Document Detail


Discharge patterns of preganglionic neurones with axons in a cardiac vagal branch in the rat.
MedLine Citation:
PMID:  14603369     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The fibre types that run in a vagal branch projecting to the rat heart are described in this study. In order to obtain spontaneous discharge in this vagal branch and optimal recording conditions, we compared the decerebrate state to urethane, urethane-chloralose and pentobarbital-chloralose anaesthesia with regard to level of chronotropic cardiac vagal tone. Administration of atropine (2 mg kg(-1), I.V.) significantly decreased baseline cardiac interval only in the decerebrate and urethane-anaesthetised rat (by 0.018 +/- 0.001 s and 0.019 +/- 0.002 s, respectively). As a result of these experiments, urethane was chosen as the anaesthetic for all subsequent studies. Using a heart rate signal-averaging method we demonstrated that rat cardiac vagal preganglionic neurones innervating the sinoatrial node should have an expiratory discharge pattern, as reported in other species. However, only 5 % of chronotropic vagal tone was found to be subject to respiratory sinus arrhythmia. A suction microelectrode method, combined with spike-triggered averaging, was employed to record activity from a total of 58 vagal afferents that had axons in this branch. Approximately 75 % of these latter sensory fibres displayed cardiac rhythm. In a separate study we also recorded 318 preganglionic neurones with axons in the right cardiac vagal branch of the rat. Respiratory-modulated preganglionic units were statistically less common than tonically firing units. Six preganglionic subtypes were categorised according to conduction velocity and respiratory discharge pattern. Myelinated B-fibre and unmyelinated C-fibre types were found to be equally prevalent and equally likely to be reflexly excited during the pulmonary chemoreflex and the peripheral arterial chemoreflexes. The electrophysiological analysis has shown how diverse the discharge patterns of the preganglionic neurones or interneurones are whose axons course in the right cardiac vagal branch of the rat. The results of these experiments demonstrate the usefulness of combining spike discrimination with multiple spike-triggered averaging to simultaneously record B and C centrifugal vagal efferents.
Authors:
Deirdre M O'Leary; James F X Jones
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Experimental physiology     Volume:  88     ISSN:  0958-0670     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2003 Nov 
Date Detail:
Created Date:  2003-11-06     Completed Date:  2004-07-16     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  711-23     Citation Subset:  IM    
Affiliation:
Department of Human Anatomy and Physiology, University College Dublin, Earlsfort Terrace, Dublin 2, Ireland.
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MeSH Terms
Descriptor/Qualifier:
Action Potentials*
Anesthetics / pharmacology
Animals
Arrhythmia, Sinus / physiopathology*
Autonomic Fibers, Preganglionic*
Axons*
Heart / drug effects,  innervation*,  physiopathology*
Heart Conduction System / drug effects,  physiology
Heart Rate*
Male
Rats
Rats, Wistar
Statistics as Topic
Vagus Nerve / drug effects,  physiopathology*
Chemical
Reg. No./Substance:
0/Anesthetics

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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