Water intake induced by spaced deliveries of salted and sweetened liquid food.

The water intake of food-deprived rats was evaluated under conditions where liquid food was presented occasionally. In the first experiment, when soybean milk alone was presented every 30 sec, little water was consumed. However, when sodium chloride was added to the soybean milk, water intake increased directly with salt concentration from 0.9 to 14.4%. At salt concentrations of 7.2 and 14.4%, the drinking induced by soybean milk resembled in several respects the adjunctive drinking educed by spaced presentations of dry food. In a second experiment, adulterating soybean milk with sugar in concentrations of 7 to 56% did not affect water intake significantly when the food was delivered every 30 seconds. These findings extend the range of conditions known to generate schedule-induced drinking, and point out a previously unknown constraint on the phenomenon.