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Omran A, Eslamimehr S, Crider AM, Neumann WL. Synthesis of 3-(3-hydroxyphenyl)pyrrolidine dopamine D 3 receptor ligands with extended functionality for probing the secondary binding pocket. Bioorg Med Chem Lett 2018; 28:1897-1902. [PMID: 29631959 DOI: 10.1016/j.bmcl.2018.03.084] [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: 01/17/2018] [Revised: 03/14/2018] [Accepted: 03/29/2018] [Indexed: 01/10/2023]
Abstract
A series of 3-(3-hydroxyphenyl)pyrrolidine analogues which incorporate N-alkyl groups and N-butylamide-linked benzamide functionality have been synthesized and their in vitro binding affinities at human dopamine receptors have been evaluated. Our ligand design strategy was to take the 3-(3-hydroxyphenyl)pyrrolidine scaffold and extend functionality from the orthosteric binding site to the secondary binding pocket for enhancing affinity and selectivity for the D3 receptor. The N-alkyl analogues constitute a homologous series from N-pentyl to N-decyl to probe the length/bulk tolerance of the secondary binding pocket of the D3 receptor. Enantiomeric 3-(3-hydroxyphenyl)pyrrolidine analogues were also prepared in order to test the chirality preference of the orthosteric binding site for this scaffold. Benzamide analogues were prepared to enhance affinity and/or selectivity based upon the results of the homologous series.
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Affiliation(s)
- Anahid Omran
- Department of Pharmaceutical Sciences, School of Pharmacy, Southern Illinois University Edwardsville, 220 University Park Drive, Edwardsville, IL 62026, USA
| | - Shakiba Eslamimehr
- Department of Pharmaceutical Sciences, School of Pharmacy, Southern Illinois University Edwardsville, 220 University Park Drive, Edwardsville, IL 62026, USA
| | - A Michael Crider
- Department of Pharmaceutical Sciences, School of Pharmacy, Southern Illinois University Edwardsville, 220 University Park Drive, Edwardsville, IL 62026, USA
| | - William L Neumann
- Department of Pharmaceutical Sciences, School of Pharmacy, Southern Illinois University Edwardsville, 220 University Park Drive, Edwardsville, IL 62026, USA.
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2
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Tu Z, Li S, Li A, Taylor M, Ho D, Malik M, Luedtke RR, Mach RH. Synthesis and in vitro pharmacological evaluation of indolyl carboxylic amide analogues as D 3 dopamine receptor selective ligands. MEDCHEMCOMM 2013; 4:1283-1289. [PMID: 24156012 PMCID: PMC3804115 DOI: 10.1039/c3md00098b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of substituted 1H-indolyl carboxylic acid amides that contain a N-(2-methoxyphenyl)piperazine or N-(2-fluoroethoxy)piperazine group were synthesized and their affinities for human dopamine D2, D3, and D4 receptors were determined. Two of these compounds, 14a and 14b, displayed high binding affinity at D3 (Ki = 0.18 and 0.4 nM, respectively), and selectivity for D3vs. D2 receptors (87-fold and 60-fold, respectively). These two compounds had low binding affinity at D4 receptors and σ receptor sites. The intrinsic activity of these compounds at D2 and D3 receptors was determined using a forskolin-dependent adenylyl cyclase inhibition assay; both 14a and 14b were found to be partial agonists. Furthermore, for compound 14a, the log D value of 2.85 suggested it has suitable lipophilicity for crossing the blood-brain-barrier.
