Journal of Applied Physiology, Vol 38, Issue 1 108-113, Copyright © 1975 by American Physiological Society
Additive effects of acetylcholine released by vagal nerve stimulation on atrial rate
L. M. Hondeghem, E. Mouton, T. Stassen and H. De Geest
In reserpinized dogs, the decrease in atrial rate (AR) as a function of the
frequency of stimulation (supramaximal strength) of a single vagal nerve
can be described satisfactorily by a rectangular hyperbola (RH). If the RH
of one vagal nerve has been determined and if one point of the RH of the
other vagal nerve is known, then the latter RH can be determined. Both RHs
being known and assuming that the acetylcholine released by the right and
left vagal nerves is additive, the slowing of AR by simultaneous
stimulation of both nerves can be predicted. A minor systematic deviation
from the predicted AR during simultaneous stimulation is usually found,
which could be accounted for by a time dependent decrease of the effect of
vagal nerve stimulation. The results are qualitatively similar during
norepinephrine infusion. We propose that, although the vagal innervation
may vary from pacemaker cell to pacemaker cell, the ratio of the activities
of the two vagal nerves is constant throughout the sinoatrial node.
