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Yang Y. Functional Selectivity of Dopamine D 1 Receptor Signaling: Retrospect and Prospect. Int J Mol Sci 2021; 22:ijms222111914. [PMID: 34769344 PMCID: PMC8584964 DOI: 10.3390/ijms222111914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 10/18/2021] [Accepted: 11/01/2021] [Indexed: 11/16/2022] Open
Abstract
Research progress on dopamine D1 receptors indicates that signaling no longer is limited to G protein-dependent cyclic adenosine monophosphate phosphorylation but also includes G protein-independent β-arrestin-related mitogen-activated protein kinase activation, regulation of ion channels, phospholipase C activation, and possibly more. This review summarizes recent studies revealing the complexity of D1 signaling and its clinical implications, and suggests functional selectivity as a promising strategy for drug discovery to magnify the merit of D1 signaling. Functional selectivity/biased receptor signaling has become a major research front because of its potential to improve therapeutics through precise targeting. Retrospective pharmacological review indicated that many D1 ligands have some degree of mild functional selectivity, and novel compounds with extreme bias at D1 signaling were reported recently. Behavioral and neurophysiological studies inspired new methods to investigate functional selectivity and gave insight into the biased signaling of several drugs. Results from recent clinical trials also supported D1 functional selectivity signaling as a promising strategy for discovery and development of better therapeutics.
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Affiliation(s)
- Yang Yang
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA 17033, USA
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Jörg M, May LT, Mak FS, Lee KCK, Miller ND, Scammells PJ, Capuano B. Synthesis and pharmacological evaluation of dual acting ligands targeting the adenosine A2A and dopamine D2 receptors for the potential treatment of Parkinson's disease. J Med Chem 2014; 58:718-38. [PMID: 25490054 DOI: 10.1021/jm501254d] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A relatively new strategy in drug discovery is the development of dual acting ligands. These molecules are potentially able to interact at two orthosteric binding sites of a heterodimer simultaneously, possibly resulting in enhanced subtype selectivity, higher affinity, enhanced or modified physiological response, and reduced reliance on multiple drug administration regimens. In this study, we have successfully synthesized a series of classical heterobivalent ligands as well as a series of more integrated and "drug-like" dual acting molecules, incorporating ropinirole as a dopamine D2 receptor agonist and ZM 241385 as an adenosine A2A receptor antagonist. The best compounds of our series maintained the potency of the original pharmacophores at both receptors (adenosine A2A and dopamine D2). In addition, the integrated dual acting ligands also showed promising results in preliminary blood-brain barrier permeability tests, whereas the classical heterobivalent ligands are potentially more suited as pharmacological tools.
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Affiliation(s)
- Manuela Jörg
- Medicinal Chemistry and ‡Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences , 381 Royal Parade, Parkville, Victoria 3052, Australia
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Langen B, Dost R, Egerland U, Stange H, Hoefgen N. Effect of PDE10A inhibitors on MK-801-induced immobility in the forced swim test. Psychopharmacology (Berl) 2012; 221:249-59. [PMID: 22147257 DOI: 10.1007/s00213-011-2567-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 10/31/2011] [Indexed: 10/15/2022]
Abstract
RATIONALE Negative symptoms of schizophrenia are insufficiently treated by current antipsychotics. However, research is limited by the lack of validated models. Clinical data indicate that phencyclidine (PCP) abuse may induce symptoms resembling negative symptoms in humans. Based on that, Noda et al. proposed a model of PCP-induced increase of immobility in the forced swim test in mice as a model of depression-like negative symptoms of schizophrenia. OBJECTIVES The aim of the study was to evaluate the effect of phosphodiesterase 10A (PDE10A) inhibition in this model which was modified by using MK-801 instead of PCP. METHODS Increase of immobility in the forced swim test was induced by repeated MK-801 treatment followed by a 2-day washout in mice. The effect of haloperidol, clozapine, risperidone and PDE10A inhibitors was evaluated in this model, on open-field activity and acute MK-801-induced hyperactivity. RESULTS Repeated MK-801 treatment significantly increased immobility in the forced swim test without affecting open-field activity. It induced hypersensitivity to the dopamine D1 agonist A-68930, suggesting a hypofunction of the D1 pathway. The increase of immobility is reversed by clozapine and PDE10A inhibitors, but not by haloperidol. Clozapine and the PDE10A inhibitors did not enhance activity at effective doses. CONCLUSION The possibility to substitute PCP by MK-801 in this model indicates that the effect is mediated by their common mechanism of NMDA antagonism. PDE10A inhibitors similar to clozapine significantly antagonize the increase of immobility, suggesting a therapeutic potential for the treatment of negative symptoms. However, further validation of the model is necessary.
