AJP - Heart and Circulatory Physiology, Vol 255, Issue 3 577-H586, Copyright © 1988 by American Physiological Society
Time course of sympathetic denervation supersensitivity in canine ventricular recovery
J. B. Martins
Department of Internal Medicine, Veterans Administration Medical Center, Iowa City, Iowa.
We studied the timing of the electrophysiological effects of sympathetic
supersensitivity with chronically implanted electrodes in the anterior and
posterior left ventricular free wall in 10 dogs. We produced denervation of
the anterior wall in six dogs by application of phenol surrounding the
anterior electrode. Drug infusions that were performed under pentobarbital
sodium anesthesia included norepinephrine, isoproterenol, and methoxamine.
In four controls there was no difference in response of the two sites.
Presynaptic supersensitivity was manifest as early as 2 days and as late as
64 days by a parallel left shift (greater than or equal to 8.3 ms) in the
norepinephrine dose to effective refractory period shortening response
curve in the anterior compared with posterior left ventricle, P less than
0.01. The isoproterenol dose-response curve was also shifted to the left by
5.6 ms (P less than 0.01) but was manifest only after 10 days and only
until 28 days from the denervation procedure. Local repolarization in the
denervated areas shortened more than the innervated areas with both drugs.
The methoxamine dose-response curve was flat, and the anterior-denervated
area was not different than the posterior-innervated area. We conclude that
recovery properties in ventricular muscle demonstrate evidence of
supersensitivity, which is neurotransmitter and beta- but not
alpha-receptor specific.