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Affiliation(s)
- Zhude Tu
- Washington University School of Medicine, St. Louis, MO, 63110, USA., Fax: +1-314-362-8555; Tel: +1-314-362-8538
| | - Shihong Li
- Washington University School of Medicine, St. Louis, MO, 63110, USA., Fax: +1-314-362-8555; Tel: +1-314-362-8538
| | - Aixiao Li
- Washington University School of Medicine, St. Louis, MO, 63110, USA., Fax: +1-314-362-8555; Tel: +1-314-362-8538
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - David Ho
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Maninder Malik
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Robert R. Luedtke
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Robert H. Mach
- Washington University School of Medicine, St. Louis, MO, 63110, USA., Fax: +1-314-362-8555; Tel: +1-314-362-8538
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3
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Ortega R, Raviña E, Masaguer CF, Areias F, Brea J, Loza MI, López L, Selent J, Pastor M, Sanz F. Synthesis, binding affinity and SAR of new benzolactam derivatives as dopamine D3 receptor ligands. Bioorg Med Chem Lett 2009; 19:1773-8. [PMID: 19217777 DOI: 10.1016/j.bmcl.2009.01.067] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 01/20/2009] [Accepted: 01/22/2009] [Indexed: 10/21/2022]
Abstract
A series of new benzolactam derivatives was synthesized and the derivatives were evaluated for their affinities at the dopamine D(1), D(2), and D(3) receptors. Some of these compounds showed high D(2) and/or D(3) affinity and selectivity over the D(1) receptor. The SAR study of these compounds revealed structural characteristics that decisively influenced their D(2) and D(3) affinities. Structural models of the complexes between some of the most representative compounds of this series and the D(2) and D(3) receptors were obtained with the aim of rationalizing the observed experimental results. Moreover, selected compounds showed moderate binding affinity on 5-HT(2A) which could contribute to reducing the occurrence of extrapyramidal side effects as potential antipsychotics.
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Affiliation(s)
- Raquel Ortega
- Departamento de Química Orgánica, Facultad de Farmacia, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
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4
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Biswas S, Zhang S, Fernandez F, Ghosh B, Zhen J, Kuzhikandathil E, Reith MEA, Dutta AK. Further Structure–Activity Relationships Study of Hybrid 7-{[2-(4-Phenylpiperazin-1-yl)ethyl]propylamino}-5,6,7,8-tetrahydronaphthalen-2-ol Analogues: Identification of a High-Affinity D3-Preferring Agonist with Potent in Vivo Activity with Long Duration of Action. J Med Chem 2007; 51:101-17. [DOI: 10.1021/jm070860r] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Swati Biswas
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Suhong Zhang
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Fernando Fernandez
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Balaram Ghosh
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Juan Zhen
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Eldo Kuzhikandathil
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Maarten E. A. Reith
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
| | - Aloke K. Dutta
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, Millhauser Laboratories, Department of Psychiatry, New York University School of Medicine, New York, New York 10016, and Department of Pharmacology and Physiology, UMDNJ—New Jersey Medical School, Newark, New Jersey 07103
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5
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Boeckler F, Gmeiner P. The structural evolution of dopamine D3 receptor ligands: structure-activity relationships and selected neuropharmacological aspects. Pharmacol Ther 2006; 112:281-333. [PMID: 16905195 DOI: 10.1016/j.pharmthera.2006.04.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Accepted: 04/13/2006] [Indexed: 01/13/2023]
Abstract
"Evolution consists largely of molecular tinkering."-Following the famous concept of the molecular geneticist and medicine Nobel laureate François Jacob, in this review we describe the structural evolution of dopamine D3 receptor ligands from the natural agonist dopamine (DA) to highly potent and subtype selective new agents by bioisosteric tinkering with well-established and privileged or novel and fancy chemical functionalities and scaffolds. Some of the more than 200 ligands presented herein have already achieved therapeutic or scientific value up to now, some will most likely achieve it in the future. Hence, great importance is not only attached to the relationship between structure and activity of the ligands, but also to their utility as pharmacological tools in animal models or as therapeutics in patients with neurological diseases or other disorders.
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Affiliation(s)
- Frank Boeckler
- Department of Medicinal Chemistry, Emil Fischer Center, Friedrich-Alexander University Erlangen-Nürnberg, Schuhstrasse 19, 91052 Erlangen, Germany.
