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Siemian JN, Woodhouse K, Liu DH, Zhang Y, Li JX. The imidazoline I 2 receptor agonist 2-BFI reduces abuse-related effects of morphine: self-administration and drug discrimination. Psychopharmacology (Berl) 2024; 241:479-487. [PMID: 38159161 DOI: 10.1007/s00213-023-06524-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 12/22/2023] [Indexed: 01/03/2024]
Abstract
RATIONALE Increasing evidence shows that imidazoline I2 receptor agonists enhance opioid-induced analgesia, suggesting that the combination of I2 receptor agonists with opioids could be a favorable strategy for pain control. However, the effect of I2 receptor agonists on the abuse liability of opioids is unknown. This study examined the impact of the I2 receptor agonist 2-BFI on some abuse-related behavioral effects of the opioid morphine in rats. OBJECTIVES The von Frey filament test was used to determine the antinociceptive effects of 2-BFI (intravenous, i.v.) in a rat model of complete Freund's adjuvant (CFA)-induced inflammatory pain. IV self-administration was used to assess the reinforcing effects of 2-BFI alone and to assess the effects of non-contingent injections of 2-BFI (i.p.) on morphine self-administration. A two-lever drug discrimination paradigm in which rats were trained to discriminate 3.2 mg/kg morphine (i.p.) from saline was used to examine whether 2-BFI or another I2 receptor agonist 2-(4,5-dihydroimidazol-2-yl)quinoline hydrochloride (BU224) affected the discriminative stimulus effects of morphine. RESULTS 2-BFI could not maintain reliable self-administration behavior in rats with no pain or CFA-treated inflammatory pain. However, pretreatment with 2-BFI (i.p.) produced dose-dependent decreases in the dose-effect curve of morphine self-administration. Both 2-BFI and BU224 did not substitute for morphine but significantly attenuated the discriminative stimulus effects of morphine. CONCLUSIONS These results suggest that I2 receptor agonists do not enhance, but in fact appear to decrease, the abuse liability of opioids, further supporting the potential utility of I2 receptor agonist-opioid combination therapy for pain control.
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Affiliation(s)
- Justin N Siemian
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Kristen Woodhouse
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | | | - Yanan Zhang
- Research Triangle Institute, Research Triangle Park, NC, USA
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA.
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2
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Parker CA, Nutt DJ, Tyacke RJ. Imidazoline-I2 PET Tracers in Neuroimaging. Int J Mol Sci 2023; 24:9787. [PMID: 37372936 DOI: 10.3390/ijms24129787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 05/24/2023] [Accepted: 05/26/2023] [Indexed: 06/29/2023] Open
Abstract
Targeting neuroinflammation, and in particular, microglial activation and astrocytosis, is a current area of the focus of new treatment interventions for a number of neurodegenerative disorders. Probing the roles of microglia and astrocytes in human disease requires the development of useful tools, such as PET imaging tools that are specific for the cell type(s) of interest. This review concentrates on the recent advances in the development of Imidazoline2 binding site (I2BS) PET tracers, which are purported to target astrocytes, and hence could represent key clinical imaging tools for targeting astrocytes in neurodegenerative disease. Five PET tracers for the I2BS are described in this review, with only one (11C-BU99008) being currently validated to GMP for clinical use, and data reported from healthy volunteers, Alzheimer's disease patients, and Parkinson's disease patients. The clinical data utilising 11C-BU99008 have revealed the potential early involvement of astrogliosis in neurodegeneration that might precede the activation of microglia, which, if confirmed, could provide a vital new means for potentially targeting neurodegeneration earlier in the disease course.
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Affiliation(s)
- Christine A Parker
- Neuropsychopharmacology Unit, Division of Psychiatry, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, UK
| | - David J Nutt
- Neuropsychopharmacology Unit, Division of Psychiatry, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Robin J Tyacke
- Neuropsychopharmacology Unit, Division of Psychiatry, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
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3
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Singh P, Singh D, Srivastava P, Mishra G, Tiwari AK. Evaluation of advanced, pathophysiologic new targets for imaging of CNS. Drug Dev Res 2023; 84:484-513. [PMID: 36779375 DOI: 10.1002/ddr.22040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 12/12/2022] [Accepted: 12/31/2022] [Indexed: 02/14/2023]
Abstract
The inadequate information about the in vivo pathological, physiological, and neurological impairments, as well as the absence of in vivo tools for assessing brain penetrance and the efficiency of newly designed drugs, has hampered the development of new techniques for the treatment for variety of new central nervous system (CNS) diseases. The searching sites such as Science Direct and PubMed were used to find out the numerous distinct tracers across 16 CNS targets including tau, synaptic vesicle glycoprotein, the adenosine 2A receptor, the phosphodiesterase enzyme PDE10A, and the purinoceptor, among others. Among the most encouraging are [18 F]FIMX for mGluR imaging, [11 C]Martinostat for Histone deacetylase, [18 F]MNI-444 for adenosine 2A imaging, [11 C]ER176 for translocator protein, and [18 F]MK-6240 for tau imaging. We also reviewed the findings for each tracer's features and potential for application in CNS pathophysiology and therapeutic evaluation investigations, including target specificity, binding efficacy, and pharmacokinetic factors. This review aims to present a current evaluation of modern positron emission tomography tracers for CNS targets, with a focus on recent advances for targets that have newly emerged for imaging in humans.
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Affiliation(s)
- Priya Singh
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University, Lucknow, Uttar Pradesh, India
| | - Deepika Singh
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University, Lucknow, Uttar Pradesh, India
| | - Pooja Srivastava
- Division of Cyclotron and Radiopharmaceuticals Sciences, Institute of Nuclear Medicine and Allied Sciences, Delhi, India
| | - Gauri Mishra
- Department of Zoology, Swami Shraddhananad College, University of Delhi, Alipur, Delhi, India
| | - Anjani K Tiwari
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University, Lucknow, Uttar Pradesh, India
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4
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Hernández-Hernández E, Ledesma-Corvi S, Yáñez-Gómez F, Garau C, Gálvez-Melero L, Bagán A, Escolano C, García-Fuster MJ. Sex differences in the antidepressant-like response and molecular events induced by the imidazoline-2 receptor agonist CR4056 in rats. Pharmacol Biochem Behav 2023; 223:173527. [PMID: 36781025 DOI: 10.1016/j.pbb.2023.173527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 02/08/2023] [Accepted: 02/08/2023] [Indexed: 02/13/2023]
Abstract
In searching for novel targets to design antidepressants, among the characterized imidazoline receptors (IR), I2 receptors are an innovative therapeutical approach since they are dysregulated in major depressive disorder and by classical antidepressant treatments. In fact, several I2 agonists have been characterized for their antidepressant-like potential, but the results in terms of efficacy were mixed and exclusively reported in male rodents. Since there are well-known sex differences in antidepressant-like efficacy, this study characterized the potential effects induced by two I2 drugs, CR4056 (i.e., most promising drug already in phase II clinical trial for its analgesic properties) and B06 (a compound from a new family of bicyclic α-iminophosphonates) under the stress of the forced-swim test in male and female rats exposed to early-life stress. Moreover, some hippocampal neuroplasticity markers related to the potential effects observed were also evaluated (i.e., FADD, p-ERK/ERK, mBDNF, cell proliferation: Ki-67 + cells). The main results replicated the only prior study reporting the efficacy of CR4056 in male rats, while providing new data on its efficacy in females, which was clearly dependent on prior early-life stress exposure. Moreover, B06 showed no antidepressant-like effects in male or female rats. Finally, CR4056 increased FADD content and decreased cell proliferation in hippocampus, without affecting p-ERK/t-ERK ratio and/or mBDNF content. Interestingly, these effects were exclusively observed in female rats, and independently of early-life conditions, suggesting some distinctive molecular underpinnings participating in the therapeutic response of CR4056 for both sexes. In conjunction, these results present CR4056 with an antidepressant-like potential, especially in female rats exposed to stress early in life, together with some neuronal correlates described in the context of these behavioral changes in females.
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Affiliation(s)
- Elena Hernández-Hernández
- IUNICS, University of the Balearic Islands, Palma, Spain; Health Research Institute of the Balearic Islands (IdISBa), Palma, Spain
| | - Sandra Ledesma-Corvi
- IUNICS, University of the Balearic Islands, Palma, Spain; Health Research Institute of the Balearic Islands (IdISBa), Palma, Spain
| | - Fernando Yáñez-Gómez
- IUNICS, University of the Balearic Islands, Palma, Spain; Health Research Institute of the Balearic Islands (IdISBa), Palma, Spain
| | - Celia Garau
- IUNICS, University of the Balearic Islands, Palma, Spain; Health Research Institute of the Balearic Islands (IdISBa), Palma, Spain
| | - Laura Gálvez-Melero
- IUNICS, University of the Balearic Islands, Palma, Spain; Health Research Institute of the Balearic Islands (IdISBa), Palma, Spain
| | - Andrea Bagán
- Laboratory of Medicinal Chemistry (Associated Unit to CSIC), Department of Pharmacology, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
| | - Carmen Escolano
- Laboratory of Medicinal Chemistry (Associated Unit to CSIC), Department of Pharmacology, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
| | - M Julia García-Fuster
- IUNICS, University of the Balearic Islands, Palma, Spain; Health Research Institute of the Balearic Islands (IdISBa), Palma, Spain.
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Jiménez-Altayó F, Cabrera A, Bagán A, Giménez-Llort L, D’Ocon P, Pérez B, Pallàs M, Escolano C. An Imidazoline 2 Receptor Ligand Relaxes Mouse Aorta via Off-Target Mechanisms Resistant to Aging. Front Pharmacol 2022; 13:826837. [PMID: 35645795 PMCID: PMC9133327 DOI: 10.3389/fphar.2022.826837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/26/2022] [Indexed: 11/13/2022] Open
Abstract
Imidazoline receptors (IR) are classified into three receptor subtypes (I1R, I2R, and I3R) and previous studies showed that regulation of I2R signaling has neuroprotective potential. In order to know if I2R has a role in modulating vascular tone in health and disease, we evaluated the putative vasoactive effects of two recently synthesized I2R ligands, diethyl (1RS,3aSR,6aSR)-5-(3-chloro-4-fluorophenyl)-4,6-dioxo-1-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole -1-phosphonate (B06) and diethyl [(1-(3-chloro-4-fluorobenzyl)-5,5-dimethyl-4-phenyl-4,5-dihydro-1H-imidazol-4-yl]phosphonate] (MCR5). Thoracic aortas from Oncins France 1 (3- to 4-months-old) and C57BL/6 (3- to 4- and 16- to 17-months-old mice) were mounted in tissue baths to measure isometric tension. In young mice of both strains, MCR5 induced greater relaxations than either B06 or the high-affinity I2R selective ligand 2-(2-benzofuranyl)-2-imidazoline (2-BFI), which evoked marginal responses. MCR5 relaxations were independent of I2R, as IR ligands did not significantly affect them, involved activation of smooth muscle KATP channels and inhibition of L-type voltage-gated Ca2+ channels, and were only slightly modulated by endothelium-derived nitric oxide (negatively) and prostacyclin (positively). Notably, despite the presence of endothelial dysfunction in old mice, MCR5 relaxations were preserved. In conclusion, the present study provides evidence against a functional contribution of I2R in the modulation of vascular tone in the mouse aorta. Moreover, the I2R ligand MCR5 is an endothelium-independent vasodilator that acts largely via I2R-independent pathways and is resistant to aging. We propose MCR5 as a candidate drug for the management of vascular disease in the elderly.