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Fowler JC, Bhattacharya S, Urban JD, Vaidehi N, Mailman RB. Receptor conformations involved in dopamine D(2L) receptor functional selectivity induced by selected transmembrane-5 serine mutations. Mol Pharmacol 2012; 81:820-31. [PMID: 22416052 DOI: 10.1124/mol.111.075457] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although functional selectivity is now widely accepted, the molecular basis is poorly understood. We have studied how aspects of transmembrane region 5 (TM5) of the dopamine D(2L) receptor interacts with three rationally selected rigid ligands (dihydrexidine, dinapsoline, and dinoxyline) and the reference compounds dopamine and quinpirole. As was expected from homology modeling, mutation of three TM5 serine residues to alanine (S5.42A, S5.43A, S5.46A) had little effect on antagonist affinity. All three mutations decreased the affinity of the agonist ligands to different degrees, S5.46A being somewhat less affected. Four functions [adenylate cyclase (AC), extracellular signal-regulated kinase 1/2 phosphorylation (MAPK), arachidonic acid release (AA), and guanosine 5'-O-(3-thio)triphosphate binding (GTPγS)] were assessed. The intrinsic activity (IA) of quinpirole was unaffected by any of the mutations, whereas S5.42A and S5.46A mutations abolished the activity of dopamine and the three rigid ligands, although dihydrexidine retained IA at MAPK function only with S5.42A. Remarkably, S5.43A did not markedly affect IA for AC and MAPK for any of the ligands and eliminated AA activity for dinapsoline and dihydrexidine but not dinoxyline. These data suggest that this mutation did not disrupt the overall conformation or signaling ability of the mutant receptors but differentially affected ligand activation. Computational studies indicate that these D(2) agonists stabilize multiple receptor conformations. This has led to models showing the stabilized conformations and interhelical and receptor-ligand contacts corresponding to the different activation pathways stabilized by various agonists. These data provide a basis for understanding D(2L) functional selectivity and rationally discovering functionally selective D(2) drugs.
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Affiliation(s)
- J Corey Fowler
- Division of Medicinal Chemistry and Toxicology Curriculum, University of North Carolina School of Medicine, Chapel Hill, NC, USA
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Rasheed N, Ahmad A, Singh N, Singh P, Mishra V, Banu N, Lohani M, Sharma S, Palit G. Differential response of A 68930 and sulpiride in stress-induced gastric ulcers in rats. Eur J Pharmacol 2010; 643:121-8. [DOI: 10.1016/j.ejphar.2010.06.032] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 05/19/2010] [Accepted: 06/16/2010] [Indexed: 11/16/2022]
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Mailman RB, Murthy V. Ligand functional selectivity advances our understanding of drug mechanisms and drug discovery. Neuropsychopharmacology 2010; 35:345-6. [PMID: 20010712 PMCID: PMC2952437 DOI: 10.1038/npp.2009.117] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Richard B Mailman
- Departments of Pharmacology and Neurology and The Neuroscience Institute, Pennsylvania State University College of Medicine and Milton S. Hershey Medical Center, Hershey, PA, USA,E-mail:
| | - Vishakantha Murthy
- Departments of Pharmacology and Neurology and The Neuroscience Institute, Pennsylvania State University College of Medicine and Milton S. Hershey Medical Center, Hershey, PA, USA
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Mailman RB, Murthy V. Third generation antipsychotic drugs: partial agonism or receptor functional selectivity? Curr Pharm Des 2010; 16:488-501. [PMID: 19909227 PMCID: PMC2958217 DOI: 10.2174/138161210790361461] [Citation(s) in RCA: 203] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 11/12/2009] [Indexed: 11/22/2022]
Abstract
Functional selectivity is the term that describes drugs that cause markedly different signaling through a single receptor (e.g., full agonist at one pathway and antagonist at a second). It has been widely recognized recently that this phenomenon impacts the understanding of mechanism of action of some drugs, and has relevance to drug discovery. One of the clinical areas where this mechanism has particular importance is in the treatment of schizophrenia. Antipsychotic drugs have been grouped according to both pattern of clinical action and mechanism of action. The original antipsychotic drugs such as chlorpromazine and haloperidol have been called typical or first generation. They cause both antipsychotic actions and many side effects (extrapyramidal and endocrine) that are ascribed to their high affinity dopamine D(2) receptor antagonism. Drugs such as clozapine, olanzapine, risperidone and others were then developed that avoided the neurological side effects (atypical or second generation antipsychotics). These compounds are divided mechanistically into those that are high affinity D(2) and 5-HT(2A) antagonists, and those that also bind with modest affinity to D(2), 5-HT(2A), and many other neuroreceptors. There is one approved third generation drug, aripiprazole, whose actions have been ascribed alternately to either D(2) partial agonism or D(2) functional selectivity. Although partial agonism has been the more widely accepted mechanism, the available data are inconsistent with this mechanism. Conversely, the D(2) functional selectivity hypothesis can accommodate all current data for aripiprazole, and also impacts on discovery compounds that are not pure D(2) antagonists.
