Preference for NaCl solutions in sham drinking Sprague-Dawley rats: water deprivation, sodium depletion, and angiotensin II.

Male Sprague-Dawley rats were fitted with closable gastric fistulas and were then tested under closed fistula (real intake) and open fistula (sham intake--fluids drain from the stomach without appreciable absorption) conditions in one of three states: fluid deprivation, sodium depletion, and infusion of angiotensin (Ang) II. Water and various concentrations of NaCl were offered to drink in 1-h one- or two-bottle intake tests. In Experiment 1, water-deprived rats with closed fistulas drank more 0.15 M NaCl than either water or 0.3 M NaCl, offered in one-bottle tests. In sham drinking tests, the intake decreased monotonically as NaCl concentration increased. In two-bottle tests, water was greatly preferred over NaCl solutions. In Experiment 2, sodium-depleted rats preferred NaCl over water, again demonstrating a peak intake at 0.15 M in closed fistula conditions. However, with the fistula open the intakes of 0.05 and 0.15 M were similar, and 0.45 M considerably lower. In Experiment 3, Ang II-infused rats consumed both water and NaCl in two-bottle tests in both open and closed fistula trials. The quantity ingested on sham trials was only modestly elevated over real intake trials with Ang II compared with sham tests in Experiments 1 and 2.