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Fragola NR, Brems BM, Mukherjee M, Cui M, Booth RG. Conformationally Selective 2-Aminotetralin Ligands Targeting the alpha2A- and alpha2C-Adrenergic Receptors. ACS Chem Neurosci 2023; 14:1884-1895. [PMID: 37104867 PMCID: PMC10628895 DOI: 10.1021/acschemneuro.3c00148] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023] Open
Abstract
Many important physiological processes are mediated by alpha2A- and alpha2C-adrenergic receptors (α2Rs), a subtype of class A G protein-coupled receptors (GPCRs). However, α2R signaling is poorly understood, and there are few approved medications targeting these receptors. Drug discovery aimed at α2Rs is complicated by the high degree of binding pocket homology between α2AR and α2CR, which confounds ligand-mediated selective activation or inactivation of signaling associated with a particular subtype. Meanwhile, α2R signaling is complex and it is reported that activating α2AR is beneficial in many clinical contexts, while activating α2CR signaling may be detrimental to these positive effects. Here, we report on a novel 5-substituted-2-aminotetralin (5-SAT) chemotype that, depending on substitution, has diverse pharmacological activities at α2Rs. Certain lead 5-SAT analogues act as partial agonists at α2ARs, while functioning as inverse agonists at α2CRs, a novel pharmacological profile. Leads demonstrate high potency (e.g., EC50 < 2 nM) at the α2AR and α2CRs regarding Gαi-mediated inhibition of adenylyl cyclase and production of cyclic adenosine monophosphate (cAMP). To help understand the molecular basis of 5-SAT α2R multifaceted functional activity, α2AR and α2CR molecular models were built from the crystal structures and 1 μs molecular dynamics (MD) simulations and molecular docking experiments were performed for a lead 5-SAT with α2AR agonist and α2CR inverse agonist activity, i.e., (2S)-5-(2'-fluorophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (FPT), in comparison to the FDA-approved (for opioid withdrawal symptoms) α2AR/α2CR agonist lofexidine. Results reveal several interactions between FPT and α2AR and α2CR amino acids that may impact the functional activity. The computational data in conjunction with experimental in vitro affinity and function results provide information to understand ligand stabilization of functionally distinct GPCR conformations regarding α2AR and α2CRs.
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Affiliation(s)
- Nicholas R. Fragola
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Brittany M. Brems
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Munmun Mukherjee
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Meng Cui
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Raymond G. Booth
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
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Harvey BH, Uys MM, Viljoen FP, Shahid M, Sonntag Q, Meyer LCR. Hippocampal monoamine changes in the Flinders sensitive line rat: A case for the possible use of selective α 2C-AR-antagonists in stress and anxiety disorders in companion animals. Res Vet Sci 2021; 135:175-183. [PMID: 33529845 DOI: 10.1016/j.rvsc.2021.01.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 01/12/2021] [Accepted: 01/21/2021] [Indexed: 12/21/2022]
Abstract
Non-selective α2-adrenoreceptor (AR) stimulation delivers favourable sedative, analgesic, muscle relaxant and anxiolytic actions in companion animals, but is associated with cardiovascular and respiratory side effects. Anxiety conditions underscore monoamine disturbances amenable to α2-AR modulation. We investigated sub-chronic (14 day s.c.) treatment with the selective α2C-AR antagonist, ORM-10921 (0.03, 0.1, 0.3 mg/kg/d) on hippocampal noradrenaline (NA), dopamine (DA), serotonin (5-HT) and their turnover levels in stress sensitive Flinders Sensitive Line (FSL) rats versus Flinders Resistant Line (FRL) controls, using high performance liquid chromatography. The effects of ORM-10921 were compared to the non-selective α2-AR antagonist, idazoxan (IDAZ; 3 mg/kg/d), and to imipramine (IMI; 15 mg/kg/d), a reference antidepressant in this model. FSL rats displayed significantly reduced 5-HT (p = 0.03) and DA (p = 0.02) levels vs. FRL controls, while NA levels showed a similar trend. ORM-10921 significantly increased NA (all doses p ≤ 0.02), 5-HT (0.1 and 0.3 mg/kg p ≤ 0.03) and DA levels (all doses p ≤ 0.03), which correlated with decreased monoamine turnover. In contrast, IDAZ significantly elevated NA (p < 0.005) and DA (p < 0.004) but not 5-HT levels. IMI also significantly increased 5-HT (p < 0.009), with a tendency to increase NA (p = 0.09) but not DA. ORM-10921 exerts similar albeit broader effects on hippocampal monoamines than IDAZ, explaining earlier established efficacy associated with α2C-AR antagonism in animal models of depression and cognitive dysfunction. These and the current studies encourage application of ORM-10921 in depression in humans, as well as raise the intriguing possibility that selective α2C-AR antagonists may be beneficial in anxiety and stress-related disorders in companion animals. Both warrant further study.
