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Frau R, Devoto P, Aroni S, Saba P, Sagheddu C, Siddi C, Santoni M, Carli M, Gessa GL. The potent α 2-adrenoceptor antagonist RS 79948 also inhibits dopamine D 2 -receptors: Comparison with atipamezole and raclopride. Neuropharmacology 2022; 217:109192. [PMID: 35850212 DOI: 10.1016/j.neuropharm.2022.109192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 07/08/2022] [Accepted: 07/11/2022] [Indexed: 11/16/2022]
Abstract
Neurochemical, electrophysiological and behavioral evidence indicate that the potent α2-adrenoceptor antagonist RS 79948 is also a dopamine (DA) D2 receptor antagonist. Thus, results from ligand binding and adenylate cyclase activity indicate that RS 79948 binds to D2 receptors and antagonized D2 receptor-mediated inhibition of cAMP synthesis at nanomolar concentrations. RESULTS: from microdialysis indicated that RS 79948 shared with the selective α2-adrenergic antagonist atipamezole the ability to increase the co-release of DA and norepinephrine (NE) from noradrenergic terminals in the medial prefrontal cortex (mPFC), except that RS 79948-induced DA release persisted after noradrenergic denervation, unlike atipamezole effect, indicating that RS 79948 releases DA from dopaminergic terminals as well. Similarly to the D2 antagonist raclopride, but unlike atipamezole, RS 79948 increased extracellular DA and DOPAC in the caudate nucleus. Electrophysiological results indicate that RS 79948 shared with raclopride the ability to activate the firing of ventral tegmental area (VTA) DA neurons, while atipamezole was ineffective. RESULTS: from behavioral studies indicated that RS 79948 exerted effects mediated by independent, cooperative and contrasting inhibition of α2-and D2 receptors. Thus, RS 79948, but not atipamezole, prevented D2-autoreceptor mediated hypomotility produced by a small dose of quinpirole. RS 79948 potentiated, more effectively than atipamezole, quinpirole-induced motor stimulation. RS 79948 antagonized, less effectively than atipamezole, raclopride-induced catalepsy. Future studies should clarify if the dual α2-adrenoceptor- and D2-receptor antagonistic action might endow RS 79948 with potential therapeutic relevance in the treatment of schizophrenia, drug dependence, depression and Parkinson's disease.
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Affiliation(s)
- Roberto Frau
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy; The Guy Everett Laboratory for Neuroscience, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
| | - Paola Devoto
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy; The Guy Everett Laboratory for Neuroscience, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy.
| | - Sonia Aroni
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
| | - Pierluigi Saba
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
| | - Claudia Sagheddu
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
| | - Carlotta Siddi
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
| | - Michele Santoni
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
| | - Marco Carli
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Italy
| | - Gian Luigi Gessa
- Department of Biomedical Sciences, Section of Neurosciences and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy; The Guy Everett Laboratory for Neuroscience, University of Cagliari, Cittadella Universitaria, Monserrato, CA, Italy
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Deluigi M, Morstein L, Schuster M, Klenk C, Merklinger L, Cridge RR, de Zhang LA, Klipp A, Vacca S, Vaid TM, Mittl PRE, Egloff P, Eberle SA, Zerbe O, Chalmers DK, Scott DJ, Plückthun A. Crystal structure of the α 1B-adrenergic receptor reveals molecular determinants of selective ligand recognition. Nat Commun 2022; 13:382. [PMID: 35046410 PMCID: PMC8770593 DOI: 10.1038/s41467-021-27911-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 12/21/2021] [Indexed: 11/25/2022] Open
Abstract
α-adrenergic receptors (αARs) are G protein-coupled receptors that regulate vital functions of the cardiovascular and nervous systems. The therapeutic potential of αARs, however, is largely unexploited and hampered by the scarcity of subtype-selective ligands. Moreover, several aminergic drugs either show off-target binding to αARs or fail to interact with the desired subtype. Here, we report the crystal structure of human α1BAR bound to the inverse agonist (+)-cyclazosin, enabled by the fusion to a DARPin crystallization chaperone. The α1BAR structure allows the identification of two unique secondary binding pockets. By structural comparison of α1BAR with α2ARs, and by constructing α1BAR-α2CAR chimeras, we identify residues 3.29 and 6.55 as key determinants of ligand selectivity. Our findings provide a basis for discovery of α1BAR-selective ligands and may guide the optimization of aminergic drugs to prevent off-target binding to αARs, or to elicit a selective interaction with the desired subtype. This study reports the X-ray structure of the α1B-adrenergic G protein-coupled receptor bound to an inverse agonist, and unveils key determinants of subtype-selective ligand binding that may help the design of aminergic drugs with fewer side-effects.
