Addictions, University at Buffalo, State University of New York, Buffalo, New York, USA
| | - Caitlin Szalkowski
- Department of Biotechnical and Clinical Laboratory Sciences, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA
| | - Rohan V Bhimani
- Neuroscience Program, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, USA
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Harada A, Suzuki K, Miura S, Hasui T, Kamiguchi N, Ishii T, Taniguchi T, Kuroita T, Takano A, Stepanov V, Halldin C, Kimura H. Characterization of the binding properties of T-773 as a PET radioligand for phosphodiesterase 10A. Nucl Med Biol 2014; 42:146-54. [PMID: 25451212 DOI: 10.1016/j.nucmedbio.2014.09.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 09/02/2014] [Accepted: 09/04/2014] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Phosphodiesterase 10A (PDE10A) is a dual-substrate PDE that hydrolyzes both cAMP and cGMP and is selectively expressed in striatal medium spiny neurons. Recent studies have suggested that PDE10A inhibition is a novel approach for the treatment of disorders such as schizophrenia and Huntington's disease. A positron emission tomography (PET) occupancy study can provide useful information for the development of PDE10A inhibitors. We discovered T-773 as a candidate PET radioligand for PDE10A and investigated its properties by in vitro autoradiography and a PET study in a monkey. METHODS Profiling of T-773 as a PET radioligand for PDE10A was conducted by in vitro enzyme inhibitory assay, in vitro autoradiography, and PET study in a monkey. RESULTS T-773 showed a high binding affinity and selectivity for human recombinant PDE10A2 in vitro; the IC50 value in an enzyme inhibitory assay was 0.77nmol/L, and selectivity over other PDEs was more than 2500-fold. In autoradiography studies using mouse, rat, monkey, or human brain sections, radiolabeled T-773 selectively accumulated in the striatum. This selective accumulation was not observed in the brain sections of Pde10a-KO mice. The binding of [(3)H]T-773 to PDE10A in rat brain sections was competitively inhibited by MP-10, a selective PDE10A inhibitor. In rat brain sections, [(3)H]T-773 bound to a single high affinity site of PDE10A with Kd values of 12.2±2.2 and 4.7±1.2nmol/L in the caudate-putamen and nucleus accumbens, respectively. In a monkey PET study, [(11)C]T-773 showed good brain penetration and striatum-selective accumulation. CONCLUSION These results suggest that [(11)C]T-773 is a potential PET radioligand for PDE10A.
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Affiliation(s)
- Akina Harada
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Kazunori Suzuki
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Shotaro Miura
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Tomoaki Hasui
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Naomi Kamiguchi
- Drug Metabolism and Pharmacokinetics Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Tsuyoshi Ishii
- Biomolecular Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Takahiko Taniguchi
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Takanobu Kuroita
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Akihiro Takano
- Center for Psychiatric Research, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Vladimir Stepanov
- Center for Psychiatric Research, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Christer Halldin
- Center for Psychiatric Research, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Haruhide Kimura
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Japan.
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Janowsky A, Eshleman AJ, Johnson RA, Wolfrum KM, Hinrichs DJ, Yang J, Zabriskie TM, Smilkstein MJ, Riscoe MK. Mefloquine and psychotomimetics share neurotransmitter receptor and transporter interactions in vitro. Psychopharmacology (Berl) 2014; 231:2771-83. [PMID: 24488404 PMCID: PMC4097020 DOI: 10.1007/s00213-014-3446-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 01/07/2014] [Indexed: 11/25/2022]
Abstract
RATIONALE Mefloquine is used for the prevention and treatment of chloroquine-resistant malaria, but its use is associated with nightmares, hallucinations, and exacerbation of symptoms of post-traumatic stress disorder. We hypothesized that potential mechanisms of action for the adverse psychotropic effects of mefloquine resemble those of other known psychotomimetics. OBJECTIVES Using in vitro radioligand binding and functional assays, we examined the interaction of (+)- and (-)-mefloquine enantiomers, the non-psychotomimetic anti-malarial agent, chloroquine, and several hallucinogens and psychostimulants with recombinant human neurotransmitter receptors and transporters. RESULTS Hallucinogens and mefloquine bound stereoselectively and with relatively high affinity (K i = 0.71-341 nM) to serotonin (5-HT) 2A but not 5-HT1A or 5-HT2C receptors. Mefloquine but not chloroquine was a partial 5-HT2A agonist and a full 5-HT2C agonist, stimulating inositol phosphate accumulation, with similar potency and efficacy as the hallucinogen dimethyltryptamine (DMT). 5-HT receptor antagonists blocked mefloquine's effects. Mefloquine had low or no affinity for dopamine D1, D2, D3, and D4.4 receptors, or dopamine and norepinephrine transporters. However, mefloquine was a very low potency antagonist at the D3 receptor and mefloquine but not chloroquine or hallucinogens blocked [(3)H]5-HT uptake by the 5-HT transporter. CONCLUSIONS Mefloquine, but not chloroquine, shares an in vitro receptor interaction profile with some hallucinogens and this neurochemistry may be relevant to the adverse neuropsychiatric effects associated with mefloquine use by a small percentage of patients. Additionally, evaluating interactions with this panel of receptors and transporters may be useful for characterizing effects of other psychotropic drugs and for avoiding psychotomimetic effects for new pharmacotherapies, including antimalarial quinolines.