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Affiliation(s)
- Brian H Harvey
- Division of Pharmacology, Center of Excellence for Pharmaceutical Sciences, North-West University (Potchefstroom Campus), Potchefstroom, South Africa; South African MRC Unit on Risk and Resilience in Mental Disorders, Department of Psychiatry and Mental Health, University of Cape Town, Cape Town, South Africa.
| | - Madeleine M Uys
- Division of Pharmacology, Center of Excellence for Pharmaceutical Sciences, North-West University (Potchefstroom Campus), Potchefstroom, South Africa
| | - Francois P Viljoen
- Division of Pharmacology, Center of Excellence for Pharmaceutical Sciences, North-West University (Potchefstroom Campus), Potchefstroom, South Africa
| | | | - Quixi Sonntag
- Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - Leith C R Meyer
- Centre for Veterinary Wildlife Studies and Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
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Yin L, Chen X, Ji H, Gao S. Dexmedetomidine protects against sepsis‑associated encephalopathy through Hsp90/AKT signaling. Mol Med Rep 2019; 20:4731-4740. [PMID: 31702043 DOI: 10.3892/mmr.2019.10718] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 09/04/2019] [Indexed: 11/06/2022] Open
Abstract
Sepsis‑associated encephalopathy (SAE) is characterized by neuronal apoptosis and changes in mental status. Accumulating evidence has. indicated that dexmedetomidine is capable of protecting the brain against external stimuli and improving cognitive dysfunctions. The aim of the present study was to investigate the possible neuroprotective effects of dexmedetomidine on SAE and the role of heat‑shock protein (Hsp)90/AKT signaling in an experimental model of sepsis. The SAE model was established by cecal ligation and perforation (CLP) in vivo and lipopolysaccharide (LPS) treated hippocampal neuronal cultures in vitro. It was found that dexmedetomidine inhibited caspase‑3, but increased the expression level ofBcl‑2 in CLP rats. CLP rats also exhibited a decreased level of phosphorylated AKT Thr 308 and Hsp90, and their expression could be reversed by treatment with dexmedetomidine. Additionally, application of dexmedetomidine increased cell survival and decreased neuronal apoptosis in vitro. Furthermore, the neuroprotective effects of dexmedetomidine could be reversed by 17‑AAG (a Hsp90 inhibitor), or wortmannin (a PI3K inhibitor). Analysis of TUNEL staining indicated that dexmedetomidine improved LPS‑induced neuronal apoptosis, which could be eradicated by AKT short hairpin RNA transfection, prazosin or yohimbine. Finally, dexmedetomidine ameliorated both the emotional and spatial cognitive disorders without alteration in locomotor activity. The present findings suggested that dexmedetomidine may protect the brain against SAE, and that the Hsp90/AKT pathway may be involved in this process.