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6
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Sanger DJ. The search for novel antipsychotics: pharmacological and molecular targets. Expert Opin Ther Targets 2005; 8:631-41. [PMID: 15584867 DOI: 10.1517/14728222.8.6.631] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
There can be little doubt that the newer, atypical, antipsychotic drugs provide improved treatment for many patients suffering from schizophrenia. However, the significant gains in tolerability produced by these drugs have not generally been accompanied by major advances in clinical efficacy. In particular, negative and cognitive symptoms, which may represent the core deficit of the disease, remain inadequately treated. There is, therefore, a pressing need for more effective drugs. A number of drug discovery and development programmes are currently underway in parallel with significant research into the basic neurobiology of the disease. All antipsychotic drugs currently used in the clinic are antagonists at dopamine D2 receptors, and dopamine neurotransmission seems likely to remain a major biological target for research. However, novel approaches to modulate dopaminergic neurotransmission selectively in relevant brain regions may be required. In addition, a range of non-dopaminergic targets including glutamate, serotonin, neurokinins and acetylcholine are also of major interest. It is likely, however, that the importance of many of these targets may lie in their relationships to and interactions with dopaminergic mechanisms. Finally, advances in genetics and molecular biology are identifying genes associated with a susceptibility to develop schizophrenia. It remains to be seen whether or not these genes and their associated proteins will provide molecular targets for successful drug discovery.
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Affiliation(s)
- David J Sanger
- Sanofi-Synthelabo Research, 31 Avenue Paul Vaillant Couturier, 92220 Bagneux, France.
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7
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Heidbreder CA, Gardner EL, Xi ZX, Thanos PK, Mugnaini M, Hagan JJ, Ashby CR. The role of central dopamine D3 receptors in drug addiction: a review of pharmacological evidence. ACTA ACUST UNITED AC 2005; 49:77-105. [PMID: 15960988 PMCID: PMC3732040 DOI: 10.1016/j.brainresrev.2004.12.033] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2004] [Revised: 10/21/2004] [Accepted: 12/06/2004] [Indexed: 10/25/2022]
Abstract
The cDNA for the dopamine D3 receptor was isolated and characterized in 1990. Subsequent studies have indicated that D3 receptors, as well as D3 receptor mRNA, are primarily localized in limbic regions in mammals. This finding led to the postulate that D3 receptors may be involved in drug dependence and addiction. However, this hypothesis has been difficult to test due to the lack of compounds with high selectivity for central D3 receptors. The interpretation of results from studies using mixed D2/D3 agonists and/or antagonists is problematic because these agents have low selectivity for D3 over D2 receptors and it is likely that their actions are primarily related to D2 receptor antagonism and possibly interaction with other neurotransmitter receptors. Currently, with the synthesis and characterization of new highly selective D3 receptor antagonists such as SB-277011-A this difficulty has been surmounted. The purpose of the present article is to review, for the first time, the effects of various putative D3 receptor selective compounds in animal models of drug dependence and addiction. The results obtained with highly selective D3 receptor antagonists such as SB-277011-A, SB-414796, and NGB-2904 indicate that central D3 receptors may play an important role in drug-induced reward, drug-taking, and cue-, drug-, and stress-induced reinstatement of drug-seeking behavior. Provided these results can be extrapolated to human drug addicts, they suggest that selective DA D3 receptor antagonists may prove effective as potential pharmacotherapeutic agents to manage drug dependence and addiction.