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Affiliation(s)
- Richard B Mailman
- Penn State University College of Medicine - Milton S. Hershey Medical Center Department of Pharmacology. R130 500 University Dr., PO Box 850, Hershey, PA 17033-0850, USA.
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Penile erection and yawning induced by dopamine D2-like receptor agonists in rats: influence of strain and contribution of dopamine D2, but not D3 and D4 receptors. Behav Pharmacol 2009; 20:303-11. [DOI: 10.1097/fbp.0b013e32832ec5aa] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Collins GT, Newman AH, Grundt P, Rice KC, Husbands SM, Chauvignac C, Chen J, Wang S, Woods JH. Yawning and hypothermia in rats: effects of dopamine D3 and D2 agonists and antagonists. Psychopharmacology (Berl) 2007; 193:159-70. [PMID: 17393143 PMCID: PMC3094913 DOI: 10.1007/s00213-007-0766-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 03/05/2007] [Indexed: 10/23/2022]
Abstract
RATIONALE Identification of behaviors specifically mediated by the dopamine D2 and D3 receptors would allow for the determination of in vivo receptor selectivity and aide the development of novel therapeutics for dopamine-related diseases. OBJECTIVES These studies were aimed at evaluating the specific receptors involved in the mediation of D2/D3 agonist-induced yawning and hypothermia. MATERIALS AND METHODS The relative potencies of a series of D2-like agonists to produce yawning and hypothermia were determined. The ability of D3-selective and D2-selective antagonists to inhibit the induction of yawning and hypothermia were assessed and a series of D2/D3 antagonists were characterized with respect to their ability to alter yawning induced by a low and high dose of PD-128,907 and sumanirole-induced hypothermia. RESULTS D3-preferring agonists induced yawning at lower doses than those required to induce hypothermia and the D2-preferring agonist, sumanirole, induced hypothermia at lower doses than were necessary to induce yawning. The rank order of D3 selectivity was pramipexole > PD-128,907 = 7-OH-DPAT = quinpirole = quinelorane > apomorphine = U91,356A. Sumanirole had only D2 agonist effects. PG01,037, SB-277,011A, and U99,194 were all D3-selective antagonists, whereas haloperidol and L-741,626 were D2-selective antagonists and nafadotride's profile of action was more similar to the D2 antagonists than to the D3 antagonists. CONCLUSIONS D3 and D2 receptors have specific roles in the mediation of yawning and hypothermia, respectively, and the analysis of these effects allow inferences to be made regarding the selectivity of D2/D3 agonists and antagonists with respect to their actions at D2 and D3 receptors.