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Affiliation(s)
- Mattia Deluigi
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Lena Morstein
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Matthias Schuster
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Christoph Klenk
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Lisa Merklinger
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.,Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, 2800 Kgs, Lyngby, Denmark
| | - Riley R Cridge
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia
| | - Lazarus A de Zhang
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia.,Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Alexander Klipp
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.,Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1-5/10, CH-8093, Zurich, Switzerland
| | - Santiago Vacca
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Tasneem M Vaid
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Peer R E Mittl
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Pascal Egloff
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Stefanie A Eberle
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Oliver Zerbe
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - David K Chalmers
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC, 3052, Australia
| | - Daniel J Scott
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia. .,Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, VIC, 3010, Australia.
| | - Andreas Plückthun
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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3
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Tseng CT, Gaulding SJ, Dancel CLE, Thorn CA. Local activation of α2 adrenergic receptors is required for vagus nerve stimulation induced motor cortical plasticity. Sci Rep 2021; 11:21645. [PMID: 34737352 PMCID: PMC8568982 DOI: 10.1038/s41598-021-00976-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 10/20/2021] [Indexed: 11/09/2022] Open
Abstract
Vagus nerve stimulation (VNS) paired with rehabilitation training is emerging as a potential treatment for improving recovery of motor function following stroke. In rats, VNS paired with skilled forelimb training results in significant reorganization of the somatotopic cortical motor map; however, the mechanisms underlying this form of VNS-dependent plasticity remain unclear. Recent studies have shown that VNS-driven cortical plasticity is dependent on noradrenergic innervation of the neocortex. In the central nervous system, noradrenergic α2 receptors (α2-ARs) are widely expressed in the motor cortex and have been critically implicated in synaptic communication and plasticity. In current study, we examined whether activation of cortical α2-ARs is necessary for VNS-driven motor cortical reorganization to occur. Consistent with previous studies, we found that VNS paired with motor training enlarges the map representation of task-relevant musculature in the motor cortex. Infusion of α2-AR antagonists into M1 blocked VNS-driven motor map reorganization from occurring. Our results suggest that local α2-AR activation is required for VNS-induced cortical reorganization to occur, providing insight into the mechanisms that may underlie the neuroplastic effects of VNS therapy.
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Affiliation(s)
- Ching-Tzu Tseng
- School of Behavioral and Brain Sciences, University of Texas at Dallas, 800 W. Campbell Rd, Richardson, TX, 75080, USA
| | - Solomon J Gaulding
- School of Behavioral and Brain Sciences, University of Texas at Dallas, 800 W. Campbell Rd, Richardson, TX, 75080, USA
| | - Canice Lei E Dancel
- School of Behavioral and Brain Sciences, University of Texas at Dallas, 800 W. Campbell Rd, Richardson, TX, 75080, USA
| | - Catherine A Thorn
- School of Behavioral and Brain Sciences, University of Texas at Dallas, 800 W. Campbell Rd, Richardson, TX, 75080, USA.
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Calu DJ, Chen YW, Kawa AB, Nair SG, Shaham Y. The use of the reinstatement model to study relapse to palatable food seeking during dieting. Neuropharmacology 2014; 76 Pt B:395-406. [PMID: 23660229 PMCID: PMC3785569 DOI: 10.1016/j.neuropharm.2013.04.030] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 03/29/2013] [Accepted: 04/16/2013] [Indexed: 12/14/2022]
Abstract
Excessive consumption of unhealthy foods is a major public health problem. While many people attempt to control their food intake through dieting, many relapse to unhealthy eating habits within a few months. We have begun to study this clinical condition in rats by adapting the reinstatement model, which has been used extensively to study relapse to drug seeking. In our adaptation of the relapse model, reinstatement of palatable food seeking by exposure to food-pellet priming, food-associated cues, or stress is assessed in food-restricted (to mimic dieting) rats after operant food-pellet self-administration training and subsequent extinction of the food-reinforced responding. In this review, we first outline the clinical problem and discuss a recent study in which we assessed the predictive validity of the reinstatement model for studying relapse to food seeking during dieting by using the anorexigenic drug fenfluramine. Next, we summarize results from our initial studies on the role of several stress- and feeding-related peptides (corticotropin-releasing factor, hypocretin, melanin-concentrating hormone, peptide YY3-36) in reinstatement of palatable food seeking. We then present results from our studies on the role of dopamine and medial prefrontal cortex in stress-induced reinstatement of food seeking. We conclude by discussing potential clinical implications. We offer two main conclusions: (1) the food reinstatement model is a simple, reliable, and valid model to study mechanisms of relapse to palatable food seeking during dieting, and to identify medications to prevent this relapse; (2) mechanisms of relapse to food seeking are often dissociable from mechanisms of ongoing food intake. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- Donna J Calu
- Behavioral Neuroscience Branch, Intramural Research Program, NIDA/NIH, Baltimore, MD, USA.