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Affiliation(s)
- Lijun Yin
- Department of Anesthesiology, Tianjin Baodi Hospital, Baodi Clinical College of Tianjin Medical University, Tianjin 301800, P.R. China
| | - Xuejun Chen
- Department of Anesthesiology, Tianjin Baodi Hospital, Baodi Clinical College of Tianjin Medical University, Tianjin 301800, P.R. China
| | - Hongbo Ji
- Department of Anesthesiology, Tianjin Baodi Hospital, Baodi Clinical College of Tianjin Medical University, Tianjin 301800, P.R. China
| | - Shunli Gao
- Department of Anesthesiology, Tianjin Baodi Hospital, Baodi Clinical College of Tianjin Medical University, Tianjin 301800, P.R. China
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The α2C-adrenoceptor antagonist, ORM-10921, exerts antidepressant-like effects in the Flinders Sensitive Line rat. Behav Pharmacol 2018; 28:9-18. [PMID: 27749317 DOI: 10.1097/fbp.0000000000000261] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Depression involves deficits in monoaminergic neurotransmission. Differential roles for α2A, B and C subtypes of the α2-adrenoceptor (AR) are evident, with selective α2C-AR antagonists purported to have antidepressant and procognitive properties. However, this has not been demonstrated in a genetic animal model of depression. The role of the α2C-AR in modulating two key depression-related behaviours in the Flinders Sensitive Line (FSL) rat was studied using a dose-response analysis following subcutaneous administration with the selective α2C-AR antagonist ORM-10921 (0.03; 0.3 mg/kg), the nonselective α2-AR antagonist idazoxan (3 mg/kg), or vehicle once daily for 14 days. Behaviour in the novel object recognition test, forced swim test (FST) and locomotor activity test was assessed. To ratify the validity of the FSL model, the reference tricyclic antidepressant imipramine (15 mg/kg, intraperitoneally) was used as a comparator drug in the FST. FSL rats demonstrated significantly increased immobility and recognition memory deficits versus Flinders Resistant Line controls, with imipramine significantly reversing said immobility. Similarly, ORM-10921 at both doses but not idazoxan significantly reversed immobility in the FST as well as attenuated cognitive deficits in FSL animals. We conclude that selective α2C-AR antagonism has potential as a novel therapeutic strategy in the treatment of depression and cognitive dysfunction.
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Effects of Beta-Adrenergic Blockade on Diabetes-Induced Neurobehavioral Alterations in Mice. NEUROPHYSIOLOGY+ 2017. [DOI: 10.1007/s11062-017-9683-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Uys MM, Shahid M, Harvey BH. Therapeutic Potential of Selectively Targeting the α 2C-Adrenoceptor in Cognition, Depression, and Schizophrenia-New Developments and Future Perspective. Front Psychiatry 2017; 8:144. [PMID: 28855875 PMCID: PMC5558054 DOI: 10.3389/fpsyt.2017.00144] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 07/24/2017] [Indexed: 12/12/2022] Open
Abstract
α2A- and α2C-adrenoceptors (ARs) are the primary α2-AR subtypes involved in central nervous system (CNS) function. These receptors are implicated in the pathophysiology of psychiatric illness, particularly those associated with affective, psychotic, and cognitive symptoms. Indeed, non-selective α2-AR blockade is proposed to contribute toward antidepressant (e.g., mirtazapine) and atypical antipsychotic (e.g., clozapine) drug action. Both α2C- and α2A-AR share autoreceptor functions to exert negative feedback control on noradrenaline (NA) release, with α2C-AR heteroreceptors regulating non-noradrenergic transmission (e.g., serotonin, dopamine). While the α2A-AR is widely distributed throughout the CNS, α2C-AR expression is more restricted, suggesting the possibility of significant differences in how these two receptor subtypes modulate regional neurotransmission. However, the α2C-AR plays a more prominent role during states of low endogenous NA activity, while the α2A-AR is relatively more engaged during states of high noradrenergic tone. Although augmentation of conventional antidepressant and antipsychotic therapy with non-selective α2-AR antagonists may improve therapeutic outcome, animal studies report distinct yet often opposing roles for the α2A- and α2C-ARs on behavioral markers of mood and cognition, implying that non-selective α2-AR antagonism may compromise therapeutic utility both in terms of efficacy and side-effect liability. Recently, several highly selective α2C-AR antagonists have been identified that have allowed deeper investigation into the function and utility of the α2C-AR. ORM-13070 is a useful positron emission tomography ligand, ORM-10921 has demonstrated antipsychotic, antidepressant, and pro-cognitive actions in animals, while ORM-12741 is in clinical development for the treatment of cognitive dysfunction and neuropsychiatric symptoms in Alzheimer's disease. This review will emphasize the importance and relevance of the α2C-AR as a neuropsychiatric drug target in major depression, schizophrenia, and associated cognitive deficits. In addition, we will present new prospects and future directions of investigation.