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Affiliation(s)
- Christian A. Heidbreder
- Centre of Excellence for Drug Discovery in Psychiatry, GlaxoSmithKline Pharmaceuticals, 37135 Verona, Italy
| | - Eliot L. Gardner
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland 21224-6823, USA
| | - Zheng-Xiong Xi
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland 21224-6823, USA
| | - Panayotis K. Thanos
- Medical Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
| | - Manolo Mugnaini
- Centre of Excellence for Drug Discovery in Psychiatry, GlaxoSmithKline Pharmaceuticals, 37135 Verona, Italy
| | - Jim J. Hagan
- Centre of Excellence for Drug Discovery in Psychiatry, GlaxoSmithKline Pharmaceuticals, 37135 Verona, Italy
| | - Charles R. Ashby
- Pharmaceutical Sciences Department, Saint John’s University, 8000 Utopia Parkway, Jamaica, NY 11439-0001, USA
- Corresponding author. Fax: +1 718 990 1877. (C.R. Ashby)
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8
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Abstract
The behavioral and pathophysiological role of the dopamine D(3) receptor, which was deduced from anatomical, lesion and drug treatment studies in the ten years following cloning of the receptor, indicated that its functions differed from those of the D(2) receptor. There is increasingly strong evidence that D(3) receptor antagonists will be effective antipsychotic agents. In this regard, an amelioration of the negative and cognitive symptoms of schizophrenia holds the most promise for D(3) receptor antagonists, a concept currently under clinical evaluation. In addition, D(3) receptors could be involved in behavioral sensitization and the potential application of D(3) receptor antagonists in the treatment of drug abuse is undergoing intensive experimental investigation.
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Affiliation(s)
- Jeffrey N Joyce
- T.H. Christopher Center for Parkinson's Disease, Sun Health Research Institute, 10515 West Santa Fe Drive, Sun City, 85351, USA.
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9
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Dutta AK, Venkataraman SK, Fei XS, Kolhatkar R, Zhang S, Reith MEA. Synthesis and biological characterization of novel hybrid 7-[[2-(4-phenyl-piperazin-1-yl)-ethyl]-propyl-amino]-5,6,7,8-tetrahydro-naphthalen-2-ol and their heterocyclic bioisosteric analogues for dopamine D2 and D3 receptors. Bioorg Med Chem 2005; 12:4361-73. [PMID: 15265488 DOI: 10.1016/j.bmc.2004.06.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Accepted: 06/11/2004] [Indexed: 11/23/2022]
Abstract
In a recent preliminary communication we described the development of a series of hybrid molecules for the dopamine D2 and D3 receptor subtypes. The design of these compounds was based on combining pharmacophoric elements of aminotetralin and piperazine molecular fragments derived from known dopamine receptor agonist and antagonist molecules. Molecules developed from this approach exhibited high affinity and selectivity for the D3 receptor as judged from preliminary [(3)H]spiperone binding data. In this report, we have expanded our previous finding by developing additional novel molecules and additionally evaluated functional activities of these novel molecules in the [(3)H]thymidine incorporation mitogenesis assay. The binding results indicated highest selectivity in the bioisosteric benzothiazole derivative N6-[2-(4-phenyl-piperazin-1-yl)-ethyl]-N6-propyl-4,5,6,7-tetrahydro-benzothiazole-2,6-diamine (14) for the D3 receptor whereas the racemic compound 7-([2-[4-(2,3-dichloro-phenyl)-piperazin-1-yl]-ethyl]-propyl-amino)-5,6,7,8-tetrahydro-naphthalen-2-ol (10c) showed the strongest potency. Mitogenesis studies to evaluate functional activity demonstrated potent agonist properties in these novel derivatives for both D2 and D3 receptors. In this regard, compound 7-[[4-(4-phenyl-piperazin-1-yl)-butyl]-prop-2-ynyl-amino]-5,6,7,8-tetrahydro-naphthalen-2-ol (7b) exhibited the most potent agonist activity at the D3 receptor, 10 times more potent than quinpirole and was also the most selective compound for the D3 receptor in this series. Racemic compound 10a was resolved; however, little separation of activity was found between the two enantiomers of 10a. The marginally more active enantiomer (-)-10a was examined in vivo using the 6-OH-DA induced unilaterally lesioned rat model to evaluate its activity in producing contralateral rotations. The results demonstrated that in comparison to the reference compound apomorphine, (-)-10a was quite potent in inducing contralateral rotations and exhibited longer duration of action.