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Raczak-Gutknecht J, Frąckowiak T, Nasal A, Kaliszan R. Mydriasis model in rats as a simple system to evaluate α2-adrenergic activity of the imidazol(in)e compounds. Pharmacol Rep 2013; 65:305-12. [DOI: 10.1016/s1734-1140(13)71006-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 10/24/2012] [Indexed: 11/30/2022]
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Packard M, Gabriele A. Peripheral anxiogenic drug injections differentially affect cognitive and habit memory: role of basolateral amygdala. Neuroscience 2009; 164:457-62. [DOI: 10.1016/j.neuroscience.2009.07.054] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 07/20/2009] [Accepted: 07/25/2009] [Indexed: 12/31/2022]
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Nair SG, Adams-Deutsch T, Epstein DH, Shaham Y. The neuropharmacology of relapse to food seeking: methodology, main findings, and comparison with relapse to drug seeking. Prog Neurobiol 2009; 89:18-45. [PMID: 19497349 PMCID: PMC2745723 DOI: 10.1016/j.pneurobio.2009.05.003] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Revised: 04/09/2009] [Accepted: 05/26/2009] [Indexed: 12/15/2022]
Abstract
Relapse to old, unhealthy eating habits is a major problem in human dietary treatments. The mechanisms underlying this relapse are unknown. Surprisingly, until recently this clinical problem has not been systematically studied in animal models. Here, we review results from recent studies in which a reinstatement model (commonly used to study relapse to abused drugs) was employed to characterize the effect of pharmacological agents on relapse to food seeking induced by either food priming (non-contingent exposure to small amounts of food), cues previously associated with food, or injections of the pharmacological stressor yohimbine. We also address methodological issues related to the use of the reinstatement model to study relapse to food seeking, similarities and differences in mechanisms underlying reinstatement of food seeking versus drug seeking, and the degree to which the reinstatement procedure provides a suitable model for studying relapse in humans. We conclude by discussing implications for medication development and future research. We offer three tentative conclusions: (1)The neuronal mechanisms of food-priming- and cue-induced reinstatement are likely different from those of reinstatement induced by the pharmacological stressor yohimbine. (2)The neuronal mechanisms of reinstatement of food seeking are possibly different from those of ongoing food-reinforced operant responding. (3)The neuronal mechanisms underlying reinstatement of food seeking overlap to some degree with those of reinstatement of drug seeking.
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Affiliation(s)
- Sunila G. Nair
- Behavioral Neuroscience Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
| | - Tristan Adams-Deutsch
- Behavioral Neuroscience Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
| | - David H. Epstein
- Clinical Pharmacology and Therapeutics Research Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
| | - Yavin Shaham
- Behavioral Neuroscience Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
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Intra-amygdala anxiogenic drug infusion prior to retrieval biases rats towards the use of habit memory. Neurobiol Learn Mem 2008; 90:616-23. [DOI: 10.1016/j.nlm.2008.06.012] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 06/24/2008] [Accepted: 06/25/2008] [Indexed: 11/24/2022]
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Fagerholm V, Scheinin M, Haaparanta M. alpha2A-adrenoceptor antagonism increases insulin secretion and synergistically augments the insulinotropic effect of glibenclamide in mice. Br J Pharmacol 2008; 154:1287-96. [PMID: 18493247 DOI: 10.1038/bjp.2008.186] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE The imidazoline-type alpha2-adrenoceptor antagonists (+/-)-efaroxan and phentolamine increase insulin secretion and reduce blood glucose levels. It is not known whether they act by antagonizing pancreatic beta-cell alpha2-adrenoceptors or by alpha2-adrenoceptor-independent mechanisms. Many imidazolines inhibit the pancreatic beta-cell KATP channel, which is the molecular target of sulphonylurea drugs used in the treatment of type II diabetes. To investigate the mechanisms of action of (+/-)-efaroxan and phentolamine, alpha2A-adrenoceptor knockout (alpha2A-KO) mice were used. EXPERIMENTAL APPROACH Effects of (+/-)-efaroxan, 5 mg kg(-1), and phentolamine, 1 mg kg(-1), on blood glucose and insulin levels were compared with those of the non-imidazoline alpha2-adrenoceptor antagonist [8aR,12aS,13aS]-5,8,8a,9,10,11,12,12a,13,13a-decahydro-3-methoxy-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]naphthyridine (RS79948-197), 1 mg kg(-1), and the sulphonylurea glibenclamide, in alpha2A-KO and control (wild type (WT)) mice. KEY RESULTS In fed WT mice, (+/-)-efaroxan, phentolamine and RS79948-197 reduced blood glucose and increased insulin levels. Fasting abolished these effects. In fed alpha2A-KO mice, (+/-)-efaroxan, phentolamine and RS79948-197 did not alter blood glucose or insulin levels, and in fasted alpha2A-KO mice, blood glucose levels were increased. Glibenclamide, at a dose only moderately efficacious in WT mice (5 mg kg(-1)), caused severe hyperinsulinaemia and hypoglycaemia in alpha2A-KO mice. This was mimicked in WT mice by co-administration of RS79948-197 with glibenclamide. CONCLUSIONS AND IMPLICATIONS These results suggest that (+/-)-efaroxan and phentolamine increase insulin secretion by inhibition of beta-cell alpha2A-adrenoceptors, and demonstrate a critical role for alpha2A-adrenoceptors in limiting sulphonylurea-induced hyperinsulinaemia and hypoglycaemia.
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Affiliation(s)
- V Fagerholm
- Turku PET Centre/Preclinical Imaging, Turku, Finland.
