The importance of angiotensin II formation in the CNS in angiostensin I - elicited thirst.

The drinking response produced by direct injection of angiotensin I and II into the brain of the rat, was studied, using the angiotensin blocking agents SQ-20,881 (SQ) and P-113 (Saralasin). SQ inhibits angiotensin converting enzyme, preventing formation of angiotensin II, while P-113 is an analogue and competitive inhibitor of angiotensin II. SQ blocked central angiotensin I drinking, but only when the enzyme inhibitor was injected into the ventricle. Angiotensin II induced thirst was not blocked by SQ. P-113 inhibited angiotensin I and II drinking responses in both the preoptic area of the hypothalamus and the lateral ventricle. These data indicate that conversion of angiotensin I to angiotensin II is important in angiotensin-induced drinking, although an independent action of angiotensin I on drinking can not be ruled out at this time.