The effect of losartan on drinking and NaCl intake in the rat in response to hyperosmotic and hypovolaemic stimuli: effect of route of administration and strain of rat.

Intracerebroventricular 100,000 pmol losartan (an AT1-receptor blocker) inhibited the initial drinking response of Wistar rats to 1 ml 2 M NaCl given subcutaneously but the intake over 3 h was not significantly inhibited. The same dose of the AT2-receptor blocker PD123319 had a more long-lasting inhibitory effect. Rats of three different strain, Wistar, Wistar-Kyoto (WK), and SH (spontaneously hypertensive), were subjected to sodium depletion using frusemide and a low-sodium diet; in the 3 h after 1.8% NaCl was made available, the intakes were 11.6 +/- 1.7 (SEM), 4.1 +/- 1.2 and 12.4 +/- 1.3 ml, respectively; water intakes in the same period averaged 4.2 +/- 1.1, 5.0 +/- 1.1 and 8.3 +/- 1.8 ml. The intake of both fluids by Wistar rats was not significantly affected by either losartan or PD123319. The intake of both saline and water in SHR rats was reduced by losartan. In evaluating the effect of antagonists to angiotensin II on the intake of water and NaCl in response to perturbations of hydromineral balance, difference in the route of administration of the stimulus and strain of the animals used must therefore be taken into account.