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Affiliation(s)
- Gregory T. Collins
- Department of Pharmacology, 1301 MSRB III, 1150 W. Medical Center Drive, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA
| | - Amy Hauck Newman
- Medicinal Chemistry Section, National Institutes on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224-0180, USA
| | - Peter Grundt
- Medicinal Chemistry Section, National Institutes on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224-0180, USA
| | - Kenner C. Rice
- Chemical Biology Research Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Bethesda, MD 20892, USA
| | - Stephen M. Husbands
- Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2, 7AY, U.K
| | - Cédric Chauvignac
- Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2, 7AY, U.K
| | - Jianyong Chen
- Departments of Internal Medicine and Medicinal Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109-0934, USA
| | - Shaomeng Wang
- Department of Pharmacology, 1301 MSRB III, 1150 W. Medical Center Drive, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA
- Departments of Internal Medicine and Medicinal Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109-0934, USA
| | - James H. Woods
- Department of Pharmacology, 1301 MSRB III, 1150 W. Medical Center Drive, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA, , Tel.: +1-734-764-9133, Fax: +1-734-764-7118
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Mailman RB. GPCR functional selectivity has therapeutic impact. Trends Pharmacol Sci 2007; 28:390-6. [PMID: 17629962 PMCID: PMC2958218 DOI: 10.1016/j.tips.2007.06.002] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 05/14/2007] [Accepted: 06/26/2007] [Indexed: 10/23/2022]
Abstract
Many in vitro data show that some ligands can cause the differential activation of signaling pathways mediated by a single receptor (termed 'functional selectivity'). It remains unclear, however, whether functionally selective properties are meaningful in vivo. Data obtained with experimental compounds that are functionally selective at the dopamine D2L receptor in vitro suggest that these properties might predict atypical behavioral actions. Moreover, the antipsychotic drug aripiprazole is commonly thought to be a D2 partial agonist, but data clearly show that aripiprazole is functionally selective in vitro. It is proposed that the effects of aripiprazole in animal models and humans can be reconciled only with its functionally selective D2 properties, not its partial D2 agonism. Together, these data provide support for the hypothesis that compounds with functionally selective properties in vitro are likely to have novel actions in vivo, opening doors to new avenues of drug discovery.
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Affiliation(s)
- Richard B Mailman
- Neurosciences Hospital, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7160, USA.
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Urban JD, Clarke WP, von Zastrow M, Nichols DE, Kobilka B, Weinstein H, Javitch JA, Roth BL, Christopoulos A, Sexton PM, Miller KJ, Spedding M, Mailman RB. Functional selectivity and classical concepts of quantitative pharmacology. J Pharmacol Exp Ther 2006; 320:1-13. [PMID: 16803859 DOI: 10.1124/jpet.106.104463] [Citation(s) in RCA: 830] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The concept of intrinsic efficacy has been enshrined in pharmacology for half of a century, yet recent data have revealed that many ligands can differentially activate signaling pathways mediated via a single G protein-coupled receptor in a manner that challenges the traditional definition of intrinsic efficacy. Some terms for this phenomenon include functional selectivity, agonist-directed trafficking, and biased agonism. At the extreme, functionally selective ligands may be both agonists and antagonists at different functions mediated by the same receptor. Data illustrating this phenomenon are presented from serotonin, opioid, dopamine, vasopressin, and adrenergic receptor systems. A variety of mechanisms may influence this apparently ubiquitous phenomenon. It may be initiated by differences in ligand-induced intermediate conformational states, as shown for the beta(2)-adrenergic receptor. Subsequent mechanisms that may play a role include diversity of G proteins, scaffolding and signaling partners, and receptor oligomers. Clearly, expanded research is needed to elucidate the proximal (e.g., how functionally selective ligands cause conformational changes that initiate differential signaling), intermediate (mechanisms that translate conformation changes into differential signaling), and distal mechanisms (differential effects on target tissue or organism). Besides the heuristically interesting nature of functional selectivity, there is a clear impact on drug discovery, because this mechanism raises the possibility of selecting or designing novel ligands that differentially activate only a subset of functions of a single receptor, thereby optimizing therapeutic action. It also may be timely to revise classic concepts in quantitative pharmacology and relevant pharmacological conventions to incorporate these new concepts.