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Affiliation(s)
- Francesc Jiménez-Altayó
- Department of Pharmacology, Therapeutics and Toxicology, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
- *Correspondence: Francesc Jiménez-Altayó,
| | - Anna Cabrera
- Department of Pharmacology, Therapeutics and Toxicology, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Andrea Bagán
- Laboratory of Medicinal Chemistry (Associated Unit to CSIC), Department of Pharmacology, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
| | - Lydia Giménez-Llort
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
- Department of Psychiatry and Forensic Medicine, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Pilar D’Ocon
- Department of Pharmacology, School of Medicine, Universidad de Valencia, Burjassot, Spain
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universidad de Valencia, Valencia, Spain
| | - Belén Pérez
- Department of Pharmacology, Therapeutics and Toxicology, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Mercè Pallàs
- Pharmacology Section, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, Institut de Neurociències, University of Barcelona, Barcelona, Spain
| | - Carmen Escolano
- Laboratory of Medicinal Chemistry (Associated Unit to CSIC), Department of Pharmacology, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
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6
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Evaluating the effects of 2-BFI and tracizoline, two potent I2-imidazoline receptor agonists, on cognitive performance and affect in middle-aged rats. Naunyn Schmiedebergs Arch Pharmacol 2021; 394:989-996. [DOI: 10.1007/s00210-020-02042-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/13/2020] [Indexed: 01/01/2023]
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7
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Hernández-Hernández E, García-Sevilla JA, García-Fuster MJ. Exploring the antidepressant-like potential of the selective I2-imidazoline receptor ligand LSL 60101 in adult male rats. Pharmacol Rep 2020; 73:288-295. [DOI: 10.1007/s43440-020-00148-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/06/2020] [Accepted: 07/24/2020] [Indexed: 12/11/2022]
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McCluskey SP, Plisson C, Rabiner EA, Howes O. Advances in CNS PET: the state-of-the-art for new imaging targets for pathophysiology and drug development. Eur J Nucl Med Mol Imaging 2020; 47:451-489. [PMID: 31541283 PMCID: PMC6974496 DOI: 10.1007/s00259-019-04488-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 08/15/2019] [Indexed: 02/07/2023]
Abstract
PURPOSE A limit on developing new treatments for a number of central nervous system (CNS) disorders has been the inadequate understanding of the in vivo pathophysiology underlying neurological and psychiatric disorders and the lack of in vivo tools to determine brain penetrance, target engagement, and relevant molecular activity of novel drugs. Molecular neuroimaging provides the tools to address this. This article aims to provide a state-of-the-art review of new PET tracers for CNS targets, focusing on developments in the last 5 years for targets recently available for in-human imaging. METHODS We provide an overview of the criteria used to evaluate PET tracers. We then used the National Institute of Mental Health Research Priorities list to identify the key CNS targets. We conducted a PubMed search (search period 1st of January 2013 to 31st of December 2018), which yielded 40 new PET tracers across 16 CNS targets which met our selectivity criteria. For each tracer, we summarised the evidence of its properties and potential for use in studies of CNS pathophysiology and drug evaluation, including its target selectivity and affinity, inter and intra-subject variability, and pharmacokinetic parameters. We also consider its potential limitations and missing characterisation data, but not specific applications in drug development. Where multiple tracers were present for a target, we provide a comparison of their properties. RESULTS AND CONCLUSIONS Our review shows that multiple new tracers have been developed for proteinopathy targets, particularly tau, as well as the purinoceptor P2X7, phosphodiesterase enzyme PDE10A, and synaptic vesicle glycoprotein 2A (SV2A), amongst others. Some of the most promising of these include 18F-MK-6240 for tau imaging, 11C-UCB-J for imaging SV2A, 11C-CURB and 11C-MK-3168 for characterisation of fatty acid amide hydrolase, 18F-FIMX for metabotropic glutamate receptor 1, and 18F-MNI-444 for imaging adenosine 2A. Our review also identifies recurrent issues within the field. Many of the tracers discussed lack in vivo blocking data, reducing confidence in selectivity. Additionally, late-stage identification of substantial off-target sites for multiple tracers highlights incomplete pre-clinical characterisation prior to translation, as well as human disease state studies carried out without confirmation of test-retest reproducibility.
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Affiliation(s)
- Stuart P McCluskey
- Invicro LLC, A Konica Minolta Company, Burlington Danes Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK.
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, UK.
| | - Christophe Plisson
- Invicro LLC, A Konica Minolta Company, Burlington Danes Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Eugenii A Rabiner
- Invicro LLC, A Konica Minolta Company, Burlington Danes Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Oliver Howes
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, UK
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Siemian JN, Shang L, Seaman RW, Zhu Q, Zhang Y, Li JX. Effects of imidazoline I2 receptor agonists on reserpine-induced hyperalgesia and depressive-like behavior in rats. Behav Pharmacol 2019; 30:429-434. [PMID: 30383551 PMCID: PMC6494737 DOI: 10.1097/fbp.0000000000000454] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Pharmacotherapies for fibromyalgia treatment are lacking. This study examined the antinociceptive and antidepressant-like effects of imidazoline I2 receptor (I2R) agonists in a reserpine-induced model of fibromyalgia in rats. Rats were treated for 3 days with vehicle or reserpine. The von Frey filament test was used to assess the antinociceptive effects of I2 receptor agonists, and the forced swim test was used to assess the antidepressant-like effects of these drugs. 2-BFI (3.2-10 mg/kg, intraperitoneally), phenyzoline (17.8-56 mg/kg, intraperitoneally), and CR4056 (3.2-10 mg/kg, intraperitoneally) all dose-dependently produced significant antinociceptive effects, which were attenuated by the I2R antagonist idazoxan. Only CR4056 significantly reduced the immobility time in the forced swim test in both vehicle-treated and reserpine-treated rats. These data suggest that I2R agonists may be useful to treat fibromyalgia-related pain and comorbid depression.
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Affiliation(s)
- Justin N. Siemian
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, New York, USA
| | - Li Shang
- Department of Nursing, Affiliated Yantai Hospital of Binzhou Medical University, Yantai, Shandong, China
| | - Robert W. Seaman
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, New York, USA
| | - Qing Zhu
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, New York, USA
- School of Pharmacy, Nantong University, Nantong, Jiangsu, China
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle Park, North Carolina, USA
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, New York, USA
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10
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Change in the Binding of [ 11C]BU99008 to Imidazoline I 2 Receptor Using Brain PET in Zucker Rats. Mol Imaging Biol 2018; 21:105-112. [PMID: 29736564 DOI: 10.1007/s11307-018-1206-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
PURPOSE The imdazoline I2 receptor (I2R) has been found in the feeding centers of the brain, such as the hypothalamus, and certain I2R ligands have been reported to stimulate food intake. Thus, it has been proposed that I2R may play a role in feeding control. [11C]BU99008 was developed as a positron emission tomography (PET) tracer for imaging of I2R. [11C]BU99008 displayed relatively high brain penetration and specific binding by brain PET studies in preclinical studies. Here, we evaluated a pathological condition caused by obesity related to I2R function by quantitative PET study using [11C]BU99008. PROCEDURES PET scans were acquired in the Zucker (ZUC) lean and fatty rats, radioactivity and metabolites of plasma were measured, and the kinetic parameters were estimated. RESULTS Radioactivity levels after the injection of [11C]BU99008 in the hypothalamus of both ZUC lean and fatty rats were highly accumulated, and then gradually decreased until 60 min after the injection. The accumulated radioactivity from 30 to 60 min after the injection in the hypothalamus of the ZUC fatty rats was 1.3 times greater than that of lean rats. The volume of distribution (VT) estimated by Logan graphical analysis in the hypothalamus of the ZUC fatty rats was 1.8 times greater than that in the ZUC lean rats. In metabolite analysis, the percentages of the unchanged form in the plasma of the ZUC fatty rats at 60 min after the injection (5.0 %) was significantly lower than that of lean rats (9.1 %). CONCLUSIONS By PET imaging using [11C]BU99008, we demonstrated that the accumulated radioactivity and estimated VT value in the feeding center of ZUC lean rats was lower than that in fatty rats. PET studies using [11C]BU99008 may contribute to elucidate a pathological condition caused by obesity related to I2R function.
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11
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Siemian JN, Wang K, Zhang Y, Li JX. Mechanisms of imidazoline I 2 receptor agonist-induced antinociception in rats: involvement of monoaminergic neurotransmission. Br J Pharmacol 2018; 175:1519-1534. [PMID: 29451703 DOI: 10.1111/bph.14161] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 12/17/2017] [Accepted: 02/04/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE Although the antinociceptive efficacies of imidazoline I2 receptor agonists have been established, the exact post-receptor mechanisms remain unknown. This study tested the hypothesis that monoaminergic transmission is critical for I2 receptor agonist-induced antinociception. EXPERIMENTAL APPROACH von Frey filaments were used to assess antinociceptive effects of two I2 receptor agonists, 2-BFI and CR4056 on chronic constriction injury (CCI)-induced neuropathic pain or complete Freund's adjuvant (CFA)-induced inflammatory pain in rats. Rectal temperature was measured to assess hypothermic effects of 2-BFI. A two-lever drug discrimination paradigm in which rats were trained to discriminate 5.6 mg·kg-1 2-BFI (i.p.) from its vehicle was used to examine the discriminative stimulus effects of 2-BFI. In each experiment, pharmacological mechanisms were investigated by combining 2-BFI or CR4056 with various pharmacological manipulations of the monoaminergic system including selective reuptake inhibition, monoamine depletion and monoamine receptor antagonism. KEY RESULTS In the CCI model, selective reuptake inhibitors of 5-HT (fluoxetine) or noradrenaline (desipramine), but not dopamine (GBR12909), enhanced 2-BFI-induced antinociception. Selective depletion of 5-HT or noradrenaline almost abolished 2-BFI-induced antinociception. 5-HT1A , 5-HT2A and α1 -adrenoceptor antagonists, but not other monoaminergic antagonists, attenuated 2-BFI and CR4056-induced antinociception in CCI and/or CFA models. However, none of these monoamine receptor antagonists significantly altered 2-BFI-induced hypothermia or discriminative stimulus effects. CONCLUSIONS AND IMPLICATIONS Antinociception induced by I2 receptor agonists was mediated by serotonergic and noradrenergic mechanisms with 5-HT1A , 5-HT2A and α1 -adrenoceptor being particularly important. In contrast, the hypothermic and discriminative stimulus effects of I2 receptor agonists were mediated by distinct, independent mechanisms.
