AJP - Heart and Circulatory Physiology, Vol 249, Issue 5 1038-H1044, Copyright © 1985 by American Physiological Society
Ganglionic blockade in conscious dogs with chronic caval constriction
W. D. Sweet, R. H. Freeman, J. O. Davis and R. C. Vari
Chronic constriction of the thoracic inferior vena cava decreases venous
return and cardiac output, increases the secretion of renin and
aldosterone, and produces sodium retention with ascites and edema
formation. The arterial pressure is maintained at normotensive levels in
this caval model by an increase in total peripheral resistance. The
objective of the present study was to compare renal and hemodynamic
responses to ganglionic blockade in the conscious thoracic caval dog to
responses obtained in another low-output model, the chronic sodium-deplete
dog, and also to the responses obtained in the normal sodium-replete dog.
The control base-line pressures averaged 103 +/- 2, 110 +/- 3, and 110 +/-
3 mmHg, respectively, in the sodium-replete, sodium-deplete, and thoracic
caval dogs (P greater than 0.05). Ganglionic blockade in the conscious dog
with caval constriction resulted in a sustained 20- to 30-mmHg fall in the
arterial pressure; a sustained fall of 20 mmHg occurred in the
sodium-deplete dogs. In contrast, ganglionic blockade failed to decrease
the blood pressure at any time in the normal sodium-replete animals.
Effective renal blood flow and creatinine clearance failed to demonstrate
sustained changes after ganglionic blockade in any group of dogs; renal
sodium excretion increased only in the normal sodium-replete dogs. These
results suggest an enhanced contribution of the sympathetic nervous system
to blood pressure maintenance in both the sodium-deplete and the caval
dogs. Although the data fail to demonstrate an important contribution of
the adrenergic system in the chronic sodium retention in these two
experimental models, decreases in renal perfusion pressure may have blunted
any potential natriuresis in these animals following ganglionic blockade.
