Inhibitory effect of atrial natriuretic factor on sympathetic
ganglionic neurotransmission in humans.
Floras, John S.
Division of Cardiology, The Toronto Hospital and The Centre for
Cardiovascular Research, University of Toronto, Toronto, Canada
APStracts 2:0086R, 1995.
Previously, I have documented an inhibitory effect of atrial
natriuretic factor (ANF) on postganglionic muscle sympathetic nerve
activity (MSNA) in normal subjects that was consistent with either a
central or ganglionic sympathoinhibitory action. To test the latter
hypothesis, I examined, in 7 young normotensive men, the effect of
saline (as vehicle) and ANF (50 ug then 50 ng/kg/min), given on two
separate days according to a random double-blind study design, on
blood pressure (BP), heart rate (HR) and MSNA, before and after
ganglionic neurotransmission was stimulated with edrophonium (ED; 12
mg iv), a rapidly reversible acetylcholinesterase inhibitor without
CNS effects, and during subsequent augmentation of central
sympathetic outflow by a cold pressor test (CPT). In 5 of these
subjects, the protocol was replicated during nitroprusside infusion
(0.4 _g/kg/min). Edrophonium increased MSNA during vehicle
(p<0.005) and nitroprusside (p<0.003), but not during ANF
infusion. The sympathoneural response to the combined stimuli of ED
and CPT was also attenuated by ANF as compared to either saline or
nitroprusside infusions. Conclusions: (1) Post ganglionic MSNA is
increased by edrophonium; (2) this facilitative effect of edrophonium
is attenuated by ANF; and (3) modulation of ganglionic
neurotransmission is one mechanism for the relative sympatho
-inhibition observed when ANF is infused at this dose.
Received 27 April 1994; accepted in final form 20 March 1995.
APS Manuscript Number R222-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 April 1995.