Preference For NaCl Solutions Research Articles

Ingestion of hypertonic NaCl vs. palatable drinks by sodium-depleted rats

This work investigated whether the preference for NaCl solution is shifted to more palatable solutions in the adult male sodium-depleted rat ( n=6–10 per group). Animals had daily access to three bottles, one containing water, another 1.8% NaCl (300 mM), and a third containing 0.9% NaCl (150 mM), Gatorade (orange—OG or grape flavored—GG), orange juice (sweetened or unsweetened, from concentrate), or 10% sucrose (no sodium). Sodium content in Gatorade and orange juice ranged from 7 to 14 mEq/l. Daily intakes were recorded for at least 5 days prior to sodium depletion. Then, the animals were depleted of sodium (diuretic plus sodium-deficient diet and water for 24 h). Then, the other two bottles were returned to the animals and the intakes were recorded for 120 min (sodium preference test, SPT). Daily intake from the third bottle (except for unsweetened orange juice) at least doubled the daily 1.8% NaCl intake. The average 1.8% NaCl intake (13±2 ml) in the SPT was higher than the intake of 10% sucrose (6±1 ml) or of any other solution (less than 6 ml). The intakes of 1.8% NaCl and 0.9% NaCl (10±3 ml) were similar during the SPT. The animals also preferred 0.9% NaCl (27±1 ml) to OG (3±1 ml) in the absence of 1.8% NaCl in the SPT. Therefore, the preference for sodium in sodium-depleted rats also applies when palatable and nutritive solutions are simultaneously available.

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 lI compared with sham tests in Experiments 1 and 2.

Reversal of the sodium chloride aversion of Fischer 344 rats by chorda tympani nerve transection.

Fischer 344 (F344) rats are atypical in their lack of preference for any concentration of NaCl solution over water. It was hypothesized that abnormal signals mediated by the chorda tympani nerve (CT) could be causally involved in NaCl avoidance by F344 rats. This study assessed whether CT transection would normalize the salt preference of F344 rats. Preference for NaCl solutions (0.6%, 0.8%, and 1.0%) versus water was assessed using two-bottle preference tests. At all concentrations tested, CT-transected animals preferred NaCl solutions to water. This preference differed dramatically from the avoidance of these solutions by controls. These findings are striking, particularly because CT transections have generally failed to significantly affect NaCl preference in other rat strains. The results are consistent with the hypothesis that in F344 rats the avoidance of the taste of NaCl stems from input mediated by the CT.

Sensory adaptation and incentive contrast as factors affecting NaCl preference

One normal rat and 6 adrenalectomized rats were tested for the effect of predrinking various concentrations of NaCl on the preference for NaCl solutions. Short term variations of the traditional 1-bottle and 2-bottle preference tests were presented to the animals and the behavior measured in terms of number of licks and consistency of choice. The results showed that an equal preference for 0.1 m NaCl and 0.25 m NaCl after predrinking a weak NaCl solution (0.01 m) changed to a strong preference for 0.25 m NaCl over 0.1 m NaCl when the animals predrank a stronger NaCl solution (0.25 m). Control tests indicated that these results could not be explained simply on the basis of sensory adaptation. It was suggested that both sensory adaptation and incentive contrast were the essential factors which controlled the preference behavior in this experiment.