AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 1 145-R152, Copyright © 1987 by American Physiological Society
Augmented pressor response to vasopressin in awake dogs after cardiac denervation
B. C. Wang, G. F. Ginter and K. L. Goetz
Hemodynamic responses to varying intravenous infusion rates of vasopressin
were studied in two groups of dogs; one group was cardiac denervated and
the other sham operated. Vasopressin given at 200, 1,000, and 5,000 fmol X
kg-1 X min-1 produced increases in aortic pressure that were significantly
greater in cardiac-denervated dogs than in sham-operated dogs. The
augmented pressor response in cardiac-denervated dogs was associated with
greater increases in total peripheral resistance in this group; decreases
in cardiac output were similar in the two groups of dogs. Vasopressin
decreased heart rate significantly in each group, but the magnitude of the
decrease was significantly smaller in cardiac-denervated dogs. In contrast
to these results, the intravenous infusion of phenylephrine or angiotensin
II in other experiments on the same dogs produced comparable increases in
aortic pressure in each group. These results are consistent with earlier
evidence indicating that vasopressin elicits more effective reflex
mechanisms to attenuate the increases in blood pressure caused by its
direct vasoconstrictor action than do other vasoconstrictor agents, such as
angiotensin II and phenylephrine. Since the infusion of vasopressin
produced a greater increase in arterial blood pressure in
cardiac-denervated dogs than it did in sham-operated control dogs, it
appears that at least part of the unique action of vasopressin may be
mediated by the potentiation of a peripheral vasodepressor reflex arising
from cardiac receptors.
