AJP - Heart and Circulatory Physiology, Vol 245, Issue 6 1073-H1076, Copyright © 1983 by American Physiological Society
Relaxation of canine saphenous vein following brief transmural nerve stimulation
T. W. Rooke, T. J. Rimele and P. M. Vanhoutte
The ability of electrical stimulation to cause relaxation in the canine
saphenous vein was evaluated. Rings of vein were studied isometrically in
organ chambers containing physiological salt solution. Prostaglandin F2
alpha produced stable contractions, during which brief periods of
electrical stimulation caused further contraction. With cessation of the
electrical stimulation, tension transiently decreased to a level below that
observed prior to the stimulation (undershoot). This poststimulation
undershoot was blocked by tetrodotoxin, phentolamine, ouabain, and
potassium-free solution; it was not affected by atropine, cimetidine,
indomethacin, ketanserin, methysergide, propranolol, pyrilamine, or removal
of the endothelium. Undershoot did not occur following electrical
stimulation during contractions evoked by norepinephrine. During
superfusion with PGF2 alpha, a brief exposure to exogenous norepinephrine
caused a transient contraction followed by a subsequent undershoot. These
results suggest that 1) the interaction of norepinephrine with
postjunctional alpha-adrenoceptors on vascular smooth muscle leads to an
increase in the activity of Na+-K+-ATPase, and 2) increased activity of
Na+-K+-ATPase is responsible for the poststimulation undershoot.