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Wingard JC, Packard MG. The amygdala and emotional modulation of competition between cognitive and habit memory. Behav Brain Res 2008; 193:126-31. [PMID: 18565602 DOI: 10.1016/j.bbr.2008.05.002] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 04/18/2008] [Accepted: 05/05/2008] [Indexed: 11/16/2022]
Abstract
The basolateral amygdala (BLA) is implicated in the neurobiology of emotion, and can also modulate the cognitive and habit memory processes mediated by the hippocampus and dorsal striatum, respectively. In a dual-solution task that can be acquired using either hippocampus-dependent or dorsal striatal-dependent learning, peripheral or intra-BLA infusion of the anxiogenic alpha(2)-adrenoreceptor antagonist RS 79948 biases rats towards the use of habit learning. In view of evidence that anxiety can promote relapse into habitual and maladaptive human behaviors, understanding the mechanism(s) by which emotional arousal can influence the relative use of multiple memory systems may prove clinically relevant. Therefore, the present experiments examined whether intra-BLA infusions of RS 79948 bias rats towards the use of habit learning directly by enhancing dorsal striatal function, or indirectly by impairing hippocampal function. Adult male Long-Evans rats were trained in one of two single-solution water plus-maze tasks. One version required the use of hippocampus-dependent "place" learning. A second version required the use of dorsal striatal-dependent "response" learning, and hippocampal mnemonic processes have been shown to interfere with acquisition of this task. Post-training intra-BLA infusions of RS 79948 (1.0 microg/0.5 microl) impaired acquisition of place learning. In contrast, intra-BLA infusions of RS 79948 enhanced response learning. Intra-BLA infusion of RS 79948 also produced an anxiogenic behavioral profile in an elevated plus-maze at the same dose (1.0 microg) that differentially influenced place and response learning. The findings suggest that intra-BLA infusion of an anxiogenic drug can influence the use of multiple memory systems by impairing hippocampus-dependent learning, thereby releasing habit memory from competing and/or inhibitory influences of cognitive memory.
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Abstract
The aim of this study was to identify receptors that mediate reflex mydriasis in pentobarbital-anesthetized rabbits, in which the cervical sympathetic nerve was sectioned unilaterally. Voltage-response curves of pupillary dilation were generated bilaterally by stimulation of the sciatic nerve. Evoked mydriatic responses were mediated mainly by efferent parasympathetic innervation, and, to a lesser extent, by sympathetic innervation. The alpha-adrenergic antagonist, phenoxybenzamine (0.3 mg/kg, intravenously (i.v.)), antagonized mydriasis of the neurally intact eye, but not that on the sympathectomized side. The alpha2-adrenergic antagonist, RS 79948 (0.3 mg/kg, i.v.), potentiated mydriasis of the normal eye, but was without either a potentiating or inhibitory effect on the mydriasis of the sympathectomized eye. In addition, the dopamine-receptor antagonist, haloperidol (1 mg/kg, i.v.), inhibited evoked mydriasis of the sympathectomized eye. These results suggest that, unlike some other species (cats and rats), alpha2-adrenoceptors do not mediate reflex mydriasis elicited by sciatic-nerve stimulation in the rabbit, and support the previous finding in humans that dopamine receptors may mediate this response.
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Affiliation(s)
- Yongxin Yu
- Department of Cell Biology, University of Oklahoma College of Medicine, Oklahoma City, OK 73190, USA.
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Packard MG, Wingard JC. Amygdala and "emotional" modulation of the relative use of multiple memory systems. Neurobiol Learn Mem 2005; 82:243-52. [PMID: 15464407 DOI: 10.1016/j.nlm.2004.06.008] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2004] [Revised: 06/16/2004] [Accepted: 06/23/2004] [Indexed: 10/26/2022]
Abstract
The basolateral amygdala modulates the cognitive and habit memory processes mediated by the hippocampus and caudate nucleus, respectively. The present experiments used a plus-maze task that can be acquired using either hippocampus-dependent "place" learning or caudate-dependent "response" learning to examine whether peripheral or intra-basolateral amygdala injection of anxiogenic drugs would bias rats towards the use of a particular memory system. In Experiment 1, adult male Long-Evans rats were trained to swim from the same start point to an escape platform located in a consistent goal arm, and received pre-training peripheral injections of the alpha(2)-adrenoceptor antagonists yohimbine (2.5 or 5.0 mg/kg), RS 79948-197 (0.05, 0.1, or 0.2 mg/kg), or vehicle. On a drug-free probe trial from a novel start point administered 24h following acquisition, vehicle treated rats predominantly displayed hippocampus-dependent place learning, whereas rats previously treated with yohimbine (2.5, 5.0 mg/kg) or RS 79948-197 (0.1 mg/kg) predominantly displayed caudate-dependent response learning. In Experiment 2, rats receiving pre-training intra-basolateral amygdala infusions of RS 79948-197 (0.1 microg/0.5 microl) also predominantly displayed response learning on a drug-free probe trial. The findings indicate (1) peripheral injections of anxiogenic drugs can influence the relative use of multiple memory systems in a manner that favors caudate-dependent habit learning over hippocampus-dependent cognitive learning, and (2) intra-basolateral amygdala infusion of anxiogenic drugs is sufficient to produce this modulatory influence of emotional state on the use of multiple memory systems.
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Affiliation(s)
- Mark G Packard
- Department of Psychology, Texas A and M University, USA.