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Affiliation(s)
- Justin N Siemian
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, NY, USA
| | - Kaixuan Wang
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, NY, USA
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle Park, NC, USA
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, NY, USA.,School of Pharmacy, Yantai University, Yantai, Shandong Province, China
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Siemian JN, Jia S, Liu JF, Zhang Y, Li JX. Neuroanatomical characterization of imidazoline I 2 receptor agonist-induced antinociception. Eur J Neurosci 2018. [PMID: 29514408 DOI: 10.1111/ejn.13899] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chronic pain is a significant public health problem with a lack of safe and effective analgesics. The imidazoline I2 receptor (I2 R) is a promising analgesic target, but the neuroanatomical structures involved in mediating I2 R-associated behaviors are unknown. I2 Rs are enriched in the arcuate nucleus, dorsal raphe (DR), interpeduncular nucleus, lateral mammillary body, medial habenula, nucleus accumbens (NAc) and paraventricular nucleus; thus, this study investigated the antinociceptive and hypothermic effects of microinjections of the I2 R agonist 2-(2-benzofuranyl)-2-imidazoline hydrochloride (2-BFI). In rats, intra-DR microinjections produced antinociception in complete Freund's adjuvant- and chronic constriction injury-induced pain models. Intra-NAc microinjections produced antinociception and increased noxious stimulus-associated side time in a place escape/avoidance paradigm. Intra-NAc pretreatment with the I2 R antagonist idazoxan but not the D1 receptor antagonist SCH23390 or the D2 receptor antagonist raclopride attenuated intra-NAc 2-BFI-induced antinociception. Intra-NAc idazoxan did not attenuate systemically administered 2-BFI-induced antinociception. Microinjections into the other regions did not produce antinociception, and in none of the regions produced hypothermia. These data suggest that I2 R activation in some but not all I2 R-enriched brain regions is sufficient to produce antinociception and supports the theory that different I2 R-associated effects are mediated via distinct receptor populations, which may in turn be distributed differentially throughout the CNS.
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Affiliation(s)
- Justin N Siemian
- Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, 102 Farber Hall, 3435 Main St., Buffalo, NY, 14214, USA
| | - Shushan Jia
- Department of Anesthesiology, Yantai Affiliated Hospital, Binzhou Medical University, Yantai, China
| | - Jian-Feng Liu
- Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, 102 Farber Hall, 3435 Main St., Buffalo, NY, 14214, USA
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle Park, NC, USA
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, 102 Farber Hall, 3435 Main St., Buffalo, NY, 14214, USA
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Role of intracellular Ca 2+ signaling in the antinociceptive and discriminative stimulus effects of the imidazoline I 2 receptor agonist 2-BFI in rats. Psychopharmacology (Berl) 2017; 234:3299-3307. [PMID: 28825118 PMCID: PMC5660937 DOI: 10.1007/s00213-017-4719-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/13/2017] [Indexed: 01/27/2023]
Abstract
RATIONALE Recent research has established the imidazoline I2 receptor as a promising target for the development of novel analgesics. However, despite an increasing understanding of imidazoline I2 receptor-mediated behavioral effects, little is known about post-I2-receptor signaling mechanisms. OBJECTIVE This study examined the effects of several inhibitors of Ca2+ signaling mechanisms on two behavioral effects of the prototypical imidazoline I2 receptor ligand 2-(2-benzofuranyl)-2-imidazoline (2-BFI). METHODS The von Frey filament test was used to examine the antinociceptive effects of 2-BFI in complete Freund's adjuvant (CFA)-induced inflammatory pain in rats. A two-lever drug discrimination paradigm in which rats were trained to discriminate 5.6 mg/kg (intraperitoneally) 2-BFI from its vehicle was used to examine the discriminative stimulus effects of 2-BFI. RESULTS The L-type Ca2+ channel blockers verapamil and nimodipine, the calmodulin antagonist W-7, and the internal Ca2+ release inhibitor ryanodine all attenuated the antinociceptive effects of 2-BFI. Oxycodone- and acetaminophen-induced antinociception was unaffected by pretreatment with the Ca2+ channel blockers. Rats learned to reliably discriminate 5.6 mg/kg 2-BFI from saline. The I2 receptor agonists BU224, RS45041, tracizoline, and CR4056 all fully substituted for 5.6 mg/kg 2-BFI while idazoxan, S22687, 2,5-dimethoxy-4-methylamphetamine (DOM), and phenyzoline produced partial or no substitution. Verapamil, nimodipine, and W-7 did not alter the discriminative stimulus effects of 2-BFI. CONCLUSION These results indicate that the antinociceptive effects of 2-BFI involve intracellular Ca2+ elevation and/or downstream Ca2+/calmodulin signaling, whereas the discriminative stimulus effects of 2-BFI are mediated by a distinct, independent mechanism.
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Effects of I 2 -imidazoline receptor (IR) alkylating BU99006 in the mouse brain: Upregulation of nischarin/I 1 -IR and μ-opioid receptor proteins and modulation of associated signalling pathways. Neurochem Int 2017; 108:169-176. [DOI: 10.1016/j.neuint.2017.03.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/16/2017] [Accepted: 03/21/2017] [Indexed: 12/12/2022]
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Kim YH, Jeong JH, Ahn DS, Chung S. Phospholipase C-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate underlies agmatine-induced suppression of N-type Ca 2+ channel in rat celiac ganglion neurons. Biochem Biophys Res Commun 2017; 484:342-347. [PMID: 28131838 DOI: 10.1016/j.bbrc.2017.01.120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 01/23/2017] [Indexed: 12/27/2022]
Abstract
Agmatine suppresses peripheral sympathetic tone by modulating Cav2.2 channels in peripheral sympathetic neurons. However, the detailed cellular signaling mechanism underlying the agmatine-induced Cav2.2 inhibition remains unclear. Therefore, in the present study, we investigated the electrophysiological mechanism for the agmatine-induced inhibition of Cav2.2 current (ICav2.2) in rat celiac ganglion (CG) neurons. Consistent with previous reports, agmatine inhibited ICav2.2 in a VI manner. The agmatine-induced inhibition of the ICav2.2 current was also almost completely hindered by the blockade of the imidazoline I2 receptor (IR2), and an IR2 agonist mimicked the inhibitory effect of agmatine on ICav2.2, implying involvement of IR2. The agmatine-induced ICav2.2 inhibition was significantly hampered by the blockade of G protein or phospholipase C (PLC), but not by the pretreatment with pertussis toxin. In addition, diC8-phosphatidylinositol 4,5-bisphosphate (PIP2) dialysis nearly completely hampered agmatine-induced inhibition, which became irreversible when PIP2 resynthesis was blocked. These results suggest that in rat peripheral sympathetic neurons, agmatine-induced IR2 activation suppresses Cav2.2 channel voltage-independently, and that the PLC-dependent PIP2 hydrolysis is responsible for the agmatine-induced suppression of the Cav2.2 channel.
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Affiliation(s)
- Young-Hwan Kim
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Ji-Hyun Jeong
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Duck-Sun Ahn
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Seungsoo Chung
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
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Keller B, García-Sevilla JA. Dysregulation of IRAS/nischarin and other potential I 1-imidazoline receptors in major depression postmortem brain: Downregulation of basal contents by antidepressant drug treatments. J Affect Disord 2017; 208:646-652. [PMID: 27836117 DOI: 10.1016/j.jad.2016.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 09/28/2016] [Accepted: 10/16/2016] [Indexed: 11/16/2022]
Abstract
BACKGROUND Major depressive disorder (MDD) has been associated with altered brain densities of imidazoline receptors (I1-IR and I2-IR types). METHODS The contents of potential I1-IR IRAS/nischarin (167kDa) and, for comparison, those of I1- (85kDa) and I2- (45kDa and 30kDa) IR proteins were quantified by western blotting in postmortem prefrontal cortex (PFC/BA9) of antidepressant-free ([MDD(-)], n=9) and antidepressant-treated ([MDD(+)], n=12) subjects and matched controls (n=19). RESULTS In MDD, regardless of antidepressant treatment (n=21), IRAS/nischarin was not altered in PFC/BA9. However, the content of IRAS/nischarin was found modestly and not significantly increased (+19%, p=0.075) in MDD(-) and significantly decreased (-24%, p=0.001) in MDD(+), revealing that basal I1-IR content was downregulated by antidepressants. Putative 85kDa I1-IR was upregulated (+35%, p=0.035) in MDD(-) but it was not reduced (-14%, p=0.37) in MDD(+). There was a positive correlation (r=0.33, p=0.037, n=40) between the contents of IRAS/nischarin and 85kDa IR proteins in PFC/BA9 (control and MDD subjects). In MDD and regardless of antidepressants, the content of cortical 45kDa I2-IR was increased (+31%, p=0.006) and that of 30kDa I2-IR decreased (-14%, p=0.002), indicating basal dysregulations of these potential IRs. LIMITATIONS MDD(+) subjects had been treated with a variety of antidepressant drugs. The results must be understood in the context of suicide victims with MDD. CONCLUSIONS The dysregulation of IRAS/nischarin in depressed brains is a major novel finding that supports a role of this potential I1-IR in the neurobiology of MDD and in the molecular mechanisms of antidepressant drugs.
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Affiliation(s)
- Benjamin Keller
- Laboratori de Neurofarmacologia, IUNICS/IdISPa, Universitat de les Illes Balears (UIB), Palma de Mallorca, Spain; Redes Temáticas de Investigación Cooperativa en Salud-Red de Trastornos Adictivos (RETICS-RTA), ISCIII, Madrid, Spain
| | - Jesús A García-Sevilla
- Laboratori de Neurofarmacologia, IUNICS/IdISPa, Universitat de les Illes Balears (UIB), Palma de Mallorca, Spain; Redes Temáticas de Investigación Cooperativa en Salud-Red de Trastornos Adictivos (RETICS-RTA), ISCIII, Madrid, Spain.
