Parasympathetic-sympathetic interactions for control of atrial rate
are maintained following, sa nodal parasympathectomy.
McGuirt, A. S., D. C. Schmacht, and J. L. Ardell.
Department of Physiology, University of South Alabama, College of
Medicine, Mobile Alabama
APStracts 3:0540H, 1996.
Methods: Autonomic control of atrial rate was evaluated in
anesthetized dogs by electrical stimulation of stellate ganglia
and/or cervical vagi before and after the intrinsic cardiac right
atrial ganglionated plexus (RAGP) was injected with the nicotinic
blocker hexamethonium, or the membrane stabilizing chemical
lidocaine, or the RAGP was surgically removed. Results: Injections of
lidocaine or hexamethonium into or surgical removal of the RAGP
eliminated the bradycardia elicited by vagal stimulation without
reducing the tachycardia induced by stellate stimulation. Yet, after
surgical ablation of the RAGP, the tachycardia induced by sympathetic
stimulation was still reduced 94% by parasympathetic stimulation.
After injections of hexamethonium or lidocaine into the RAGP, the
sympathetically induced tachycardia was reduced 39% and 85%,
respectively, by parasympathetic stimulation. After RAGP ablation,
when atrial rate was increased by infusion of [beta]-adrenergic
agonists, parasympathetic stimulation reduced atrial rate by 13%.
Conclusions: SA nodal parasympathectomy, produced by disrupting the
RAGP, eliminates direct vagal control of the SA node while leaving
prejunctional parasympathetic projections to sympathetic efferents
innervating the SA node intact.
Received 26 August 1996; accepted in final form 5 December 1996.
APS Manuscript Number H771-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996