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Yu Y, Koss MC. Rat clonidine mydriasis model: imidazoline receptors are not involved. Auton Neurosci 2005; 117:17-24. [PMID: 15620566 DOI: 10.1016/j.autneu.2004.10.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Revised: 10/05/2004] [Accepted: 10/08/2004] [Indexed: 11/20/2022]
Abstract
The clonidine mydriasis model in rats has been widely applied in preclinical research to characterize alpha(2)-adrenoceptor antagonistic properties of drugs. The present study was undertaken to pharmacologically determine if imidazoline I(1) receptors are also involved in this model system. Sigmoid dose-response curves for pupillary dilation were produced in pentobarbital anesthetized rats by intravenous administration of increasing doses of agonists (guanabenz for alpha(2)-adrenoceptors, clonidine for both alpha(2)-adrenoceptors and imidazoline I(1) receptors, and rilmenidine for imidazoline I(1) receptors). Two antagonists (RS 79948 for alpha(2)-adrenoceptors and efaroxan for imidazoline I(1) receptors) were used to antagonize the mydriasis elicited by those three agonists, with antagonistic potencies calculated. In additional experiments, we examined the effect of the selective imidazoline I(1) receptor antagonist, AGN 192403, on clonidine-induced mydriasis. The results showed that pupillary response curves elicited by guanabenz, clonidine and rilmenidine were competitively antagonized by both RS 79948 (0.03-1 mg/kg) and efaroxan (0.03-1 mg/kg) in a dose-related fashion. The potencies of either antagonist against the three agonists were not significantly different. AGN 192403 (5 mg/kg) did not significantly shift the clonidine mydriasis curve. These results suggest that imidazoline I(1) receptors are not functionally involved in the rat clonidine mydriasis model and support this in vivo system as a useful model for studies of alpha(2)-adrenoceptors.
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Affiliation(s)
- Yongxin Yu
- Department of Cell Biology, University of Oklahoma College of Medicine, Oklahoma City, OK 73190, USA.
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14
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Fagerholm V, Philipp M, Hein L, Scheinin M. [Ethyl-3H]RS-79948-197 α2-adrenoceptor autoradiography validation in α2-adrenoceptor knockout mice. Eur J Pharmacol 2004; 497:301-9. [PMID: 15336948 DOI: 10.1016/j.ejphar.2004.06.065] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Revised: 06/24/2004] [Accepted: 06/30/2004] [Indexed: 11/21/2022]
Abstract
[Ethyl-(3)H][8aR,12aS,13aS]-5,8,8a,9,10,11,12,12a,13,13a-decahydro-3-methoxy-12-(ethylsulfonyl)-6H-isoquino[2,1-g][1,6]naphthyridine ([ethyl-(3)H]RS-79948-197) was evaluated for alpha(2)-adrenoceptor autoradiography in brain sections from wild-type mice and alpha(2A)- and alpha(2ABC)-adrenoceptor knockout mice. Receptor numbers were 83% lower in cortex and 28% lower in caudate putamen of alpha(2A)-knockout mice than in wild-type mice. No specific binding was seen in alpha(2ABC)-knockout mice. [Ethyl-(3)H]RS-79948-197 saturation binding parameters were compared to those of [(3)H]2-(2,3-dihydro-2-methoxy-1,4-benzodioxan-2-yl)-4,5-dihydro-1H-imidazoline ([(3)H]RX821002) and [methyl-(3)H]17alpha-hydroxy-20alpha-yohimban-16beta-carboxylic acid methyl ester ([methyl-(3)H]rauwolscine). [Ethyl-(3)H-]RS-79948-197 detected a larger number of both alpha(2A)- and alpha(2B/C)-adrenoceptors than [(3)H]RX821002, while [methyl-(3)H]rauwolscine only underestimated the number of alpha(2A)-adrenoceptors. Oxymetazoline and prazosin competed for [ethyl-(3)H]RS-79948-197 binding with the expected rank order of affinities. Higher than necessary [ethyl-(3)H]RS-79948-197 concentrations resulted in a rapid increase in non-specific binding. Slow dissociation kinetics, high specific radioactivity and high alpha(2)-adrenoceptor affinity (slightly lower for the alpha(2A)-adrenoceptor than for the other subtypes) confer [ethyl-(3)H]RS-79948-197 distinct advantages compared to [(3)H]RX821002 for detection of alpha(2)-adrenoceptor subtypes in a mixed alpha(2)-adrenoceptor population.
