Effects of guanfacin and nitroprusside on the haemodynamics and oxygen consumption of Brahman steers.
1. The systemic vascular resistance (SVR) and oxygen consumption of high grade Brahman (Bos indicus) steers were measured before and after treatment with guanfacin and nitroprusside to test whether the decreased whole-body oxygen consumption seen with guanfacin treatment is due to less oxygen consumption by vascular smooth muscle. 2. Guanfacin changed oxygen consumption by -31% but raised SVR by 61%. Nitroprusside had no significant effect on oxygen consumption but changed SVR by -20%. Moreover, with guanfacin, the changes in oxygen consumption and SVR were temporally incongruent. 3. We conclude that the lowered whole-body oxygen consumption caused by guanfacin was not due to decreased consumption by vascular tissue.
Gazzola
C
C
Division of Forage and Animal Management, Queensland Department of Primary Industries, Tropical Cattle Research Center, Rockhampton M.C., Australia.
Magner
T
T
Berger
K T
KT
Hunter
R A
RA
D000818:Animals; D002417:Cattle / Q000502:physiology*; D016316:Guanfacine / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D008954:Models, Biological; D009599:Nitroprusside / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects*; D014655:Vascular Resistance / Q000187:drug effects
D009599:Nitroprusside; D016316:Guanfacine