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Kawamura K, Shimoda Y, Yui J, Zhang Y, Yamasaki T, Wakizaka H, Hatori A, Xie L, Kumata K, Fujinaga M, Ogawa M, Kurihara Y, Nengaki N, Zhang MR. A useful PET probe [ 11C]BU99008 with ultra-high specific radioactivity for small animal PET imaging of I 2-imidazoline receptors in the hypothalamus. Nucl Med Biol 2016; 45:1-7. [PMID: 27835825 DOI: 10.1016/j.nucmedbio.2016.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 10/14/2016] [Accepted: 10/24/2016] [Indexed: 01/23/2023]
Abstract
INTRODUCTION A positron emission tomography (PET) probe with ultra-high specific radioactivity (SA) enables measuring high receptor specific binding in brain regions by avoiding mass effect of the PET probe itself. It has been reported that PET probe with ultra-high SA can detect small change caused by endogenous or exogenous ligand. Recently, Kealey et al. developed [11C]BU99008, a more potent PET probe for I2-imidazoline receptors (I2Rs) imaging, with a conventional SA (mean 76GBq/μmol) showed higher specific binding in the brain. Here, to detect small change of specific binding for I2Rs caused by endogenous or exogenous ligand in an extremely small region, such as hypothalamus in the brain, we synthesized and evaluated [11C]BU99008 with ultra-high SA as a useful PET probe for small-animal PET imaging of I2Rs. METHODS [11C]BU99008 was prepared by [11C]methylation of N-desmethyl precursor with [11C]methyl iodide. Biodistribution, metabolite analysis, and brain PET studies were conducted in rats. RESULTS [11C]BU99008 with ultra-high SA in the range of 5400-16,600GBq/μmol were successfully synthesized (n=7), and had appropriate radioactivity for in vivo study. In the biodistribution study, the mean radioactivity levels in all investigated tissues except for the kidney did not show significant difference between [11C]BU99008 with ultra-high SA and that with conventional SA. In the metabolite analysis, the percentage of unchanged [11C]BU99008 at 30min after the injection of probes with ultra-high and conventional SA was similar in rat brain and plasma. In the PET study of rats' brain, radioactivity level (AUC30-60 min) in the hypothalamus of rats injected with [11C]BU99008 with ultra-high SA (64 [SUV ∙ min]) was significantly higher than that observed for that with conventional SA (50 [SUV ∙ min]). The specific binding of [11C]BU99008 with ultra-high SA (86% of total binding) for I2R was higher than that of conventional SA (76% of total binding). CONCLUSION A PET study using [11C]BU99008 with ultra-high SA would thus contribute to the detection of small changes in or small regions with I2R expression and hence may be useful in elucidating new functions of I2R.
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Affiliation(s)
- Kazunori Kawamura
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan.
| | - Yoko Shimoda
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Joji Yui
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Yiding Zhang
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Tomoteru Yamasaki
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Hidekatsu Wakizaka
- Department of Medical Physics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Akiko Hatori
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Lin Xie
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Katsushi Kumata
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Masayuki Fujinaga
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
| | - Masanao Ogawa
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Yusuke Kurihara
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Nobuki Nengaki
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan; SHI Accelerator Service Ltd., Tokyo 141-0032, Japan
| | - Ming-Rong Zhang
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan
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Kornicka A, Wasilewska A, Sączewski J, Hudson AL, Boblewski K, Lehmann A, Gzella K, Belka M, Sączewski F, Gdaniec M, Rybczyńska A, Bączek T. 1-[(Imidazolidin-2-yl)imino]-1H-indoles as new hypotensive agents: synthesis andin vitroandin vivobiological studies. Chem Biol Drug Des 2016; 89:400-410. [DOI: 10.1111/cbdd.12846] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/13/2016] [Accepted: 08/19/2016] [Indexed: 11/28/2022]
Affiliation(s)
- Anita Kornicka
- Department of Chemical Technology of Drugs; Medical University of Gdańsk; Gdańsk Poland
| | - Aleksandra Wasilewska
- Department of Chemical Technology of Drugs; Medical University of Gdańsk; Gdańsk Poland
| | - Jarosław Sączewski
- Department of Organic Chemistry; Medical University of Gdańsk; Gdańsk Poland
| | - Alan L. Hudson
- Department of Pharmacology; University of Alberta; Edmonton Canada
| | - Konrad Boblewski
- Department of Pathophysiology; Medical University of Gdańsk; Gdańsk Poland
| | - Artur Lehmann
- Department of Pathophysiology; Medical University of Gdańsk; Gdańsk Poland
| | - Karol Gzella
- Department of Chemical Technology of Drugs; Medical University of Gdańsk; Gdańsk Poland
| | - Mariusz Belka
- Department of Pharmaceutical Chemistry; Medical University of Gdańsk; Gdańsk Poland
| | - Franciszek Sączewski
- Department of Chemical Technology of Drugs; Medical University of Gdańsk; Gdańsk Poland
| | - Maria Gdaniec
- Faculty of Chemistry; A. Mickiewicz University; Poznań Poland
| | | | - Tomasz Bączek
- Department of Pharmaceutical Chemistry; Medical University of Gdańsk; Gdańsk Poland
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Sączewski J, Hudson A, Scheinin M, Wasilewska A, Sączewski F, Rybczyńska A, Ferdousi M, Laurila JM, Boblewski K, Lehmann A, Watts H, Ma D. Transfer of SAR information from hypotensive indazole to indole derivatives acting at α-adrenergic receptors: In vitro and in vivo studies. Eur J Med Chem 2016; 115:406-15. [PMID: 27031216 DOI: 10.1016/j.ejmech.2016.03.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 03/09/2016] [Accepted: 03/10/2016] [Indexed: 12/24/2022]
Abstract
In a search for novel antihypertensive drugs we applied scaffold hopping from the previously described α1-adrenergic receptor antagonists, 1-[(imidazolin-2-yl)methyl]indazoles. The aim was to investigate whether the α-adrenergic properties of the indazole core were transferable to the indole core. The newly obtained 1-[(imidazolin-2-yl)methyl]indole analogues were screened in vitro for their binding affinities for α1-and α2-adrenoceptors, which allowed the identification of the target-based SAR transfer (T_SAR transfer) as well as structure-based SAR transfer (S_SAR transfer) events. However, when screened in vivo with use of anaesthetized male Wistar rats, the new indole ligands showed a different hemodynamic profile than expected. Instead of the immediate hypotensive effect characteristic of peripheral vasodilatator α1 blockers, a biphasic effect was observed, reminiscent of clonidine-like centrally acting antihypertensive agents. This was supported by subsequent in vitro functional studies in [(35)S]GTPγS binding assay, where the indole analogues displayed partial agonist properties at α2-adrenergic receptors. Since no correlation was found between the in vitro binding to α-adrenoceptors and the in vivo hemodynamic effects of the two series of indazole and indole bioisosteric compounds, in a search for new imidazoline-containing adrenergic drugs, the structure-based SAR transfer information obtained from in vitro binding studies should be treated with caution.
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Affiliation(s)
- Jaroslaw Sączewski
- Department of Organic Chemistry, Medical University of Gdańsk, 80-416, Gdańsk, Poland.
| | - Alan Hudson
- Department of Pharmacology, 9-47 Medical Sciences Building, University of Alberta, Edmonton, T6G 2H7, Canada
| | - Mika Scheinin
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, and Turku University Hospital, FI-20014 Turku, Finland
| | - Aleksandra Wasilewska
- Department of Chemical Technology of Drugs, Medical University of Gdańsk, 80-416, Gdańsk, Poland
| | - Franciszek Sączewski
- Department of Chemical Technology of Drugs, Medical University of Gdańsk, 80-416, Gdańsk, Poland
| | | | - Mehnaz Ferdousi
- Department of Pharmacology, 9-47 Medical Sciences Building, University of Alberta, Edmonton, T6G 2H7, Canada
| | - Jonne M Laurila
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, and Turku University Hospital, FI-20014 Turku, Finland
| | - Konrad Boblewski
- Department of Pathophysiology, Medical University of Gdansk, Poland
| | - Artur Lehmann
- Department of Pathophysiology, Medical University of Gdansk, Poland
| | - Helena Watts
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Imperial College London, Chelsea and Westminster Hospital, London, UK
| | - Daqing Ma
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Imperial College London, Chelsea and Westminster Hospital, London, UK
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Keller B, García-Sevilla JA. Immunodetection and subcellular distribution of imidazoline receptor proteins with three antibodies in mouse and human brains: Effects of treatments with I1- and I2-imidazoline drugs. J Psychopharmacol 2015; 29:996-1012. [PMID: 26038110 DOI: 10.1177/0269881115586936] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Various imidazoline receptor (IR) proteins have been proposed to mediate the effects of selective I1- and I2-IR drugs. However, the association of these IR-binding proteins with classic I1- and I2-radioligand binding sites remains somewhat controversial. In this study, three IR antibodies (anti-NISCH and anti-nischarin for I1-IRs; and anti-IRBP for I1/I2-IRs) were used to immunodetect, characterize and compare IR protein patterns in brain (mouse and human; total homogenate, subcellular fractionation, grey and white matter) and some cell systems (neurones, astrocytes, human platelets). Various immunoreactive IRs (specific molecular weight bands coincidently detected with the different antibodies) were related to I1-IR (167 kDa, 105/115 kDa and 85 kDa proteins) or I2-IR (66 kDa, 45 kDa and 30 kDa proteins) types. The biochemical characterization of cortical 167 kDa protein, localized in the membrane/cytosol but not in the nucleus, indicated that this I1-IR also forms part of higher order nischarin-related complexes. The contents of I1-IR (167 kDa, 105/115 kDa, and 85 kDa) proteins in mouse brain cortex were upregulated by treatment with I1-drugs (moxonidine, efaroxan) but not with I2-drugs (BU-224, LSL 61122). Conversely, the contents of I2-IR (66 kDa, 45 kDa and 30 kDa) proteins in mouse brain cortex were modulated by treatment with I2-drugs (decreases after BU-224 and LSL 61122, and increases after idazoxan) but not with I1-drugs (with the exception of moxonidine). These findings further indicate that brain immunoreactive IR proteins exist in multiple forms that can be grouped in the already known I1- and I2-IR types, which are expressed both in neurones and astrocytes.