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Affiliation(s)
- Veronica Fagerholm
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4B, FI-20520 Turku, Finland
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15
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Yu Y, Ramage AG, Koss MC. Pharmacological studies of 8-OH-DPAT-induced pupillary dilation in anesthetized rats. Eur J Pharmacol 2004; 489:207-13. [PMID: 15087245 DOI: 10.1016/j.ejphar.2004.03.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2003] [Revised: 02/02/2004] [Accepted: 03/02/2004] [Indexed: 11/17/2022]
Abstract
Serotonin (5-HT)(1A) receptor agonists have been reported to produce mydriasis in mice, and miosis in rabbits and humans. However, the underlying mechanisms for this action are unclear. This study was undertaken in an attempt to explore the mechanism by which 5-HT(1A) receptors are involved in the modulation of pupillary size in pentobarbital-anesthetized rats. Intravenous administration of the 5-HT(1A) receptor agonist, (2R)-(+)-8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide (8-OH-DPAT; 0.003-3 mg/kg), elicited dose-dependent pupillary dilation, which was not affected by section of the preganglionic cervical sympathetic nerve. 8-OH-DPAT-elicited mydriatic responses were attenuated by the selective 5-HT(1A) receptor antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide maleate (WAY 100635; 0.3-1 mg/kg, i.v.), as well as by the selective alpha(2)-adrenoceptor antagonist, (8aR,12aS,13aS)-5,8,8a,9,10,11,12,12a,13,13a-dechydro-3-methoxy-12-(ethylsulfonyl)-6H-isoquino[2,1-g][1,6]naphthyridine hydrochloride (RS 79948; 0.3 mg/kg, i.v.), but not by the selective alpha(1)-adrenoceptor antagonist, prazosin (0.3 mg/kg, i.v.). Mydriatic responses elicited by the alpha(2)-adrenoceptor agonist, guanabenz (0.003-0.3 mg/kg, i.v.), were not antagonized by WAY 100635 (0.3-1 mg/kg, i.v.). To determine whether central nervous system (CNS) 5-HT(1A) receptors, like alpha(2)-adrenoceptors, are involved in reflex mydriasis, voltage response curves of pupillary dilation were constructed by stimulation of the sciatic nerve in anesthetized rats. WAY 100635 (1 mg/kg, i.v.) did not antagonize the evoked reflex mydriasis, which, however, was blocked by RS 79948 (0.3 mg/kg, i.v.). Taken together, these results suggest that 8-OH-DPAT produces pupillary dilation in anesthetized rats by stimulating CNS 5-HT(1A) receptors, which in turn trigger the release of norepinephrine, presumably from the locus coeruleus. The latter reduces parasympathetic neuronal tone to the iris sphincter muscle by stimulation of postsynaptic alpha(2)-adrenoceptors within the Edinger-Westphal nucleus. Unlike alpha(2)-adrenoceptors, 5-HT(1A) receptors in the CNS do not mediate reflex mydriasis evoked by sciatic nerve stimulation.
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MESH Headings
- 8-Hydroxy-2-(di-n-propylamino)tetralin/administration & dosage
- 8-Hydroxy-2-(di-n-propylamino)tetralin/antagonists & inhibitors
- 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacokinetics
- Adrenergic alpha-2 Receptor Antagonists
- Animals
- Dose-Response Relationship, Drug
- Electric Stimulation
- Guanabenz/pharmacology
- Injections, Intravenous
- Isoquinolines/pharmacology
- Male
- Mydriasis/chemically induced
- Mydriasis/prevention & control
- Naphthyridines/pharmacology
- Piperazines/pharmacology
- Pupil/drug effects
- Pupil/physiology
- Pyridines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT1A/administration & dosage
- Receptor, Serotonin, 5-HT1A/physiology
- Receptors, Adrenergic, alpha-2/administration & dosage
- Receptors, Adrenergic, alpha-2/physiology
- Sciatic Nerve/pathology
- Sciatic Nerve/physiology
- Serotonin 5-HT1 Receptor Antagonists
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Affiliation(s)
- Yongxin Yu
- Department of Cell Biology, University of Oklahoma College of Medicine, Oklahoma City, OK 73190, USA.
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16
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Lee B, Tiefenbacher S, Platt DM, Spealman RD. Pharmacological blockade of alpha2-adrenoceptors induces reinstatement of cocaine-seeking behavior in squirrel monkeys. Neuropsychopharmacology 2004; 29:686-93. [PMID: 14872205 DOI: 10.1038/sj.npp.1300391] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Converging evidence suggests a role for noradrenergic mechanisms in stress-induced reinstatement of cocaine seeking in animals. Yohimbine, an alpha(2)-adrenoceptor antagonist, is known to be anxiogenic and induce stress-related responses in humans and animals. Here, we tested the ability of yohimbine to reinstate cocaine-seeking behavior and induce behavioral and physiological signs characteristic of stress in squirrel monkeys. Monkeys were trained to self-administer cocaine under a second-order schedule of i.v. drug injection. Drug seeking subsequently was extinguished by substituting saline for cocaine injections and omitting the cocaine-paired stimulus. The ability of yohimbine and the structurally distinct alpha(2)-adrenoceptor antagonist RS-79948 to reinstate cocaine-seeking behavior was assessed by administering priming injections immediately before test sessions in which the cocaine-paired stimulus was either present or absent. Priming injections of yohimbine (0.1-0.56 mg/kg, i.m.) or RS-79948 (0.01-0.1 mg/kg, i.m.) induced dose-related reinstatement of cocaine-seeking behavior. The magnitude of yohimbine-induced reinstatement was similar regardless of the presence or absence of the cocaine-paired stimulus. Yohimbine also significantly increased salivary cortisol levels, a physiological marker of stress, as well as scratching and self-grooming, behavioral markers of stress in nonhuman primates. In drug interaction experiments, pretreatment with the alpha(2)-adrenoceptor agonist clonidine (0.1-0.3 mg/kg, i.m.) dose-dependently inhibited yohimbine-induced reinstatement of cocaine seeking. In contrast, pretreatment with the dopamine receptor antagonist flupenthixol failed to inhibit yohimbine-induced reinstatement of cocaine seeking. The results show that pharmacological blockade of alpha(2)-adrenoceptors can induce reinstatement of cocaine-seeking behavior and characteristic stress responses in squirrel monkeys, providing a potentially useful model of stress-induced relapse to drug seeking.