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MESH Headings
- Animals
- Humans
- Ligands
- Protein Conformation
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/drug effects
- Receptors, Adrenergic, beta-2/physiology
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/drug effects
- Receptors, Cell Surface/physiology
- Receptors, Dopamine D1/chemistry
- Receptors, Dopamine D1/drug effects
- Receptors, Dopamine D1/physiology
- Receptors, Dopamine D2/chemistry
- Receptors, Dopamine D2/drug effects
- Receptors, Dopamine D2/physiology
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/physiology
- Receptors, Opioid, mu/chemistry
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/physiology
- Receptors, Vasopressin/chemistry
- Receptors, Vasopressin/drug effects
- Receptors, Vasopressin/physiology
- Signal Transduction
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Affiliation(s)
- Jonathan D Urban
- Curriculum in Toxicology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7160, USA
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12
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Neurotoxins and medicinals for the treatment of Parkinson’s disease. Part 2: dopamine receptors and their agonists. Pharm Chem J 2005. [DOI: 10.1007/s11094-006-0014-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Gay EA, Urban JD, Nichols DE, Oxford GS, Mailman RB. Functional selectivity of D2 receptor ligands in a Chinese hamster ovary hD2L cell line: evidence for induction of ligand-specific receptor states. Mol Pharmacol 2004; 66:97-105. [PMID: 15213300 DOI: 10.1124/mol.66.1.97] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There are now several examples of single G protein-coupled receptors to which binding of specific agonists causes differential effects on the associated signaling pathways. The dopamine D(2) receptor is of special importance because the selective activation of functional pathways has been shown both in vitro and in situ. For this reason, the present work characterized a series of rigid D(2) agonists in Chinese hamster ovary cells transfected with the human D(2L) receptor using three distinct functional endpoints: inhibition of cAMP synthesis, stimulation of mitogen-activated protein (MAP) kinase phosphorylation, and activation of G protein-coupled inwardly rectifying potassium channels (GIRKs). In this system, S-propylnorapomorphine (SNPA), R-propylnorapomorphine (RNPA), dihydrexidine (DHX), dinapsoline (DNS), and dinoxyline (DNX) all inhibited forskolin-stimulated adenylate cyclase activity to the same extent as the prototypical D(2) agonist quinpirole (QP). The rank order of potency was the following: RNPA >> QP = DNX > SNPA > DHX = DNS. For MAP kinase phosphorylation, DHX, DNS, DNX, and RNPA had efficacy similar to QP, whereas SNPA was a partial agonist. The rank order of potency for MAP kinase phosphorylation was RNPA >> QP = DNX > DHX > DNS = SNPA. DNX activated GIRK channels to the same extent as QP, whereas DHX and DNS were partial agonists, and RNPA and SNPA caused no appreciable activation. These findings indicate that DHX, DNS, RNPA, and SNPA have atypical functional properties at the hD(2L) receptor and display different patterns of functional selectivity. We hypothesize that this functional selectivity may be a result of ligand induction of specific conformations of the D(2L) receptor that activate only selected signaling pathways.
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Affiliation(s)
- Elaine A Gay
- Department of Psychiatry, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7160, USA
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Kilts JD, Connery HS, Arrington EG, Lewis MM, Lawler CP, Oxford GS, O'Malley KL, Todd RD, Blake BL, Nichols DE, Mailman RB. Functional selectivity of dopamine receptor agonists. II. Actions of dihydrexidine in D2L receptor-transfected MN9D cells and pituitary lactotrophs. J Pharmacol Exp Ther 2002; 301:1179-89. [PMID: 12023553 DOI: 10.1124/jpet.301.3.1179] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
D(2)-like dopamine receptors mediate functional changes via activation of inhibitory G proteins, including those that affect adenylate cyclase activity, and potassium and calcium channels. Although it is assumed that the binding of a drug to a single isoform of a D(2)-like receptor will cause similar changes in all receptor-mediated functions, it has been demonstrated in brain that the dopamine agonists dihydrexidine (DHX) and N-n-propyl-DHX are "functionally selective". The current study explores the underlying mechanism using transfected MN9D cells and D(2)-producing anterior pituitary lactotrophs. Both dopamine and DHX inhibited adenylate cyclase activity in a concentration-dependent manner in both systems, effects blocked by D(2), but not D(1), antagonists. In the MN9D cells, quinpirole and R-(-)-N-propylnorapomorphine (NPA) also inhibited the K(+)-stimulated release of [(3)H]dopamine in a concentration-responsive, antagonist-reversible manner. Conversely, neither DHX, nor its analogs, inhibited K(+)-stimulated [(3)H]dopamine release, although they antagonized the effects of quinpirole. S-(+)-NPA actually had the reverse functional selectivity profile from DHX (i.e., it was a full agonist at D(2L) receptors coupled to inhibition of dopamine release, but a weak partial agonist at D(2L) receptor-mediated inhibition of adenylate cyclase). In lactotrophs, DHX had little intrinsic activity at D(2) receptors coupled to G protein-coupled inwardly rectifying potassium channels, and actually antagonized the effects of dopamine at these D(2) receptors. Together, these findings provide compelling evidence for agonist-induced functional selectivity with the D(2L) receptor. Although the underlying molecular mechanism is controversial (e.g., "conformational induction" versus "drug-active state selection"), such data are irreconcilable with the widely held view that drugs have "intrinsic efficacy".
