AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 5 1076-R1083, Copyright © 1989 by American Physiological Society
Regional hemodynamic changes following hypovolemia in conscious rats
S. M. Gardiner, A. M. Compton and T. Bennett
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, United Kingdom.
Regional hemodynamic responses to subcutaneous injection of hyperoncotic
polyethylene glycol (PEG) were assessed in Long-Evans (i.e., normal) and
Brattleboro [i.e., arginine vasopressin (AVP)-deficient] rats with
chronically implanted, pulsed Doppler probes. The results were compared
with saline-injected time controls. PEG injection elicited an early (30
min) selective mesenteric vasoconstriction in Long-Evans rats; 4-5 h after
PEG the mesenteric vasoconstriction was greater in Long-Evans than in
Brattleboro rats, but the renal and hindquarters vasoconstrictions were
similar in both strains. There was a transient mesenteric vasodilatation
[with no change in blood pressure (BP)] in Long-Evans rats given an
antagonist of the V1-receptor actions of AVP 5 h after PEG. In the presence
of the AVP antagonist, Long-Evans rats showed a marked dependence on the
vasoconstrictor actions of the renin-angiotensin system for the maintenance
of BP, similar to Brattleboro rats. Both strains also showed marked
hypotensive responses to inhibition of sympathoadrenal activity (with
pentolinium). Hence, AVP has clear-cut hemodynamic effects after PEG
administration, but its role is not indispensable.