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Affiliation(s)
- Buyean Lee
- Harvard Medical School, New England Primate Research Center, Southborough, MA 01772-9102, USA.
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17
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Yu Y, Koss MC. Studies of alpha-adrenoceptor antagonists on sympathetic mydriasis in rabbits. J Ocul Pharmacol Ther 2003; 19:255-63. [PMID: 12828843 DOI: 10.1089/108076803321908374] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This study was undertaken to identify the alpha-adrenergic receptor type responsible for sympathetically evoked mydriasis in pentobarbital-anesthetized rabbits. Frequency-response curves of pupillary dilation were generated by stimulation of the preganglionic cervical sympathetic nerve (1-64 Hz). Evoked mydriatic responses were inhibited by systemic administration of nonselective alpha-adrenergic antagonists, phentolamine (0.3-10 mg/kg) and phenoxybenzamine (0.03-0.3 mg/kg), as well as the selective alpha(1)-adrenergic antagonist, prazosin (0.1-1 mg/kg). The alpha(2)-adrenergic antagonist, RS 79948 (0.3 mg/kg, i.v.) was without inhibitory effect, but potentiated the mydriatic response. In addition, the selective alpha(1A)-adrenoceptor antagonist, 5-methylurapidil (0.1-1 mg/kg, i.v.), antagonized the elicited mydriasis in a dose-dependent fashion. Unlike previous observations that prazosin does not block the adrenoceptor in rabbit iris dilator muscle, our results suggest that prazosin is effective in inhibiting neuronally elicited mydriasis in this species, and that alpha(1A)-adrenoceptors appear to mediate the response.
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Affiliation(s)
- Yongxin Yu
- Department of Cell Biology, University of Oklahoma College of Medicine, Oklahoma City 73190, USA.
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18
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Abstract
1. Experiments were undertaken to determine if the imidazoline/alpha2-adrenoceptor agonist, rilmenidine, would produce mydriasis in cats and, if so, to delineate its site of action and determine if this effect is mediated by imidazoline receptors or alpha2-adrenoceptors. 2. Rilmenidine produced dose-related pupillary dilator responses in pentobarbital anaesthetized cats that were independent of sympathetic innervation to the iris but were dependent upon intact parasympathetic neuronal tone. The ED50 for rilmenidine-induced pupillary dilation was approximately 200 microg kg(-1), i.v., and was sustained for at least 1 h. 3. The highly selective alpha2-adrenoceptor antagonist, RS-79948, administered either before or after rilmenidine, antagonized rilmenidine-induced mydriasis. Neuronally induced reflex inhibition of parasympathetic nerve activity was also inhibited by administration of RS-79948. 4. These results suggest that rilmenidine acts like clonidine to produce pupillary dilation by inhibition of parasympathetic tone to the iris sphincter and that this central nervous system parasympatho-inhibition is mediated by alpha2-adrenoceptors, rather than imidazoline receptors.
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Affiliation(s)
- M C Koss
- Department of Cell Biology, University of Oklahoma College of Medicine, PO Box 26901, Oklahoma City, OK 73190, USA
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Zhu QM, Lesnick JD, Jasper JR, MacLennan SJ, Dillon MP, Eglen RM, Blue DR. alpha 2A-adrenoceptors, not I1-imidazoline receptors, mediate the hypotensive effects of rilmenidine and moxonidine in conscious mice. In vivo and in vitro studies. Ann N Y Acad Sci 1999; 881:287-9. [PMID: 10415927 DOI: 10.1111/j.1749-6632.1999.tb09371.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
MESH Headings
- Animals
- Antihypertensive Agents/pharmacology
- Blood Pressure/drug effects
- Cell Line
- Dogs
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Humans
- Hypotension/chemically induced
- Imidazoles/pharmacology
- Imidazoline Receptors
- In Vitro Techniques
- Male
- Mice
- Mice, Inbred Strains
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Norepinephrine/pharmacology
- Oxazoles/pharmacology
- Quinolizines/pharmacokinetics
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/physiology
- Receptors, Drug/physiology
- Rilmenidine
- Saphenous Vein/drug effects
- Saphenous Vein/physiology
- Transfection
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Affiliation(s)
- Q M Zhu
- Center for Biological Research, Roche Bioscience, Palo Alto, California 94304, USA.