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Affiliation(s)
- Aaron Janowsky
- Research Service (R&D22), VA Medical Center, 3710 SW US Veterans Hospital Road, Portland, OR, 97239, USA,
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van Veghel D, Cleynhens J, Pearce LV, DeAndrea-Lazarus IA, Blumberg PM, Van Laere K, Verbruggen A, Bormans G. New transient receptor potential vanilloid subfamily member 1 positron emission tomography radioligands: synthesis, radiolabeling, and preclinical evaluation. ACS Chem Neurosci 2013; 4:624-34. [PMID: 23421633 DOI: 10.1021/cn300233v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The transient receptor potential vanilloid subfamily member 1 (TRPV1) cation channel is known to be involved in pain nociception and neurogenic inflammation, and accumulating evidence suggests that it plays an important role in several central nervous system (CNS)-related disorders. TRPV1-specific positron emission tomography (PET) radioligands can serve as powerful tools in TRPV1-related (pre)clinical research and drug design. We have synthesized several potent TRPV1 antagonists and accompanying precursors for radiolabeling with carbon-11 or fluorine-18. The cinnamic acid derivative [(11)C]DVV24 and the aminoquinazoline [(18)F]DVV54 were successfully synthesized, and their biological behavior was studied. In addition, the in vivo behavior of a (123)I-labeled analogue of iodo-resiniferatoxin (I-RTX), a well-known TRPV1 antagonist, was evaluated. The binding affinities of DVV24 and DVV54 for human TRPV1 were 163 ± 28 and 171 ± 48 nM, respectively. [(11)C]DVV24, but not [(18)F]DVV54 or (123)I-RTX, showed retention in the trigeminal nerve, known to abundantly express TRPV1. Nevertheless, it appears that ligands with higher binding affinities will be required to allow in vivo imaging of TRPV1 via PET.
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Affiliation(s)
- Daisy van Veghel
- Laboratory for Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49 box 821, 3000 Leuven, Belgium
| | - Jan Cleynhens
- Laboratory for Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49 box 821, 3000 Leuven, Belgium
| | - Larry V. Pearce
- Laboratory of Cancer Biology and
Genetics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 37, Room 4048,
37 Convent Drive, MSC 4255, Bethesda, Maryland 20892-4255, United
States
| | - Ian A. DeAndrea-Lazarus
- Laboratory of Cancer Biology and
Genetics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 37, Room 4048,
37 Convent Drive, MSC 4255, Bethesda, Maryland 20892-4255, United
States
| | - Peter M. Blumberg
- Laboratory of Cancer Biology and
Genetics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 37, Room 4048,
37 Convent Drive, MSC 4255, Bethesda, Maryland 20892-4255, United
States
| | - Koen Van Laere
- Nuclear Medicine and
Molecular Imaging, University Hospital and KU Leuven, Leuven, Belgium
| | - Alfons Verbruggen
- Laboratory for Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49 box 821, 3000 Leuven, Belgium
| | - Guy Bormans
- Laboratory for Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Campus Gasthuisberg O&N2, Herestraat 49 box 821, 3000 Leuven, Belgium
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Farkas S, Nagy K, Jia Z, Hortobágyi T, Varrone A, Halldin C, Csiba L, Gulyás B. Signal transduction pathway activity compensates dopamine D₂/D₃ receptor density changes in Parkinson's disease: a preliminary comparative human brain receptor autoradiography study with [³H]raclopride and [³⁵S]GTPγS. Brain Res 2012; 1453:56-63. [PMID: 22480734 DOI: 10.1016/j.brainres.2012.03.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 03/05/2012] [Accepted: 03/06/2012] [Indexed: 11/25/2022]
Abstract
The degeneration of dopaminergic nigrostriatal pathway in Parkinson's disease (PD) results in alterations of the dopamine receptor system. In the present study we have investigated the relationship between the disease related changes of expressed dopamine D₂/D₃ receptor density and the corresponding intracellular signal transduction route in cortical and sub-cortical brain structures in the human brain. Dopamine D₂/D₃ receptor autoradiography (ARG), using [³H]raclopride, and agonist stimulated [³⁵S]GTPγS (guanosine 5'-O-[γ-thio]triphosphate) binding autoradiography have been performed in human striatum, cingulate gyrus and medial frontal gyrus samples obtained from six deceased PD patients and six age matched control subjects. Receptor densities were expressed as fmol/gram tissue protein for [³H]raclopride; agonist stimulated [³⁵S]GTPγS binding was expressed in fmol/gram tissue and its change was expressed in percentage values above basal binding. Our results indicate that whereas there is a decrease of the dopamine D₂/D₃ receptors in the striatum demonstrated by classical receptor autoradiography (controls and PD: 24.08±2.06 fmol/gram (mean±SEM) and 18.43±2.82 fmol/gram, respectively; p<0.05), the corresponding agonist stimulated [³⁵S]GTPγS binding autoradiography shows unchanged basal [³⁵S]GTPγS binding (controls and PD: 199±17 fmol/g and 198±21 fmol/g, respectively; n.s.) and, at the same time, no change in stimulation (controls and PD: 0.40±4.57% and 1.51±2.27%, respectively; n.s.). In cingular gyrus and medial frontal gyrus neither the dopamine D₂/D₃ receptor densities nor the [³⁵S]GTPγS binding displayed significant differences between PD and age matched control brain samples, whereas the [³⁵S]GTPγS binding values were markedly higher in PD. These preliminary findings may indicate a possible compensatory mechanism in striatal regions of PD brains: the loss of the dopamine receptors in the striatum appears to be compensated by an increased post-synaptic intracellular signal transduction route activity. However, the accurate interpretation of the present findings requires detailed further studies.
