AJP - Heart and Circulatory Physiology, Vol 242, Issue 1 7-12, Copyright © 1982 by American Physiological Society
Effects of glucagon on cardiac chronotropic response to vagal stimulation in the dog
S. L. Stuesse, M. N. Levy and H. Zieske
Glucagon accelerates the heart independent of sympathetic nervous system
stimulation. The effect of glucagon on the chronotropic responses to
repetitive bursts of vagal stimulation was determined in open-chest
anesthesized dogs. When the cervical vagi were stimulated at constant
frequencies, the change in heart rate was not affected by glucagon
administration, i.e., no vagolytic effect caused by glucagon was apparent.
Thus glucagon did not alter the reaction of acetylcholine with cardiac
postsynaptic receptors. When the vagi were stimulated intermittently with
one short burst of vagal stimuli delivered each cardiac cycle, the
resultant heart period was dependent on the time of vagal stimulus
delivery. Both maximum and minimum cardiac cycle lengths obtained during
phasic vagal stimulation were decreased by glucagon. As it has been
previously demonstrated that vagal impulses to the heart tend to be
clustered during certain times of the cardiac cycle, by accelerating the
heart glucagon may shift the cardiac response to vagal stimulation.
