| Opposite to alpha2-adrenergic agonists, an imidazoline I1 selective compound does not influence reflex bradycardia in rabbits. | |
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MedLine Citation:
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PMID: 16464646 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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This work aimed to study the respective effects of central alpha2-adrenergic receptors (alpha2-ARS) and I1 imidazoline receptors (I1Rs) in the facilitatory effects of imidazoline-like drugs on the reflex bradycardia (RB). Experiments were performed in anaesthetized rabbits. The reflex bradycardic response was induced by phenylephrine injected i.v. LNP 509, rilmenidine and dexmedetomidine were administered intracisternally (i.c.). LNP509 (1 mg/kg, i.c.), a ligand highly selective for I1Rs, induced hypotension (54+/-3 vs. 93+/-2 mm Hg) and bradycardia (260+/-13 vs. 322+/-13 beats/min) (p<0.05, n=5) but did not affect RB. Rilmenidine (1 microg/kg, i.c.), a hybrid ligand which binds to both I1 and alpha2-ARS, also decreased arterial pressure (61+/-2 vs. 101+/-2 mm Hg) and heart rate (260+/-4 vs. 308+/-8) (p<0.01, n=5); it potentiated the RB (maximum R-R interval: 284+/-17 vs. 196+/-6 ms) (p<0.05, n=5). Dexmedetomidine (1 microg/kg, i.c.), a ligand selective for alpha2-ARs, reduced blood pressure (53+/-3 vs. 104+/-2 mm Hg) and heart rate (246+/-4 vs. 312+/-8 beats/min) (p<0.05, n=5) and potentiated the RB (maximum R-R interval: 518+/-38 vs. 194+/-4 ms) (p<0.05, n=5). The potentiation of RB was much greater than that observed with rilmenidine and was significantly prevented by L-NNA injected centrally. This study shows that: (i) an exclusive action on I1Rs which decreases arterial pressure, does not potentiate the RB ii) activation of alpha2-ARs potentiates the RB (iii) the R-R prolongation caused by alpha2-ARs stimulation is prevented by central NOS inhibition. |
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Authors:
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Guata Yoro Sy; Pascal Bousquet; Josiane Feldman |
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Publication Detail:
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Type: Journal Article Date: 2006-02-07 |
Journal Detail:
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Title: Autonomic neuroscience : basic & clinical Volume: 128 ISSN: 1566-0702 ISO Abbreviation: Auton Neurosci Publication Date: 2006 Jul |
Date Detail:
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Created Date: 2006-06-20 Completed Date: 2006-09-08 Revised Date: 2009-08-12 |
Medline Journal Info:
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Nlm Unique ID: 100909359 Medline TA: Auton Neurosci Country: Netherlands |
Other Details:
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Languages: eng Pagination: 19-24 Citation Subset: IM |
Affiliation:
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Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, INSERM U 715, Faculté de Médecine, Université Louis Pasteur, 11 rue Humann, 67000 Strasbourg, France. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adrenergic alpha-Agonists
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pharmacology Animals Autonomic Nervous System / drug effects*, physiology Baroreflex / drug effects*, physiology Blood Pressure / drug effects, physiology Bradycardia / chemically induced*, physiopathology Brain Stem / drug effects*, physiology Cyclopropanes / pharmacology Dexmedetomidine / pharmacology Drug Interactions / physiology Drug Synergism Enzyme Inhibitors / pharmacology Heart / drug effects*, innervation, physiology Heart Rate / drug effects, physiology Imidazoline Receptors Male Nitric Oxide / biosynthesis Nitric Oxide Synthase / antagonists & inhibitors, metabolism Oxazoles / pharmacology Phenylephrine / pharmacology Pyrroles / pharmacology Rabbits Receptors, Adrenergic, alpha-2 / agonists, metabolism Receptors, Drug / agonists*, metabolism Reticular Formation / drug effects, physiology Solitary Nucleus / drug effects, physiology |
| Chemical | |
Reg. No./Substance:
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0/Adrenergic alpha-Agonists; 0/Cyclopropanes; 0/Enzyme Inhibitors; 0/Imidazoline Receptors; 0/LNP 509; 0/Oxazoles; 0/Pyrroles; 0/Receptors, Adrenergic, alpha-2; 0/Receptors, Drug; 0/imidazoline receptor 2; 10102-43-9/Nitric Oxide; 113775-47-6/Dexmedetomidine; 54187-04-1/rilmenidine; 59-42-7/Phenylephrine; EC 1.14.13.39/Nitric Oxide Synthase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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