AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 4 426-R433, Copyright © 1985 by American Physiological Society
Short-latency tachycardia evoked by stimulation of muscle and cutaneous afferents
A. J. Gelsema, L. N. Bouman and J. M. Karemaker
The short-latency effect on heart rate of peripheral nerve stimulation was
studied in decerebrate cats. Selective activation (17-40 microA, 100 Hz, 1
s long) of low-threshold fibers in the nerves to the triceps surae muscle
yielded isometric contractions of maximal force that were accompanied by a
cardiac cycle length shortening within 0.4 s from the start of stimulation.
This effect was abolished by pharmacologically induced neuromuscular
blockade. The cardiac cycle length shortening during paralysis reappeared
after a 6- to 10-fold increase of the stimulation strength. Cutaneous
(sural) nerve stimulation (15-25 microA, 100 Hz, 1 s long) elicited reflex
contractions in the stimulated limb, which were also accompanied by a
cardiac acceleration with similar latency. Paralysis prevented the reflex
contractions and reduced the cardiac response in some cats and abolished it
in others. The response reappeared in either case after a 5- to 10-fold
increase of the stimulus strength. It is concluded that muscle nerve and
cutaneous nerve activity both cause a similar cardiac acceleration with a
latency of less than 0.4 s. The response to muscle nerve stimulation is
elicited by activity in group III afferents. It is excluded that the
cardiac response to nerve stimulation is secondary to a change in the
respiratory pattern.
