Document Detail

Cardiovascular responses of sinoaortic-denervated rats to intracerebroventricular injection of alpha 1- and alpha 2-adrenoceptor agonists.
MedLine Citation:
PMID:  1350994     Owner:  NLM     Status:  MEDLINE    
The aim of the present work was to analyse the cardiovascular responses induced by i.c.v. administration of the alpha 1- and alpha 2-adrenoceptor agonists, phenylephrine and clonidine, respectively, in conscious normal and sinoaortic-denervated rats. Sinoaortic denervation involves changes in central and peripheral catecholaminergic pathways. Clonidine (1-10 micrograms) produced a dose-dependent rise in blood pressure and a bradycardiac response in sham-operated animals, whereas in sinoaortic-denervated rats it provoked a brief rise in blood pressure followed by a marked fall as well as bradycardia. The responses involved mostly activation of central alpha 2-adrenoceptors, but the blood pressure responses induced by clonidine in sinoaortic-denervated rats may also have involved alpha 1-adrenoceptors. The bradycardia induced by the alpha 2-agonist in both groups of rats involved preferentially central alpha 2-adrenoceptors but also partially stimulated alpha 1-adrenoceptors. Phenylephrine, at a dose of 10-60 micrograms, induced a rise in blood pressure and a bradycardiac response while 90 micrograms produced a biphasic pressure response (early transient rise followed by a fall) as well as bradycardia in both sham-operated and sinoaortic-denervated animals. Phenylephrine activated alpha 1-adrenoceptors in every case, but the fall in blood pressure and the bradycardia also involved alpha 2-adrenoceptors. The responses were significantly higher in the sinoaortic-denervated rats than in the sham-operated. Our findings suggest that arterial baroreceptor reflexes can modify the effects of alpha-agonists initiated in the central nervous system. Sinoaortic denervation preparations enable one to unmask the depressor response to clonidine and also demonstrate the true magnitude of the phenylephrine response.
D Ricci; C A Taira; M A Enero
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  European journal of pharmacology     Volume:  212     ISSN:  0014-2999     ISO Abbreviation:  Eur. J. Pharmacol.     Publication Date:  1992 Mar 
Date Detail:
Created Date:  1992-07-13     Completed Date:  1992-07-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  1254354     Medline TA:  Eur J Pharmacol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  195-200     Citation Subset:  IM    
Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, UBA, CONICET, Buenos Aires, Argentina.
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MeSH Terms
Adrenergic alpha-Agonists / administration & dosage,  antagonists & inhibitors,  pharmacology*
Adrenergic alpha-Antagonists / pharmacology
Blood Pressure / drug effects*
Clonidine / pharmacology
Dioxanes / pharmacology
Heart Rate / drug effects*
Injections, Intraventricular
Phenylephrine / pharmacology
Prazosin / pharmacology
Pressoreceptors / physiology*
Rats, Inbred Strains
Reg. No./Substance:
0/Adrenergic alpha-Agonists; 0/Adrenergic alpha-Antagonists; 0/Dioxanes; 19216-56-9/Prazosin; 4205-90-7/Clonidine; 59-42-7/Phenylephrine; 79944-58-4/Idazoxan

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