Central infusion of the AT(1) receptor antagonist losartan inhibits thirst but not sodium appetite in cattle

Experiments in cattle compared the effects of intracerebroventricular (ICV) infusions of losartan and PD-123319 on water intake caused by water restriction, ICV infusion of hypertonic NaCl, or ICV infusion of angiotensin II (ANG II). The effects of these receptor antagonists on sodium intake caused by sodium depletion were also examined. Losartan infusion caused dose-dependent inhibition of the high water intake caused by the physiological stimulus of water restriction or by ANG II infusion but did not affect salt appetite. PD-123319 infused at equimolar or greater (in ANG II experiments) doses did not affect water intake or salt intake due to sodium depletion. The results of these ICV infusion experiments confirm our earlier proposal that the physiological regulation of water intake in cattle may be mediated by ANG II acting centrally via AT(1) receptors. The dose of losartan that inhibited thirst in cattle did not inhibit sodium appetite, nor did an equimolar dose of PD-123319.