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Affiliation(s)
- Szabolcs Farkas
- Department of Neurology, University of Debrecen Medical and Health Science Center, H-4012 Debrecen, Hungary
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Farkas S, Nagy K, Jia Z, Harkany T, Palkovits M, Donohou SR, Pike VW, Halldin C, Máthé D, Csiba L, Gulyás B. The decrease of dopamine D₂/D₃ receptor densities in the putamen and nucleus caudatus goes parallel with maintained levels of CB₁ cannabinoid receptors in Parkinson's disease: a preliminary autoradiographic study with the selective dopamine D₂/D₃ antagonist [³H]raclopride and the novel CB₁ inverse agonist [¹²⁵I]SD7015. Brain Res Bull 2012; 87:504-10. [PMID: 22421165 DOI: 10.1016/j.brainresbull.2012.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 02/28/2012] [Indexed: 01/24/2023]
Abstract
Cannabinoid type-1 receptors (CB₁Rs) modulate synaptic neurotransmission by participating in retrograde signaling in the adult brain. Increasing evidence suggests that cannabinoids through CB₁Rs play an important role in the regulation of motor activities in the striatum. In the present study, we used human brain samples to examine the relationship between CB₁R and dopamine receptor density in case of Parkinson's disease (PD). Post mortem putamen, nucleus caudatus and medial frontal gyrus samples obtained from PD patients were used for CB₁R and dopamine D₂/D₃ receptor autoradiography. [¹²⁵I]SD7015, a novel selective CB₁R inverse agonist, developed by a number of the present co-authors, and [³H]raclopride, a dopamine D₂/D₃ antagonist, were used as radioligands. Our results demonstrate unchanged CB₁R density in the putamen and nucleus caudatus of deceased PD patients, treated with levodopa (L-DOPA). At the same time dopamine D₂/D₃ receptors displayed significantly decreased density levels in case of PD putamen (control: 47.97 ± 10.00 fmol/g, PD: 3.73 ± 0.07 fmol/g (mean ± SEM), p<0.05) and nucleus caudatus (control: 30.26 ± 2.48 fmol/g, PD: 12.84 ± 5.49 fmol/g, p<0.0005) samples. In contrast to the putamen and the nucleus caudatus, in the medial frontal gyrus neither receptor densities were affected. Our data suggest the presence of an unaltered CB₁R population even in late stages of levodopa treated PD. This further supports the presence of an intact CB₁R population which, in line with the conclusion of earlier publications, may be utilized as a pharmacological target in the treatment of PD. Furthermore we found discrepancy between a maintained CB₁R population and a decreased dopamine D₂/D₃ receptor population in PD striatum. The precise explanation of this conundrum requires further studies with simultaneous examination of the central cannabinoid and dopaminergic systems in PD using higher sample size.
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Affiliation(s)
- Szabolcs Farkas
- Department of Neurology, University of Debrecen, H-4012 Debrecen, Hungary
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Cumming P. Absolute abundances and affinity states of dopamine receptors in mammalian brain: A review. Synapse 2011; 65:892-909. [DOI: 10.1002/syn.20916] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 01/14/2011] [Indexed: 12/14/2022]
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Palner M, Kjaerby C, Knudsen GM, Cumming P. Effects of unilateral 6-OHDA lesions on [3H]-N-propylnorapomorphine binding in striatum ex vivo and vulnerability to amphetamine-evoked dopamine release in rat. Neurochem Int 2011; 58:243-7. [DOI: 10.1016/j.neuint.2010.12.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 12/01/2010] [Accepted: 12/06/2010] [Indexed: 11/16/2022]
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