1
|
Dixit MP, Thakre PP, Pannase AS, Aglawe MM, Taksande BG, Kotagale NR. Imidazoline binding sites mediates anticompulsive-like effect of agmatine in marble-burying behavior in mice. Eur J Pharmacol 2014; 732:26-31. [PMID: 24657463 DOI: 10.1016/j.ejphar.2014.02.045] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 02/04/2014] [Accepted: 02/23/2014] [Indexed: 02/07/2023]
Abstract
Agmatine is a cationic amine formed by decarboxylation of l-arginine by the mitochondrial enzyme arginine decarboxylase and widely distributed in mammalian brain. Although the precise function of endogenous agmatine has been largely remained unclear, its exogenous administration demonstrated beneficial effects in several neurological and psychiatric disorders. This study was planned to examine the role of imidazoline binding sites in the anticompulsive-like effect of agmatine on marble-burying behavior. Agmatine (20 and 40mg/kg, ip), mixed imidazoline I1/α2 agonists clonidine (60µg/kg, ip) and moxonidine (0.25mg/kg, ip), and imidazoline I2 agonist 2- BFI (10mg/kg, ip) showed significant inhibition of marble burying behavior in mice. In combination studies, the anticompulsive-like effect of agmatine (10mg/kg, ip) was significantly potentiated by prior administration of moxonidine (0.25mg/kg, ip) or clonidine (30µg/kg,) or 2-BFI (5mg/kg, ip). Conversely, efaroxan (1mg/kg, ip), an I1 antagonist and idazoxan (0.25mg/kg, ip), an I2 antagonist completely blocked the anticompulsive-like effect of agmatine (10mg/kg, ip). These drugs at doses used here did not influence the basal locomotor activity in experimental animals. These results clearly indicated the involvement of imidazoline binding sites in anti-compulsive-like effect of agmatine. Thus, imidazoline binding sites can be explored further as novel therapeutic target for treatment of anxiety and obsessive compulsive disorders.
Collapse
Affiliation(s)
- Madhura P Dixit
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Prajwal P Thakre
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Akshay S Pannase
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Manish M Aglawe
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Brijesh G Taksande
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Nandkishor R Kotagale
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India.
| |
Collapse
|
2
|
Wróblewska M, Kasprzyk J, Sączewski F, Kornicka A, Boblewski K, Lehmann A, Rybczyńska A. Marsanidine and 7-Me-marsanidine, the new hypotensive imidazolines augment sodium and urine excretion in rats. Pharmacol Rep 2013; 65:1025-32. [DOI: 10.1016/s1734-1140(13)71085-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 03/18/2013] [Indexed: 11/26/2022]
|
3
|
Wiczling P, Nasal A, Kubik Ł, Kaliszan R. A new pH/organic modifier gradient RP HPLC method for convenient determination of lipophilicity and acidity of drugs as applied to established imidazoline agents. Eur J Pharm Sci 2012; 47:1-5. [DOI: 10.1016/j.ejps.2012.04.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 04/25/2012] [Accepted: 04/26/2012] [Indexed: 10/28/2022]
|
4
|
New imidazoline/α2-adrenoceptors affecting compounds—4(5)-(2-aminoethyl)imidazoline (dihydrohistamine) derivatives. Synthesis and receptor affinity studies. Bioorg Med Chem 2011; 19:156-67. [DOI: 10.1016/j.bmc.2010.11.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 11/16/2010] [Accepted: 11/17/2010] [Indexed: 11/22/2022]
|
5
|
Comparison of agmatine with moxonidine and rilmenidine in morphine dependence in vitro: role of imidazoline I(1) receptors. Eur J Pharmacol 2009; 612:1-8. [PMID: 19356733 DOI: 10.1016/j.ejphar.2009.03.077] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 03/08/2009] [Accepted: 03/23/2009] [Indexed: 11/20/2022]
Abstract
Moxonidine and rilmenidine are classical imidazoline I(1) receptor agonists, and used as anti-hypertension drugs in clinical practice. Agmatine is an imidazoline I(1) receptor endogenous ligand as well as its agonist, but more and more evidences suggest it has no influence on blood pressure. In the present study we compared the effects of moxonidine, rilmenidine and agmatine in the development of morphine dependence, and investigated the role of imidazoline I(1) receptor in the effects of these agents. Chinese hamster ovary cells co-expressing mu opioid receptor and imidazoline receptor antisera-selected protein (IRAS), the strong candidate for imidazoline I(1) receptor, were used as the cell line. cAMP overshoot, which represents an opioid dependent state in vitro, was measured to study the effects on morphine dependence. siRNA against IRAS was carried out to investigate the role of imidazoline I(1) receptor. Moxonidine and rilmenidine (0.01-10 microM) were ineffective on cAMP level in the cells when given alone, and failed to inhibit chronic morphine exposure, naloxone-precipitated cAMP overshoot when co-pretreated with morphine. Agmatine (0.01-10 microM) by itself was ineffective but co-pretreated with morphine concentration-dependently inhibited chronic morphine exposure, naloxone-precipitated cAMP overshoot in the cells. Furthermore, we found that the inhibitory effect of agmatine (100 nM and 1 microM) on cAMP overshoot was significantly reduced by siRNA against IRAS. This study indicates that agmatine can inhibit the development of morphine dependence in vitro, whereas moxonidine and rilmenidine have no the effect. Imidazoline I(1) receptor plays an important role in agmatine inhibiting morphine dependence.