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Affiliation(s)
- Benjamin Keller
- Laboratori de Neurofarmacologia, IUNICS-IdISPa, Universitat de les Illes Balears, Palma de Mallorca, Spain and Redes Temáticas de Investigación Cooperativa en Salud-Red de Trastornos Adictivos (RETICS-RTA), ISCIII, Madrid, Spain
| | - Jesús A García-Sevilla
- Laboratori de Neurofarmacologia, IUNICS-IdISPa, Universitat de les Illes Balears, Palma de Mallorca, Spain and Redes Temáticas de Investigación Cooperativa en Salud-Red de Trastornos Adictivos (RETICS-RTA), ISCIII, Madrid, Spain
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Anti-hyperalgesic effects of imidazoline I2 receptor ligands in a rat model of inflammatory pain: interactions with oxycodone. Psychopharmacology (Berl) 2015; 232:3309-18. [PMID: 26037946 PMCID: PMC4537836 DOI: 10.1007/s00213-015-3983-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 05/24/2015] [Indexed: 10/23/2022]
Abstract
RATIONALE Emerging preclinical evidence suggests that imidazoline I2 receptor ligands may be effective analgesics. Quantitative analysis of the combined I2 receptor ligands and opioids is needed for the justification of combination therapy. OBJECTIVE This study systematically examined the anti-hyperalgesic and response rate-suppressing effects of selective I2 receptor ligands (2-BFI and phenyzoline) alone and in combination with oxycodone in rats. METHODS Von Frey filament test was used to examine the anti-hyperalgesic effects of drugs in a rat model of complete Freund's adjuvant (CFA)-induced inflammatory pain. Schedule-controlled responding was used to assess the rate-altering effects of study drugs. Duration of actions of individual drugs (2-BFI, phenyzoline, and oxycodone) alone or in combination was studied. Dose-addition analysis was employed to assess the anti-hyperalgesic interactions between drugs. RESULTS Oxycodone (0.1-3.2 mg/kg, i.p.), 2-BFI (1-17.8 mg/kg, i.p.), and phenyzoline (17.8-56 mg/kg, i.p.) all dose-dependently produced significant antinociceptive effects. When studied as combinations, 2-BFI and oxycodone produced additive interactions while phenyzoline and oxycodone produced supra-additive interactions under all fixed ratios. The same drug combinations did not alter or significantly reduced the operant responding depending on the ratios of the drug combinations. CONCLUSIONS Quantitative analysis of the anti-hyperalgesic effects of I2 receptor ligands strongly supports the therapeutic potential of I2 receptor ligands against inflammatory pain. In addition, the data reveal that phenyzoline is superior to the prototypic I2 receptor ligand 2-BFI for the management of pain and warrants further consideration as a novel analgesic.
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In vivo evaluation of a new 18F-labeled PET ligand, [18F]FEBU, for the imaging of I2-imidazoline receptors. Nucl Med Biol 2015; 42:406-12. [DOI: 10.1016/j.nucmedbio.2014.12.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/01/2014] [Accepted: 12/19/2014] [Indexed: 11/20/2022]
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The modulatory action of harmane on serotonergic neurotransmission in rat brain. Brain Res 2015; 1597:57-64. [DOI: 10.1016/j.brainres.2014.11.056] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/27/2014] [Accepted: 11/27/2014] [Indexed: 02/06/2023]
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Qiu Y, He XH, Zhang Y, Li JX. Discriminative stimulus effects of the novel imidazoline I₂ receptor ligand CR4056 in rats. Sci Rep 2014; 4:6605. [PMID: 25308382 PMCID: PMC4194429 DOI: 10.1038/srep06605] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 09/22/2014] [Indexed: 01/27/2023] Open
Abstract
This study examined whether a novel imidazoline I2 receptor ligand CR4056 could serve as a discriminative stimulus and whether it shares similar discriminative stimulus effects with other reported I2 receptor ligands. Eight male Sprague-Dawley rats were trained to discriminate 10.0 mg/kg CR4056 (i.p.) from vehicle in a two-lever food-reinforced drug discrimination procedure. Once rats acquired the discrimination, substitution and combination studies were conducted to elucidate the underlying receptor mechanisms. All rats acquired CR4056 discrimination after an average of 26 training sessions. Several I2 receptor ligands (phenyzoline, tracizoline, RS45041, and idazoxan, 3.2–75 mg/kg, i.p.) all occasioned > 80% CR4056-associated lever responding. Other drugs that occasioned partial or no CR4056-associated lever responding included methamphetamine, ketamine, the endogenous imidazoline ligand agmatine, the monoamine oxidase (MAO) inhibitor harmane, the α2-adrenoceptor agonist clonidine, the μ-opioid receptor agonists morphine and methadone, and the selective I2 receptor ligands BU224 and 2-BFI. The α1 adrenoceptor antagonist WB4101, α2 adrenoceptor antagonist yohimbine and μ-opioid receptor antagonist naltrexone failed to alter the stimulus effects of CR4056. Together, these results show that CR4056 can serve as a discriminative stimulus in rats, which demonstrates high pharmacological specificity and appears to be mediated by imidazoline I2 receptors.
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Affiliation(s)
- Yanyan Qiu
- 1] Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA [2] Department of Physiology, School of Basic Medical Sciences, Wuhan University, Hubei, China
| | - Xiao-Hua He
- Department of Physiology, School of Basic Medical Sciences, Wuhan University, Hubei, China
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle Park, NC, USA
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
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Fluorinated analogues of marsanidine, a highly α2-AR/imidazoline I1 binding site-selective hypotensive agent. Synthesis and biological activities. Eur J Med Chem 2014; 87:386-97. [PMID: 25282262 DOI: 10.1016/j.ejmech.2014.09.083] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 09/25/2014] [Accepted: 09/26/2014] [Indexed: 01/25/2023]
Abstract
The aim of these studies was to establish the influence of fluorination of the indazole ring on the pharmacological properties of two selective α2-adrenoceptor (α2-AR) agonists: 1-[(imidazolidin-2-yl)imino]-1H-indazole (marsanidine, A) and its methylene analogue 1-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-1H-indazole (B). Introduction of fluorine into the indazole ring of A and B reduced both binding affinity and α2-AR/I1 imidazoline binding site selectivity. The most α2-AR-selective ligands were 6-fluoro-1-[(imidazolidin-2-yl)imino]-1H-indazole (6c) and 7-fluoro-1-[(imidazolidin-2-yl)imino]-1H-indazole (6d). The in vivo cardiovascular properties of fluorinated derivatives of A and B revealed that in both cases the C-7 fluorination leads to compounds with the highest hypotensive and bradycardic activities. The α2-AR partial agonist 6c was prepared as a potential lead compound for development of a radiotracer for PET imaging of brain α2-ARs.
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Garau C, Miralles A, García-Sevilla JA. Chronic treatment with selective I2-imidazoline receptor ligands decreases the content of pro-apoptotic markers in rat brain. J Psychopharmacol 2013; 27:123-34. [PMID: 22719017 DOI: 10.1177/0269881112450785] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Selective I(2)-imidazoline receptor ligands induce neuroprotection through various molecular mechanisms including blockade of N-methyl-D-aspartate (NMDA) receptors. To investigate new neuroprotective mechanisms associated with I(2)-imidazoline receptors, the effects of selective (2-styryl-2-imidazoline (LSL 61122), 2-(2-benzofuranyl)-2-imidazoline (2-BFI), 2-(4,5-dihydroimidazol-2-yl) quinoline hydrochloride (BU-224)) and non-selective (idazoxan) I(2)-drugs on canonical apoptotic pathways were assessed in rat brain cortex. The acute treatment with LSL 61122 (10 mg/kg) reduced the content of mitochondrial (pro-apoptotic) Bax (-33%) and cytochrome c (-31%), which was prevented by idazoxan, an I(2)-receptor antagonist. The sustained stimulation of I(2)-imidazoline receptors with selective drugs (10 mg/kg, every 12 h for seven days) was associated with down-regulation of key components of the extrinsic (Fas receptor: -20%; Fas associated protein with death domain (FADD) adaptor: -47-54%) and/or intrinsic (Bax: -20-23%; cytochrome c: -22-28%) apoptotic signalling and/or up-regulation of survival anti-apoptotic factors (p-Ser194 FADD/FADD ratio: +1.6-2.5-fold; and/or Bcl-2/Bax ratio: +1.5-fold), which in the long-term could dampen cell death in the brain. Similar chronic treatments with LSL 60101 (the imidazole analogue of 2-BFI) and idazoxan (a mixed I(2)/α(2)-ligand) did not induce significant alterations of pro- or anti-apoptotic proteins. The disclosed anti-apoptotic mechanisms of selective I(2)-imidazoline drugs may work in concert with other molecular mechanisms of neuroprotection (e.g. blockade of NMDA receptors) that are engaged by I(2)-ligands.
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Affiliation(s)
- Celia Garau
- Laboratori de Neurofarmacologia, Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), Universitat de les Illes Balears, Palma de Mallorca, Spain
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Kealey S, Turner EM, Husbands SM, Salinas CA, Jakobsen S, Tyacke RJ, Nutt DJ, Parker CA, Gee AD. Imaging imidazoline-I2 binding sites in porcine brain using 11C-BU99008. J Nucl Med 2012; 54:139-44. [PMID: 23223380 DOI: 10.2967/jnumed.112.108258] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Changes in the density of imidazoline-I(2) binding sites have been observed in a range of neurologic disorders including Alzheimer's disease, Huntington's chorea, and glial tumor; however, the precise function of these sites remains unclear. A PET probe for I(2) binding sites would further our understanding of the target and may find application as a biomarker for early disease diagnosis. Compound BU99008 has previously been identified as a promising I(2) ligand from autoradiography studies, displaying high affinity and good selectivity toward the target. In this study, BU99008 was radiolabeled with (11)C in order to image the I(2) binding sites in vivo using PET. METHODS (11)C-BU99008 was radiolabeled by N-alkylation of the desmethyl precursor using (11)C-methyl iodide. A series of PET experiments was performed to investigate the binding of (11)C-BU99008 in porcine brains, in the presence or absence of a nonradiolabeled, competing I(2) ligand, BU224. RESULTS (11)C-BU99008 was obtained in good yield and specific activity. In vivo, (11)C-BU99008 displayed good brain penetration and gave a heterogeneous distribution with high uptake in the thalamus and low uptake in the cortex and cerebellum. (11)C-BU99008 brain kinetics were well described by the 1-tissue-compartment model, which was used to provide estimates for the total volume of distribution (V(T)) across brain regions of interest. Baseline V(T) values were ranked in the following order: thalamus > striatum > hippocampus > frontal cortex ≥ cerebellum, consistent with the known distribution and concentration of I(2) binding sites. Administration of a selective I(2) binding site ligand, BU224, reduced the V(T) to near-homogeneous levels in all brain regions. CONCLUSION (11)C-BU99008 appears to be a suitable PET radioligand for imaging the I(2) binding sites in vivo.