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Affiliation(s)
- Jason D Kilts
- Department of Psychiatry, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7160, USA
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Mottola DM, Kilts JD, Lewis MM, Connery HS, Walker QD, Jones SR, Booth RG, Hyslop DK, Piercey M, Wightman RM, Lawler CP, Nichols DE, Mailman RB. Functional selectivity of dopamine receptor agonists. I. Selective activation of postsynaptic dopamine D2 receptors linked to adenylate cyclase. J Pharmacol Exp Ther 2002; 301:1166-78. [PMID: 12023552 DOI: 10.1124/jpet.301.3.1166] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dihydrexidine (DHX), the first high-affinity D(1) dopamine receptor full agonist, is only 10-fold selective for D(1) versus D(2) receptors, having D(2) affinity similar to the prototypical agonist quinpirole. The D(2) functional properties of DHX and its more D(2) selective analog N-n-propyl-dihydrexidine (PrDHX) were explored in rat brain and pituitary. DHX and PrDHX had binding characteristics to D(2) receptors in rat striatum typical of D(2) agonists, binding to both high- and low-affinity sites and being sensitive to guanine-nucleotides. Consistent with these binding data, both DHX and PrDHX inhibited forskolin-stimulated cAMP synthesis in striatum with a potency and intrinsic activity equivalent to that of quinpirole. Unexpectedly, however, DHX and PrDHX had little functional effect at D(2) receptors expressed on dopaminergic neurons that mediate inhibition of cell firing, dopamine release, or dopamine synthesis. Quantitative receptor competition autoradiography demonstrated that DHX bound to D(2) receptors in striatum (predominantly postsynaptic receptor sites) with equal affinity as D(2) sites in the substantia nigra (autoreceptor sites). The data from these experiments, coupled with what is known about the location of specific dopamine receptor isoforms, lead to the hypothesis that DHX, after binding to D(2L) and D(2S) receptors, causes agonist-typical functional changes only at some of these receptors. This phenomenon (herein termed "functional selectivity") suggests that drugs may be targeted not only at specific receptor isoforms but also at separate functions mediated by a single isoform, yielding novel approaches to drug discovery.
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Affiliation(s)
- David M Mottola
- Department of Psychiatry, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7160, USA
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Nadal R. Pharmacology of the atypical antipsychotic remoxipride, a dopamine D2 receptor antagonist. CNS DRUG REVIEWS 2001; 7:265-82. [PMID: 11607043 PMCID: PMC6741677 DOI: 10.1111/j.1527-3458.2001.tb00199.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Remoxipride is a substituted benzamide that acts as a weak but very selective antagonist of dopamine D2 receptors. It was introduced by Astra (Roxiam) at the end of the eighties and was prescribed as an atypical antipsychotic. This article reviews its putative selective effects on mesolimbic versus nigrostriatal dopaminergic systems. In animals, remoxipride has minimal cataleptic effects at doses that block dopamine agonist-induced hyperactivity. These findings are predictive of antipsychotic activity with a low likelihood of extrapyramidal symptoms. Remoxipride also appears to be effective in more recent animal models of schizophrenia, such as latent inhibition or prepulse inhibition. In clinical studies, remoxipride shows a relatively low incidence of extrapyramidal side effects and its effects on prolactin release are short-lasting and generally mild. The clinical efficacy of remoxipride is similar to that of haloperidol or chlorpromazine. Although its clinical use was severely restricted in 1993, due to reports of aplastic anemia in some patients receiving remoxipride, this drug has been found to exhibit relatively high selectivity for dopamine D2 receptors making remoxipride an interesting tool for neurochemical and behavioral studies.
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Affiliation(s)
- R Nadal
- Department of Psychobiology and Methodology of Health Sciences, Universitat Autònoma de Barcelona, Bellaterra, E-08193 Barcelona, Spain.
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