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Affiliation(s)
- Aloke K Dutta
- Wayne State University, Department of Pharmaceutical Sciences, Applebaum College of Pharmacy and Health Science, RM# 3128, Detroit, MI 48202, USA.
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10
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Lenz C, Boeckler F, Hübner H, Gmeiner P. Analogues of FAUC 73 revealing new insights into the structural requirements of nonaromatic dopamine D3 receptor agonists. Bioorg Med Chem 2004; 12:113-7. [PMID: 14697776 DOI: 10.1016/j.bmc.2003.10.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Employing the nonaromatic D3 agonist FAUC 73 as a lead compound, the dopaminergic enynes 1a,b and the diene 2 (FAUC 206) were synthesized via palladium-catalyzed cross-coupling. FAUC 206 showed remarkable D3 affinity and enhanced selectivity over D4 when compared to the lead compound. To learn more about the bioactive structure of the diene moiety, computational studies including DFT-based conformational analysis and calculations of the magnetic shielding properties were performed. The electrostatic properties of the pharmacophoric pi-systems were visualized by diagnostic MEP maps.
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Affiliation(s)
- Carola Lenz
- Department of Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University, Schuhstrasse 19, D-91052, Erlangen, Germany
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11
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Mach UR, Hackling AE, Perachon S, Ferry S, Wermuth CG, Schwartz JC, Sokoloff P, Stark H. Development of Novel 1,2,3,4-Tetrahydroisoquinoline Derivatives and Closely Related Compounds as Potent and Selective Dopamine D3 Receptor Ligands. Chembiochem 2004; 5:508-18. [PMID: 15185375 DOI: 10.1002/cbic.200300784] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Based on N-alkylated 1,2,3,4-tetrahydroisoquinoline derivatives, which are structurally related to the partial agonist BP 897, a series of novel, selective dopamine D3 receptor antagonists has been synthesised. Derivatisation included changes in the arylamide moiety and the tetrahydroisoquinoline substructure leading to compounds with markedly improved selectivities and affinities in the low nanomolar concentration range. From the 55 structures presented here, (E)-3-(4-iodophenyl)-N-(4-(1,2,3,4-tetrahydroisoquinolin-2-yl)butyl)acrylamide (51) has high affinity (Ki(hD3)=12 nM) and a 123-fold preference for the D3 receptor relative to the D2 receptor subtype. Its pharmacological profile offers the prospect of a novel radioligand as a tool for various dopamine D3-receptor-related in vitro and in vivo investigations.
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Affiliation(s)
- Ulrich R Mach
- Institut für Pharmazeutische Chemie, Johann Wolfgang Goethe-Universität, Marie Curie Strasse 9, 60439 Frankfurt am Main, Germany
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12
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Millan MJ, Cussac D, Gobert A, Lejeune F, Rivet JM, Mannoury La Cour C, Newman-Tancredi A, Peglion JL. S32504, a novel naphtoxazine agonist at dopamine D3/D2 receptors: I. Cellular, electrophysiological, and neurochemical profile in comparison with ropinirole. J Pharmacol Exp Ther 2004; 309:903-20. [PMID: 14978194 DOI: 10.1124/jpet.103.062398] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
S32504 [(+)-trans-3,4,4a,5,6,10b-hexahydro-9-carbamoyl-4-propyl-2H-naphth[1,2-b]-1,4-oxazine] displayed marked affinity for cloned, human (h)D(3) receptors (pK(i), 8.1) at which, in total G-protein ([(35)S]GTPgammaS binding, guanosine-5'-O-(3-[(35)S]thio)-triphosphate), Galpha(i3) (antibody capture/scintillation proximity), and mitogen-activated protein kinase (immunoblot) activation procedures, it behaved as an agonist: pEC(50) values, 8.7, 8.6, and 8.5, respectively. These actions were blocked by haloperidol and the selective D(3) receptor antagonist S33084 [(3aR,9bS)-N-[4-(8-cyano-1,3a,4,9b-tetrahydro-3H-benzopyrano[3,4-c]pyrrole-2-yl)-butyl]-(4-phenyl) benzamide)]. S32504 showed lower potency at hD(2S) and hD(2L) receptors in [(35)S]GTPgammaS binding (pEC(50) values, 6.4 and 6.7) and antibody capture/scintillation proximity (hD(2L), pEC(50), 6.6) procedures. However, reflecting signal amplification, it potently stimulated hD(2L) receptor-coupled mitogen-activated protein kinase (pEC(50), 8.6). These actions were blocked by haloperidol and the selective D(2) receptor antagonist L741,626 [4-(4-chlorophenyl)-1-(1H-indol-3-ylmethyl)piperidin-4-ol]. The affinity of S32504 for hD(4) receptors was low (5.3) and negligible for hD(1) and hD(5) receptors (pK(i), <5.0). S32504 showed weak agonist properties at serotonin(1A) ([(35)S]GTPgammaS binding, pEC(50), 5.0) and serotonin(2A) (G(q), pEC(50), 5.2) receptors and low affinity for other (>50) sites. In anesthetized rats, S32504 (0.0025-0.01 mg/kg, i.v.) suppressed electrical activity of ventrotegmental dopaminergic neurons. Correspondingly, S32504 (0.0025-0.63 mg/kg, s.c.) potently reduced dialysis levels (and synthesis) of dopamine in striatum, nucleus accumbens, and frontal cortex of freely moving rats, actions blocked by haloperidol and L741,626 but not by S33084. In contrast, S32504 only weakly inhibited serotonergic transmission and failed to affect noradrenergic transmission. Actions of S32504 were expressed stereospecifically versus its less active enantiomer S32601 [(-)-trans-3,4,4a,5,6,10b-hexahydro-9-carbomoyl-4-propyl-2H-naphth[1,2-b]-1,4-oxazine]. Although the D(3)/D(2) agonist and antiparkinsonian agent ropinirole mimicked the profile of S32504, it was less potent. In conclusion, S32504 is a potent and selective agonist at dopamine D(3) and D(2) receptors.
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Affiliation(s)
- Mark J Millan
- Psychopharmacology Department, Institut de Recherches Servier, Paris, France.
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13
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Abstract
Upon receipt in the dorsal horn (DH) of the spinal cord, nociceptive (pain-signalling) information from the viscera, skin and other organs is subject to extensive processing by a diversity of mechanisms, certain of which enhance, and certain of which inhibit, its transfer to higher centres. In this regard, a network of descending pathways projecting from cerebral structures to the DH plays a complex and crucial role. Specific centrifugal pathways either suppress (descending inhibition) or potentiate (descending facilitation) passage of nociceptive messages to the brain. Engagement of descending inhibition by the opioid analgesic, morphine, fulfils an important role in its pain-relieving properties, while induction of analgesia by the adrenergic agonist, clonidine, reflects actions at alpha(2)-adrenoceptors (alpha(2)-ARs) in the DH normally recruited by descending pathways. However, opioids and adrenergic agents exploit but a tiny fraction of the vast panoply of mechanisms now known to be involved in the induction and/or expression of descending controls. For example, no drug interfering with descending facilitation is currently available for clinical use. The present review focuses on: (1) the organisation of descending pathways and their pathophysiological significance; (2) the role of individual transmitters and specific receptor types in the modulation and expression of mechanisms of descending inhibition and facilitation and (3) the advantages and limitations of established and innovative analgesic strategies which act by manipulation of descending controls. Knowledge of descending pathways has increased exponentially in recent years, so this is an opportune moment to survey their operation and therapeutic relevance to the improved management of pain.
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Affiliation(s)
- Mark J Millan
- Department of Psychopharmacology, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy/Seine, Paris, France.
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