Effects of subfornical organ lesions on acutely induced thirst and salt appetite.
We examined the role of the subfornical organ (SFO) in stimulating thirst and salt appetite using two procedures that initiate water and sodium ingestion within 1-2 h of extracellular fluid depletion. The first procedure used injections of a diuretic (furosemide, 10 mg/kg sc) and a vasodilator (minoxidil, 1-3 mg/kg ia) to produce hypotension concurrently with hypovolemia. The resulting water and sodium intakes were inhibited by intravenous administration of ANG II receptor antagonist (sarthran, 8 micrograms . kg(-1). min(-1)) or angiotensin-converting enzyme inhibitor (captopril, 2.5 mg/h). The second procedure used injections of furosemide (10 mg/kg sc) and a low dose of captopril (5 mg/kg sc) to initiate water and sodium ingestion upon formation of ANG II in the brain. Electrolytic lesions of the SFO greatly reduced the water intakes, and nearly abolished the sodium intakes, produced by these relatively acute treatments. These results contrast with earlier findings showing little effect of SFO lesions on sodium ingestion after longer-term extracellular fluid depletion.
Thunhorst
R L
RL
Departments of Psychology and Pharmacology and the Cardiovascular Center, University of Iowa, Iowa City, Iowa 52242-1407, USA. thunhors@blue.weeg.uiowa.edu
Beltz
T G
TG
Johnson
A K
AK
D000804:Angiotensin II / Q000031:analogs & derivatives / Q000494:pharmacology; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001810:Blood Volume; D002216:Captopril / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D017673:Sodium Chloride, Dietary; D013356:Subfornical Organ / Q000503:physiopathology*; D013894:Thirst / Q000187:drug effects / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects; D014882:Water-Electrolyte Balance / Q000187:drug effects
D000806:Angiotensin-Converting Enzyme Inhibitors; D017673:Sodium Chloride, Dietary; D000804:Angiotensin II; C014805:angiotensin II, Sar(1)-Thr(8)-; D002216:Captopril