Collapse
|
6
|
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.
Collapse
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
| | | | | | | | | |
Collapse
|
7
|
Sabetkasaie M, Khansefid N, Ladgevardi MARS. Possible role of NMDA receptors in antinociception induced by rilmenidine in mice in the formalin test. Eur J Pain 2006; 11:535-41. [PMID: 16934506 DOI: 10.1016/j.ejpain.2006.07.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 06/20/2006] [Accepted: 07/10/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVES The aim of the study was to investigate the possible role of MK-801, an NMDA antagonist, in analgesia induced by rilmenidine, an imidazoline (I(1)) agonist, in mice in the formalin test. METHODS 25 microl of formalin 2.5% was injected into the dorsal surface of the right hind paw of the mouse. Pain response was scored after formalin injection for a period of 50 min. A weighted average of nociceptive score, ranging from 0 to 3, was calculated. The mean +/-SEM of scores between 0-5 and 15-40 min after formalin injection was presented. RESULTS The study showed that rilmenidine (1.25, 2.5 and 5 mg/kg, i.p.) produced analgesia dose-dependently (p<0.001) in formalin test. In addition, the results demonstrated that efaroxan (0.1 and 1 mg/kg, i.p.) could reduce the antinociceptive effect of rilmenidine (2.5 mg/kg, i.p.) (p<0.01) in animals, however, yohimbine (0.1 and 0.2 mg/kg, i.p.) could not block the analgesia induced by rilmenidine (2.5 mg/kg, i.p.) (p>0.05). On the other hand, MK-801 (0.05 mg/kg, i.p.) reduced the pain related behaviors in mice (p>0.05). Moreover, our findings demonstrated that MK-801 (0.01 mg/kg, i.p.) could potentiate the analgesic effect of rilmenidine (1.25 mg/kg, i.p.) significantly (p<0.01). CONCLUSIONS The present study suggests that imidazoline (I(1)) receptors play an important role in mediating the antinociception induced by rilmenidine in formalin test. Furthermore, it may be concluded that there is an interaction between NMDA receptors and imidazoline (I(1)) binding sites.
Collapse
Affiliation(s)
- Masoomeh Sabetkasaie
- Department of Pharmacology and Neuroscience Research Center, School of Medicine, Shaheed Beheshti University of Medical Sciences, P.O. Box 19835-355, Tehran, Iran.
| | | | | |
Collapse
|
8
|
Georges F, Caillé S, Vouillac C, Le Moine C, Stinus L. Role of imidazoline receptors in the anti-aversive properties of clonidine during opiate withdrawal in rats. Eur J Neurosci 2005; 22:1812-6. [PMID: 16197523 DOI: 10.1111/j.1460-9568.2005.04356.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Clonidine is used as a treatment for heroin addiction. Previous studies have reported that clonidine attenuated conditioned place aversion (CPA) to naloxone-precipitated opiate withdrawal by acting on alpha2 adrenoceptors (alpha2R). However, clonidine acts as a partial agonist both at alpha2R and at imidazoline-1 receptors (I1Rs). The current study was designed to determine the role of I1R in the induction of naloxone-induced CPA in morphine-dependent rats. Morphine dependence was induced by subcutaneous implantation of morphine pellets. Morphine-dependent rats were tested in a three-chamber place-aversion apparatus. A range of agonists were chosen on the basis of their differential selectivity for alpha2R and I1R. As expected, pretreatment with clonidine prevented naloxone-induced CPA. By contrast, pretreatment with a selective alpha2R agonist (UK14304) failed to prevent the CPA. We then tested whether the high affinity of clonidine for I1R was responsible for the difference between these two alpha2R agonists. Rilmenidine (a mixed alpha2R/I1R agonist) attenuated aversion to opiate withdrawal in a dose-dependent manner. The action of clonidine on I1R was studied by co-administering clonidine with RX821002, a specific alpha2R antagonist. Co-treatment with RX821002 and clonidine blocked naloxone-induced CPA. These results indicate that the pharmacologically protective effects of clonidine on naloxone-induced CPA are related to actions on I1RS as well as alpha2Rs.
