EFFECT OF AN ANGIOTENSIN CONVERTING ENZYME-INHIBITOR (SQ-14,225) O O-BETA-ADRENERGIC AND ANGIOTENSIN-INDUCED THIRSTS

The effect of acute administration of SQ 14,225, a new angiotensin converting enzyme inhibitor, on the drinking response of female rats administered either isoprenaline, angiotensin I, or angiotensin II was studied during 2 h after treatment. Administration of isoprenaline (25 μg/kg body wt) was accompanied by a significant increase in water intake when compared with saline-treated controls. Acute administration of a constant dose of isoprenaline (25 μg/kg body wt) and increasing doses of SQ 14,225 (5-50 mg/kg) was accompanied by a dose-related, linear decrease in water intake. Acute administration of either angiotensin I or angiotensin II (200 μg/kg body wt) was accompanied by a significant increase in water intake. The dipsogenic response to angiotensin II was not affected by acute administration of 35 mg SQ 14,225/kg body wt. However, at the same dose of SQ 14,225, angiotensin I-induced thirst was attenuated. Since isoprenaline-induced and angiotensin I-induced, but not angiotensin II-induced, thirsts are blocked by SQ 14,225, the results suggest that isoprenaline-induced thirst is mediated by way of the renin-angiotensin system. © 1979.