Na depletion-induced Na appetite of sheep is independent of brain angiotensin II.
Previous experiments indicated that the Na appetite of Na-deplete sheep is decreased by systemically administered captopril. The assumption that captopril does not readily cross the blood-brain barrier, lead to the conclusion that circulating ANG II acting in brain areas without a blood-brain barrier, i.e., circumventricular organs such as the subfornical organ or organum vasculosum of the lamina terminalis, contributes to Na appetite induced by Na depletion. The present experiments investigated the possibility that systemically administered captopril does, in fact, cross the blood-brain-barrier and thereby influence brain angiotensin II formation and that brain angiotensin II contributes to Na depletion-induced Na appetite of sheep. The results showed that systemically administered captopril blocked water intake caused by intracerebroventricular infusion of angiotensin I, and that Na depletion induced Na appetite was not decreased by intracerebroventricular infusion of various antagonists of the renin-angiotensin system. Thus, the results suggest that although captopril crosses the blood-brain-barrier and can influence the formation of brain angiotensin II, brain angiotensin II is not involved in the Na appetite of Na-deplete sheep.
Weisinger
R S
RS
University of Melbourne, Parkville, Australia. Richard_Weisinger.HFI@muwaye.unimelb.edu.au
Blair-West
J R
JR
Denton
D A
DA
Tarjan
E
E
D000804:Angiotensin II / Q000502:physiology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001066:Appetite / Q000187:drug effects / Q000502:physiology*; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D002216:Captopril / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D005260:Female; D012756:Sheep; D012982:Sodium, Dietary / Q000008:administration & dosage*; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D000806:Angiotensin-Converting Enzyme Inhibitors; D012982:Sodium, Dietary; D000804:Angiotensin II; D002216:Captopril