Role of arteria baroreceptor input on thirst and urinary responses to intracerebroventricular angiotensin II.
Intracerebroventricular (icv) infusion of angiotensin II (ANG II) in rats elicits greater water intake under hypotensive, compared with normotensive, conditions. The present experiments used sinoaortic baroreceptor-denervated (SAD) rats and sham-operated rats to examine if the modulatory effects of arterial blood pressure on water intake in response to icv ANG II are mediated by arterial baroreceptors. Mean arterial blood pressure (MAP) was raised or lowered by intravenous (i.v.) infusions of phenylephrine (1 or 10 micrograms.kg-1 x min-1) or minoxidil (25 micrograms.kg-1 x min-1), respectively. The angiotensin-converting enzyme inhibitor captopril (0.33 mg/min) was infused i.v. to prevent the endogenous formation of ANG II during testing. Urinary excretion of water and solutes was measured throughout. Water intake elicited by icv ANG II was inversely related to changes in MAP. Specifically, rats drank more water in response to icv ANG II when MAP was reduced by minoxidil but drank less water when MAP was elevated by phenylephrine. The influence of changing MAP on the icv ANG II-induced drinking responses was not affected by SAD. These results suggest that the modulatory effects of arterial blood pressure on icv ANG II-induced drinking can occur in the absence of sinoaortic baroreceptor input.
Thunhorst
R L
RL
Department of Psychology, University of Iowa 52242.
Lewis
S J
SJ
Johnson
A K
AK
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001158:Arteries / Q000294:innervation*; D001794:Blood Pressure / Q000187:drug effects; D001810:Blood Volume; D001834:Body Water / Q000378:metabolism; D001921:Brain / Q000502:physiology*; D003714:Denervation; D004231:Diuresis / Q000187:drug effects; D004326:Drinking / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D011311:Pressoreceptors / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013894:Thirst / Q000502:physiology*; D014556:Urine / Q000737:chemistry
D000804:Angiotensin II