Collapse
Affiliation(s)
- F Georges
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5541 'Interactions Neuronales et Comportements', BP28, Université Victor Segalen, Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux cedex, France.
| | | | | | | | | |
Collapse
|
9
|
Sharma V, Tepe JJ. Diastereochemical Diversity of Imidazoline Scaffolds via Substrate Controlled TMSCl Mediated Cycloaddition of Azlactones. Org Lett 2005; 7:5091-4. [PMID: 16235965 DOI: 10.1021/ol052118w] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] We report herein a trimethylsilyl chloride mediated substrate controlled 1,3-dipolar cycloaddition for the diastereoselective synthesis of either syn- or anti-imidazolines. This method provides scaffolds with four points of diversity and control over two stereocenters.
Collapse
Affiliation(s)
- Vasudha Sharma
- Department of Chemistry, Michigan State University, East Lansing, 48823, USA
| | | |
Collapse
|
10
|
Dragan U, Stephan S, Jean-Daniel E, Pascal B, Hugues G. LNP 906, the first high-affinity photoaffinity ligand selective for I1 imidazoline receptors. Br J Pharmacol 2005; 142:609-17. [PMID: 15178642 PMCID: PMC1574957 DOI: 10.1038/sj.bjp.0705784] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1 The hypotensive effect of imidazoline-like drugs, such as clonidine, was attributed both to alpha2-adrenergic receptors and nonadrenergic imidazoline receptors, which are divided into I1, I2 and I3 subtypes. 2 We have recently synthesized a derivative of (2-(2-chloro-4-iodo-phenylamino)-5-methyl-pyrroline (LNP 911), the first high-affinity and selective ligand for I1 receptors (I1R), with a photoactivable function (LNP 906). 3 This work aims to test whether this derivative retained the binding properties of LNP 911 and bound irreversibly to I1R. 4 Binding studies showed that LNP 906 exhibited nanomolar affinity for I1R and was selective for I1R over I2 receptors and alpha2-adrenergic receptors (alpha2Ars). 5 Upon exposure to u.v. light, LNP 906 irreversibly blocked the binding of [125I]-paraiodoclonidine (PIC) to I1R, time- and dose-dependently, on PC12 cell membranes and interacted with I1R in a reversible and competitive manner in the absence of light. Pharmacological studies showed that this blockade was prevented by the concomitant presence of rilmenidine (a well-known I1 agonist), but not by rauwolscine (an alpha2 antagonist). 6 Finally, LNP 906 clearly antagonized the decrease in forskolin-stimulated cAMP level induced by rilmenidine, but not by melatonin. 7 These results indicate that LNP 906 is the first high-affinity and selective photoaffinity ligand for I1R and that it behaves as an I1R antagonist.
Collapse
Affiliation(s)
- Urosevic Dragan
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, INSERM E 0333, Faculté de Médecine, Université Louis Pasteur, 11 rue Humann, 67000 Strasbourg, France
| | - Schann Stephan
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, INSERM E 0333, Faculté de Médecine, Université Louis Pasteur, 11 rue Humann, 67000 Strasbourg, France
| | - Ehrhardt Jean-Daniel
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, INSERM E 0333, Faculté de Médecine, Université Louis Pasteur, 11 rue Humann, 67000 Strasbourg, France
| | - Bousquet Pascal
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, INSERM E 0333, Faculté de Médecine, Université Louis Pasteur, 11 rue Humann, 67000 Strasbourg, France
| | - Greney Hugues
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, INSERM E 0333, Faculté de Médecine, Université Louis Pasteur, 11 rue Humann, 67000 Strasbourg, France
- Author for correspondence:
| |
Collapse
|
11
|
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.