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Affiliation(s)
- Steven Kealey
- Institute of Psychiatry, De Crespigny Park, King's College London, London, United Kingdom.
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28
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An XF, Zhang Y, Winter JC, Li JX. Effects of imidazoline I2 receptor agonists and morphine on schedule-controlled responding in rats. Pharmacol Biochem Behav 2012; 101:354-9. [DOI: 10.1016/j.pbb.2012.01.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 01/24/2012] [Accepted: 01/31/2012] [Indexed: 11/24/2022]
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Tonello R, Villarinho JG, da Silva Sant'Anna G, Tamiozzo L, Machado P, Trevisan G, Pinto Martins MA, Ferreira J, Rubin MA. The potential antidepressant-like effect of imidazoline I2 ligand 2-BFI in mice. Prog Neuropsychopharmacol Biol Psychiatry 2012; 37:15-21. [PMID: 22122878 DOI: 10.1016/j.pnpbp.2011.11.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 10/31/2011] [Accepted: 11/14/2011] [Indexed: 12/17/2022]
Abstract
The compound 2-(2-benzofuranyl)-2-imidazoline (2-BFI) is a 2-imidazoline derivative that selectively inhibits the in vitro activity of monoamine oxidase-A and it is also an imidazoline I(2) agonist. However, the antidepressant potential of this compound and its mechanism of action have not been well defined. Therefore, in this study we investigated the antidepressant-like effect of 2-BFI in mice. 2-BFI (100 and 300μmol/kg, s.c.) significantly reduced the immobility time on the tail suspension test (TST) without changing locomotion in the open field test. The reduced the immobility time of 2-BFI (100μmol/kg, s.c.) was confirmed with the forced swimming test (FST). The antidepressant-like effect of 2-BFI (100μmol/kg, s.c.) in the TST was prevented by pretreatment with idazoxan (0.4μmol/kg, i.p., a I(2) site antagonist), methysergide (4μmol/kg, i.p., a non-selective serotonergic receptor antagonist) and haloperidol (0.1μmol/kg, i.p., a non-selective dopaminergic receptor antagonist). The anxiolytic effect of 2-BFI was also evaluated, using the elevated plus-maze test. 2-BFI (300μmol/kg, s.c.) was able to significantly increase the % of number of entries and the % of time spent in the open arms, indicating that it possesses an anxiolytic effect at high doses. In conclusion, these results suggest that the antidepressant-like effect of 2-BFI might involve serotonergic, dopaminergic and imidazoline systems, and then the imidazoline site could represent a new pharmacological target for the treatment of depression.
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Affiliation(s)
- Raquel Tonello
- Programa de Pós-graduação em Ciências Biológicas, Bioquímica Toxicológica, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
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30
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Tyacke RJ, Fisher A, Robinson ESJ, Grundt P, Turner EM, Husbands SM, Hudson AL, Parker CA, Nutt DJ. Evaluation and initial in vitro and ex vivo characterization of the potential positron emission tomography ligand, BU99008 (2-(4,5-dihydro-1H-imidazol-2-yl)-1- methyl-1H-indole), for the imidazoline₂ binding site. Synapse 2012; 66:542-51. [PMID: 22290740 DOI: 10.1002/syn.21541] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 01/12/2012] [Accepted: 01/23/2012] [Indexed: 11/06/2022]
Abstract
The density of the Imidazoline₂ binding site (I₂BS) has been shown to change in psychiatric conditions such as depression and addiction, along with neurodegenerative disorders such as Alzheimer's disease and Huntington's chorea. The presence of I₂BS on glial cells and the possibility that they may in some way regulate glial fibrillary acidic protein has led to increased interest into the role of I₂BS and I₂BS ligands in conditions characterized by marked gliosis. In addition, it has been suggested that I₂BS may be a marker for human glioblastomas. Therefore, the development of a positron emission tomography (PET) radioligand for the I₂BS would be of major benefit in our understanding of these conditions. We now report the successful synthesis and initial pharmacological evaluation of potential PET radioligands for the I₂BS as well as the tritiation and characterization of the most favorable of the series, BU99008 (6), both in vitro and ex vivo in rat. The series as a whole demonstrated excellent affinity and selectivity for the I₂BS, with BU99008 (6) selected as the lead candidate to be taken forward for in vivo assessment. BU99008 (6) showed very good affinity for the I₂BS (K(i) of 1.4 nM; K(d) = 1.3 nM), good selectivity compared with the α₂ -adrenoceptor (909-fold). In addition, following peripheral administration, [³H]BU99008 demonstrated a heterogenous uptake into the rat brain consistent with the known distribution of the I₂BS in vivo. This, and the amenability of BU99008 (6) to radiolabeling with a positron-emitting radioisotope, indicates its potential as a PET radioligand for imaging the I₂BS in vivo.
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Affiliation(s)
- Robin J Tyacke
- Neuropsychopharmacology Unit, Centre for Pharmacology and Therapeutics, Hammersmith Hospital Campus, Imperial College London, London W12 0NN, United Kingdom.
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Kawamura K, Kimura Y, Yui J, Wakizaka H, Yamasaki T, Hatori A, Kumata K, Fujinaga M, Yoshida Y, Ogawa M, Nengaki N, Fukumura T, Zhang MR. PET study using [11C]FTIMD with ultra-high specific activity to evaluate I2-imidazoline receptors binding in rat brains. Nucl Med Biol 2012; 39:199-206. [DOI: 10.1016/j.nucmedbio.2011.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 06/29/2011] [Accepted: 07/26/2011] [Indexed: 10/17/2022]
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Synthesis and biological activities of 2-[(heteroaryl)methyl]imidazolines. Bioorg Med Chem 2012; 20:108-16. [DOI: 10.1016/j.bmc.2011.11.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 11/12/2011] [Accepted: 11/14/2011] [Indexed: 10/15/2022]
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Saczewski J, Hudson A, Laird S, Rybczyńska A, Boblewski K, Lehmann A, Ma D, Maze M, Watts H, Gdaniec M. N-(Imidazolidin-2-ylidene)-1-arylmethanamine oxides: synthesis, structure and pharmacological evaluation. Arch Pharm (Weinheim) 2011; 345:33-42. [PMID: 22083875 DOI: 10.1002/ardp.201100028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 02/24/2011] [Accepted: 03/02/2011] [Indexed: 11/10/2022]
Abstract
A high yielding three-step procedure was applied for the synthesis of N-(imidazolidin-2-ylidene)-1-arylmethanamine oxides 3 (α-aminonitrones) starting from the easily accessible imidazolidin-2-one O-benzyl oxime 1. The α-aminonitrone-α-iminohydroxyloamine tautomerism of these products was studied theoretically and the structures of the synthesised compounds were confirmed by single crystal X-ray crystallographic analysis. The compounds were evaluated in vitro for their binding affinities to α(1) and α(2) adrenoceptors as well as imidazoline I(1) and I(2) receptors. The highest potencies at the α(2) adrenergic receptors were observed for compounds bearing biphenyl (4h, K(i) = 9 nM) and naphthyl (4i, K(i) = 92 nM) moieties. Compounds 4h and 4i were further tested in vivo for their cardiovascular and sedative-hypnotic effects in rats.
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Affiliation(s)
- Jarosław Saczewski
- Department of Chemical Technology of Drugs, Medical University of Gdansk, Gdańsk, Poland.
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Kawamura K, Maeda J, Hatori A, Okauchi T, Nagai Y, Higuchi M, Suhara T, Fukumura T, Zhang MR. In vivo and in vitro imaging of I2 imidazoline receptors in the monkey brain. Synapse 2011; 65:452-5. [DOI: 10.1002/syn.20897] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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35
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3-[(Imidazolidin-2-yl)imino]indazole ligands with selectivity for the α2-adrenoceptor compared to the imidazoline I1 receptor. Bioorg Med Chem 2011; 19:321-9. [DOI: 10.1016/j.bmc.2010.11.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 11/04/2010] [Accepted: 11/08/2010] [Indexed: 11/20/2022]
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Semenova S, Markou A. The alpha2 adrenergic receptor antagonist idazoxan, but not the serotonin-2A receptor antagonist M100907, partially attenuated reward deficits associated with nicotine, but not amphetamine, withdrawal in rats. Eur Neuropsychopharmacol 2010; 20:731-46. [PMID: 20627663 PMCID: PMC3545706 DOI: 10.1016/j.euroneuro.2010.05.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 04/01/2010] [Accepted: 05/04/2010] [Indexed: 11/27/2022]
Abstract
Based on phenomenological similarities between anhedonia (reward deficits) associated with drug withdrawal and the negative symptoms of schizophrenia, we showed previously that the atypical antipsychotic clozapine attenuated reward deficits associated with psychostimulant withdrawal. Antagonism of alpha(2) adrenergic and 5-HT(2A) receptors may contribute to these effects of clozapine. We investigated here whether blockade of alpha(2) or 5-HT(2A) receptors by idazoxan and M100907, respectively, would reverse anhedonic aspects of psychostimulant withdrawal. Idazoxan treatment facilitated recovery from spontaneous nicotine, but not amphetamine, withdrawal by attenuating reward deficits and increase the number of somatic signs. Thus, alpha(2) adrenoceptor blockade may have beneficial effects against nicotine withdrawal and may be involved in the effects of clozapine previously observed. M100907 worsened the anhedonia associated with nicotine and amphetamine withdrawal, suggesting that monotherapy with M100907 may exacerbate the expression of the negative symptoms of schizophrenia or nicotine withdrawal symptoms in people, including schizophrenia patients, attempting to quit smoking.
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Affiliation(s)
- Svetlana Semenova
- Department of Psychiatry, School of Medicine, University of California San Diego, 9500 Gilman Drive, M/C 0603, La Jolla, CA 92093-0603, USA.