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Affiliation(s)
- Madeleine Monique Uys
- Division of Pharmacology, Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
| | | | - Brian Herbert Harvey
- Division of Pharmacology, Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
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Uys M, Shahid M, Sallinen J, Dreyer W, Cockeran M, Harvey BH. The α2C-adrenoceptor antagonist, ORM-10921, has antipsychotic-like effects in social isolation reared rats and bolsters the response to haloperidol. Prog Neuropsychopharmacol Biol Psychiatry 2016; 71:108-16. [PMID: 27381554 DOI: 10.1016/j.pnpbp.2016.07.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 06/28/2016] [Accepted: 07/01/2016] [Indexed: 02/04/2023]
Abstract
Early studies suggest that selective α2C-adrenoceptor (AR)-antagonism has anti-psychotic-like and pro-cognitive properties. However, this has not been demonstrated in an animal model of schizophrenia with a neurodevelopmental construct. The beneficial effects of clozapine in refractory schizophrenia and associated cognitive deficits have, among others, been associated with its α2C-AR modulating activity. Altered brain-derived neurotrophic factor (BDNF) has been linked to schizophrenia and cognitive deficits. We investigated whether the α2C-AR antagonist, ORM-10921, could modulate sensorimotor gating and cognitive deficits, as well as alter striatal BDNF levels in the social isolation reared (SIR) model of schizophrenia, comparing its effects to clozapine and the typical antipsychotic, haloperidol, the latter being devoid of α2C-AR-activity. Moreover, the ability of ORM-10921 to augment the effects of haloperidol on the above parameters was also investigated. Animals received subcutaneous injection of either ORM-10921 (0.01mg/kg), clozapine (5mg/kg), haloperidol (0.2mg/kg), haloperidol (0.2mg/kg)+ORM-10921 (0.01mg/kg) or vehicle once daily for 14days, followed by assessment of novel object recognition (NOR), prepulse inhibition (PPI) of startle response and striatal BDNF levels. SIR significantly attenuated NOR memory as well as PPI, and reduced striatal BDNF levels vs. social controls. Clozapine, ORM-10921 and haloperidol+ORM-10921, but not haloperidol alone, significantly improved SIR-associated deficits in PPI and NOR, with ORM-10921 also significantly improving PPI deficits vs. haloperidol-treated SIR animals. Haloperidol+ORM-10921 significantly reversed reduced striatal BDNF levels in SIR rats. α2C-AR-antagonism improves deficits in cognition and sensorimotor gating in a neurodevelopmental animal model of schizophrenia and bolsters the effects of a typical antipsychotic, supporting a therapeutic role for α2C-AR-antagonism in schizophrenia.
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Affiliation(s)
- Madeleine Uys
- Division of Pharmacology, North-West University (Potchefstroom Campus), Potchefstroom 2520, South Africa.
| | | | | | - Walter Dreyer
- Center of Excellence for Pharmaceutical Sciences, North-West University (Potchefstroom Campus), Hoffman Street, Potchefstroom 2520, South Africa.
| | - Marike Cockeran
- Medicines Usage in South Africa, North-West University (Potchefstroom Campus), Hoffman Street, Potchefstroom 2520, South Africa.
| | - Brian H Harvey
- Center of Excellence for Pharmaceutical Sciences, North-West University (Potchefstroom Campus), Hoffman Street, Potchefstroom 2520, South Africa.