Collapse
|
12
|
Sabetkasaie M, Vala S, Khansefid N, Hosseini AR, Sadat Ladgevardi MAR. Clonidine and guanfacine-induced antinociception in visceral pain: possible role of α2/I2 binding sites. Eur J Pharmacol 2004; 501:95-101. [PMID: 15464067 DOI: 10.1016/j.ejphar.2004.08.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 07/30/2004] [Accepted: 08/04/2004] [Indexed: 01/15/2023]
Abstract
Visceral pain is one of the most common forms of pain which is poorly understood. We now studied the influence of imidazoline/guanidinium compounds such as clonidine and guanfacine on visceral pain in the presence or absence of yohimbine and benazoline. To produce visceral pain-related behaviours, formalin (10%) was administered by inserting a fine cannula into the colon via the anus. Each experiment took 1 h. Clonidine (0.001, 0.01 and 0.1 mg/kg, i.p.) and guanfacine (2.5, 5 and 10 mg/kg, i.p.) produced analgesia dose dependently. The clonidine response was inhibited by yohimbine (0.2 mg/kg, i.p.). On the other hand, benazoline (5 mg/kg, i.p.) blocked the antinociceptive effect of guanfacine (5 mg/kg). Benazoline (2.5 and 5 mg/kg) itself also induced analgesia in inflammatory colonic pain. In this study, we used morphine to ensure that the behavioural responses were pain-related. Our results showed that morphine (2.5, 5 and 10 mg/kg, s.c.) produced a dose-dependent antinociception. The morphine (7 mg/kg, s.c.) response was reduced by naloxone (2 mg/kg, i.p.). However, we concluded that both imidazoline (I(2)) and alpha(2)-adrenoceptors may play a role in producing analgesia in visceral pain.
Collapse
Affiliation(s)
- Masoumeh Sabetkasaie
- Department of Pharmacology and Neuroscience Research Center, School of Medicine, Shaheed Beheshti University of Medical Sciences, P.O. Box 19835-355, Tehran, Iran.
| | | | | | | | | |
Collapse
|
13
|
Georges F, Aston-Jones G. Prolonged activation of mesolimbic dopaminergic neurons by morphine withdrawal following clonidine: participation of imidazoline and norepinephrine receptors. Neuropsychopharmacology 2003; 28:1140-9. [PMID: 12700697 DOI: 10.1038/sj.npp.1300161] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The alpha2 adrenoceptor (alpha2R) agonist clonidine is used as a treatment for heroin addiction. Substantial evidence indicates that dopaminergic and noradrenergic systems have key roles in opiate dependence and withdrawal but the possible interactions between these two pathways remain unclear. The objective of this study was to establish the effects of clonidine pretreatment on ventral tegmental area dopaminergic (VTA DA) neuronal activity during morphine withdrawal. Responses of VTA DA neurons to withdrawal precipitated by naltrexone were characterized in anesthetized rats using extracellular recordings. As expected, withdrawal produced a marked inhibition of VTA DA neuronal activity. However, pretreatment with clonidine prevented this inhibition induced by withdrawal, and instead produced a long-lasting activation of firing rate (+50%) and burst firing (+19%). In contrast, pretreatment with a more selective alpha2R agonist, UK14304, did not prevent the inhibition of VTA DA neuron activity during withdrawal. We tested whether the high affinity of clonidine for imidazoline-1 receptors (I1Rs) was responsible for the difference between these two alpha2R agonists. In morphine-dependent rats pretreated with rilmenidine (mixed alpha2R/I1R agonist), precipitation of withdrawal elicited a 22% increase of VTA DA impulse activity. The action of clonidine on I1Rs was studied by coadministering clonidine with RX821002, a specific alpha2R antagonist. Pretreatment with RX821002 plus clonidine prevented the inhibition of VTA DA activity during withdrawal but failed to produce excitation. These results indicate that the pharmacological effects of clonidine on VTA DA neurons during morphine withdrawal is related to actions on I1Rs as well as alpha2Rs.
Collapse
Affiliation(s)
- François Georges
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19104, USA
| | | |
Collapse
|
14
|
Touzeau F, Arrault A, Guillaumet G, Scalbert E, Pfeiffer B, Rettori MC, Renard P, Mérour JY. Synthesis and biological evaluation of new 2-(4,5-dihydro-1H-imidazol-2-yl)-3,4-dihydro-2H-1,4-benzoxazine derivatives. J Med Chem 2003; 46:1962-79. [PMID: 12723959 DOI: 10.1021/jm021050c] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
2-(4,5-Dihydro-1H-imidazol-2-yl)-3,4-dihydro-2H-1,4-benzoxazine derivatives and tricyclic analogues with a fused additional ring on the nitrogen atom of the benzoxazine moiety have been prepared and evaluated for their cardiovascular effects as potential antihypertensive agents. The imidazoline ring was generated by reaction of the corresponding ethyl ester with ethylenediamine. Affinities for imidazoline binding sites (IBS) I(1) and I(2) and alpha(1) and alpha(2) adrenergic receptors were evaluated as well as the effects on mean arterial blood pressure (MAP) and heart rate (HR) of spontaneously hypertensive rats. With few exceptions the most active compounds on MAP were those with high affinities for IBS and alpha(2) receptor. Among these, compound 4h was the most interesting and is now, together with its enantiomers, under complementary pharmacological evaluation.
