AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 3 796-R801, Copyright © 1994 by American Physiological Society
Regulation of plasma vasopressin by plasma osmolality and carotid sinus pressure in anesthetized rabbits
C. S. Scott, J. Sharp-Kehl, C. A. Redekopp and J. R. Ledsome
Department of Physiology, University of British Columbia, Vancouver, Canada.
The purpose of the experiments was to investigate the effect of changes in
carotid sinus baroreceptor stimulation on plasma vasopressin (AVP) at
different plasma osmolalities in the anesthetized artificially ventilated
rabbit. Both carotid sinuses were isolated and perfused with blood at
servo-controlled pressures. The vagus and aortic depressor nerves were
sectioned bilaterally to eliminate input from atrial and aortic arch
baroreceptors. Saline (0.3%, wt/vol) was infused to lower plasma
osmolality, and 5% saline was infused to raise plasma osmolality. At three
plasma osmolalities, the carotid sinus pressure (CSP) was changed from 100
mmHg to 40 and 140 mmHg and returned to 100 mmHg. There were no changes in
plasma AVP in response to changes in CSP at low plasma osmolality (289
mosmol/kgH2O), but at medium (309 mosmol/kgH2O) and high (323 mosmol/kgH2O)
osmolality, plasma AVP was higher at 40 than at 140 mmHg CSP. The
relationship between plasma AVP and plasma osmolality was expressed as a
linear regression at each CSP. Changes in CSP changed the sensitivity but
not the threshold of the osmotic control of AVP release.