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Chaussenot R, Edeline JM, Le Bec B, El Massioui N, Laroche S, Vaillend C. Cognitive dysfunction in the dystrophin-deficient mouse model of Duchenne muscular dystrophy: A reappraisal from sensory to executive processes. Neurobiol Learn Mem 2015; 124:111-22. [PMID: 26190833 DOI: 10.1016/j.nlm.2015.07.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 07/09/2015] [Accepted: 07/10/2015] [Indexed: 01/08/2023]
Abstract
Duchenne muscular dystrophy (DMD) is associated with language disabilities and deficits in learning and memory, leading to intellectual disability in a patient subpopulation. Recent studies suggest the presence of broader deficits affecting information processing, short-term memory and executive functions. While the absence of the full-length dystrophin (Dp427) is a common feature in all patients, variable mutation profiles may additionally alter distinct dystrophin-gene products encoded by separate promoters. However, the nature of the cognitive dysfunctions specifically associated with the loss of distinct brain dystrophins is unclear. Here we show that the loss of the full-length brain dystrophin in mdx mice does not modify the perception and sensorimotor gating of auditory inputs, as assessed using auditory brainstem recordings and prepulse inhibition of startle reflex. In contrast, both acquisition and long-term retention of cued and trace fear memories were impaired in mdx mice, suggesting alteration in a functional circuit including the amygdala. Spatial learning in the water maze revealed reduced path efficiency, suggesting qualitative alteration in mdx mice learning strategy. However, spatial working memory performance and cognitive flexibility challenged in various behavioral paradigms in water and radial-arm mazes were unimpaired. The full-length brain dystrophin therefore appears to play a role during acquisition of associative learning as well as in general processes involved in memory consolidation, but no overt involvement in working memory and/or executive functions could be demonstrated in spatial learning tasks.
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Affiliation(s)
- Rémi Chaussenot
- Paris-Saclay Neuroscience Institute, UMR 9197, CNRS, F-91405 Orsay, France; Univ. Paris-Sud, UMR 9197, F-91405 Orsay, France; Université Paris-Saclay, France
| | - Jean-Marc Edeline
- Paris-Saclay Neuroscience Institute, UMR 9197, CNRS, F-91405 Orsay, France; Univ. Paris-Sud, UMR 9197, F-91405 Orsay, France; Université Paris-Saclay, France
| | - Benoit Le Bec
- Paris-Saclay Neuroscience Institute, UMR 9197, CNRS, F-91405 Orsay, France; Univ. Paris-Sud, UMR 9197, F-91405 Orsay, France; Université Paris-Saclay, France
| | - Nicole El Massioui
- Paris-Saclay Neuroscience Institute, UMR 9197, CNRS, F-91405 Orsay, France; Univ. Paris-Sud, UMR 9197, F-91405 Orsay, France; Université Paris-Saclay, France
| | - Serge Laroche
- Paris-Saclay Neuroscience Institute, UMR 9197, CNRS, F-91405 Orsay, France; Univ. Paris-Sud, UMR 9197, F-91405 Orsay, France; Université Paris-Saclay, France
| | - Cyrille Vaillend
- Paris-Saclay Neuroscience Institute, UMR 9197, CNRS, F-91405 Orsay, France; Univ. Paris-Sud, UMR 9197, F-91405 Orsay, France; Université Paris-Saclay, France.
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Gilsbach R, Hein L. Presynaptic metabotropic receptors for acetylcholine and adrenaline/noradrenaline. Handb Exp Pharmacol 2008:261-88. [PMID: 18064417 DOI: 10.1007/978-3-540-74805-2_9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Presynaptic metabotropic receptors for acetylcholine and adrenaline/noradrenaline were first described more than three decades ago. Molecular cloning has resulted in the identification of five G protein-coupled muscarinic receptors (M(1) - M(5)) which mediate the biological effects of acetylcholine. Nine adrenoceptors (alpha(1ABD),alpha(2ABC),beta(123)) transmit adrenaline/noradrenaline signals between cells. The lack of sufficiently subtype-selective ligands has prevented identification of the physiological role and therapeutic potential of these receptor subtypes for a long time. Recently, mouse lines with targeted deletions for all muscarinic and adrenoceptor genes have been generated. This review summarizes the results from these gene-targeting studies with particular emphasis on presynaptic auto- and heteroreceptor functions of muscarinic and adrenergic receptors. Specific knowledge about the function of receptor subtypes will enhance our understanding of the physiological role of the cholinergic and adrenergic nervous system and open new avenues for subtype-selective therapeutic strategies.