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37
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Imaging of I2-imidazoline receptors by small-animal PET using 2-(3-fluoro-[4-11C]tolyl)-4,5-dihydro-1H-imidazole ([11C]FTIMD). Nucl Med Biol 2010; 37:625-35. [DOI: 10.1016/j.nucmedbio.2010.02.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 02/26/2010] [Accepted: 02/28/2010] [Indexed: 11/23/2022]
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38
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Kimura A, Tyacke RJ, Robinson JJ, Husbands SM, Minchin MC, Nutt DJ, Hudson AL. Identification of an imidazoline binding protein: creatine kinase and an imidazoline-2 binding site. Brain Res 2009; 1279:21-8. [PMID: 19410564 PMCID: PMC2722693 DOI: 10.1016/j.brainres.2009.04.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Revised: 03/28/2009] [Accepted: 04/22/2009] [Indexed: 12/11/2022]
Abstract
Drugs that bind to imidazoline binding proteins have major physiological actions. To date, three subtypes of such proteins, I(1), I(2) and I(3), have been proposed, although characterisations of these binding proteins are lacking. I(2) binding sites are found throughout the brain, particularly dense in the arcuate nucleus of the hypothalamus. Selective I(2) ligands demonstrate antidepressant-like activity and the identity of the proteins that respond to such ligands remained unknown until now. Here we report the isolation of a approximately 45 kDa imidazoline binding protein from rabbit and rat brain using a high affinity ligand for the I(2) subtype, 2-BFI, to generate an affinity column. Following protein sequencing of the isolated approximately 45 kDa imidazoline binding protein, we identified it to be brain creatine kinase (B-CK). B-CK shows high binding capacity to selective I(2) ligands; [(3)H]-2-BFI (5 nM) specifically bound to B-CK (2330+/-815 fmol mg protein(-1)). We predicted an I(2) binding pocket near the active site of B-CK using molecular modelling. Furthermore, B-CK activity was inhibited by a selective I(2) irreversible ligand, where 20 microM BU99006 reduced the enzyme activity by 16%, confirming the interaction between B-CK and the I(2) ligand. In summary, we have identified B-CK to be the approximately 45 kDa imidazoline binding protein and we have demonstrated the existence of an I(2) binding site within this enzyme. The importance of B-CK in regulating neuronal activity and neurotransmitter release may well explain the various actions of I(2) ligands in brain and the alterations in densities of I(2) binding sites in psychiatric disorders.
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Key Words
- 2-bfi, 2-(2-benzofuranyl)2-imidazoline
- bu224, 2-(4,5-dihydroimidaz-2-yl)quinoline
- bu99006, 5-isothiocyanoato-2-benzofuranyl-2-imidazoline
- b-ck, brain creatine kinase
- ck, creatine kinase
- gold, genetic optimisation for ligand docking
- gr, glucose-responsive
- i2, imidazoline-2 subtype
- katp channel, atp sensitive potassium channel
- mao, monoamine oxidase
- moe, molecular operating environment
- imidazoline binding protein
- creatine kinase
- 2-bfi
- harmane and psychiatric disorders
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Affiliation(s)
- Atsuko Kimura
- Psychopharmacology Unit, University of Bristol, BS1 3NY, UK
| | | | - James J. Robinson
- Department of Pharmacy and Pharmacology, University of Bath, BA2 7AY, UK
| | | | | | - David J. Nutt
- Psychopharmacology Unit, University of Bristol, BS1 3NY, UK
| | - Alan L. Hudson
- Department of Pharmacology, 9-70 Medical Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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Smith KL, Jessop DS, Finn DP. Modulation of stress by imidazoline binding sites: implications for psychiatric disorders. Stress 2009; 12:97-114. [PMID: 19006007 DOI: 10.1080/10253890802302908] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
In this review, we present evidence for the involvement of imidazoline binding sites (IBS) in modulating responses to stress, through central control of monoaminergic and hypothalamo-pituitary-adrenal (HPA) axis activity. Pharmacological and physiological evidence is presented for differential effects of different IBS subtypes on serotoninergic and catecholaminergic pathways involved in control of basal and stress-stimulated HPA axis activity. IBS ligands can modulate behavioural and neuroendocrine responses in animal models of stress, depression and anxiety, and a body of evidence exists for alterations in central IBS expression in psychiatric patients, which can be normalised partially or fully by treatment with antidepressants. Dysfunction in monoaminergic systems and the HPA axis under basal and stress-induced activation has been extensively reported in psychiatric illnesses. On the basis of the literature, we suggest a potential therapeutic role for selective IBS ligands in the treatment of depression and anxiety disorders.
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Affiliation(s)
- Karen L Smith
- Department of Pharmacology and Therapeutics, NCBES Neuroscience Cluster, National University of Ireland, Galway, Ireland
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Sa̧czewski F, Kornicka A, Rybczyńska A, Hudson AL, Miao SS, Gdaniec M, Boblewski K, Lehmann A. 1-[(Imidazolidin-2-yl)imino]indazole. Highly α2/I1 Selective Agonist: Synthesis, X-ray Structure, and Biological Activity. J Med Chem 2008; 51:3599-608. [DOI: 10.1021/jm800112s] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Franciszek Sa̧czewski
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Anita Kornicka
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Apolonia Rybczyńska
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Alan L. Hudson
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Shu Sean Miao
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Maria Gdaniec
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Konrad Boblewski
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
| | - Artur Lehmann
- Department of Chemical Technology of Drugs and Department of Pathophysiology, Medical University of Gdańsk, 80-416 Gdańsk, Poland, Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada, and Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznań, Poland
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Piletz J, Baker R, Halaris A. Platelet imidazoline receptors as state marker of depressive symptomatology. J Psychiatr Res 2008; 42:41-9. [PMID: 17166518 PMCID: PMC2358986 DOI: 10.1016/j.jpsychires.2006.10.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2006] [Revised: 10/26/2006] [Accepted: 10/26/2006] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Previous studies have shown that imidazoline receptors (IR-1) are increased in platelets and frontal cortex of depressed patients, and this up-regulation is normalized (down-regulated) after antidepressant drug treatments. It has been hypothesized that IR-1 up-regulation during the depressive episode may be a state marker for depressive symptomatology. The goal of the present study was to address the state versus trait question. METHOD Twelve healthy subjects (six males and six females) met stringent inclusion and exclusion criteria for physical and mental health. They received desipramine for 6 weeks in order to simulate the length of time and dosing used previously to obtain an IR-1 down-regulation and a therapeutic response in depressed patients. Outcome and safety measures included clinical, psychological, and cardiovascular assessments obtained throughout the study. Plasma concentrations of desipramine were measured throughout the 6 weeks of treatment and again after 2 weeks following tapered discontinuation of desipramine. Platelet receptors were assessed by Western blotting and radioligand binding assays. RESULTS Healthy subjects taking desipramine experienced mild dysphoric effects but there were no adverse events. The binding of 8 nM p-[(125)I]clonidine to IR-1 and alpha(2)-adrenoceptors in healthy subjects did not change during desipramine treatment. The immunodensity of the 33 kDa band associated with IR-1 gradually increased to a maximum, by week-6, of 26% higher than baseline (p < 0.01 compared to baseline). Two weeks after desipramine discontinuation, there was a decline in alpha(2)-adrenoceptor binding and 33 kDa band's immunodensity (p = 0.04). CONCLUSIONS The findings support the hypothesis that platelet IR-1 binding sites are a marker of mood state rather than of antidepressant-induced pharmacological regulation. By comparison, platelet alpha(2)-adrenoceptors appear to be regulated by desipramine as a pharmacological effect independent of mood state.
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Affiliation(s)
- John Piletz
- Department of Psychiatry and Behavioral Neuroscience, Loyola University Medical Center, Maywood, IL 60153, United States
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42
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Abu Ghazaleh H, Lalies MD, Husbands SM, Nutt DJ, Hudson AL. The effect of 1-(4,5-dihydro-1H-imidazol-2-yl) isoquinoline on monoamine release and turnover in the rat frontal cortex. Neurosci Lett 2007; 422:109-13. [PMID: 17602837 DOI: 10.1016/j.neulet.2007.05.054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Revised: 05/17/2007] [Accepted: 05/18/2007] [Indexed: 11/23/2022]
Abstract
Imidazoline-(2) binding sites (I(2)-BS) are widely distributed in rat brain and our studies have shown that drugs selective for these sites regulate central extrasynaptic monoamine concentrations. Radioligand binding studies have recently shown that BU98008 (1-[4,5-dihydro-1H-imidazol-2-yl] isoquinoline) displays high affinity at I(2)-binding sites. The aim of this study was set to assess the pharmacological actions of BU98008 in a functional in vivo model using the technique of in vivo brain microdialysis. Systemic injection of 20 mg/kg BU98008 produced an 85% rise in extracellular noradrenaline levels compared with basal values in the rat frontal cortex. Further experiments demonstrated that peripheral administration of 10 and 20 mg/kg BU98008 elicited a transient 25% elevation in dopamine overflow compared with basal values and simultaneously produced an 18% decrease in extracellular DOPAC (3-4-dihydroxyphenylacetic acid) levels compared to basal values. In addition, BU98008 did not appear to affect serotonergic neurotransmission in the frontal cortex. In conclusion, the present study demonstrates that BU98008 shares some functional similarities with known selective I(2)-BS ligands.
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Affiliation(s)
- Haya Abu Ghazaleh
- Psychopharmacology Unit, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK
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43
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Zeidan MP, Zomkowski ADE, Rosa AO, Rodrigues ALS, Gabilan NH. Evidence for imidazoline receptors involvement in the agmatine antidepressant-like effect in the forced swimming test. Eur J Pharmacol 2007; 565:125-31. [PMID: 17445795 DOI: 10.1016/j.ejphar.2007.03.027] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Revised: 03/05/2007] [Accepted: 03/06/2007] [Indexed: 11/23/2022]
Abstract
This study investigated the involvement of the imidazoline receptors in the antidepressant-like effect of agmatine in the forced swimming test. The antidepressant-like effects of agmatine (10 mg/kg, i.p.) in the forced swimming test was blocked by pretreatment of mice with efaroxan (1 mg/kg, i.p., an imidazoline I1/alpha2-adrenoceptor antagonist), idazoxan (0.06 mg/kg, i.p., an imidazoline I2/alpha2-adrenoceptor antagonist) and antazoline (5 mg/kg, i.p., a ligand with high affinity for the I2 receptor). A subeffective dose of agmatine (0.001 mg/kg, i.p.) produced a synergistic antidepressant-like effect with clonidine (0.06 mg/kg, i.p, an imidazoline I1/alpha2-adrenoceptor agonist), moxonidine (0.5 mg/kg, i.p., an imidazoline I1/alpha2-adrenoceptor agonist), antazoline (1 mg/kg, i.p.) and MK-801 (0.001 mg/kg, i.p., a non-competitive NMDA receptor antagonist), but not with efaroxan (1 mg/kg, i.p.) and idazoxan (0.06 mg/kg, i.p.). Pretreatment of mice with yohimbine (1 mg/kg, i.p., an alpha2-adrenoceptor antagonist) blocked the synergistic antidepressant-like effect of agmatine (0.001 mg/kg, i.p.) with clonidine (0.06 mg/kg, i.p). A subeffective dose of MK-801 (0.001 mg/kg, i.p.) produced a synergistic antidepressant-like effect with antazoline (5 mg/kg, i.p.), but not with efaroxan (1 mg/kg, i.p.) or idazoxan (0.06 mg/kg, i.p.). In conclusion, this study suggests that the anti-immobility effect of agmatine in the forced swimming test is dependent on its interaction with imidazoline I1 and I2 receptors.
