Inhibition of water intake by ouabain administration in sheep

Intracarotid infusion of ouabain (1280 ng/min) over 4 1/2 hr virtually abolished water intake of sheep in response to intracarotid infusion of either angiotensin II (800 ng/min) or 4 M NaCl (1.6 ml/min for 20 min. Ouabain treatment did not affect mean arterial pressure either before or during infusion of angiotensin. Neither ouabain nor angiotensin administration affected plasma [Na] or [K] or CSF [K]. During ouabain, but not during control infusion, angiotensin administration significantly decreased CSF [Na]. Ouabain administration also decreased water intake after 23 1/2 or 48 hr water deprivation. In the 23 1/2 hr deprivation experiments, food was made available immediately prior to water presentation and the ingestion of food appeared to ameliorate the reduction in water intake. Food intake itself, was decreased in some animals, during ouabain treatment. Ouabain infused at 960 ng/min resulted in significant, but smaller, reductions in water intake induced by angiotensin, 4 M NaCl, and 48 hr water deprivation. It was concluded that ouabain treatment affected water intake by influence on Na transport either in the thirst receptors or at some other level in the neural system between receptor and effector.