Document Detail

Cardioinhibitory actions of clonidine assessed by cardiac vagal motoneuron recordings.
MedLine Citation:
PMID:  18475155     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Cardiac vagal activity is now considered as an important therapeutic target. However, there is a lack of direct data on how cardiac vagal motoneurons respond to parasympathomimetic agents. METHODS: Rats were anesthetized with urethane and mechanically ventilated. Single-unit activity was recorded in the nucleus ambiguus from cardiac vagal motoneurons, identified by antidromic activation from the cardiac vagal branch and their barosensitivity. RESULTS: Nitroprusside lowered systolic blood pressure, increased heart rate and inhibited cardiac vagal motoneuron activity (n = 5 cells in five rats). Clonidine 1-100 microg kg(-1) intravenously, however, lowered systolic blood pressure, but it increased cardiac vagal motoneuron activity (n = 8 cells in eight rats). It also enhanced their barosensitivity. An unsuspected further finding was that clonidine significantly increased the occurrence of cardiac vagal motoneuron firing spikes separated by short (< 30 ms) interspike intervals ('doublet'). CONCLUSION: Such grouped patterns are known to enhance neurotransmitter release. Therefore, these data provide a new mechanism by which clonidine can further potentiate parasympathetic actions on the heart.
Emil Toader; Andrei Cividjian; Nicolas Rentero; Robin M McAllen; Luc Quintin
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of hypertension     Volume:  26     ISSN:  0263-6352     ISO Abbreviation:  J. Hypertens.     Publication Date:  2008 Jun 
Date Detail:
Created Date:  2008-05-13     Completed Date:  2008-07-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8306882     Medline TA:  J Hypertens     Country:  England    
Other Details:
Languages:  eng     Pagination:  1169-80     Citation Subset:  IM    
Department of Physiology, CNRS UMR5123-University of Lyon, Lyon, France.
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MeSH Terms
Adrenergic alpha-Agonists / pharmacology*
Clonidine / pharmacology*
Heart / drug effects,  innervation*
Motor Neurons / drug effects*
Nitroprusside / pharmacology
Rats, Sprague-Dawley
Vagus Nerve / drug effects*
Vasodilator Agents / pharmacology
Reg. No./Substance:
0/Adrenergic alpha-Agonists; 0/Vasodilator Agents; 15078-28-1/Nitroprusside; 4205-90-7/Clonidine

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