Effect of drinking on angiotensin-II-induced shifts in regional cerebral blood flow in the rat.
A map of brain regions affected by central administration of the octapeptide angiotensin II (AII) and that would further reflect the consequences of AII's well-known dipsogenic action was developed. Regional cerebral blood flow (rCBF) as an indicator of neuronal activity was measured in conscious rats shortly after an ICV bolus injection of 100 ng AII or saline vehicle (VEH). AII-treated animals were further subdivided into two groups that were either permitted to drink [AII (W+)] or whose water was removed when drinking was attempted [AII (W-)]. When compared to VEH condition, blood flow increased significantly within 1 min after AII treatment in 33 of 53 regions sampled in those rats not given an opportunity to drink. In 11 of these 33 regions, ingestion of a small amount of water was associated with a reversal of AII-induced elevation in blood flow [i.e., AII (W+) less than AII (W-)]; these regions included the organum vasculosum lamina terminalis, rostral lateral hypothalamus, supraoptic nuclei, rostral zona incerta, and median eminence. A group of similarly treated rats exhibited a significant elevation of mean arterial blood pressure following AII treatment without significant shifts in arterial blood gases, pH, or bicarbonate. These data are consistent with prominent involvement of the anteroventral third ventricular region of the rat brain. The results further indicate that rCBF may be a sensitive measure for the identification of central sites of action of AII as a dipsogenic agent and may reveal distinctions between regions associated primarily with initiation of drinking and those reflecting the results of subsequent behavioral events.
Czech
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DA
Department of Psychology, Marquette University, Milwaukee, WI 53233.
Stein
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EA
D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004326:Drinking / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D000804:Angiotensin II