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Affiliation(s)
- Ralf Gilsbach
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Albertstrasse 25, 79104, Freiburg, Germany
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Hein L. Adrenoceptors and signal transduction in neurons. Cell Tissue Res 2006; 326:541-51. [PMID: 16896948 DOI: 10.1007/s00441-006-0285-2] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Accepted: 06/13/2006] [Indexed: 10/24/2022]
Abstract
The adrenergic system is an essential regulator of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions. The endogenous catecholamines epinephrine and norepinephrine activate G-protein-coupled receptors to transmit their signal across the plasma membrane. These adrenoceptors can be divided into three different groups: the alpha(1)-receptors (alpha(1A), alpha(1B), alpha(1D)), alpha(2)-receptors (alpha(2A), alpha(2B), alpha(2C)), and beta-receptors (beta(1), beta(2), beta(3)). This review summarizes recent findings in the field of adrenoceptor signaling in neurons and includes a discussion of receptor-associated proteins, receptor dimerization, subcellular trafficking, and fluorescence optical methods for studying the kinetics of adrenergic signaling. Spatio-temporal imaging may become an important future tool for identifying the physiological significance of these complex signaling mechanisms in vivo. Gene-targeted mouse models carrying deletions in alpha(2)-adrenoceptor have provided detailed insights into specific neuronal functions of the three alpha(2)-receptor subtypes.
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Affiliation(s)
- Lutz Hein
- Institut für Exp. und Klin. Pharmakologie und Toxikologie, Universität Freiburg, Albertstrasse 25, 79104 Freiburg im Breisgau, Germany.
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Clapcote SJ, Roder JC. Deletion polymorphism of Disc1 is common to all 129 mouse substrains: implications for gene-targeting studies of brain function. Genetics 2006; 173:2407-10. [PMID: 16751659 PMCID: PMC1569715 DOI: 10.1534/genetics.106.060749] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report that the Disc1 gene in all extant 129 mouse inbred substrains has a deletion, previously considered specific to the 129S6/SvEv substrain, which is predicted to abolish production of the full-length protein. This finding has implications for the study of knockout mice generated from 129-derived embryonic stem cells.
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Affiliation(s)
- Steven J Clapcote
- Mount Sinai Hospital Research Institute, Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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Millan MJ. Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application. Pharmacol Ther 2006; 110:135-370. [PMID: 16522330 DOI: 10.1016/j.pharmthera.2005.11.006] [Citation(s) in RCA: 419] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 11/28/2005] [Indexed: 12/20/2022]
Abstract
Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.
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Affiliation(s)
- Mark J Millan
- Institut de Recherches Servier, Centre de Recherches de Croissy, Psychopharmacology Department, 125, Chemin de Ronde, 78290-Croissy/Seine, France.
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Abstract
Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.
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Affiliation(s)
- Mark J Millan
- Psychopharmacology Department, Centre de Rescherches de Croissy, Institut de Recherches (IDR) Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, Paris, France.
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Philipp M, Brede M, Hein L. Physiological significance of alpha(2)-adrenergic receptor subtype diversity: one receptor is not enough. Am J Physiol Regul Integr Comp Physiol 2002; 283:R287-95. [PMID: 12121839 DOI: 10.1152/ajpregu.00123.2002] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Alpha(2)-adrenergic receptors mediate part of the diverse biological effects of the endogenous catecholamines epinephrine and norepinephrine. Three distinct subtypes of alpha(2)-adrenergic receptors, alpha(2A), alpha(2B), alpha(2C), have been identified from multiple species. Because of the lack of sufficiently subtype-selective ligands, the specific biological functions of these receptor subtypes were largely unknown until recently. Gene-targeted mice carrying deletions in the genes encoding for individual alpha(2)-receptor subtypes have added important new insight into the physiological significance of adrenergic receptor diversity. Two different strategies have emerged to regulate adrenergic signal transduction. Some biological functions are controlled by two counteracting alpha(2)-receptor subtypes, e.g., alpha(2A)-receptors decrease sympathetic outflow and blood pressure, whereas the alpha(2B)-subtype increases blood pressure. Other biological functions are regulated by synergistic alpha(2)-receptor subtypes. The inhibitory presynaptic feedback loop that tightly regulates neurotransmitter release from adrenergic nerves also requires two receptor subtypes, alpha(2A) and alpha(2C). Similarly, nociception is controlled at several levels by one of the three alpha(2)-receptor subtypes. Further investigation of the specific function of alpha(2)-subtypes will greatly enhance our understanding of the relevance of closely related receptor proteins and point out novel therapeutic strategies for subtype-selective drug development.
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Affiliation(s)
- Melanie Philipp
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, 97078 Würzburg, Germany
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