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20
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Zhu QM, Lesnick JD, Jasper JR, MacLennan SJ, Dillon MP, Eglen RM, Blue DR. Cardiovascular effects of rilmenidine, moxonidine and clonidine in conscious wild-type and D79N alpha2A-adrenoceptor transgenic mice. Br J Pharmacol 1999; 126:1522-30. [PMID: 10217548 PMCID: PMC1565905 DOI: 10.1038/sj.bjp.0702429] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/1998] [Revised: 12/14/1998] [Accepted: 12/21/1998] [Indexed: 11/09/2022] Open
Abstract
1. We investigated the cardiovascular effects of rilmenidine, moxonidine and clonidine in conscious wild-type and D79N alpha2A-adrenoceptor mice. The in vitro pharmacology of these agonists was determined at recombinant (human) alpha2-adrenoceptors and at endogenous (dog) alpha2A-adrenoceptors. 2. In wild-type mice, rilmenidine, moxonidine (100, 300 and 1000 microg kg(-1), i.v.) and clonidine (30, 100 and 300 microg kg(-1), i.v.) dose-dependently decreased blood pressure and heart rate. 3. In D79N alpha2A-adrenoceptor mice, responses to rilmenidine and moxonidine did not differ from vehicle control. Clonidine-induced hypotension was absent, but dose-dependent hypertension and bradycardia were observed. 4. In wild-type mice, responses to moxonidine (1 mg kg(-1), i.v.) were antagonized by the non-selective, non-imidazoline alpha2-adrenoceptor antagonist, RS-79948-197 (1 mg kg(-1), i.v.). 5. Affinity estimates (pKi) at human alpha2A-, alpha2B- and alpha2C-adrenoceptors, respectively, were: rilmenidine (5.80, 5.76 and 5.33), moxonidine (5.37, <5 and <5) and clonidine (7.21, 7.16 and 6.87). In a [35S]-GTPgammaS incorporation assay, moxonidine and clonidine were alpha2A-adrenoceptor agonists (pEC50/intrinsic activity relative to noradrenaline): moxonidine (5.74/0.85) and clonidine (7.57/0.32). 6. In dog saphenous vein, concentration-dependent contractions were observed (pEC50/intrinsic activity relative to noradrenaline): rilmenidine (5.83/0.70), moxonidine (6.48/0.98) and clonidine (7.22/0.83). Agonist-independent affinities were obtained with RS-79948-197. 7. Thus, expression of alpha2A-adrenoceptors is a prerequisite for the cardiovascular effects of moxonidine and rilmenidine in conscious mice. There was no evidence of I1-imidazoline receptor-mediated effects. The ability of these compounds to act as alpha2A-adrenoceptor agonists in vitro supports this conclusion.
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Affiliation(s)
- Q-M Zhu
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
| | - J D Lesnick
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
| | - J R Jasper
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
| | - S J MacLennan
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
| | - M P Dillon
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
| | - R M Eglen
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
| | - D R Blue
- Center for Biological Research, Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, California 94304, U.S.A
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Uhlén S, Dambrova M, Näsman J, Schiöth HB, Gu Y, Wikberg-Matsson A, Wikberg JE. [3H]RS79948-197 binding to human, rat, guinea pig and pig alpha2A-, alpha2B- and alpha2C-adrenoceptors. Comparison with MK912, RX821002, rauwolscine and yohimbine. Eur J Pharmacol 1998; 343:93-101. [PMID: 9551719 DOI: 10.1016/s0014-2999(97)01521-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The Kd values of the recently introduced radioligand [3H]RS79948-197 ((8a R,12aS,13a-S)-5,8,8a,9,10,11,12,12a,13,13a-decahydro-3-metho xy-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]naphthyridine) were determined for the recombinant human and rat alpha2A-, alpha2B- and alpha2C- as well as guinea pig alpha2B- and alpha2c-adrenoceptors expressed in COS (CV-1 Origin, SV40) cells. In addition, the Kd values were also determined for [3H]RS79948-197 for the guinea pig spleen alpha2A-adrenoceptor and for pig alpha2A-, alpha2B- and alpha2C-adrenoceptors in membranes obtained from kidney and striatum. Available radioligands for alpha2-adrenoceptors, besides [3H]RS79948-197 are the tritiated forms of MK912 ((2S,12bS)1',3'-dimethylspiro(1,3,4,5',6,6',7,12b-octa hydro-2H-benzo[b]furo[2,3-a]quinazoline)-2,4'-pyrimidin-2'-one), RX821002 (2-methoxy-idazoxan), rauwolscine and yohimbine. In the present article the binding constants of all these substances for the alpha2A-, alpha2B- and alpha2C-adrenoceptor subtypes in human, pig, rat and guinea pig are reviewed. In all species tested MK912 was alpha2C-selective, RX821002 showed a minor alpha2A-selectivity, whereas [3H]RS79948-197 was non-selective among the alpha2-adrenoceptor subtypes, showing high affinity for all three subtypes. Rauwolscine and yohimbine showed relatively low affinities for nmost of the alpha2-adrenoceptor subtypes investigated, the exception being rauwolscine having high affinity for the human and porcine alpha2C-adrenoceptors.
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Affiliation(s)
- S Uhlén
- BioMedical Centre, Department of Pharmaceutical Biosciences, Uppsala University, Sweden.
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