Water intake elicited by injections of angiotensin II into preoptic area of rats.

Drinking in response to unilateral injections of angiotensin II (AII) into the preoptic area is relatively weak and a relatively high dose of AII is required. A comparison was made of the drinking elicited by bilateral and unilateral injections of AII. Reliable drinking was observed when 5 X 10(-12) mol of AII in 0.2 microliter was injected bilaterally into the preoptic area, and in some animals when the dose of AII was 0.5 X 10(-12) mol in 0.2 microliter. The volumes of water intake were significantly larger with bilateral injections compared to unilateral injections. By injection of tritiated AII to elicit drinking and subsequent autoradiographic analysis of brain sections, it was shown that the injections were confined to the preoptic region and did not reach the cerebral ventricles. The results suggest that 1) bilateral injections may be more appropriate for comparing the preoptic region with other putative angiotensin receptive sites, 2) there is a greater responsiveness of the preoptic region to bilateral as compared with unilateral injections, and 3) the AII receptive area is diffusely represented in the region of the medial preoptic nucleus.