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Affiliation(s)
- Mariana P Zeidan
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, Florianópolis, 88040-900, SC, Brazil
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44
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Paterson LM, Tyacke RJ, Robinson ESJ, Nutt DJ, Hudson AL. In vitro and in vivo effect of BU99006 (5-isothiocyanato-2-benzofuranyl-2-imidazoline) on I2 binding in relation to MAO: Evidence for two distinct I2 binding sites. Neuropharmacology 2007; 52:395-404. [PMID: 17045310 DOI: 10.1016/j.neuropharm.2006.08.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 08/02/2006] [Accepted: 08/03/2006] [Indexed: 10/24/2022]
Abstract
BU99006 is an irreversible I(2) ligand which selectively inactivates I(2) binding sites, making it an ideal tool with which to study I(2) site mechanism. We sought to determine the effects of BU99006 on I(2) binding in relation to monoamine oxidase (MAO), and the time course of these effects. In vitro, rat brain membranes that were pre-treated with 10 microM BU99006 showed no change in MAO activity, despite suffering a significant reduction in [(3)H]2BFI binding (52.5+/-19.6 to 8.5+/-3.8 fmol mg(-1), 84%). Furthermore, reversible I(2) ligands 2BFI and BU224 were able to inhibit MAO, whether treated with BU99006 or not. In vivo, a 5 mg kg(-1) i.v. dose of BU99006 in rats rapidly reduced [(3)H]2BFI binding with similar magnitude (85%, maximal reduction after 20 min), without effect on either MAO activity or the specific binding of selective MAO-A and MAO-B radioligands. Moreover, following this irreversible treatment, recovery of central [(3)H]2BFI binding occurred with a rapid half-life of 4.3 h in rat brain (2.0 h in mouse), which is not consistent with a site on MAO. These data indicate that the high affinity site which is occupied by [(3)H]2BFI and irreversibly binds BU99006, is not the same as that which causes inhibition of MAO, and may point to the existence of another I(2) binding site.
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Affiliation(s)
- Louise M Paterson
- Psychopharmacology Unit, Dorothy Hodgkin Building, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
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45
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Di Rocco A, Nasser S, Werner P. Inhaled cocaine used to relieve "off" periods in patients with Parkinson disease and unpredictable motor fluctuations: a report of 2 cases. J Clin Psychopharmacol 2006; 26:689-90. [PMID: 17110842 DOI: 10.1097/01.jcp.0000245564.44778.d1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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46
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Saczewski F, Tabin P, Tyacke RJ, Maconie A, Saczewski J, Kornicka A, Nutt DJ, Hudson AL. 2-(4,5-Dihydroimidazol-2-yl)benzimidazoles as highly selective imidazoline I2/adrenergic α2 receptor ligands. Bioorg Med Chem 2006; 14:6679-85. [PMID: 16782348 DOI: 10.1016/j.bmc.2006.05.062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2006] [Revised: 05/19/2006] [Accepted: 05/31/2006] [Indexed: 11/25/2022]
Abstract
2-(4,5-Dihydroimidazol-2-yl)benzimidazoles have been identified as selective imidazoline I2/alpha2-adrenoceptor ligands. 4-Methyl (2) and 4-chloro (4) derivatives display I2 affinity at nanomolar concentration (Ki=4.4 and 17.7 nM, respectively) and high I2/alpha2 selectivity ratio=4226 and 5649, respectively. An evidence has been obtained that pKa value influences considerably the I2/alpha2-selectivity ratio of this class of imidazoline I2 receptor ligands.
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Affiliation(s)
- Francieszek Saczewski
- Department of Chemical Technology of Drugs, Medical University of Gdańsk, 80-416 Gdańsk, Poland.
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Kagawa K, Hayashi Y, Itoh I, Iwasaki M, Takada K, Kamibayashi T, Yamatodani A, Mashimo T. Identification of the Central Imidazoline Receptor Subtype Involved in Modulation of Halothane-Epinephrine Arrhythmias in Rats. Anesth Analg 2005; 101:1689-1694. [PMID: 16301242 DOI: 10.1213/01.ane.0000184185.69471.f6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We previously reported that imidazoline receptors in the central nervous system are involved in modulation of halothane-epinephrine arrhythmias. These receptors have been subclassified as I1 and I2 subtypes, but it is not known which receptor subtype is involved in halothane-epinephrine-induced arrhythmias. We designed the present study to clarify the involvement of central imidazoline receptor subtype in the modulation of halothane-epinephrine-induced arrhythmias. Rats were anesthetized with halothane and monitored continuously for systemic arterial blood pressure and premature ventricular contractions. The arrhythmogenic dose of epinephrine was defined as the smallest dose that produces three or more premature ventricular contractions within a 15-s period. Intracisternal moxonidine dose-dependently inhibited the epinephrine-induced arrhythmias during halothane anesthesia. Intracisternal efaroxan, a selective I1 antagonist with little affinity for I2 subtype, but not rauwolscine, an alpha2 antagonist without affinity for imidazoline receptors, blocked the antiarrhythmic effect of moxonidine. Intracisternal BU 224 and 2-BFI, selective I2 ligands, also inhibited the epinephrine-induced arrhythmias dose-dependently; however, these effects were abolished by efaroxan. We conclude that central I1, but not I2, receptors play an important role in inhibition of halothane-epinephrine arrhythmia.
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Affiliation(s)
- Kiyokazu Kagawa
- Department of *Anesthesiology and †Medical Physics School of Allied Health Sciences, Osaka University Faculty of Medicine, Japan
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Anderson NJ, Tyacke RJ, Husbands SM, Nutt DJ, Hudson AL, Robinson ESJ. In vitro and ex vivo distribution of [3H]harmane, an endogenous beta-carboline, in rat brain. Neuropharmacology 2005; 50:269-76. [PMID: 16242163 DOI: 10.1016/j.neuropharm.2005.08.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 08/23/2005] [Accepted: 08/25/2005] [Indexed: 11/24/2022]
Abstract
The endogenous beta-carboline, harmane, has been shown to bind to monoamine oxidase A (MAO-A) and a separate, high affinity, non-MAO site. Research in our laboratory has shown that harmane is an active component of clonidine-displacing substance (CDS), the proposed endogenous ligand for imidazoline binding sites (IBS). In the present study we have investigated the distribution of [3H]harmane in rat brain, and related the binding profile to the distribution of the MAO-A selective ligand [3H]Ro41-1049 and the I2BS ligand [3H]2-BFI. The in vivo distribution of [3H]harmane following intravenous administration was also investigated. Receptor autoradiography revealed a highly significant correlation for the distribution of [3H]harmane and [3H]Ro41-1049, and a significant correlation for [3H]harmane and the I2BS ligand [3H]2-BFI. The in vivo distribution of [3H]harmane suggests that the ligand accumulates in the adrenal gland and throughout the brain with the primary route of excretion occurring via the duodenum. In conclusion, these studies have shown that [3H]harmane labels a population of binding sites that reflect the distribution of MAO-A. Further evidence for a non-MAO, IBS [3H]harmane population has not been shown but the high level of expression of the MAO-A site is likely to have masked the much smaller population of I2BS.
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Affiliation(s)
- Neil J Anderson
- Department of Pharmacology, School of Medical Sciences, University Walk, Clifton, Bristol, BS8 1TD, UK
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Anderson NJ, Lupo PA, Nutt DJ, Hudson AL, Robinson ESJ. Characterisation of imidazoline I2 binding sites in pig brain. Eur J Pharmacol 2005; 519:68-74. [PMID: 16109401 DOI: 10.1016/j.ejphar.2005.06.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2005] [Accepted: 06/28/2005] [Indexed: 11/29/2022]
Abstract
The imidazoline I2 binding sites in the central nervous system have previously been described in several different species including rat, mouse, rabbit and frog. The present study has investigated the imidazoline I2 binding site, and its relationship to the monoamine oxidase isoforms, in pig whole brain and compared the results obtained with data from other species. Results from saturation binding studies revealed that the imidazoline I2-selective ligand, [3H]2BFI (2-(2-benzofuranyl)-2-imidazoline) labelled a single saturable population of sites with a KD=6.6 nM and Bmax=771.7 fmol/mg protein. The pharmacological characterisation of the sites was similar to that previously reported with a rank order of potency for the imidazoline I2 ligands of 2BFI>BU224>Idazoxan>BU226. Displacement by the imidazoline I1 ligands was low affinity and the monoamine oxidase inhibitors displaced with micromolar affinity. The majority of compounds displaced the binding in a monophasic manner, however, displacement by the putative endogenous ligand, harmane was biphasic. The relative populations of the two monoamine oxidase isoforms revealed a 10 fold greater expression of monoamine oxidase B relative to monoamine oxidase A. These data confirm the presence of imidazoline I2 binding sites in pig brain and show that their pharmacology is characteristic of that seen in other species. The proportion of monoamine oxidase A and B expressed in the pig brain is similar to that seen in the human brain therefore, given the association between imidazoline I2 binding sites and monoamine oxidase, the pig may provide a more useful model for human imidazoline I2 binding sites than other species such as the rat.
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Affiliation(s)
- Neil J Anderson
- Department of Pharmacology, School of Medical Sciences, University Walk, Clifton, Bristol BS8 1TD, UK
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50
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Dardonville C, Rozas I. Imidazoline binding sites and their ligands: an overview of the different chemical structures. Med Res Rev 2004; 24:639-61. [PMID: 15224384 DOI: 10.1002/med.20007] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Since Bousquet et al. discovered the imidazoline binding sites (IBS) two decades ago, when they realized that the antihypertensive drug clonidine interacts not only with the alpha2-adrenenoceptors (alpha2-AR) but also with a distinct imidazoline preferring binding site, these receptors have been paid a great deal of attention. At least two subtypes, I1 and I2, have been characterised based on their binding affinity for different radioligands, but their structures still remain unknown. The pharmacological profile of these IBSs has been the objective of several and very thorough reviews. However, a medicinal chemistry overview of the different IBS ligands prepared to date has never been attempted. In this study, we attempt to compile all the different chemical structures reported to date as IBS ligands and classify them in function of their chemical structure and binding affinity for the different IBS subtypes. Thus, we comment on the different endogenous IBS ligands known as well as the drugs described to interact with the I1-IBS which have found application as antihypertensive drugs. Then, we review those compounds described in the literature to interact with the I2-IBS, classifying them by their chemical families (imidazolines, guanidines, 2-aminoimidazolines, beta-carbolines). Finally, some conclusions are drawn.
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