Collapse
MESH Headings
- Adrenal Medulla/metabolism
- Animals
- Antihypertensive Agents/chemical synthesis
- Antihypertensive Agents/chemistry
- Antihypertensive Agents/pharmacology
- Binding Sites
- Blood Pressure/drug effects
- Cattle
- Frontal Lobe/drug effects
- Frontal Lobe/metabolism
- Heart Rate/drug effects
- Imidazoles/chemical synthesis
- Imidazoles/chemistry
- Imidazoles/pharmacology
- Imidazoline Receptors
- In Vitro Techniques
- Kidney/drug effects
- Kidney/metabolism
- Oxazines/chemical synthesis
- Oxazines/chemistry
- Oxazines/pharmacology
- Rabbits
- Radioligand Assay
- Rats
- Rats, Inbred SHR
- Rats, Wistar
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Drug/drug effects
- Receptors, Drug/metabolism
- Stereoisomerism
- Structure-Activity Relationship
Collapse
Affiliation(s)
- Frédérique Touzeau
- Institut de Chimie Organique et Analytique, UMR-CNRS 6005, BP 6759, Université d'Orléans, 45067 Orléans Cedex 2, France
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Greney H, Urosevic D, Schann S, Dupuy L, Bruban V, Ehrhardt JD, Bousquet P, Dontenwill M. [125I]2-(2-chloro-4-iodo-phenylamino)-5-methyl-pyrroline (LNP 911), a high-affinity radioligand selective for I1 imidazoline receptors. Mol Pharmacol 2002; 62:181-91. [PMID: 12065769 DOI: 10.1124/mol.62.1.181] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The I1 subtype of imidazoline receptors (I1R) is a plasma membrane protein that is involved in diverse physiological functions. Available radioligands used so far to characterize the I(1)R were able to bind with similar affinities to alpha2-adrenergic receptors (alpha2-ARs) and to I1R. This feature was a major drawback for an adequate characterization of this receptor subtype. New imidazoline analogs were therefore synthesized and the present study describes one of these compounds, 2-(2-chloro-4-iodo-phenylamino)-5-methyl-pyrroline (LNP 911), which was of high affinity and selectivity for the I1R. LNP 911 was radioiodinated and its binding properties characterized in different membrane preparations. Saturation experiments with [125I]LNP 911 revealed a single high affinity binding site in PC-12 cell membranes (K(D) = 1.4 nM; B(max) = 398 fmol/mg protein) with low nonspecific binding. [125I]LNP 911 specific binding was inhibited by various imidazolines and analogs but was insensitive to guanosine-5'-O-(3-thio)triphosphate. The rank order of potency of some competing ligands [LNP 911, PIC, rilmenidine, 4-chloro-2-(imidazolin-2-ylamino)-isoindoline (BDF 6143), lofexidine, and clonidine] was consistent with the definition of [125I]LNP 911 binding sites as I1R. However, other high-affinity I1R ligands (moxonidine, efaroxan, and benazoline) exhibited low affinities for these binding sites in standard binding assays. In contrast, when [125I]LNP 911 was preincubated at 4 degrees C, competition curves of moxonidine became biphasic. In this case, moxonidine exhibited similar high affinities on [125I]LNP 911 binding sites as on I1R defined with [125I]PIC. Moxonidine proved also able to accelerate the dissociation of [125I]LNP 911 from its binding sites. These results suggest the existence of an allosteric modulation at the level of the I1R, which seems to be corroborated by the dose-dependent enhancement by LNP 911 of the agonist effects on the adenylate cyclase pathway associated to I1R. Because [125I]LNP 911 was unable to bind to the I2 binding site and alpha2AR, our data indicate that [125I]LNP 911 is the first highly selective radioiodinated probe for I1R with a nanomolar affinity. This new tool should facilitate the molecular characterization of the I1 imidazoline receptor.
Collapse
Affiliation(s)
- Hugues Greney
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, Faculté de Medecine, Strasbourg, France
| | | | | | | | | | | | | | | |
Collapse
|